In this study, we thoroughly examined the impact of heat treatments and hole count (p) on the properties of LnSrBaCu<sub>3</sub>O<sub>6+z</sub> (Ln = Eu, Sm, Nd) compounds. We focused on prepar...In this study, we thoroughly examined the impact of heat treatments and hole count (p) on the properties of LnSrBaCu<sub>3</sub>O<sub>6+z</sub> (Ln = Eu, Sm, Nd) compounds. We focused on preparation, X-ray diffraction with Rietveld refinement, AC susceptibility, DC resistivity measurements, and heat treatment effects. Two heat treatment types were applied: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. As the rare earth Ln’s ionic radius increased, certain parameters notably changed. Specifically, c parameter, surface area S, and volume V increased, while critical temperature Tc and holes (p) in the CuO<sub>2</sub> plane decreased. The evolution of these parameters with rare earth Ln’s ionic radius in [AO] heat treatment is linear. Regardless of the treatment, the structure is orthorhombic for Ln = Eu, tetragonal for Ln = Nd, orthorhombic for Ln = Sm [AO], and pseudo-tetragonal for Sm [O]. The highest critical temperature is reached with Ln = Eu (Tc [AO] = 87.1 K). Notably, for each sample, Tc [AO] surpasses Tc [O]. Observed data stems from factors including rare earth ionic size, improved cationic and oxygen chain order, holes count p in Cu(2)O<sub>2</sub> planes, and in-phase purity of [AO] samples. Our research strives to clearly demonstrate that the density of holes (p) within the copper plane stands as a determinant impacting the structural, electrical, and superconducting properties of these samples. Meanwhile, the other aforementioned parameters contribute to shaping this density (p).展开更多
The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron pr...The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and energy dispersive spectroscopy(EDS).The solidus and liquidus of single crystal alloy were obtained by differential scanning calorimetry(DSC).Results show that the mosaic-like eutectic and fan-like eutectic are dissolved at first,and the coarseγ'phase is dissolved later during the solution heat treatment of 1,390°C/2 h+1,310°C/4 h+1,320°C/10 h+air cooling(AC).The composition segregations of Al,Ta,W and Re are 0.99,0.96,1.04 and 1.16,respectively,which close to 1.The incipient melting is caused by the low local temperature of the alloy,and the micropore region with a lower melting point is the preferred position for incipient melting.展开更多
The effects of extrusion and heat treatments on the microstructure and mechanical properties of Mg-8Zn-1Al-0.5Cu- 0.5Mn magnesium alloy were investigated. Bimodal microstructure is formed in this alloy when it is extr...The effects of extrusion and heat treatments on the microstructure and mechanical properties of Mg-8Zn-1Al-0.5Cu- 0.5Mn magnesium alloy were investigated. Bimodal microstructure is formed in this alloy when it is extruded at 230 and 260 ℃, and complete DRX occurs at the extruding temperature of 290 ℃. The basal texture of as-extruded alloys is reduced gradually with increasing extrusion temperature due to the larger volume fraction of reerystallized structure at higher temperatures. For the alloy extruded at 290 ℃, four different heat treatments routes were investigated. After solution ＋ aging treatments, the grains sizes become larger. Finer and far more densely dispersed precipitates are found in the alloy with solution ＋ double-aging treatments compared with alloy with solution ＋ single-aging treatment. Tensile properties are enhanced remarkably by solution ＋ double-aging treatment with the yield strength, tensile strength and elongation being 298 MPa, 348 MPa and 18%, respectively. This is attributed to the combined effects of fine dynamically reerystallized grains and the uniformly distributed finer precipitates.展开更多
The effect of heat treatments on laser additive manufacturing(LAM)Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy(TC17)was studied aiming to optimize its microstructure and mechanical properties.The as-deposited sample exhibits...The effect of heat treatments on laser additive manufacturing(LAM)Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy(TC17)was studied aiming to optimize its microstructure and mechanical properties.The as-deposited sample exhibits features of a mixed priorβgrain structure consisting of equiaxed and columnar grains,intragranular ultra-fineαlaths and numerous continuous grain boundaryα(αGB).After being pre-annealed inα+βregion(840°C)and standard solution and aging treated,the continuousαGB becomes coarser and the precipitate free zone(PFZ)nearby theαGB transforms into a zone filled with ultra-fine secondaryα(αS)but no primaryα(αP).When pre-annealed in singleβregion(910°C),allαphases transform intoβphase and the alloying elements distribute uniformly near the grain boundary.DiscontinuousαGB and uniform mixture ofαP andαS near grain boundary form after subsequent solution and aging treatment.The two heat treatments can improve the tensile mechanical properties of LAM TC17to satisfy the aviation standard for TC17.展开更多
Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after soln...Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after solntionized at 525 ℃ for 12 h. The evolution of the phase constituents from as-cast to cast-T4 was as follows： α-Mg solid solution＋Mg5（Gd,Y） entectic compound→α-Mg solid solution＋ spheroidized Mg5（Gd, Y） phase→α-Mg supersaturated solid solution＋cuboid-shaped compound （Mg2Y3Gd2）. And the precipitation sequences of Mg-15Gd-5Y-0.5Zr alloy were observed, according to the hardness response to isothermal ageing at 225-300 ℃ for 0-128 h.展开更多
To reveal the affecting mechanism of cooling rate on lamellarαprecipitation,the precipitation behaviors of lamellarαphase in IMI834 titanium alloy during isothermal and non-isothermal heat treatments were quantitati...To reveal the affecting mechanism of cooling rate on lamellarαprecipitation,the precipitation behaviors of lamellarαphase in IMI834 titanium alloy during isothermal and non-isothermal heat treatments were quantitatively characterized using experimental analysis.Critical precipitation temperatures at various cooling rates were obtained using thermal dilatation testing.Using metallographic microscopy,electron microprobe analysis,and data fitting methods,the quantitative evolution models of average width,volume fraction,and solute concentration in theαandβphases were built for different temperatures or cooling rates.A comparison between the two precipitation behaviors showed that the average width and volume fraction of lamellarαphase under non-isothermal conditions were smaller than those under isothermal conditions.With increasing cooling rate,the average width and volume fraction were decreased significantly,and the critical precipitation temperatures were reduced.This phenomenon is mainly attributed to the decreased diffusion velocity of solutes Al,Mo,and Nb with increasing cooling rate.展开更多
This study focused on modifying heat treatment schemes to enhance the mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr alloy.Different three-stage solution treatment schemes((460℃,32 h)+(520℃,24 h)+(5...This study focused on modifying heat treatment schemes to enhance the mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr alloy.Different three-stage solution treatment schemes((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))and aging temperatures(125,175,225℃)were designed for comparison.The microstructure evolutions were analyzed by optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that the three-stage solution treatment of(460℃,32 h)+(520℃,24 h)+(530℃,12 h)could dissolve most of the secondary phases.The TEM results illustrated that fineδ'(Al_(3)Li)particles were homogeneously distributed in the matrix after aging at 175℃for 8 h,accompanied by a small amount of lath-shaped S′(Al_(2)CuMg)and plate-like T_(1)(Al_(2)CuLi)phases.The best comprehensive properties of yield strength of 376 MPa,ultimate tensile strength of 458 MPa and elongation of 4.1%were obtained by the optimal heat treatment scheme((460℃,32 h)+(520℃,24 h)+(530℃,12 h)+(175℃,8 h)).展开更多
Microstructural evolution and the relationship between microstructure and property during heat treatments in a new NiAl-based alloy(Ni-26.6Al-13.4Cr-8.1Co-4.3Ti-1.3W-0.9Mo,molar fraction,%))were investigated.The as-ca...Microstructural evolution and the relationship between microstructure and property during heat treatments in a new NiAl-based alloy(Ni-26.6Al-13.4Cr-8.1Co-4.3Ti-1.3W-0.9Mo,molar fraction,%))were investigated.The as-cast alloy is composed of NiAl matrix and Cr3Ni2 phase with poor ductility.The Cr3Ni2 phase is distributed as a network along the NiAl grain boundaries.Subsequent heat treatment(1 523 K,20 h,air cooling+1 123 K,16 h,furnace cooling)leads to the dissolution of Cr3Ni2 phase and the precipitation of lath-shaped Ni3Al phase andα-Cr particles,resulting in the improvement of compressive properties and fracture toughness at room temperature.Followed by long-term thermal exposure(1 173 K,8 500 h),it is found that the residual Cr3Ni2 phase keeps stable while theα-Cr particles coarsen and a great mass of lath-shaped Ni3Al precipitates are degenerated,which compromises most of the above improvements of mechanical properties through heat treatment.展开更多
The solidification-precipitation behavior of Al-Mg-Si multicomponent alloys has long been an absorbing topic. Experiments were carried out to analyze the precipitation behaviors of Al-Mg-Si alloys under different heat...The solidification-precipitation behavior of Al-Mg-Si multicomponent alloys has long been an absorbing topic. Experiments were carried out to analyze the precipitation behaviors of Al-Mg-Si alloys under different heat treatments. All specimens were homogenized at 570 ℃ for 8 h, and then solution treated at 540 ℃ for 55 min. Subsequently, the specimens were age treated for different times at temperatures of 100 ℃, 150 ℃ and 180 ℃, respectively. The experimental results show that the occurrence of dispersed free zones （DFZ） is caused by the uneven distribution of dispersed phase. During the aging process, pre-β＂ phases form at the initial stage and an aging temperature of 100 ℃is too low to complete the transformation of pre-β＂ to β＂. At 150℃, the precipitation sequence is concluded as SSSS-pre-β＂-pre-β＂＋β＂-β＂-β＇-β. Moreover, changes in sizes and densities of the pre-β＂, β＂and β＇ phases during the aging process has an important influence on the evolution of microhardness and electrical resistivity. The microhardness peak value of 150 ℃ is similar to that of 180 ℃, which is -141 HV. While, at 100℃, the microhardness increases slowly, and the attainable value is 127 HV up to 19 days. When the aging temperature is 100 ℃, the electrical resistivity has the highest average value. When the aging temperature exceeds 100 ℃, with the occurrence and growth of β＂and β＇, the resistivity has a distinct decrease with prolonged aging time.展开更多
The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the inter...The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the interlamellar spacing(λ)andγgrain size at colony boundaries are generally coarsened.Whereas,when the alloy was first annealed at 1300℃ and then aged at 800℃ for 24 h,this coarsening of related microstructures appears less pronounced.The suggested annealing temperatures for the forged Ti−42Al−5Mn alloy are in the range of 1250−1300℃.It was found that,on the condition of the same annealing system,both the strength and ductility were improved as the aging temperature changed from 1000 to 800℃.The secondary precipitatedβo(β_(o,sec))at colony boundaries could be responsible for improving the strength,and theγphase at colony boundaries with the grain size about 6μm might be one of the main reasons for the better ductility.展开更多
In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosi...In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.展开更多
In this paper,the microstructures and rolling contact fatigue behaviors of laser cladding Inconel 625 coatings with or without post-heat treatments were analyzed.The results revealed that the fatigue resistance of the...In this paper,the microstructures and rolling contact fatigue behaviors of laser cladding Inconel 625 coatings with or without post-heat treatments were analyzed.The results revealed that the fatigue resistance of the laser cladding coating after any post-heat treatment was worse than that of the as-deposited coating.First,through the finite element analysis,the distribution of stress along the thickness direction of the coating was obtained,and it was concluded that the bonding interface between the coating and the matrix had little effect on the fatigue properties of the coating.Then X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometry(EDS)were used to analyze the microstructure and failure morphology.The results revealed that the subsurface failure morphology of the coatings showed a consistent correlation with rolling fatigue property after different heat treatments.The TCP phase and carbides have been shown in the laser cladding coating.The coating after stress relieved annealing exhibited chain-shaped granular carbides on the grain boundaries which could accelerate crack propagation.The aging heat treatment made small amounts of Laves phase dissolved in the coating,while the dispersed phase was precipitated which could result in the formation of pores.And the solution treatment made large amounts of Laves phase dissolved,while the rod-shape brittle phases were generated which was easy to fracture and contribute to crack initiation and spalling.展开更多
The effects of heat treatment(heating temperature and pH) on the structures and emulsifying properties of caseins were systematically studied by spectroscopy.Heat treatment from 60to 100℃resulted in an increase in th...The effects of heat treatment(heating temperature and pH) on the structures and emulsifying properties of caseins were systematically studied by spectroscopy.Heat treatment from 60to 100℃resulted in an increase in their fluorescence intensity,hydrodynamic diameter,turbidity and emulsifying activity index,but decreased the size polydispersity of caseins.In the pH range of 5.5to 7.0,the fluorescence intensity,hydrodynamic diameter,turbidity and emulsifying properties decreased with increased heating pH,but the size polydispersity of caseins increased with increased pH.The relationship between the surface fluorescence intensity and emulsifying activity was also investigated,revealing a correlation coefficient of 0.90.These results suggested that heat treatment could be used to modify the structures and emulsifying properties of caseins by appropriately selecting heating conditions.展开更多
The factors of heat treatments were discussed, which affect the formability of two low carbon, low alloy steels. Experiment concerns mechanical properties, R-values, orientation intensity, texture internal friction an...The factors of heat treatments were discussed, which affect the formability of two low carbon, low alloy steels. Experiment concerns mechanical properties, R-values, orientation intensity, texture internal friction and their relationship with annealing and ageing.展开更多
This study aims to investigate the effects of heat treatments on the microstructure ofγ-TiAl alloys.Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat trea...This study aims to investigate the effects of heat treatments on the microstructure ofγ-TiAl alloys.Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat treatments.Their microstructures were studied by both optical and scanning electron microscopies.The chemical compositions of two ingots were determined as well.The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within1270 to 1185℃.A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures.They are distributed at grain boundaries when holding at a higher temperature,such as 1260℃.However,B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185℃.Furthermore,the effects of heat treatments on grain refinement and other microstructural parameters are discussed.展开更多
Design of heat treatments is related to the key technology for development of nickel-based single crystal superalloys(Ni-SXs). Based on the full understanding of the solidification characteristics, this work applies o...Design of heat treatments is related to the key technology for development of nickel-based single crystal superalloys(Ni-SXs). Based on the full understanding of the solidification characteristics, this work applies optimization design of heat treatments for a second-generation Ni-SX. Microstructure evolution and creep properties are compared in the material under conventional/standard(Std.) and optimized(Opt.) treatments. For the Std. sample,strong dendritic segregations determine inconsistent microstructure evolution in the dendritic(D) and interdendritic region(ID), while the latter serves as weak area to have the prior microcrack initiation, damaging overall performance of the alloy. The Opt. treatment applies higher homogenization temperature, leading to overall reduced segregations, while not inducing incipient melting. A lower temperature of first-step ageing is used to lower the size ofγ'particles. These help to form the more uniform microstructure in dendritic and interdendritic region and relieve the inconsistent microstructure evolution. The balanced local strength makes ID no longer as the weak area,thus restricting microcrack initiation. Great improvement of high temperature and low stress property is obtained by this progress, leading to the pronounced increase of creep rupture life under 1100 °C/140 MPa.展开更多
Various heat treatments were conducted on Inconel 718 superalloy,and the resultant microstructures and properties were investigated to analyze the mechanisms of heat treatments.Results show that the type and quantity ...Various heat treatments were conducted on Inconel 718 superalloy,and the resultant microstructures and properties were investigated to analyze the mechanisms of heat treatments.Results show that the type and quantity of precipitate phases and the grain size have different effects on the properties of Inconel 718 superalloy after various heat treatments.Theγ"andγ'phases as well as grain size mainly influence the strength,and theδphase mainly influences the plasticity.Besides,the precipitation ofγ"andγ'strengthening phases can improve the yield strength.The alloy strength is inversely proportional to mean grain size when theγ"andγ'phases have similar contents.The plasticity is susceptible to the content and shape ofδphase.A proper amount ofδphase is beneficial to the plasticity,but excessiveδphase degrades plasticity.展开更多
Ti6Al4V alloy manufactured by electron powder bed fusion(EPBF)was separately heat-treated by stress-relief annealing at 600℃,annealing at 800℃,and solid solution at 920℃ for 1 h.Then,the friction and wear tests wer...Ti6Al4V alloy manufactured by electron powder bed fusion(EPBF)was separately heat-treated by stress-relief annealing at 600℃,annealing at 800℃,and solid solution at 920℃ for 1 h.Then,the friction and wear tests were conducted on the samples before and after heat treatment to analyze the properties and mechanism of friction and wear behavior.Results show that the sample annealed at 600℃ for 1 h has the optimal wear resistance,and the wear mass loss reduces by 44%.The sample annealed at 800℃ for 1 h possesses the optimal anti-friction performance,and the coefficient of friction reduces by 14%.This research provides a simple heat treatment method to improve the friction and wear resistance of Ti6Al4V alloy manufactured by EPBF.展开更多
The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM)...The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM),transmission electron microscopy(TEM)and tensile tests.The results show that the microstructure of solution-treated alloy comprises NiTi matrix,Ti_(2)Ni and(Nb,Ti)ss phases.After aging treatment at 700℃for 6 and100 h,the distribution of Ti_(2)Ni and(Nb,Ti)ss precipitates increases in uniformity.No new type of precipitate is observed in the specimen aged at 700℃.After aging at800℃for 100 h,numerous nanosized Ni_(2)TiAl phases are precipitated within the grains.Solution and aging treatments improve the tensile properties at room temperature.Tensile strength and ductility are improved after solution treatment at 1100℃plus aging treatment at 800℃for 6 h or 700℃for 100 h.With aging time prolonging to 100 h at 800℃,the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation.展开更多
Magnesium(Mg)alloys are considered to be a new generation of revolutionary medical metals.Laser-beam powder bed fusion(PBF-LB)is suitable for fabricating metal implants withpersonalized and complicated structures.Howe...Magnesium(Mg)alloys are considered to be a new generation of revolutionary medical metals.Laser-beam powder bed fusion(PBF-LB)is suitable for fabricating metal implants withpersonalized and complicated structures.However,the as-built part usually exhibits undesirable microstructure and unsatisfactory performance.In this work,WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment.Although a high densification rate of 99.91%was achieved using suitable processes,the as-built parts exhibited anisotropic and layeredmicrostructure with heterogeneously precipitated Nd-rich intermetallic.After heat treatment,fine and nano-scaled Mg24Y5particles were precipitated.Meanwhile,theα-Mg grainsunderwent recrystallization and turned coarsened slightly,which effectively weakened thetexture intensity and reduced the anisotropy.As a consequence,the yield strength and ultimate tensile strength were significantly improved to(250.2±3.5)MPa and(312±3.7)MPa,respectively,while the elongation was still maintained at a high level of 15.2%.Furthermore,the homogenized microstructure reduced the tendency of localized corrosion and favoredthe development of uniform passivation film.Thus,the degradation rate of WE43 parts was decreased by an order of magnitude.Besides,in-vitro cell experiments proved their favorable biocompatibility.展开更多
文摘In this study, we thoroughly examined the impact of heat treatments and hole count (p) on the properties of LnSrBaCu<sub>3</sub>O<sub>6+z</sub> (Ln = Eu, Sm, Nd) compounds. We focused on preparation, X-ray diffraction with Rietveld refinement, AC susceptibility, DC resistivity measurements, and heat treatment effects. Two heat treatment types were applied: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. As the rare earth Ln’s ionic radius increased, certain parameters notably changed. Specifically, c parameter, surface area S, and volume V increased, while critical temperature Tc and holes (p) in the CuO<sub>2</sub> plane decreased. The evolution of these parameters with rare earth Ln’s ionic radius in [AO] heat treatment is linear. Regardless of the treatment, the structure is orthorhombic for Ln = Eu, tetragonal for Ln = Nd, orthorhombic for Ln = Sm [AO], and pseudo-tetragonal for Sm [O]. The highest critical temperature is reached with Ln = Eu (Tc [AO] = 87.1 K). Notably, for each sample, Tc [AO] surpasses Tc [O]. Observed data stems from factors including rare earth ionic size, improved cationic and oxygen chain order, holes count p in Cu(2)O<sub>2</sub> planes, and in-phase purity of [AO] samples. Our research strives to clearly demonstrate that the density of holes (p) within the copper plane stands as a determinant impacting the structural, electrical, and superconducting properties of these samples. Meanwhile, the other aforementioned parameters contribute to shaping this density (p).
基金The authors would like to express their sincere thanks to the financial support from the Key Project of National Natural Science Foundation of China(No.U16642548).
文摘The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and energy dispersive spectroscopy(EDS).The solidus and liquidus of single crystal alloy were obtained by differential scanning calorimetry(DSC).Results show that the mosaic-like eutectic and fan-like eutectic are dissolved at first,and the coarseγ'phase is dissolved later during the solution heat treatment of 1,390°C/2 h+1,310°C/4 h+1,320°C/10 h+air cooling(AC).The composition segregations of Al,Ta,W and Re are 0.99,0.96,1.04 and 1.16,respectively,which close to 1.The incipient melting is caused by the low local temperature of the alloy,and the micropore region with a lower melting point is the preferred position for incipient melting.
基金Project(2013CB632205)supported by the National Basic Research Program of ChinaProject(51274184)supported by the National Natural Science Foundation of China
文摘The effects of extrusion and heat treatments on the microstructure and mechanical properties of Mg-8Zn-1Al-0.5Cu- 0.5Mn magnesium alloy were investigated. Bimodal microstructure is formed in this alloy when it is extruded at 230 and 260 ℃, and complete DRX occurs at the extruding temperature of 290 ℃. The basal texture of as-extruded alloys is reduced gradually with increasing extrusion temperature due to the larger volume fraction of reerystallized structure at higher temperatures. For the alloy extruded at 290 ℃, four different heat treatments routes were investigated. After solution ＋ aging treatments, the grains sizes become larger. Finer and far more densely dispersed precipitates are found in the alloy with solution ＋ double-aging treatments compared with alloy with solution ＋ single-aging treatment. Tensile properties are enhanced remarkably by solution ＋ double-aging treatment with the yield strength, tensile strength and elongation being 298 MPa, 348 MPa and 18%, respectively. This is attributed to the combined effects of fine dynamically reerystallized grains and the uniformly distributed finer precipitates.
基金Project(BX201600010) supported by the National Postdoctoral Program for Innovative Talents of ChinaProject(2015QNRC001) supported by the Young Elite Scientist Sponsorship Program of China
文摘The effect of heat treatments on laser additive manufacturing(LAM)Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy(TC17)was studied aiming to optimize its microstructure and mechanical properties.The as-deposited sample exhibits features of a mixed priorβgrain structure consisting of equiaxed and columnar grains,intragranular ultra-fineαlaths and numerous continuous grain boundaryα(αGB).After being pre-annealed inα+βregion(840°C)and standard solution and aging treated,the continuousαGB becomes coarser and the precipitate free zone(PFZ)nearby theαGB transforms into a zone filled with ultra-fine secondaryα(αS)but no primaryα(αP).When pre-annealed in singleβregion(910°C),allαphases transform intoβphase and the alloying elements distribute uniformly near the grain boundary.DiscontinuousαGB and uniform mixture ofαP andαS near grain boundary form after subsequent solution and aging treatment.The two heat treatments can improve the tensile mechanical properties of LAM TC17to satisfy the aviation standard for TC17.
基金the Major State Basic Research Development Program of China (973 Program, 5133001E)
文摘Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after solntionized at 525 ℃ for 12 h. The evolution of the phase constituents from as-cast to cast-T4 was as follows： α-Mg solid solution＋Mg5（Gd,Y） entectic compound→α-Mg solid solution＋ spheroidized Mg5（Gd, Y） phase→α-Mg supersaturated solid solution＋cuboid-shaped compound （Mg2Y3Gd2）. And the precipitation sequences of Mg-15Gd-5Y-0.5Zr alloy were observed, according to the hardness response to isothermal ageing at 225-300 ℃ for 0-128 h.
基金financial supports from the National Natural Science Foundation of China(No.51675433)the Natural Science Foundation for Distinguished Young Scholars of Shaanxi Province,China(No.2019JC-09)。
文摘To reveal the affecting mechanism of cooling rate on lamellarαprecipitation,the precipitation behaviors of lamellarαphase in IMI834 titanium alloy during isothermal and non-isothermal heat treatments were quantitatively characterized using experimental analysis.Critical precipitation temperatures at various cooling rates were obtained using thermal dilatation testing.Using metallographic microscopy,electron microprobe analysis,and data fitting methods,the quantitative evolution models of average width,volume fraction,and solute concentration in theαandβphases were built for different temperatures or cooling rates.A comparison between the two precipitation behaviors showed that the average width and volume fraction of lamellarαphase under non-isothermal conditions were smaller than those under isothermal conditions.With increasing cooling rate,the average width and volume fraction were decreased significantly,and the critical precipitation temperatures were reduced.This phenomenon is mainly attributed to the decreased diffusion velocity of solutes Al,Mo,and Nb with increasing cooling rate.
基金the National Natural Science Foundation of China(Nos.51871148,51821001)the United Fund of National Department of Education and Equipment Development,China(No.6141A02033245).
文摘This study focused on modifying heat treatment schemes to enhance the mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr alloy.Different three-stage solution treatment schemes((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))and aging temperatures(125,175,225℃)were designed for comparison.The microstructure evolutions were analyzed by optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that the three-stage solution treatment of(460℃,32 h)+(520℃,24 h)+(530℃,12 h)could dissolve most of the secondary phases.The TEM results illustrated that fineδ'(Al_(3)Li)particles were homogeneously distributed in the matrix after aging at 175℃for 8 h,accompanied by a small amount of lath-shaped S′(Al_(2)CuMg)and plate-like T_(1)(Al_(2)CuLi)phases.The best comprehensive properties of yield strength of 376 MPa,ultimate tensile strength of 458 MPa and elongation of 4.1%were obtained by the optimal heat treatment scheme((460℃,32 h)+(520℃,24 h)+(530℃,12 h)+(175℃,8 h)).
文摘Microstructural evolution and the relationship between microstructure and property during heat treatments in a new NiAl-based alloy(Ni-26.6Al-13.4Cr-8.1Co-4.3Ti-1.3W-0.9Mo,molar fraction,%))were investigated.The as-cast alloy is composed of NiAl matrix and Cr3Ni2 phase with poor ductility.The Cr3Ni2 phase is distributed as a network along the NiAl grain boundaries.Subsequent heat treatment(1 523 K,20 h,air cooling+1 123 K,16 h,furnace cooling)leads to the dissolution of Cr3Ni2 phase and the precipitation of lath-shaped Ni3Al phase andα-Cr particles,resulting in the improvement of compressive properties and fracture toughness at room temperature.Followed by long-term thermal exposure(1 173 K,8 500 h),it is found that the residual Cr3Ni2 phase keeps stable while theα-Cr particles coarsen and a great mass of lath-shaped Ni3Al precipitates are degenerated,which compromises most of the above improvements of mechanical properties through heat treatment.
基金financially supported by the Natural Science Foundation of Shandong Province(ZR2016EMQ11)the Major Research and Development Program of Shandong Province(2017GGX20119),China
文摘The solidification-precipitation behavior of Al-Mg-Si multicomponent alloys has long been an absorbing topic. Experiments were carried out to analyze the precipitation behaviors of Al-Mg-Si alloys under different heat treatments. All specimens were homogenized at 570 ℃ for 8 h, and then solution treated at 540 ℃ for 55 min. Subsequently, the specimens were age treated for different times at temperatures of 100 ℃, 150 ℃ and 180 ℃, respectively. The experimental results show that the occurrence of dispersed free zones （DFZ） is caused by the uneven distribution of dispersed phase. During the aging process, pre-β＂ phases form at the initial stage and an aging temperature of 100 ℃is too low to complete the transformation of pre-β＂ to β＂. At 150℃, the precipitation sequence is concluded as SSSS-pre-β＂-pre-β＂＋β＂-β＂-β＇-β. Moreover, changes in sizes and densities of the pre-β＂, β＂and β＇ phases during the aging process has an important influence on the evolution of microhardness and electrical resistivity. The microhardness peak value of 150 ℃ is similar to that of 180 ℃, which is -141 HV. While, at 100℃, the microhardness increases slowly, and the attainable value is 127 HV up to 19 days. When the aging temperature is 100 ℃, the electrical resistivity has the highest average value. When the aging temperature exceeds 100 ℃, with the occurrence and growth of β＂and β＇, the resistivity has a distinct decrease with prolonged aging time.
基金the Jihua Laboratory Scientific Research Project,China (No.X210291TL210)the National Natural Science Foundation of China (No.51971215)the Natural Science Foundation of Liaoning Province of China (No.2019-MS-330)。
文摘The microstructural evolution and tensile properties of a forged Ti−42Al−5Mn alloy subjected to different heat treatments were studied.The results showed that,when the forged alloy was aged at 800℃ for 24 h,the interlamellar spacing(λ)andγgrain size at colony boundaries are generally coarsened.Whereas,when the alloy was first annealed at 1300℃ and then aged at 800℃ for 24 h,this coarsening of related microstructures appears less pronounced.The suggested annealing temperatures for the forged Ti−42Al−5Mn alloy are in the range of 1250−1300℃.It was found that,on the condition of the same annealing system,both the strength and ductility were improved as the aging temperature changed from 1000 to 800℃.The secondary precipitatedβo(β_(o,sec))at colony boundaries could be responsible for improving the strength,and theγphase at colony boundaries with the grain size about 6μm might be one of the main reasons for the better ductility.
基金funded by the National Natural Science Foundation of China (Grant No.11972018)sponsored by the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry (Grant No. 6141B012858)。
文摘In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.
基金This work was financially supported by the National Natural Science Foundation of China(No.51875425)Open Fund of Shandong Key Laboratory of Corrosion Science(No.KLCS201907).
文摘In this paper,the microstructures and rolling contact fatigue behaviors of laser cladding Inconel 625 coatings with or without post-heat treatments were analyzed.The results revealed that the fatigue resistance of the laser cladding coating after any post-heat treatment was worse than that of the as-deposited coating.First,through the finite element analysis,the distribution of stress along the thickness direction of the coating was obtained,and it was concluded that the bonding interface between the coating and the matrix had little effect on the fatigue properties of the coating.Then X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometry(EDS)were used to analyze the microstructure and failure morphology.The results revealed that the subsurface failure morphology of the coatings showed a consistent correlation with rolling fatigue property after different heat treatments.The TCP phase and carbides have been shown in the laser cladding coating.The coating after stress relieved annealing exhibited chain-shaped granular carbides on the grain boundaries which could accelerate crack propagation.The aging heat treatment made small amounts of Laves phase dissolved in the coating,while the dispersed phase was precipitated which could result in the formation of pores.And the solution treatment made large amounts of Laves phase dissolved,while the rod-shape brittle phases were generated which was easy to fracture and contribute to crack initiation and spalling.
基金International Science&Technology Cooperation Program of China(2011DFA32550)Ministry of Science and Technology of China(2012BAD12B08)
文摘The effects of heat treatment(heating temperature and pH) on the structures and emulsifying properties of caseins were systematically studied by spectroscopy.Heat treatment from 60to 100℃resulted in an increase in their fluorescence intensity,hydrodynamic diameter,turbidity and emulsifying activity index,but decreased the size polydispersity of caseins.In the pH range of 5.5to 7.0,the fluorescence intensity,hydrodynamic diameter,turbidity and emulsifying properties decreased with increased heating pH,but the size polydispersity of caseins increased with increased pH.The relationship between the surface fluorescence intensity and emulsifying activity was also investigated,revealing a correlation coefficient of 0.90.These results suggested that heat treatment could be used to modify the structures and emulsifying properties of caseins by appropriately selecting heating conditions.
基金This boas was financially seaported by SAIC FUND 3166A.
文摘The factors of heat treatments were discussed, which affect the formability of two low carbon, low alloy steels. Experiment concerns mechanical properties, R-values, orientation intensity, texture internal friction and their relationship with annealing and ageing.
基金financially supported by the National Natural Science Foundation of China(Nos.U1808216,51671026,and 51671016)the National Key Research and Development Program of China(Nos.2020YFB1710100 and 2018YFB1106000)+2 种基金the State Key Lab of Advanced Metals and Materials(No.2019-ZD05)the Beijing Natural Science Foundation(No.2222092)the National Science and Technology Major Project(No.J2019-VI-00030116)。
文摘This study aims to investigate the effects of heat treatments on the microstructure ofγ-TiAl alloys.Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat treatments.Their microstructures were studied by both optical and scanning electron microscopies.The chemical compositions of two ingots were determined as well.The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within1270 to 1185℃.A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures.They are distributed at grain boundaries when holding at a higher temperature,such as 1260℃.However,B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185℃.Furthermore,the effects of heat treatments on grain refinement and other microstructural parameters are discussed.
基金financially supported by the National Natural Science Foundation of China (No.91960201)the Key Basic Research Program of Zhejiang Province (No.2020C01002)+2 种基金Zhejiang Provincial Natural Science Foundation of China (Nos.LR22E010003 and Q23E010029)the National Science and Technology Major Project of China (No.J2019-III-0008-0051)the Fundamental Research Funds for the Central Universities(No.226-2022-00050)。
文摘Design of heat treatments is related to the key technology for development of nickel-based single crystal superalloys(Ni-SXs). Based on the full understanding of the solidification characteristics, this work applies optimization design of heat treatments for a second-generation Ni-SX. Microstructure evolution and creep properties are compared in the material under conventional/standard(Std.) and optimized(Opt.) treatments. For the Std. sample,strong dendritic segregations determine inconsistent microstructure evolution in the dendritic(D) and interdendritic region(ID), while the latter serves as weak area to have the prior microcrack initiation, damaging overall performance of the alloy. The Opt. treatment applies higher homogenization temperature, leading to overall reduced segregations, while not inducing incipient melting. A lower temperature of first-step ageing is used to lower the size ofγ'particles. These help to form the more uniform microstructure in dendritic and interdendritic region and relieve the inconsistent microstructure evolution. The balanced local strength makes ID no longer as the weak area,thus restricting microcrack initiation. Great improvement of high temperature and low stress property is obtained by this progress, leading to the pronounced increase of creep rupture life under 1100 °C/140 MPa.
基金National Natural Science Foundation of China(52175353)Shanxi Province Patent Conversion Special Plan Program(202201001)Shanxi Province Key Research and Development Program(202102150401002)。
文摘Various heat treatments were conducted on Inconel 718 superalloy,and the resultant microstructures and properties were investigated to analyze the mechanisms of heat treatments.Results show that the type and quantity of precipitate phases and the grain size have different effects on the properties of Inconel 718 superalloy after various heat treatments.Theγ"andγ'phases as well as grain size mainly influence the strength,and theδphase mainly influences the plasticity.Besides,the precipitation ofγ"andγ'strengthening phases can improve the yield strength.The alloy strength is inversely proportional to mean grain size when theγ"andγ'phases have similar contents.The plasticity is susceptible to the content and shape ofδphase.A proper amount ofδphase is beneficial to the plasticity,but excessiveδphase degrades plasticity.
基金National Natural Science Foundation of China(51975036)Guangdong Province Key R&D Project(2018B090904004)。
文摘Ti6Al4V alloy manufactured by electron powder bed fusion(EPBF)was separately heat-treated by stress-relief annealing at 600℃,annealing at 800℃,and solid solution at 920℃ for 1 h.Then,the friction and wear tests were conducted on the samples before and after heat treatment to analyze the properties and mechanism of friction and wear behavior.Results show that the sample annealed at 600℃ for 1 h has the optimal wear resistance,and the wear mass loss reduces by 44%.The sample annealed at 800℃ for 1 h possesses the optimal anti-friction performance,and the coefficient of friction reduces by 14%.This research provides a simple heat treatment method to improve the friction and wear resistance of Ti6Al4V alloy manufactured by EPBF.
基金financially supported by the National Natural Science Foundation of China(Nos.51571036 and 51201016)。
文摘The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM),transmission electron microscopy(TEM)and tensile tests.The results show that the microstructure of solution-treated alloy comprises NiTi matrix,Ti_(2)Ni and(Nb,Ti)ss phases.After aging treatment at 700℃for 6 and100 h,the distribution of Ti_(2)Ni and(Nb,Ti)ss precipitates increases in uniformity.No new type of precipitate is observed in the specimen aged at 700℃.After aging at800℃for 100 h,numerous nanosized Ni_(2)TiAl phases are precipitated within the grains.Solution and aging treatments improve the tensile properties at room temperature.Tensile strength and ductility are improved after solution treatment at 1100℃plus aging treatment at 800℃for 6 h or 700℃for 100 h.With aging time prolonging to 100 h at 800℃,the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation.
基金supported by the following funds:National Natural Science Foundation of China(51935014,52165043)Jiangxi Provincial Cultivation Program for Academic and Technical Leaders of Major Subjects(20225BCJ23008)+1 种基金Jiangxi Provincial Natural Science Foundation(20224ACB204013,20224ACB214008)Scientific Research Project of Anhui Universities(KJ2021A1106)。
文摘Magnesium(Mg)alloys are considered to be a new generation of revolutionary medical metals.Laser-beam powder bed fusion(PBF-LB)is suitable for fabricating metal implants withpersonalized and complicated structures.However,the as-built part usually exhibits undesirable microstructure and unsatisfactory performance.In this work,WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment.Although a high densification rate of 99.91%was achieved using suitable processes,the as-built parts exhibited anisotropic and layeredmicrostructure with heterogeneously precipitated Nd-rich intermetallic.After heat treatment,fine and nano-scaled Mg24Y5particles were precipitated.Meanwhile,theα-Mg grainsunderwent recrystallization and turned coarsened slightly,which effectively weakened thetexture intensity and reduced the anisotropy.As a consequence,the yield strength and ultimate tensile strength were significantly improved to(250.2±3.5)MPa and(312±3.7)MPa,respectively,while the elongation was still maintained at a high level of 15.2%.Furthermore,the homogenized microstructure reduced the tendency of localized corrosion and favoredthe development of uniform passivation film.Thus,the degradation rate of WE43 parts was decreased by an order of magnitude.Besides,in-vitro cell experiments proved their favorable biocompatibility.
