Room-temperature(RT) formability is a key factor to broaden the applications of rolled Mg alloy sheets in the industry. However, rolled Mg alloy sheets generally form strong basal texture, where the(0001) poles align ...Room-temperature(RT) formability is a key factor to broaden the applications of rolled Mg alloy sheets in the industry. However, rolled Mg alloy sheets generally form strong basal texture, where the(0001) poles align parallel to the normal direction(ND). This hinders the activation of(0001) [1120] basal slip, limiting the RT formability. Therefore, texture weakening, i.e., the inclination of the(0001) poles from the ND, plays an important role to improve the RT formability. Recrystallization is crucial to control the textural development in Mg,and currently, the texture weakening is commonly achieved using static recrystallization(SRX). However, the type of slipping and twinning,which are activated during rolling, affect the textural features after SRX. It is also demonstrated that shear bands and preferential grain growth are important factors to tailor the texture during SRX. Indeed, dynamic recrystallization(DRX) easily occurs during rolling in Mg, which also affects the final rolling texture, while the effect of DRX on the textural formation is not extensively studied for the development of RT-formable Mg alloy sheets. Therefore, the effect of these factors on the textural development in rolled Mg is reviewed in this manuscript.Additionally, the ideal microstructure and texture for RT-formable Mg alloy sheets are still controversial. The RT-formability includes stretch forming(biaxial tension), bending(plane strain tension), and deep-drawing. In particular, the stretch forming is commonly used to evaluate the RT-formability of rolled Mg. Although the stretch formability has been improved by recent studies, the further improvement is necessary owing to the relatively low formability of rolled Mg compared with that of rolled Fe and Al. Based on the relationship between the microstructure/texture and stretch formability provided in the literature, the design guidance for high stretch formability is proposed in this review.展开更多
Three kinds of ultra-high-strength steels are subjected to uniaxial tensile,forming limit,and hole expansion tests to characterize their material forming properties.Results show that the elongation of S1500 reaches 12...Three kinds of ultra-high-strength steels are subjected to uniaxial tensile,forming limit,and hole expansion tests to characterize their material forming properties.Results show that the elongation of S1500 reaches 12.9%and is higher than that of MS1500 with the same strength grade but is lower than that of QP980.The forming limit of S1500 steel is higher than that of MS1500 but lower than that of QP980.The instantaneous n-value of the material changes with the volume fraction of retained austenite.The hole expansion ratios of S1500,MS1500,and QP980 steels are 31.3%,32.2%,and 28.3%,respectively.The hole expansion ratio of QP steel increases slightly with the increase in strength grade.This behavior is contrary to the change trend of elongation and forming limit.Among the three kinds of materials,QP980 steel has the best global formability,and S1500 steel has better global formability than martensitic steel with a similar strength grade.The local formability of the materials improves slightly with the decrease in the amount of retained austenite.MS1500 may have the best local formability in accordance with engineering practice.展开更多
Mg and its alloys have continued to attract interest for several structural and super-sensitive applications because of their light weight and good combination of engineering properties.However for some of these appli...Mg and its alloys have continued to attract interest for several structural and super-sensitive applications because of their light weight and good combination of engineering properties.However for some of these applications,high plastic deformability is required to achieve desired component shapes and configurations;unfortunately,Mg and its alloys have low formability.Scientifically,the plastic behaviour of Mg and its alloys ranks among the most complex and difficult to reconcile in metallic material systems.But basically,the HCP crystal structure coupled with low stacking fault energies(SFE)are largely linked to the poor ductility exhibited by Mg alloys.These innate material characteristics have regrettably limited wide spread applicability of Mg and its alloys.Several research efforts aimed at exploring processing strategies to make these alloys more amenable for high formability–mediated engineering use have been reported and still ongoing.This paper reviews the structural metallurgy of Mg alloys and its influence on mechanical behaviour,specifically,plasticity characteristics.It also concisely presents various processing routes(Alloying,Traditional Forming and Severe Plastic Deformation(SPD))which have been explored to enhance plastic deformability in Mg and its alloys.Grain refinement and homogenising of phases,reducing CRSS between slip modes,twinning suppression to activate non-basal slip,and weakening and randomisation of the basal texture were observed as the formability enhancing strategies explored in the reviewed processes.While identifying the limitations of these strategies,further areas to be explored for enhancing plasticity of Mg alloys are highlighted.展开更多
AA 6061 alloy and interstitial-free(IF)steel plates were joined by the friction stir welding(FSW)method,and the microstructure,mechanical properties,and biaxial stretch formability of the friction stir welded(FSWed)pa...AA 6061 alloy and interstitial-free(IF)steel plates were joined by the friction stir welding(FSW)method,and the microstructure,mechanical properties,and biaxial stretch formability of the friction stir welded(FSWed)parts were investigated.The results indicate that the FSWed parts showed optimum tensile strength during FSW with the 0.4-mm offset position of the tool.The Fe4Al13 intermetallic compound formed in the defect-free intersection of AA 6061 and IF-steel plates during FSW.The hardness of the IF-steel part of the FSWed region increased almost 90%relative to its initial hardness of HV0.2 105.The tensile and yield strengths of FSWed regions were approximately 170 MPa and 145 MPa,respectively.According to the formability tests,the Erichsen Index(EI)of the IF-steel,AA 6061,and the FSWed samples were determined to be 2.9 mm,1.9 mm,and 2.1 mm,respectively.The EI of the FSWed sample was almost the same as that of the AA 6061 alloy.However,it decreased compared with that of the IF-steel.The force at EI(FEI)was approximately 1180 N for the FSWed condition.This value is approximately 70%higher than that of AA 6061 alloy.展开更多
This study is conducted to develop an innovative and attractive selective laser melting(SLM)method to produce 316 L stainless steel materials with excellent mechanical performance and complex part shape.In this work,t...This study is conducted to develop an innovative and attractive selective laser melting(SLM)method to produce 316 L stainless steel materials with excellent mechanical performance and complex part shape.In this work,the subregional manufacturing strategy,which separates the special parts from the components using an optimized process,was proposed.The results showed that produced 316 L materials exhibited superior strength of^755 MPa and good ductility.In the as-built parts,austenite with preferred orientation of the(220)plane,δ-ferrite,and a small amount of CrO phases were present.In addition,the crystal size was fine,which contributed to the enhancement of the parts’mechanical properties.The structural anisotropy mechanism of the materials was also investigated for a group of half-sized samples with variable inclination directions.This technique was used to fabricate a set of impellers with helical bevels and high-precision planetary gears,demonstrating its strong potential for use in practical applications.展开更多
Aluminum alloy 5 A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability a...Aluminum alloy 5 A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability and microstructure of target sheet in overlapping sheets bulging process. Sheet sliding experiment was performed to measure interface friction coefficient of 5 A02/SUS304 in different lubricating conditions and normal pressure. Overlapping sheets bulging experiment of 5 A02/SUS304 was carried out to investigate the influence of interface friction on limit bulging height, wall thickness distribution, microstructure and fracture morphology of 5 A02 bulging specimens. The results showed that increase of the interface friction coefficient of 5 A02/SUS304 could effectively improve the limit bulging height and deformation uniformity of 5 A02. And the fracture style of 5 A02 transformed from toughness fracture of dimples-micropores gathered to fault slip separation fracture. Therefore, target sheet bulging formability is improved with the increase of interface friction coefficient.展开更多
The stretching tests of the commercial AZ31 Mg alloy were conducted at 130 ℃, 170 ℃, 210 ℃, at the forming speeds of 10 mm/min and 50 mm/min, respectively. The formability of AZ31 sheets at high temperature was eva...The stretching tests of the commercial AZ31 Mg alloy were conducted at 130 ℃, 170 ℃, 210 ℃, at the forming speeds of 10 mm/min and 50 mm/min, respectively. The formability of AZ31 sheets at high temperature was evaluated by forming limit diagrams (FLD). The fracture morphologies were analyzed using a scanning electron microscope. The results show that the FLD of AZ31 Mg alloy is affected by the forming temperature, in another word, the formability increases with the increasing of the forming temperature. That may be because the non-basal slip system starts to move by thermal activation at high forming temperature. It is also demonstrated that the formability of the AZ31 Mg alloy is on the decline with the increasing of the forming speed. The slipping performs thoroughly to release the stress during the deformation if the forming speed decreases. In addition, the higher the forming temperature is, the more obvious the effect of the forming speed is. The forming temperature is the main dominating factor on the formability of AZ31 Mg alloy.展开更多
Single point incremental forming(SPIF)is an innovative sheet forming process with a high economic pay-off.The formability in this process can be maximized by executing forming with a tool of specific small radius,rega...Single point incremental forming(SPIF)is an innovative sheet forming process with a high economic pay-off.The formability in this process can be maximized by executing forming with a tool of specific small radius,regarded as threshold critical radius.Its value has been reported as 2.2 mm for 1 mm thick sheet materials.However,with a change in the forming conditions specifically in the sheet thickness and step size,the critical radius is likely to alter due to a change in the bending condition.The main aim of the present study is to undertake this point into account and develop a relatively generic condition.The study is composed of experimental and numerical investigations.The maximum wall angle(θmax)without sheet fracturing is regarded as sheet formability.A number of sheet materials are formed to fracture and the trends correlating formability with normalized radius(i.e.,R/To where R is the tool-radius and To is the sheet thickness)are drawn.These trends confirm that there is a critical tool-radius(Rc)that maximizes the formability in SPIF.Furthermore,it is found that the critical radius is not fixed rather it shows dependence on the sheet thickness such that Rc=βTo,whereβvaries from 2.2 to 3.3 as the thickness increases from 1 mm to 3 mm.The critical radius,however,remains insensitive to variation in step size ranging from 0.3 mm to 0.7 mm.This is also observed that the selection of tool with R<Rc narrows down the formability window not only on the higher side but also on the lower side.The higher limit,as revealed by the experimental and FEA results,diminishes due to excessive shearing because of in-plane biaxial compression,and the lower limit reduces due to pillowing in the bottom of part.The new tool-radius condition proposed herein study would be helpful in maximizing the formability of materials in SPIF without performing experimental trials.展开更多
A proposal for two types of press close to die,including blank coming in die and Blank cov-ering die,and four criteria for formability is put forward in the study of the superplastic airbulge forming of the metallic t...A proposal for two types of press close to die,including blank coming in die and Blank cov-ering die,and four criteria for formability is put forward in the study of the superplastic airbulge forming of the metallic thin wall components.A dimensionless weigh mathematic modelfor the criteria of superplastic air bulge forming is developed to be:Q<sub>w</sub>=1.56（WS）/（HF）+2.37(0-π/（180）-r/（r<sub>0</sub>）+0.19The superior formability of components is approaching,if Q<sub>W</sub>≥1,and the worse,if Q<sub>W</sub>【1.Itwas confirmed by practice that the above mentioned model is accurate sufficiently.展开更多
In this study, the bending formability of an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y–0.5 MM(AZXWMM91100, wt%) alloy at room temperature is significantly improved through application of a combined precompression and...In this study, the bending formability of an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y–0.5 MM(AZXWMM91100, wt%) alloy at room temperature is significantly improved through application of a combined precompression and subsequent annealing(PCA) treatment. As the amount of precompression applied along the extrusion direction(ED)(i.e., the total strain) increases from 4% to 6%, the area fraction of ED-oriented grains of the PCA-treated alloy increases, which consequently causes an improvement in its bending formability because these grains accommodate larger tensile strain along the ED during bending. As the temperature of the subsequent annealing treatment increases from 350 ℃ to 450 ℃, both the area fraction of the ED-oriented grains and the average grain size increase, and the residual dislocation density decreases owing to the promotion of boundary migration and occurrence of the recovery process at higher temperatures.Consequently, the bending formability of both the 4%-precompressed and the 6%-precompressed samples increases with an increase in the annealing temperature. However, when the precompressed samples are annealed at 300 ℃, their bending formability is lower than that of the extruded alloy because the dislocations formed by precompression remain even after the subsequent annealing at this temperature.展开更多
The formability of intermediate compounds for thirteen kinds of binary molten salt systems, including 1 179 phase diagrams was discussed by pattern recognition method with bond parameters as features. These systems we...The formability of intermediate compounds for thirteen kinds of binary molten salt systems, including 1 179 phase diagrams was discussed by pattern recognition method with bond parameters as features. These systems were MeX Me′X, MeX Me′X 2, MeX Me′X 3, MeX Me′X 4, MeX 2 Me′X 2, MeX 2 Me′X 3, MeX 2 Me′X 4, MeX 3 Me′X 3, MeNO 3 Me′(NO 3) 2, Me 2SO 4 Me′SO 4 (Me, Me′ denote metallic elements, X denotes halogen), Me AX B Me′ CX D (X is CrO 2- 4, WO 2- 4 or MoO 2- 4), and common cation systems MeX MeX′, MeX Me 2X′ (Me, Me′ denote metallic elements, X, X′ denote anion forming elements or radicals). It had been found that molten salt systems forming intermediate compounds and ones without intermediate compound distribute in different regions. Moreover, six general regularities for the formation of intermediate compounds in binary molten salt systems had been summarized on the basis of thirteen semi empirical models, which was obtained from the known phase diagrams.[展开更多
Bending and tension deformations were performed on Mg-1.3 wt%Zn-0.2 wt%RE-0.3 wt%Zr(ZEK100)alloy sheets that initially had a transverse direction(TD)-split texture.The effects of bending and tension deformations on th...Bending and tension deformations were performed on Mg-1.3 wt%Zn-0.2 wt%RE-0.3 wt%Zr(ZEK100)alloy sheets that initially had a transverse direction(TD)-split texture.The effects of bending and tension deformations on the texture formation and room-temperature formability of specimens were investigated.The specimen subjected to 3-pass bending and tension deformations exhibited an excellent Erichsen value of 9.6 mm.However,the Erichsen value deterioration was observed in the specimen subjected to 7-pass deformations.The rolling direction-split texture developed on the surface with an increasing pass number of deformations.Conversely,the clear TD-split texture remained at the central part.As a result,a quadrupole texture was macroscopically developed with an increasing pass number of deformations.The reduction in anisotropy by the formation of the quadrupole texture is suggested to be the main reason for the improvement in stretch formability.By contrast,the generation of coarse grains near the surface is suggested to be the direct cause for the deterioration of the stretch formability of the specimen subjected to 7-pass deformations.展开更多
The glass formability of Ni<sub>75</sub>B<sub>17</sub>Si<sub>8</sub> melt and the thermostability of this metallic glass formedfrom the the melt can be enhanced by eliminating the h...The glass formability of Ni<sub>75</sub>B<sub>17</sub>Si<sub>8</sub> melt and the thermostability of this metallic glass formedfrom the the melt can be enhanced by eliminating the heterogeneous catalystg. The purificationwas done by cyclical superheating melt in special glasses and subsequently cyclicallysuperheating it in an electromagnetic levitation apparatus. The purified Ni<sub>75</sub>B<sub>17</sub>Si<sub>8</sub> amorphoussample sized up to 20 <sup> </sup>I0 x 0.5 mm was prepared as four times the thickness of unpurifiedones.展开更多
In this study,the formability of transformation-induced plasticity (TRIP) steel is studied during deep-drawing processes with preforming.The effects of preforming on theminimum thickness of can are investigated with a...In this study,the formability of transformation-induced plasticity (TRIP) steel is studied during deep-drawing processes with preforming.The effects of preforming on theminimum thickness of can are investigated with a constitutive model accompanying strain-induced martensite transformation in prestrain condition.The constitutive model has been implemented into ABAQUS/UMAT for analysis of TRIP steel-forming processes.The results show that preforming slightly influences the thickness uniformity of TRIP steel in forming.展开更多
In this paper, the production technology of transformation induced plasticity （TRIP） steel was first introduced into the steel tube manufacture field to produce the steel tubes with high strength and plasticity. The...In this paper, the production technology of transformation induced plasticity （TRIP） steel was first introduced into the steel tube manufacture field to produce the steel tubes with high strength and plasticity. The TRIP seamless steel tubes with the microstructure of ferrite, bainite, retained austenite and a little martensite were successfully fabricated using a cold-drawn steel tube with two-stage heat treatment technique and continu- ous heat treatment process, respectively. The ring tensile test and cold bend test were carried out to study the formability of the newly developed TRIP seamless steel tube. The results showed that the TRIP seamless steel tubes have a good cold formability, and they are available to be used in the tube hydroforming process. In ad- dition, the equipment of continuous heat treatment developed in the current study can be used to produce TRIP steel tube, and it may serve as an important reference for the industrial production of TRIP steel tube.展开更多
The application of four widely used anisotropic yield criteria,namely,Hill'48,Hill'90,Barlat'89,and Yld2000,on the formability analysis of an automobile aluminum sheet is investigated. The applicability an...The application of four widely used anisotropic yield criteria,namely,Hill'48,Hill'90,Barlat'89,and Yld2000,on the formability analysis of an automobile aluminum sheet is investigated. The applicability and reliability of these four yield criteria are identified on the basis of uniaxial tensile and stamping tests of an aluminum covering panel by embedding the specimen in the corresponding finite element models. Results show that the strain distribution and safety margin of the aluminum sheet after stamping can be predicted with a high accuracy by applying Yld2000 compared to those subjected to the three other yield criteria. The significant effects of the anisotropic plastic characteristics of the aluminum sheet on stamping are discussed by applying the advanced simulation technology.展开更多
High temperature mechanical properties and formability of the AZ61 magnesium alloy are evalu-ated in this paper. Tensile tests were conducted to obtain the formability parameters at elevated temperatures of up to 400...High temperature mechanical properties and formability of the AZ61 magnesium alloy are evalu-ated in this paper. Tensile tests were conducted to obtain the formability parameters at elevated temperatures of up to 400℃. The results showed that at higher temperature, yield strength and ultimate tensile strength of the material decrease significantly, while the material experiences an increase in ductility (maximum elongation before break). A model has been created in finite ele-ment software Abaqus to further study the deep drawability of the AZ61 Mg alloy. Effects of dif-ferent process parameters such as punch and die geometry, forming speed and temperature as well as blank-holder force on square cup drawing of the AZ61 alloy were investigated and optimum process parameters are obtained which can be used as a design guide in sheet metal forming industry.展开更多
A commercially available laser marking system based on diode-pumped Nd:YVO<sub>4</sub> laser was used for creating grid patterns for forming strain analysis of a dual-phase steel. The aim was to determine ...A commercially available laser marking system based on diode-pumped Nd:YVO<sub>4</sub> laser was used for creating grid patterns for forming strain analysis of a dual-phase steel. The aim was to determine and analyze the influence of laser working parameters on the formability of sheet material by means of an in-depth characterization of this induced microstructural and geometric inhomogeneity. The electrochemical etching served as the reference method without the negative effect of generating inhomogeneity. The formability was evaluated using the cupping test according to Erichsen. While the quantification of geometric inhomogeneity was based on the determination of the notch factor, light microscopy and microhardness measurement were used for the evaluation of microstructural inhomogeneity. Furthermore, on the basis of the results an empirical regression model was established which described in terms of quantity the relationship between the examined factors such as laser power, pulse frequency and scanning speed as well as the command variable and the mark depth. The results showed that microstructural inhomogeneity in the used marking parameters due to their locally very limited formation did not have an appreciable influence on the mechanical properties. In contrast to this, the induced geometric inhomogeneity had a marked influence on the material formability.展开更多
In this study,the effects of pre-strain-induced tensile twins(TTWs)and controlled heat treatment on the formability behavior of AZX311 Mg alloy sheets were investigated.A 4%compressive strain was applied to pre-strain...In this study,the effects of pre-strain-induced tensile twins(TTWs)and controlled heat treatment on the formability behavior of AZX311 Mg alloy sheets were investigated.A 4%compressive strain was applied to pre-strain the sheets using the in-plane compression(IPC)technique along the rolling direction(RD)to introduce TTWs.The pre-strained(PS)samples were subsequently heat-treated at 250℃,350℃,and 400℃ independently for 1 hr,and are termed as PSA1,PSA2,and PSA3,respectively.Erichsen cupping tests were conducted to assess the formability of the sheet samples under different initial conditions.The results showed that the PS sample heat-treated at 250℃ for 1hr exhibited a decrease in the Erichsen index(IE)compared to the as-rolled sample,whereas PSA2 and PSA3 samples showed an increase in IE values.Microtexture analysis revealed that most of the TTWs generated through pre-twinning were stable at 250℃;however,the twin volume fraction reduced to 41%at 350℃ compared to the PS samples due to enhanced thermal activity at that temperature.Furthermore,PSA2 samples showed severe grain coarsening in some areas of the sample,and the fraction of such grains increased in the PSA3 samples.The stretch formability(IE value)of PSA2 samples showed a 32.3%increase compared to the as-rolled specimens.Additionally,the analysis of the deformed specimen at failure under the Erichsen test indicated that considerable detwinning occurs in the PS and PSA1 samples,whereas dislocation slip activity dominates in the PSA2 and PSA3 samples during stretch forming.Apart from detwinning and dislocation slip,deformation twins were also observed in all samples after the Erichsen test.Thus,this work highlights the importance of texture control and its underlying mechanisms via pre-twinning followed by heat treatment and their impact on the room temperature(RT)stretch formability of AZX311 Mg alloy sheets.展开更多
基金supported by JSPS KAKENHI Grant Numbers JP22H00259 and JP22K18900。
文摘Room-temperature(RT) formability is a key factor to broaden the applications of rolled Mg alloy sheets in the industry. However, rolled Mg alloy sheets generally form strong basal texture, where the(0001) poles align parallel to the normal direction(ND). This hinders the activation of(0001) [1120] basal slip, limiting the RT formability. Therefore, texture weakening, i.e., the inclination of the(0001) poles from the ND, plays an important role to improve the RT formability. Recrystallization is crucial to control the textural development in Mg,and currently, the texture weakening is commonly achieved using static recrystallization(SRX). However, the type of slipping and twinning,which are activated during rolling, affect the textural features after SRX. It is also demonstrated that shear bands and preferential grain growth are important factors to tailor the texture during SRX. Indeed, dynamic recrystallization(DRX) easily occurs during rolling in Mg, which also affects the final rolling texture, while the effect of DRX on the textural formation is not extensively studied for the development of RT-formable Mg alloy sheets. Therefore, the effect of these factors on the textural development in rolled Mg is reviewed in this manuscript.Additionally, the ideal microstructure and texture for RT-formable Mg alloy sheets are still controversial. The RT-formability includes stretch forming(biaxial tension), bending(plane strain tension), and deep-drawing. In particular, the stretch forming is commonly used to evaluate the RT-formability of rolled Mg. Although the stretch formability has been improved by recent studies, the further improvement is necessary owing to the relatively low formability of rolled Mg compared with that of rolled Fe and Al. Based on the relationship between the microstructure/texture and stretch formability provided in the literature, the design guidance for high stretch formability is proposed in this review.
文摘Three kinds of ultra-high-strength steels are subjected to uniaxial tensile,forming limit,and hole expansion tests to characterize their material forming properties.Results show that the elongation of S1500 reaches 12.9%and is higher than that of MS1500 with the same strength grade but is lower than that of QP980.The forming limit of S1500 steel is higher than that of MS1500 but lower than that of QP980.The instantaneous n-value of the material changes with the volume fraction of retained austenite.The hole expansion ratios of S1500,MS1500,and QP980 steels are 31.3%,32.2%,and 28.3%,respectively.The hole expansion ratio of QP steel increases slightly with the increase in strength grade.This behavior is contrary to the change trend of elongation and forming limit.Among the three kinds of materials,QP980 steel has the best global formability,and S1500 steel has better global formability than martensitic steel with a similar strength grade.The local formability of the materials improves slightly with the decrease in the amount of retained austenite.MS1500 may have the best local formability in accordance with engineering practice.
文摘Mg and its alloys have continued to attract interest for several structural and super-sensitive applications because of their light weight and good combination of engineering properties.However for some of these applications,high plastic deformability is required to achieve desired component shapes and configurations;unfortunately,Mg and its alloys have low formability.Scientifically,the plastic behaviour of Mg and its alloys ranks among the most complex and difficult to reconcile in metallic material systems.But basically,the HCP crystal structure coupled with low stacking fault energies(SFE)are largely linked to the poor ductility exhibited by Mg alloys.These innate material characteristics have regrettably limited wide spread applicability of Mg and its alloys.Several research efforts aimed at exploring processing strategies to make these alloys more amenable for high formability–mediated engineering use have been reported and still ongoing.This paper reviews the structural metallurgy of Mg alloys and its influence on mechanical behaviour,specifically,plasticity characteristics.It also concisely presents various processing routes(Alloying,Traditional Forming and Severe Plastic Deformation(SPD))which have been explored to enhance plastic deformability in Mg and its alloys.Grain refinement and homogenising of phases,reducing CRSS between slip modes,twinning suppression to activate non-basal slip,and weakening and randomisation of the basal texture were observed as the formability enhancing strategies explored in the reviewed processes.While identifying the limitations of these strategies,further areas to be explored for enhancing plasticity of Mg alloys are highlighted.
基金supported by “The World Academy of Sciences(TWAS)under the Visiting Researchers program of TWAS-UNESCO Associateship Scheme(No.3240290077)”
文摘AA 6061 alloy and interstitial-free(IF)steel plates were joined by the friction stir welding(FSW)method,and the microstructure,mechanical properties,and biaxial stretch formability of the friction stir welded(FSWed)parts were investigated.The results indicate that the FSWed parts showed optimum tensile strength during FSW with the 0.4-mm offset position of the tool.The Fe4Al13 intermetallic compound formed in the defect-free intersection of AA 6061 and IF-steel plates during FSW.The hardness of the IF-steel part of the FSWed region increased almost 90%relative to its initial hardness of HV0.2 105.The tensile and yield strengths of FSWed regions were approximately 170 MPa and 145 MPa,respectively.According to the formability tests,the Erichsen Index(EI)of the IF-steel,AA 6061,and the FSWed samples were determined to be 2.9 mm,1.9 mm,and 2.1 mm,respectively.The EI of the FSWed sample was almost the same as that of the AA 6061 alloy.However,it decreased compared with that of the IF-steel.The force at EI(FEI)was approximately 1180 N for the FSWed condition.This value is approximately 70%higher than that of AA 6061 alloy.
基金supported by the Key R&D Programs of Sichuan Province of China (No. 2018GZ0145)the Science and Technology Planning Projects of Zigong of Sichuan Province (No. 2018CDZG-1)the Major Scientific and Technological Key Bidding Projects in Panzhihua Experimental Zone (No. 1640STC30166/01)
文摘This study is conducted to develop an innovative and attractive selective laser melting(SLM)method to produce 316 L stainless steel materials with excellent mechanical performance and complex part shape.In this work,the subregional manufacturing strategy,which separates the special parts from the components using an optimized process,was proposed.The results showed that produced 316 L materials exhibited superior strength of^755 MPa and good ductility.In the as-built parts,austenite with preferred orientation of the(220)plane,δ-ferrite,and a small amount of CrO phases were present.In addition,the crystal size was fine,which contributed to the enhancement of the parts’mechanical properties.The structural anisotropy mechanism of the materials was also investigated for a group of half-sized samples with variable inclination directions.This technique was used to fabricate a set of impellers with helical bevels and high-precision planetary gears,demonstrating its strong potential for use in practical applications.
基金Funded by the National Natural Science Foundation of China(No.51575364)the Program for Liaoning Innovation Talents in University(No.LR2017069)the Shenyang Science and Technology Innovation Support Program for Young Talented People(No.RC180189)
文摘Aluminum alloy 5 A02 with low plasticity was used as target sheet, and stainless steel SUS304 with good plasticity was used as overlapping sheet to investigate the effect of interface friction on bulging formability and microstructure of target sheet in overlapping sheets bulging process. Sheet sliding experiment was performed to measure interface friction coefficient of 5 A02/SUS304 in different lubricating conditions and normal pressure. Overlapping sheets bulging experiment of 5 A02/SUS304 was carried out to investigate the influence of interface friction on limit bulging height, wall thickness distribution, microstructure and fracture morphology of 5 A02 bulging specimens. The results showed that increase of the interface friction coefficient of 5 A02/SUS304 could effectively improve the limit bulging height and deformation uniformity of 5 A02. And the fracture style of 5 A02 transformed from toughness fracture of dimples-micropores gathered to fault slip separation fracture. Therefore, target sheet bulging formability is improved with the increase of interface friction coefficient.
文摘The stretching tests of the commercial AZ31 Mg alloy were conducted at 130 ℃, 170 ℃, 210 ℃, at the forming speeds of 10 mm/min and 50 mm/min, respectively. The formability of AZ31 sheets at high temperature was evaluated by forming limit diagrams (FLD). The fracture morphologies were analyzed using a scanning electron microscope. The results show that the FLD of AZ31 Mg alloy is affected by the forming temperature, in another word, the formability increases with the increasing of the forming temperature. That may be because the non-basal slip system starts to move by thermal activation at high forming temperature. It is also demonstrated that the formability of the AZ31 Mg alloy is on the decline with the increasing of the forming speed. The slipping performs thoroughly to release the stress during the deformation if the forming speed decreases. In addition, the higher the forming temperature is, the more obvious the effect of the forming speed is. The forming temperature is the main dominating factor on the formability of AZ31 Mg alloy.
基金Fundamental Research Funds for the Central Universities[Grant No.NS2015055 and No.NP2020413]High-End Foreign Experts Project with Universities Directly under the Administration of Ministries and Commissions of the Central Government[Grant No.011951G19061]+1 种基金National Natural Science Foundation of China[Grant No.51105202]the Deanship of Scientific Research at King Saud University for funding this work through research group number RG-1439-027.
文摘Single point incremental forming(SPIF)is an innovative sheet forming process with a high economic pay-off.The formability in this process can be maximized by executing forming with a tool of specific small radius,regarded as threshold critical radius.Its value has been reported as 2.2 mm for 1 mm thick sheet materials.However,with a change in the forming conditions specifically in the sheet thickness and step size,the critical radius is likely to alter due to a change in the bending condition.The main aim of the present study is to undertake this point into account and develop a relatively generic condition.The study is composed of experimental and numerical investigations.The maximum wall angle(θmax)without sheet fracturing is regarded as sheet formability.A number of sheet materials are formed to fracture and the trends correlating formability with normalized radius(i.e.,R/To where R is the tool-radius and To is the sheet thickness)are drawn.These trends confirm that there is a critical tool-radius(Rc)that maximizes the formability in SPIF.Furthermore,it is found that the critical radius is not fixed rather it shows dependence on the sheet thickness such that Rc=βTo,whereβvaries from 2.2 to 3.3 as the thickness increases from 1 mm to 3 mm.The critical radius,however,remains insensitive to variation in step size ranging from 0.3 mm to 0.7 mm.This is also observed that the selection of tool with R<Rc narrows down the formability window not only on the higher side but also on the lower side.The higher limit,as revealed by the experimental and FEA results,diminishes due to excessive shearing because of in-plane biaxial compression,and the lower limit reduces due to pillowing in the bottom of part.The new tool-radius condition proposed herein study would be helpful in maximizing the formability of materials in SPIF without performing experimental trials.
文摘A proposal for two types of press close to die,including blank coming in die and Blank cov-ering die,and four criteria for formability is put forward in the study of the superplastic airbulge forming of the metallic thin wall components.A dimensionless weigh mathematic modelfor the criteria of superplastic air bulge forming is developed to be:Q<sub>w</sub>=1.56（WS）/（HF）+2.37(0-π/（180）-r/（r<sub>0</sub>）+0.19The superior formability of components is approaching,if Q<sub>W</sub>≥1,and the worse,if Q<sub>W</sub>【1.Itwas confirmed by practice that the above mentioned model is accurate sufficiently.
基金supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government(MSIP, South Korea,No. 2019R1A2C1085272)。
文摘In this study, the bending formability of an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y–0.5 MM(AZXWMM91100, wt%) alloy at room temperature is significantly improved through application of a combined precompression and subsequent annealing(PCA) treatment. As the amount of precompression applied along the extrusion direction(ED)(i.e., the total strain) increases from 4% to 6%, the area fraction of ED-oriented grains of the PCA-treated alloy increases, which consequently causes an improvement in its bending formability because these grains accommodate larger tensile strain along the ED during bending. As the temperature of the subsequent annealing treatment increases from 350 ℃ to 450 ℃, both the area fraction of the ED-oriented grains and the average grain size increase, and the residual dislocation density decreases owing to the promotion of boundary migration and occurrence of the recovery process at higher temperatures.Consequently, the bending formability of both the 4%-precompressed and the 6%-precompressed samples increases with an increase in the annealing temperature. However, when the precompressed samples are annealed at 300 ℃, their bending formability is lower than that of the extruded alloy because the dislocations formed by precompression remain even after the subsequent annealing at this temperature.
文摘The formability of intermediate compounds for thirteen kinds of binary molten salt systems, including 1 179 phase diagrams was discussed by pattern recognition method with bond parameters as features. These systems were MeX Me′X, MeX Me′X 2, MeX Me′X 3, MeX Me′X 4, MeX 2 Me′X 2, MeX 2 Me′X 3, MeX 2 Me′X 4, MeX 3 Me′X 3, MeNO 3 Me′(NO 3) 2, Me 2SO 4 Me′SO 4 (Me, Me′ denote metallic elements, X denotes halogen), Me AX B Me′ CX D (X is CrO 2- 4, WO 2- 4 or MoO 2- 4), and common cation systems MeX MeX′, MeX Me 2X′ (Me, Me′ denote metallic elements, X, X′ denote anion forming elements or radicals). It had been found that molten salt systems forming intermediate compounds and ones without intermediate compound distribute in different regions. Moreover, six general regularities for the formation of intermediate compounds in binary molten salt systems had been summarized on the basis of thirteen semi empirical models, which was obtained from the known phase diagrams.[
文摘Bending and tension deformations were performed on Mg-1.3 wt%Zn-0.2 wt%RE-0.3 wt%Zr(ZEK100)alloy sheets that initially had a transverse direction(TD)-split texture.The effects of bending and tension deformations on the texture formation and room-temperature formability of specimens were investigated.The specimen subjected to 3-pass bending and tension deformations exhibited an excellent Erichsen value of 9.6 mm.However,the Erichsen value deterioration was observed in the specimen subjected to 7-pass deformations.The rolling direction-split texture developed on the surface with an increasing pass number of deformations.Conversely,the clear TD-split texture remained at the central part.As a result,a quadrupole texture was macroscopically developed with an increasing pass number of deformations.The reduction in anisotropy by the formation of the quadrupole texture is suggested to be the main reason for the improvement in stretch formability.By contrast,the generation of coarse grains near the surface is suggested to be the direct cause for the deterioration of the stretch formability of the specimen subjected to 7-pass deformations.
文摘The glass formability of Ni<sub>75</sub>B<sub>17</sub>Si<sub>8</sub> melt and the thermostability of this metallic glass formedfrom the the melt can be enhanced by eliminating the heterogeneous catalystg. The purificationwas done by cyclical superheating melt in special glasses and subsequently cyclicallysuperheating it in an electromagnetic levitation apparatus. The purified Ni<sub>75</sub>B<sub>17</sub>Si<sub>8</sub> amorphoussample sized up to 20 <sup> </sup>I0 x 0.5 mm was prepared as four times the thickness of unpurifiedones.
基金supported by the National Natural Science Foundation of China (No.51075266)the Ministry of Education and Ministry of Finance of China for"Knowledge-based Ship-Design Hyper-Integrated Platform (KSHIP) "(No.200512)
文摘In this study,the formability of transformation-induced plasticity (TRIP) steel is studied during deep-drawing processes with preforming.The effects of preforming on theminimum thickness of can are investigated with a constitutive model accompanying strain-induced martensite transformation in prestrain condition.The constitutive model has been implemented into ABAQUS/UMAT for analysis of TRIP steel-forming processes.The results show that preforming slightly influences the thickness uniformity of TRIP steel in forming.
文摘In this paper, the production technology of transformation induced plasticity （TRIP） steel was first introduced into the steel tube manufacture field to produce the steel tubes with high strength and plasticity. The TRIP seamless steel tubes with the microstructure of ferrite, bainite, retained austenite and a little martensite were successfully fabricated using a cold-drawn steel tube with two-stage heat treatment technique and continu- ous heat treatment process, respectively. The ring tensile test and cold bend test were carried out to study the formability of the newly developed TRIP seamless steel tube. The results showed that the TRIP seamless steel tubes have a good cold formability, and they are available to be used in the tube hydroforming process. In ad- dition, the equipment of continuous heat treatment developed in the current study can be used to produce TRIP steel tube, and it may serve as an important reference for the industrial production of TRIP steel tube.
文摘The application of four widely used anisotropic yield criteria,namely,Hill'48,Hill'90,Barlat'89,and Yld2000,on the formability analysis of an automobile aluminum sheet is investigated. The applicability and reliability of these four yield criteria are identified on the basis of uniaxial tensile and stamping tests of an aluminum covering panel by embedding the specimen in the corresponding finite element models. Results show that the strain distribution and safety margin of the aluminum sheet after stamping can be predicted with a high accuracy by applying Yld2000 compared to those subjected to the three other yield criteria. The significant effects of the anisotropic plastic characteristics of the aluminum sheet on stamping are discussed by applying the advanced simulation technology.
文摘High temperature mechanical properties and formability of the AZ61 magnesium alloy are evalu-ated in this paper. Tensile tests were conducted to obtain the formability parameters at elevated temperatures of up to 400℃. The results showed that at higher temperature, yield strength and ultimate tensile strength of the material decrease significantly, while the material experiences an increase in ductility (maximum elongation before break). A model has been created in finite ele-ment software Abaqus to further study the deep drawability of the AZ61 Mg alloy. Effects of dif-ferent process parameters such as punch and die geometry, forming speed and temperature as well as blank-holder force on square cup drawing of the AZ61 alloy were investigated and optimum process parameters are obtained which can be used as a design guide in sheet metal forming industry.
文摘A commercially available laser marking system based on diode-pumped Nd:YVO<sub>4</sub> laser was used for creating grid patterns for forming strain analysis of a dual-phase steel. The aim was to determine and analyze the influence of laser working parameters on the formability of sheet material by means of an in-depth characterization of this induced microstructural and geometric inhomogeneity. The electrochemical etching served as the reference method without the negative effect of generating inhomogeneity. The formability was evaluated using the cupping test according to Erichsen. While the quantification of geometric inhomogeneity was based on the determination of the notch factor, light microscopy and microhardness measurement were used for the evaluation of microstructural inhomogeneity. Furthermore, on the basis of the results an empirical regression model was established which described in terms of quantity the relationship between the examined factors such as laser power, pulse frequency and scanning speed as well as the command variable and the mark depth. The results showed that microstructural inhomogeneity in the used marking parameters due to their locally very limited formation did not have an appreciable influence on the mechanical properties. In contrast to this, the induced geometric inhomogeneity had a marked influence on the material formability.
基金supported by the Science and Engineering Research Board(SERB),a statutory body of the Department of Science&Technology(DST),Government of India through the Start-up Research Grant(SRG)scheme(File No.SRG/2020/000341).
文摘In this study,the effects of pre-strain-induced tensile twins(TTWs)and controlled heat treatment on the formability behavior of AZX311 Mg alloy sheets were investigated.A 4%compressive strain was applied to pre-strain the sheets using the in-plane compression(IPC)technique along the rolling direction(RD)to introduce TTWs.The pre-strained(PS)samples were subsequently heat-treated at 250℃,350℃,and 400℃ independently for 1 hr,and are termed as PSA1,PSA2,and PSA3,respectively.Erichsen cupping tests were conducted to assess the formability of the sheet samples under different initial conditions.The results showed that the PS sample heat-treated at 250℃ for 1hr exhibited a decrease in the Erichsen index(IE)compared to the as-rolled sample,whereas PSA2 and PSA3 samples showed an increase in IE values.Microtexture analysis revealed that most of the TTWs generated through pre-twinning were stable at 250℃;however,the twin volume fraction reduced to 41%at 350℃ compared to the PS samples due to enhanced thermal activity at that temperature.Furthermore,PSA2 samples showed severe grain coarsening in some areas of the sample,and the fraction of such grains increased in the PSA3 samples.The stretch formability(IE value)of PSA2 samples showed a 32.3%increase compared to the as-rolled specimens.Additionally,the analysis of the deformed specimen at failure under the Erichsen test indicated that considerable detwinning occurs in the PS and PSA1 samples,whereas dislocation slip activity dominates in the PSA2 and PSA3 samples during stretch forming.Apart from detwinning and dislocation slip,deformation twins were also observed in all samples after the Erichsen test.Thus,this work highlights the importance of texture control and its underlying mechanisms via pre-twinning followed by heat treatment and their impact on the room temperature(RT)stretch formability of AZX311 Mg alloy sheets.
