Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties,and the microalloying strategy is the most frequently adopted method for such a p...Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties,and the microalloying strategy is the most frequently adopted method for such a purpose.In this paper,recent advances in lengthscale-dependent scandium (Sc) microalloying effects in Al-Cu model alloys are reviewed.In coarse-grained Al-Cu alloys,the Sc-aided Cu/Sc/vacancies complexes that act as heterogeneous nuclei and Sc segregation at the θ′-Al_(2)Cu/matrix interface that reduces interfacial energy contribute significantly to θ′precipitation.By grain size refinement to the fine/ultrafine-grained scale,the strongly bonded Cu/Sc/vacancies complexes inhibit Cu and vacancy diffusing toward grain boundaries,promoting the desired intragranular θ′precipitation.At nanocrystalline scale,the applied high strain producing high-density vacancies results in the formation of a large quantity of (Cu Sc,vacancy)-rich atomic complexes with high thermal stability,outstandingly improving the strength/ductility synergy and preventing the intractable low-temperature precipitation.This review recommends the use of microalloying technology to modify the precipitation behaviors toward better combined mechanical properties and thermal stability in Al alloys.展开更多
The mechanisms of oxide metallurgy include inducing the formation of intragranular acicular ferrite(IAF)using micron-sized inclusions and restricting the growth of prior austenite grains(PAGs)by nanosized particles du...The mechanisms of oxide metallurgy include inducing the formation of intragranular acicular ferrite(IAF)using micron-sized inclusions and restricting the growth of prior austenite grains(PAGs)by nanosized particles during welding.The chaotically oriented IAF and refined PAGs inhibit crack initiation and propagation in the steel,resulting in high impact toughness.This work summarizes the com-bined effect of deoxidizers and alloying elements,with the aim to provide a new perspective for the research and practice related to im-proving the impact toughness of the heat affected zone(HAZ)during the high heat input welding.Ti complex deoxidation with other strong deoxidants,such as Mg,Ca,Zr,and rare earth metals(REMs),can improve the toughness of the heat-affected zone(HAZ)by re-fining PAGs or increasing IAF contents.However,it is difficult to identify the specific phase responsible for IAF nucleation because ef-fective inclusions formed by complex deoxidation are usually multiphase.Increasing alloying elements,such as C,Si,Al,Nb,or Cr,con-tents can impair HAZ toughness.A high C content typically increases the number of coarse carbides and decreases the potency of IAF formation.Si,Cr,or Al addition leads to the formation of undesirable microstructures.Nb reduces the high-temperature stability of the precipitates.Mo,V,and B can enhance HAZ toughness.Mo-containing precipitates present good thermal stability.VN or V(C,N)is ef-fective in promoting IAF nucleation due to its good coherent crystallographic relationship with ferrite.The formation of the B-depleted zone around the inclusion promotes IAF formation.The interactions between alloying elements are complex,and the effect of adding dif-ferent alloying elements remains to be evaluated.In the future,the interactions between various alloying elements and their effects on ox-ide metallurgy,as well as the calculation of the nucleation effects of effective inclusions using first principles calculations will become the focus of oxide metallurgy.展开更多
Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with a...Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with and without microalloying Ca(0.26 wt.%) to explore the effects of nanoscale precipitates on their corrosion behavior in detail via experimental analyses and theoretical calculations. The results suggested the peak-aged ZK60 alloy with Ca addition showed improved corrosion resistance in comparison with the alloys without Ca,owing to the contribution of Ca on the refinement of precipitates and increase in their number density. Although the precipitates and Mg matrix formed micro-galvanic couples leading to dissolution, the fine and dense precipitates could generate “in-situ pinning” effect on the corrosion products, forming a spider-web-like structure and improving the corrosion inhibition ability accordingly. The pinning effect was closely related to the size and number density of precipitates. This study provided important insight into the design and development of advanced corrosion resistant Mg alloys.展开更多
We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-ea...We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-earth and microalloying elements on the structure of hypereutectoid rails and optimize the composition design of hypereutectoid rails.Scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and other characterization techniques were employed to quantitatively analyzed the effects of different microalloying elements,including rare-earth elements,on pearlite lamellar spacing,cementite characteristics,and dislocation density.It was found that the lamellar spacing was reduced by adding various microalloying elements.Cementite lamellar thickness decreased with the refinement of pearlite lamellar spacing while the cementite content per unit volume increased.Local cementite spheroidization,dispersed in the ferrite matrix in granular form and thus playing the role of dispersion strengthening,was observed upon adding cerium(Ce).The contributions of dislocation density to the alloy strength of four steel sheet samples with and without the addition of nickel,Ce,and Ce–copper(Cu)composite were 26,27,32,and 37 MPa,respectively,indicating that the Ce–Cu composite had the highest dislocation strengthening effect.The Ce–Cu composite has played a meaningful role in the cementite characteristics and dislocation strengthening,which provides a theoretical basis for optimizing the composition design of hypereutectoid rails in actual production conditions.展开更多
The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increas...The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increase the cost of alloy largely.The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored.The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25-30%at room temperature.Moreover,these alloys exhibit much better corrosion resistance than AZ31 alloy.The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems.The deformation becomes more homogeneous and the resultant textures after deformation are weakened.展开更多
Mg-0.5Bi-0.5Sn alloys with and without microalloying with 0.5 wt%Mn were subjected to extrusion,and the effect of Mn microalloying on the microstructural characteristic and corrosion behavior of the extruded alloys wa...Mg-0.5Bi-0.5Sn alloys with and without microalloying with 0.5 wt%Mn were subjected to extrusion,and the effect of Mn microalloying on the microstructural characteristic and corrosion behavior of the extruded alloys was investigated.The results indicated that the average grain size and the density of dislocations decreased,and a new Mg_(26.67)Mn_(65.47)Fe_(7.86)second phase as well as grain boundary segregation of Sn atoms could be observed in certain micro-regions of the extruded dilute Mg-0.5Bi-0.5Sn-0.5 Mn alloy.The tailoring of microstructure resulted in the significant enhancement in corrosion resistance(R_(p)increased from 1095.91Ωcm^(2)to 5008.79Ωcm^(2)).In addition,grain boundary segregation resulted in intergranular corrosion and led to the dissolution of Sn atoms.Hence,the dissolution rate of the matrix in Mg-0.5Bi-0.5Sn-0.5Mn alloy could be inhibited by the corrosion product film containing an intermediate product(SnO_(2)).展开更多
Carbon neutrality of the steel industry requires the development of high-strength steel.The mechanical properties of low-alloy steel can be considerably improved at a low cost by adding a small amount of titanium(Ti)e...Carbon neutrality of the steel industry requires the development of high-strength steel.The mechanical properties of low-alloy steel can be considerably improved at a low cost by adding a small amount of titanium(Ti)element,namely Ti microalloying,whose performance is related to Ti-contained second phase particles including inclusions and precipitates.By proper controlling the precipitation behaviors of these particles during different stages of steel manufacture,fine-grained microstructure and strong precipitation strengthening effects can be obtained in low-alloy steel.Thus,Ti microalloying can be widely applied to produce high strength steel,which can replace low strength steels heavily used in various areas currently.This article reviews the characteristics of the chemical and physical metallurgies of Ti microalloying and the effects of Ti microalloying on the phase formation,microstructural evolution,precipitation behavior of low-carbon steel during the steel making process,especially the thin slab casting and continuous rolling process and the mechanical properties of final steel products.Future development of Ti microalloying is also proposed to further promote the application of Ti microalloying technology in steel to meet the requirement of low-carbon economy.展开更多
The influences of Ca and Ce/La microalloying on the microstructure evolution and bio-corrosion resistances of extruded Mg-Zn alloys have been systematically investigated in the current study.Compared with single Ca or...The influences of Ca and Ce/La microalloying on the microstructure evolution and bio-corrosion resistances of extruded Mg-Zn alloys have been systematically investigated in the current study.Compared with single Ca or Ce/La addition,the Ca-Ce/La cooperative microalloying results in an outstanding grain refinement,because the fine secondary phase particles effectively hinder the recrystallized grain growth.The coarse Ca2Mg6Zn3 phases promote the formation of Ca3(PO4)2 or hydroxyapatite particles during the immersion process and accelerate the dissolution of the corrosion product film,which destroys its integrity and results in the deterioration of anti-corrosive performance.The Ce/La elements can be dispersed within the conventional Mg7Zn3 phases,which reduce the internal galvanic corrosion between Mg matrix and the secondary phases,leading to an obvious improvement of corrosion resistance.Therefore,the Ca-Ce/La cooperative microalloying achieves a homogenous fine-grained microstructure and improves the protective ability of surface film,which will pave a new avenue for the design of biomedical Mg alloys in the coming future.展开更多
In this study, 7A52 aluminum alloy sheets of 4 mm in thickness were welded by tungsten inert gas welding using microalloying welding wires containing traces of Zr and Er. The influence of rare earth elements Zr and Er...In this study, 7A52 aluminum alloy sheets of 4 mm in thickness were welded by tungsten inert gas welding using microalloying welding wires containing traces of Zr and Er. The influence of rare earth elements Zr and Er on the microstructure and mechanical properties of the welded joints was analyzed by optical microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, hardness testing, and tensile mechanical properties testing. Systematic analyses indicate that the addition of trace amounts of Er and Zr leads to the formation of fine Al3Er, Al3Zr, and Al3（Zr,Er） phases that favor significant grain refinement in the weld zone. Besides, the tensile strength and hardness of the welded joints were obviously improved with the addition of Er and Zr, as evidenced by the increase in tensile strength and elongation by 40 MPa and 1.4%, respectively, and by the welding coefficient of 73%.展开更多
The microstructure and martensite substructure of as-cast martensitic high-Cr cast iron by injection microalloying have been studied by usig SEM and TEM.The relationship between distribution of alloying elements and p...The microstructure and martensite substructure of as-cast martensitic high-Cr cast iron by injection microalloying have been studied by usig SEM and TEM.The relationship between distribution of alloying elements and phase formation of carbide,as well as various branching and distortion of carbide,have been analysed by X-ray diffractometer and EPMA.展开更多
The microstructure and properties of boron-modified copper-base alloys were investigated by tension,corrosion,corrosive wear and erosion tests.The results show that by adding boron in copper-base alloys,the strength a...The microstructure and properties of boron-modified copper-base alloys were investigated by tension,corrosion,corrosive wear and erosion tests.The results show that by adding boron in copper-base alloys,the strength and hardness of alloys increase,the plasticity decreases somewhat;the corrosion,corrosive wear and erosion resistance of boron-modified copper-base alloys improve obviously.The microalloying mechanism of boron in copper-base alloys was found.展开更多
Based on their hot ductilities, Nb, V and Ti microalloying steels can be classified into two groups. The first group includes steels with lower carbon content (≤0.10%). Ductilities of steels of this group recover and...Based on their hot ductilities, Nb, V and Ti microalloying steels can be classified into two groups. The first group includes steels with lower carbon content (≤0.10%). Ductilities of steels of this group recover and rise with decreasing temperature when temperature lowers to below 825℃. Another group includes steels which contain more carbon (>0.12%) or contain more Nb and V. The low ductility temperature Region Ⅲ for steels of mis group extends to temperature as low as 725℃. The occurrence of the transverse corner cracks of the Nb, V and Ti microalloying steel CC slabs has be considerably decreased by stabilizing casting speed, increasing mold steel level automatic control ratio,enhancing caster segment radial alignment and adopting proper secondary cooling patterns to make slab corner temperature at straightening out off the low ductility temperature region.展开更多
Deformation-induced ferrite transformation （DIFT） has been proved to be an effective approach to refine ferrite grains. This paper shows that the ferrite grains can further be refined through combination of DIFT and...Deformation-induced ferrite transformation （DIFT） has been proved to be an effective approach to refine ferrite grains. This paper shows that the ferrite grains can further be refined through combination of DIFT and V or V-N microalloying. Vanadium dissolved in γ matrix restrains DIFT. During deformation, vanadium carbonitrides rapidly precipitate due to strain-induced precipitation, which causes decrease in vanadium dissolved in matrix and indirectly accelerates DIFT. Under heavy deformation, deformation induced ferrite （DIF） grains in V microalloyed steel were finer than those in V free steel. The more V added to steel, the finer DIF grains obtained. Moreover, the addition of N to V microalloyed steels can remarkably accelerate precipitation of V, and then promote DIFT. However, DIF grains in V-N microalloyed steel easily coarsen.展开更多
High-nitrogen stainless bearing steel(HNSBS)with ultra-high tensile strength(∼2403 MPa)and good toughness(∼80.0 J)was obtained by V-microalloying,overcoming the strength-toughness trade-off of conventional V-free HN...High-nitrogen stainless bearing steel(HNSBS)with ultra-high tensile strength(∼2403 MPa)and good toughness(∼80.0 J)was obtained by V-microalloying,overcoming the strength-toughness trade-off of conventional V-free HNSBS.In this work,since V-microalloying facilitated the enrichment of interstitial atoms(C and N)in precipitates,the content of interstitial atoms in the matrix was reduced accordingly(i.e.,interstitial partitioning).On the one hand,V-microalloying reduced the substantial intergranular precipitates and transformed the precipitates from M_(23)C_(6)+M_(2)N into V-containing M_(23)C_(6)+M_(2)N+MN with multi-scale particle sizes,causing a coupling strengthening effect,which contributed to the toughness and additional strength increase.On the other hand,V-microalloying controlled interstitial partitioning,effectively refined coarse retained austenite(RA),increased the fraction of dislocation martensite,and reduced the fraction of twin martensite.The more film-like RA and dislocation martensite with high dislocation density coordinated plastic deformation and prevented crack propagation,thus obviously enhancing the strength and toughness of 0.2 V steel.This study provides a new route to develop high-performance HNSBS for aerospace applications.展开更多
Microalloying elements play a crucial role in mechanical properties and phase stability of metallic alloys.In this work,we employ first-principles calculations and atomic-scale high-angle annular dark-field scanning t...Microalloying elements play a crucial role in mechanical properties and phase stability of metallic alloys.In this work,we employ first-principles calculations and atomic-scale high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)to find promising microalloying elements that will improve the stability and properties ofβ"/Al interface andβ"phase in Al–Mg-Si alloys.First,we define a substitution energy for evaluating the stability ofβ"phase andβ"/Al interface with microalloying elements doped.Then,experiments of HAADF-STEM imaging are carried out to verify the calculational results.Next,using the most stable structures doped with microalloying elements,the mechanical properties of theβ"bulk and theβ"/Al interface were calculated and analyzed.At last,we have figured out the effects of all considered microalloying elements and obtained a rule that the stable occupancy of solute atoms is related to their own radius and the radius of Mg,Si,and Al.These findings will provide some theoretical basis for future microalloying strategies of Al–Mg-Si alloys.展开更多
Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing th...Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decreasing the impact energy.Scanning electron microscopy and optical microscopy studies revealed grain refinement effect of both Vand V+Ti-microadditions.The micro-hardness measurements of the ferrite phase confirmed the precipitation strengthening effect of microalloying elements.展开更多
The effects of Cr, Ni and Cu on the corrosion behavior of low carbon microalloying steel in a CI- containing environment were investigated. The results revealed that the corrosion process could be divided into the ini...The effects of Cr, Ni and Cu on the corrosion behavior of low carbon microalloying steel in a CI- containing environment were investigated. The results revealed that the corrosion process could be divided into the initial stage in which the corrosion rate increased with accumulation of corrosion products and the later stage in which homogeneous and compact inner rust layers started to protect steel substrate out of corrosion mediums. The results of X-ray diffraction （XRD） indicated that the rust layers of the three-group steels （Cr, Cr-Ni and Cr-Ni-Cu steels） were composed of α-FeOOH, β-FeOOH, γ-FeOOH, Fe3O4 and large amounts of amorphous compounds. The content of amorphous compounds of Cr-Ni-Cu steel was about 2%-3% more than that of Cr-Ni steel. The results of electron probe microanalysis （EPMA） showed that Cr concentrated mainly in the inner region of the rust of Cr-Ni-Cu steel, inner/outer interface especially, whereas Ni was uniformly distributed all over the rust and Cu was noticed rarely after 73 wet/dry cycles. The addition of Cr and Ni was beneficial to the formation of dense and compact inner rust layer, which was the most important reason for the improvement of corrosion resistance of experimental steel.展开更多
As a kind of important light alloys,the Al alloys exhibit mechanical properties that are closely related to the microstructures.Changing the main alloying elements and adjusting heat treatments are usually approaches ...As a kind of important light alloys,the Al alloys exhibit mechanical properties that are closely related to the microstructures.Changing the main alloying elements and adjusting heat treatments are usually approaches to tune the microstructure and hence artificially control the mechanical properties.However,the windows for the two approaches have become quite narrow,after extensive studies in the last half of century.Microalloying has become the most promising strategy to further modify the microstructure and improve the mechanical properties of Al alloys,among which the element of scandium(Sc)is especially powerful.In this paper,the recent progresses in Al alloys microalloyed with Sc are briefly reviewed,focusing on the microstructural characterization,strengthening response,and underlying mechanisms.The possible key research points are also proposed for the further development of Al alloys microalloyed with Sc and other rare earth elements.展开更多
This research studied the mechanisms of Ca and Zn microalloying on the enhancement of ductility of extruded Mg-Gd sheet by combing electron backscattered diffraction and slip trace analysis.The ductility and microstru...This research studied the mechanisms of Ca and Zn microalloying on the enhancement of ductility of extruded Mg-Gd sheet by combing electron backscattered diffraction and slip trace analysis.The ductility and microstructure of extruded Mg-0.6Gd and Mg-0.6Gd-0.3Ca-0.2Zn(wt%)sheets were investigated.Basal slip was the main deformation mode under investigation.Ca and Zn microalloying increased the frequency of grain boundaries(GBs)with misorientation angles(θs)<35°,promoted slip transfer across GBs and restricted the basal slip localization.In addition,there were a higher number of GB cracks homogeneously distributed in the Mg-0.6Gd sheet than in the Mg-0.6Gd-0.3Ca-0.2Zn sheet,attributed to the increased cohesion of GBs.The enhancement of basal slip,the suppression of slip localization and the suppression of GB cracking were contributed to the increased ductility for Mg-0.6Gd-0.3Ca-0.2Zn sheet.展开更多
Fe83（Cox,Niy）（B11Si2P3C1）1-x,y/17（x,y=1–3）amorphous alloys with high saturation magnetic flux density（Bs）and excellent soft-magnetic properties were developed and then the microalloying and clustering effects...Fe83（Cox,Niy）（B11Si2P3C1）1-x,y/17（x,y=1–3）amorphous alloys with high saturation magnetic flux density（Bs）and excellent soft-magnetic properties were developed and then the microalloying and clustering effects were explored.The microalloying of Co and Ni improves the Bsfrom 1.65 T to 1.67–1.72 T and 1.66–1.68 T,respectively.The Ni-doped alloys exhibit better soft-magnetic properties,containing a low coercivity（Hc） of about 5.0 A/m and a high Effective permeability（μe）of（8–10）×10^3,whereas the microalloying of Co leads to a deteriorative Hc of 5.0–13.0 A/m and a μeof（5–8）×10^3.Moreover,microalloying of Ni can increase the ductile-brittle transition（DBT）temperature of the ribbons,while a totally opposite effect is found in the Co-doped alloys.The formation of dense α-Fe（Co,Ni）clusters during annealing process is used to explain the distinct effects of Co and Ni microalloying on the magnetic properties and bending toughness.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52201135,52271115,U23A6013,92360301,and U2330203)the 111 Project of China(No.BP2018008)+1 种基金the Shaanxi Province Innovation Team Project,China(No.2024RS-CXTD-58)supported by the International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies and by the open research fund of Suzhou Laboratory。
文摘Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties,and the microalloying strategy is the most frequently adopted method for such a purpose.In this paper,recent advances in lengthscale-dependent scandium (Sc) microalloying effects in Al-Cu model alloys are reviewed.In coarse-grained Al-Cu alloys,the Sc-aided Cu/Sc/vacancies complexes that act as heterogeneous nuclei and Sc segregation at the θ′-Al_(2)Cu/matrix interface that reduces interfacial energy contribute significantly to θ′precipitation.By grain size refinement to the fine/ultrafine-grained scale,the strongly bonded Cu/Sc/vacancies complexes inhibit Cu and vacancy diffusing toward grain boundaries,promoting the desired intragranular θ′precipitation.At nanocrystalline scale,the applied high strain producing high-density vacancies results in the formation of a large quantity of (Cu Sc,vacancy)-rich atomic complexes with high thermal stability,outstandingly improving the strength/ductility synergy and preventing the intractable low-temperature precipitation.This review recommends the use of microalloying technology to modify the precipitation behaviors toward better combined mechanical properties and thermal stability in Al alloys.
基金supported by the National Natural Science Foundation of China(No.U1960202).
文摘The mechanisms of oxide metallurgy include inducing the formation of intragranular acicular ferrite(IAF)using micron-sized inclusions and restricting the growth of prior austenite grains(PAGs)by nanosized particles during welding.The chaotically oriented IAF and refined PAGs inhibit crack initiation and propagation in the steel,resulting in high impact toughness.This work summarizes the com-bined effect of deoxidizers and alloying elements,with the aim to provide a new perspective for the research and practice related to im-proving the impact toughness of the heat affected zone(HAZ)during the high heat input welding.Ti complex deoxidation with other strong deoxidants,such as Mg,Ca,Zr,and rare earth metals(REMs),can improve the toughness of the heat-affected zone(HAZ)by re-fining PAGs or increasing IAF contents.However,it is difficult to identify the specific phase responsible for IAF nucleation because ef-fective inclusions formed by complex deoxidation are usually multiphase.Increasing alloying elements,such as C,Si,Al,Nb,or Cr,con-tents can impair HAZ toughness.A high C content typically increases the number of coarse carbides and decreases the potency of IAF formation.Si,Cr,or Al addition leads to the formation of undesirable microstructures.Nb reduces the high-temperature stability of the precipitates.Mo,V,and B can enhance HAZ toughness.Mo-containing precipitates present good thermal stability.VN or V(C,N)is ef-fective in promoting IAF nucleation due to its good coherent crystallographic relationship with ferrite.The formation of the B-depleted zone around the inclusion promotes IAF formation.The interactions between alloying elements are complex,and the effect of adding dif-ferent alloying elements remains to be evaluated.In the future,the interactions between various alloying elements and their effects on ox-ide metallurgy,as well as the calculation of the nucleation effects of effective inclusions using first principles calculations will become the focus of oxide metallurgy.
基金the support of the National Natural Science Foundation of China (Grant Nos.51901174,52005389)the China Postdoctoral Science Foundation (Nos.2020M673383,2020M673389)the Fundamental Research Funds for the Central Universities (xzy012020001)。
文摘Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with and without microalloying Ca(0.26 wt.%) to explore the effects of nanoscale precipitates on their corrosion behavior in detail via experimental analyses and theoretical calculations. The results suggested the peak-aged ZK60 alloy with Ca addition showed improved corrosion resistance in comparison with the alloys without Ca,owing to the contribution of Ca on the refinement of precipitates and increase in their number density. Although the precipitates and Mg matrix formed micro-galvanic couples leading to dissolution, the fine and dense precipitates could generate “in-situ pinning” effect on the corrosion products, forming a spider-web-like structure and improving the corrosion inhibition ability accordingly. The pinning effect was closely related to the size and number density of precipitates. This study provided important insight into the design and development of advanced corrosion resistant Mg alloys.
基金the National Natural Science Foundation of China(No.51361021)the Inner Mongolia Science and Technology Major Project(No.ZDZX2018024)。
文摘We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-earth and microalloying elements on the structure of hypereutectoid rails and optimize the composition design of hypereutectoid rails.Scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and other characterization techniques were employed to quantitatively analyzed the effects of different microalloying elements,including rare-earth elements,on pearlite lamellar spacing,cementite characteristics,and dislocation density.It was found that the lamellar spacing was reduced by adding various microalloying elements.Cementite lamellar thickness decreased with the refinement of pearlite lamellar spacing while the cementite content per unit volume increased.Local cementite spheroidization,dispersed in the ferrite matrix in granular form and thus playing the role of dispersion strengthening,was observed upon adding cerium(Ce).The contributions of dislocation density to the alloy strength of four steel sheet samples with and without the addition of nickel,Ce,and Ce–copper(Cu)composite were 26,27,32,and 37 MPa,respectively,indicating that the Ce–Cu composite had the highest dislocation strengthening effect.The Ce–Cu composite has played a meaningful role in the cementite characteristics and dislocation strengthening,which provides a theoretical basis for optimizing the composition design of hypereutectoid rails in actual production conditions.
文摘The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increase the cost of alloy largely.The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored.The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25-30%at room temperature.Moreover,these alloys exhibit much better corrosion resistance than AZ31 alloy.The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems.The deformation becomes more homogeneous and the resultant textures after deformation are weakened.
基金jointly supported by the National Natural Science Foundation of China(Grant nos.:51704209,51701060)Natural Science Foundation of Shanxi Province(Grant no.:201801D121088)+2 种基金Shanxi Province Science Foundation for Youths(Grant no.:2016021063)Shanxi Scholarship Council of China(Grant no.:2019032)the Science and Technology Major Project of Shanxi Province(Grant nos.:20191102008,20191102007)。
文摘Mg-0.5Bi-0.5Sn alloys with and without microalloying with 0.5 wt%Mn were subjected to extrusion,and the effect of Mn microalloying on the microstructural characteristic and corrosion behavior of the extruded alloys was investigated.The results indicated that the average grain size and the density of dislocations decreased,and a new Mg_(26.67)Mn_(65.47)Fe_(7.86)second phase as well as grain boundary segregation of Sn atoms could be observed in certain micro-regions of the extruded dilute Mg-0.5Bi-0.5Sn-0.5 Mn alloy.The tailoring of microstructure resulted in the significant enhancement in corrosion resistance(R_(p)increased from 1095.91Ωcm^(2)to 5008.79Ωcm^(2)).In addition,grain boundary segregation resulted in intergranular corrosion and led to the dissolution of Sn atoms.Hence,the dissolution rate of the matrix in Mg-0.5Bi-0.5Sn-0.5Mn alloy could be inhibited by the corrosion product film containing an intermediate product(SnO_(2)).
基金financially support by the National Natural Science Foundation of China(Nos.52104369 and 52071038)the China Postdoctoral Science Foundation(No.2021M700374)the State Key Laboratory for Advanced Metals and Materials(No.2020Z-02)。
文摘Carbon neutrality of the steel industry requires the development of high-strength steel.The mechanical properties of low-alloy steel can be considerably improved at a low cost by adding a small amount of titanium(Ti)element,namely Ti microalloying,whose performance is related to Ti-contained second phase particles including inclusions and precipitates.By proper controlling the precipitation behaviors of these particles during different stages of steel manufacture,fine-grained microstructure and strong precipitation strengthening effects can be obtained in low-alloy steel.Thus,Ti microalloying can be widely applied to produce high strength steel,which can replace low strength steels heavily used in various areas currently.This article reviews the characteristics of the chemical and physical metallurgies of Ti microalloying and the effects of Ti microalloying on the phase formation,microstructural evolution,precipitation behavior of low-carbon steel during the steel making process,especially the thin slab casting and continuous rolling process and the mechanical properties of final steel products.Future development of Ti microalloying is also proposed to further promote the application of Ti microalloying technology in steel to meet the requirement of low-carbon economy.
基金the National Natural Science Foundation(Grant nos.5177117&51671152 and 51874225)the Key Research and Development Program of Shanxi Province(Grant nos.2020KWZ-007 and 2018ZDXMGY-149)the Youth Innovation Team of Shanxi Universities and the Natural Science Foundation of Jilin Province(Grant no.20180414016GH).
文摘The influences of Ca and Ce/La microalloying on the microstructure evolution and bio-corrosion resistances of extruded Mg-Zn alloys have been systematically investigated in the current study.Compared with single Ca or Ce/La addition,the Ca-Ce/La cooperative microalloying results in an outstanding grain refinement,because the fine secondary phase particles effectively hinder the recrystallized grain growth.The coarse Ca2Mg6Zn3 phases promote the formation of Ca3(PO4)2 or hydroxyapatite particles during the immersion process and accelerate the dissolution of the corrosion product film,which destroys its integrity and results in the deterioration of anti-corrosive performance.The Ce/La elements can be dispersed within the conventional Mg7Zn3 phases,which reduce the internal galvanic corrosion between Mg matrix and the secondary phases,leading to an obvious improvement of corrosion resistance.Therefore,the Ca-Ce/La cooperative microalloying achieves a homogenous fine-grained microstructure and improves the protective ability of surface film,which will pave a new avenue for the design of biomedical Mg alloys in the coming future.
文摘In this study, 7A52 aluminum alloy sheets of 4 mm in thickness were welded by tungsten inert gas welding using microalloying welding wires containing traces of Zr and Er. The influence of rare earth elements Zr and Er on the microstructure and mechanical properties of the welded joints was analyzed by optical microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, hardness testing, and tensile mechanical properties testing. Systematic analyses indicate that the addition of trace amounts of Er and Zr leads to the formation of fine Al3Er, Al3Zr, and Al3（Zr,Er） phases that favor significant grain refinement in the weld zone. Besides, the tensile strength and hardness of the welded joints were obviously improved with the addition of Er and Zr, as evidenced by the increase in tensile strength and elongation by 40 MPa and 1.4%, respectively, and by the welding coefficient of 73%.
文摘The microstructure and martensite substructure of as-cast martensitic high-Cr cast iron by injection microalloying have been studied by usig SEM and TEM.The relationship between distribution of alloying elements and phase formation of carbide,as well as various branching and distortion of carbide,have been analysed by X-ray diffractometer and EPMA.
基金Supported by the National Natural Science Foundation of China。
文摘The microstructure and properties of boron-modified copper-base alloys were investigated by tension,corrosion,corrosive wear and erosion tests.The results show that by adding boron in copper-base alloys,the strength and hardness of alloys increase,the plasticity decreases somewhat;the corrosion,corrosive wear and erosion resistance of boron-modified copper-base alloys improve obviously.The microalloying mechanism of boron in copper-base alloys was found.
文摘Based on their hot ductilities, Nb, V and Ti microalloying steels can be classified into two groups. The first group includes steels with lower carbon content (≤0.10%). Ductilities of steels of this group recover and rise with decreasing temperature when temperature lowers to below 825℃. Another group includes steels which contain more carbon (>0.12%) or contain more Nb and V. The low ductility temperature Region Ⅲ for steels of mis group extends to temperature as low as 725℃. The occurrence of the transverse corner cracks of the Nb, V and Ti microalloying steel CC slabs has be considerably decreased by stabilizing casting speed, increasing mold steel level automatic control ratio,enhancing caster segment radial alignment and adopting proper secondary cooling patterns to make slab corner temperature at straightening out off the low ductility temperature region.
文摘Deformation-induced ferrite transformation （DIFT） has been proved to be an effective approach to refine ferrite grains. This paper shows that the ferrite grains can further be refined through combination of DIFT and V or V-N microalloying. Vanadium dissolved in γ matrix restrains DIFT. During deformation, vanadium carbonitrides rapidly precipitate due to strain-induced precipitation, which causes decrease in vanadium dissolved in matrix and indirectly accelerates DIFT. Under heavy deformation, deformation induced ferrite （DIF） grains in V microalloyed steel were finer than those in V free steel. The more V added to steel, the finer DIF grains obtained. Moreover, the addition of N to V microalloyed steels can remarkably accelerate precipitation of V, and then promote DIFT. However, DIF grains in V-N microalloyed steel easily coarsen.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.U1960203,52004060,and 52174308)Fundamental Research Funds for the Central Universities(Grant Nos.N2125017 and N2225031)+1 种基金Program of Introducing Talents of Discipline to Universities(Grant No.B21001)Liaoning Pilot Base Project(No.2022JH24/10200026)。
文摘High-nitrogen stainless bearing steel(HNSBS)with ultra-high tensile strength(∼2403 MPa)and good toughness(∼80.0 J)was obtained by V-microalloying,overcoming the strength-toughness trade-off of conventional V-free HNSBS.In this work,since V-microalloying facilitated the enrichment of interstitial atoms(C and N)in precipitates,the content of interstitial atoms in the matrix was reduced accordingly(i.e.,interstitial partitioning).On the one hand,V-microalloying reduced the substantial intergranular precipitates and transformed the precipitates from M_(23)C_(6)+M_(2)N into V-containing M_(23)C_(6)+M_(2)N+MN with multi-scale particle sizes,causing a coupling strengthening effect,which contributed to the toughness and additional strength increase.On the other hand,V-microalloying controlled interstitial partitioning,effectively refined coarse retained austenite(RA),increased the fraction of dislocation martensite,and reduced the fraction of twin martensite.The more film-like RA and dislocation martensite with high dislocation density coordinated plastic deformation and prevented crack propagation,thus obviously enhancing the strength and toughness of 0.2 V steel.This study provides a new route to develop high-performance HNSBS for aerospace applications.
基金financially supported by the National Natural Science Foundation of China(Nos.52001119,51831004,and 52171006)the Fundamental Research Funds for the Central Universities.
文摘Microalloying elements play a crucial role in mechanical properties and phase stability of metallic alloys.In this work,we employ first-principles calculations and atomic-scale high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)to find promising microalloying elements that will improve the stability and properties ofβ"/Al interface andβ"phase in Al–Mg-Si alloys.First,we define a substitution energy for evaluating the stability ofβ"phase andβ"/Al interface with microalloying elements doped.Then,experiments of HAADF-STEM imaging are carried out to verify the calculational results.Next,using the most stable structures doped with microalloying elements,the mechanical properties of theβ"bulk and theβ"/Al interface were calculated and analyzed.At last,we have figured out the effects of all considered microalloying elements and obtained a rule that the stable occupancy of solute atoms is related to their own radius and the radius of Mg,Si,and Al.These findings will provide some theoretical basis for future microalloying strategies of Al–Mg-Si alloys.
文摘Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decreasing the impact energy.Scanning electron microscopy and optical microscopy studies revealed grain refinement effect of both Vand V+Ti-microadditions.The micro-hardness measurements of the ferrite phase confirmed the precipitation strengthening effect of microalloying elements.
基金supported by the High Technology Research and Development Program of China (No. 2007AA03Z504)the Fundamental Research Funds for the Central Universities (No. N100507002)
文摘The effects of Cr, Ni and Cu on the corrosion behavior of low carbon microalloying steel in a CI- containing environment were investigated. The results revealed that the corrosion process could be divided into the initial stage in which the corrosion rate increased with accumulation of corrosion products and the later stage in which homogeneous and compact inner rust layers started to protect steel substrate out of corrosion mediums. The results of X-ray diffraction （XRD） indicated that the rust layers of the three-group steels （Cr, Cr-Ni and Cr-Ni-Cu steels） were composed of α-FeOOH, β-FeOOH, γ-FeOOH, Fe3O4 and large amounts of amorphous compounds. The content of amorphous compounds of Cr-Ni-Cu steel was about 2%-3% more than that of Cr-Ni steel. The results of electron probe microanalysis （EPMA） showed that Cr concentrated mainly in the inner region of the rust of Cr-Ni-Cu steel, inner/outer interface especially, whereas Ni was uniformly distributed all over the rust and Cu was noticed rarely after 73 wet/dry cycles. The addition of Cr and Ni was beneficial to the formation of dense and compact inner rust layer, which was the most important reason for the improvement of corrosion resistance of experimental steel.
基金financially supported by the National Natural Science Foundation of China(Nos.51621063,51625103,51722104,51790482,and 51761135031)the Program of the Ministry of Education of China for Introducing Talents of Discipline to Universities(No.BP2018008)supported by the International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies。
文摘As a kind of important light alloys,the Al alloys exhibit mechanical properties that are closely related to the microstructures.Changing the main alloying elements and adjusting heat treatments are usually approaches to tune the microstructure and hence artificially control the mechanical properties.However,the windows for the two approaches have become quite narrow,after extensive studies in the last half of century.Microalloying has become the most promising strategy to further modify the microstructure and improve the mechanical properties of Al alloys,among which the element of scandium(Sc)is especially powerful.In this paper,the recent progresses in Al alloys microalloyed with Sc are briefly reviewed,focusing on the microstructural characterization,strengthening response,and underlying mechanisms.The possible key research points are also proposed for the further development of Al alloys microalloyed with Sc and other rare earth elements.
基金financial supports from the National Key Research and Development Program of China(2016YFB0101700 and 2016YFB0301104)the National Natural Science Foundation of China(U1764253,U2037601,51971044 and 52001037)+2 种基金the National Defense Basic Scientific Research program of China,the Qinghai Science and Technology Program(2018GX-A1)the Chongqing Science and Technology Commission(cstc2017zdcy-zdzx X0006)Chongqing Scientific&Technological Talents Program(KJXX2017002)。
文摘This research studied the mechanisms of Ca and Zn microalloying on the enhancement of ductility of extruded Mg-Gd sheet by combing electron backscattered diffraction and slip trace analysis.The ductility and microstructure of extruded Mg-0.6Gd and Mg-0.6Gd-0.3Ca-0.2Zn(wt%)sheets were investigated.Basal slip was the main deformation mode under investigation.Ca and Zn microalloying increased the frequency of grain boundaries(GBs)with misorientation angles(θs)<35°,promoted slip transfer across GBs and restricted the basal slip localization.In addition,there were a higher number of GB cracks homogeneously distributed in the Mg-0.6Gd sheet than in the Mg-0.6Gd-0.3Ca-0.2Zn sheet,attributed to the increased cohesion of GBs.The enhancement of basal slip,the suppression of slip localization and the suppression of GB cracking were contributed to the increased ductility for Mg-0.6Gd-0.3Ca-0.2Zn sheet.
基金mainly supported by the National Natural Science Foundation of China (Grant Nos.51601206,51671206)Ningbo International Cooperation Projects (Grant No.2015D10022)Ningbo Major Project for Science and Technology (Grant No.201401B1003003)
文摘Fe83（Cox,Niy）（B11Si2P3C1）1-x,y/17（x,y=1–3）amorphous alloys with high saturation magnetic flux density（Bs）and excellent soft-magnetic properties were developed and then the microalloying and clustering effects were explored.The microalloying of Co and Ni improves the Bsfrom 1.65 T to 1.67–1.72 T and 1.66–1.68 T,respectively.The Ni-doped alloys exhibit better soft-magnetic properties,containing a low coercivity（Hc） of about 5.0 A/m and a high Effective permeability（μe）of（8–10）×10^3,whereas the microalloying of Co leads to a deteriorative Hc of 5.0–13.0 A/m and a μeof（5–8）×10^3.Moreover,microalloying of Ni can increase the ductile-brittle transition（DBT）temperature of the ribbons,while a totally opposite effect is found in the Co-doped alloys.The formation of dense α-Fe（Co,Ni）clusters during annealing process is used to explain the distinct effects of Co and Ni microalloying on the magnetic properties and bending toughness.
