The thermomechanical behavior of precipitation-hardened aluminum alloy AA7022-T6 was studied using isothermal compression at temperatures of 623−773 K and strain rates of 0.01−1 s^−1.The experimental results indicated...The thermomechanical behavior of precipitation-hardened aluminum alloy AA7022-T6 was studied using isothermal compression at temperatures of 623−773 K and strain rates of 0.01−1 s^−1.The experimental results indicated that dynamic recrystallization(DRX)is a predominant hot deformation mechanism,especially at elevated temperatures and low strain rates.The modified Johnson−Cook(J−C)and the strain compensated Arrhenius-type models were developed to predict the hot flow behavior under different deformation conditions.The correlation coefficients of modified J−C model and the strain compensated Arrhenius-type models were 0.9914 and 0.9972,respectively,their average relative errors(ARE)were 6.074%and 4.465%,respectively,and their root mean square errors(RMSE)were 10.611 and 1.665 MPa,respectively,indicating that the strain compensated Arrhenius-type model can predict the hot flow stress of AA7022-T6 aluminum alloy with an appropriate accuracy.展开更多
In order to effectively predict the fracture of AA7075-T6 sheet, the forming limit curves of AA7075-T6 high-strength sheet were drawn according to Morciniak Kuczyski (M K) model and Lou Huh criterion, respectively. Th...In order to effectively predict the fracture of AA7075-T6 sheet, the forming limit curves of AA7075-T6 high-strength sheet were drawn according to Morciniak Kuczyski (M K) model and Lou Huh criterion, respectively. The errors between the predicted values of the two theoretical prediction models and experimental values were calculated by error analysis. The forming limit curves were verified by the punch stretch test to evaluate the prediction accuracy of M K model and Lou Huh criterion. The error analysis results show that the mean error of Lou Huh criterion with the optimal parameters for all tensile specimens is 25.04%, while the mean error of M K model for all tensile specimens is 74.24%. The prediction accuracy of Lou Huh criterion in predicting the fracture of AA7075-T6 sheet is higher. The punch stretch test results show that the forming limit curve drawn by Lou Huh criterion can effectively predict the fracture of AA7075-T6 sheet, but the prediction accuracy of M K model is relatively poor.展开更多
A new phenomenological and empirically-based constitutive model was proposed to modify the term in the original Johnson−Cook constitutive model.The new model can be used to describe and predict the flow stress of AA10...A new phenomenological and empirically-based constitutive model was proposed to modify the term in the original Johnson−Cook constitutive model.The new model can be used to describe and predict the flow stress of AA1070 aluminum with different initial grain sizes in the hot working process.This developed model considers thermal softening,strain-rate hardening,strain hardening,initial grain size,and interactions with each other and can correctly model the behavior of AA1070 at elevated temperature with different strains,strain rates,and initial grain sizes.The hot flow behavior of AA1070 was investigated through compression tests over wide ranges of temperature from 623 to 773 K,strain rate from 0.005 to 0.5 s−1 and initial grain size from 50 to 450μm.Results show that the initial grain size has a significant effect on the flow behavior of AA1070.Then,correlation coefficient(R),average absolute relative error(AARE),and relative error were examined for comparative predictability of the model.Results show that flow stresses for different initial grain sizes calculated by the new proposed model perfectly correlate with experimental ones,with a mean relative error of 1.19%,which confirms that the new modified Johnson−Cook relation can give a precise estimation of the hot flow stress of AA1070 aluminum by considering the initial grain size.展开更多
Microstructure evolution during the homogenization heat treatment of an Al?Mg?Si?Fe?Mn(AA6xxx)alloy wasinvestigated using a combination of modelling and experimental studies.The model is based on the CALPHAD-coupledho...Microstructure evolution during the homogenization heat treatment of an Al?Mg?Si?Fe?Mn(AA6xxx)alloy wasinvestigated using a combination of modelling and experimental studies.The model is based on the CALPHAD-coupledhomogenization heat treatment model originally developed for AA3xxx alloys(i.e.,Al?Mn?Fe?Si).In this work,the model wasadapted to the more complex AA6xxx system(Al?Mg?Si?Mn?Fe)to predict the evolution of critical microstructural features suchas the spatial distribution of solute,the type and fraction of constituent particles and dispersoid number density and size distribution.Experiments were also conducted using three direct chill(DC)cast AA6xxx alloys with different Mn levels subjected to varioushomogenization treatments.The resulting microstructures were characterized using a range of techniques including scanning electronmicroscopy,electron microprobe analysis(EPMA),XRD,and electrical resistivity measurements.The model predictions werecompared with the experimental measurements,and reasonable agreement was found.展开更多
Aluminum alloy 5083(AA5083)processed by large-scale Equal-channel angular pressing(ECAP)is an excellent engineering material with great prospects for industrial applications.An accurate assessment of the underlying co...Aluminum alloy 5083(AA5083)processed by large-scale Equal-channel angular pressing(ECAP)is an excellent engineering material with great prospects for industrial applications.An accurate assessment of the underlying constitutive relationships with easily determined material constants is critical for the predictive design and informed processing of such structural materials.To develop such a design framework,uniaxial dynamic compressive tests over a wide range of temperatures(293-573 K)were carried out for an ECAP-processed AA5083 alloy.Additionally,the microstructure before and after dynamic loading was characterized by SEM and TEM.Based on the experimental results,a new dynamic constitutive model,based on thermal activation theory,was established to describe the plastic flow behavior of the AA5083 alloy that incorporates the effects of plastic strain,temperature,and strain rate.The input parameters of the new model were determined using a particle swarm optimization(PSO)method.The model predictions show excellent agreement with experimental results,which suggests that the current predictive constitutive model is highly effective in reproducing the dynamic deformation behavior of the large-scale ECAP-processed AA5083.展开更多
The hot deformation behavior of AA2014forging aluminum alloy was investigated by isothermal compression tests attemperatures of350-480°C and strain rates of0.001-1s-1on a Gleeble-3180simulator.The corresponding m...The hot deformation behavior of AA2014forging aluminum alloy was investigated by isothermal compression tests attemperatures of350-480°C and strain rates of0.001-1s-1on a Gleeble-3180simulator.The corresponding microstructures of thealloys under different deformation conditions were studied using optical microscopy(OM),electron back scattered diffraction(EBSD)and transmission electron microscopy(TEM).The processing maps were constructed with strains of0.1,0.3,0.5and0.7.The results showed that the instability domain was more inclined to occur at strain rates higher than0.1s-1and manifested in theform of local non-uniform deformation.At the strain of0.7,the processing map showed two stability domains:domain I(350-430°C,0.005-0.1s-1)and domain II(450-480°C,0.001-0.05s-1).The predominant softening mechanisms in both of the twodomains were dynamic recovery.Uniform microstructures were obtained in domain I,and an extended recovery occurred in domainII,which would lead to the potential sub-grain boundaries progressively transforming into new high-angle grain boundaries.Theoptimum hot working parameters for the AA2014forging aluminum alloy were determined to be370-420°C and0.008-0.08s-1.展开更多
The influences of process parameters on mechanical properties of AA6082in the hot forming and cold-die quenching(HFQ)process were analysed experimentally.Transmission electron microscopy was used to observe the precip...The influences of process parameters on mechanical properties of AA6082in the hot forming and cold-die quenching(HFQ)process were analysed experimentally.Transmission electron microscopy was used to observe the precipitate distribution and to thus clarify strengthening mechanism.A new model was established to describe the strengthening of AA6082by HFQ process in this novel forming technique.The material constants in the model were determined using a genetic algorithm tool.This strengthening model for AA6082can precisely describe the relationship between the strengths of formed workpieces and process parameters.The predicted results agree well with the experimental ones.The Pearson correlation coefficient,average absolute relative error,and root-mean-square error between the calculated and experimental hardness values are0.99402,2.0054%,and2.045,respectively.The model is further developed into an FE code ABAQUS via VUMAT to predict the mechanical property variation of a hot-stamped cup in various ageing conditions.展开更多
文摘The thermomechanical behavior of precipitation-hardened aluminum alloy AA7022-T6 was studied using isothermal compression at temperatures of 623−773 K and strain rates of 0.01−1 s^−1.The experimental results indicated that dynamic recrystallization(DRX)is a predominant hot deformation mechanism,especially at elevated temperatures and low strain rates.The modified Johnson−Cook(J−C)and the strain compensated Arrhenius-type models were developed to predict the hot flow behavior under different deformation conditions.The correlation coefficients of modified J−C model and the strain compensated Arrhenius-type models were 0.9914 and 0.9972,respectively,their average relative errors(ARE)were 6.074%and 4.465%,respectively,and their root mean square errors(RMSE)were 10.611 and 1.665 MPa,respectively,indicating that the strain compensated Arrhenius-type model can predict the hot flow stress of AA7022-T6 aluminum alloy with an appropriate accuracy.
基金Project (51775481) supported by the National Natural Science Foundation of ChinaProject (E2019203418) supported by the Natural Science Foundation of Hebei Province, ChinaProject (ZD2017078) supported by the Science and Technology Plan of Hebei Higher School of Education Department, China。
文摘In order to effectively predict the fracture of AA7075-T6 sheet, the forming limit curves of AA7075-T6 high-strength sheet were drawn according to Morciniak Kuczyski (M K) model and Lou Huh criterion, respectively. The errors between the predicted values of the two theoretical prediction models and experimental values were calculated by error analysis. The forming limit curves were verified by the punch stretch test to evaluate the prediction accuracy of M K model and Lou Huh criterion. The error analysis results show that the mean error of Lou Huh criterion with the optimal parameters for all tensile specimens is 25.04%, while the mean error of M K model for all tensile specimens is 74.24%. The prediction accuracy of Lou Huh criterion in predicting the fracture of AA7075-T6 sheet is higher. The punch stretch test results show that the forming limit curve drawn by Lou Huh criterion can effectively predict the fracture of AA7075-T6 sheet, but the prediction accuracy of M K model is relatively poor.
文摘A new phenomenological and empirically-based constitutive model was proposed to modify the term in the original Johnson−Cook constitutive model.The new model can be used to describe and predict the flow stress of AA1070 aluminum with different initial grain sizes in the hot working process.This developed model considers thermal softening,strain-rate hardening,strain hardening,initial grain size,and interactions with each other and can correctly model the behavior of AA1070 at elevated temperature with different strains,strain rates,and initial grain sizes.The hot flow behavior of AA1070 was investigated through compression tests over wide ranges of temperature from 623 to 773 K,strain rate from 0.005 to 0.5 s−1 and initial grain size from 50 to 450μm.Results show that the initial grain size has a significant effect on the flow behavior of AA1070.Then,correlation coefficient(R),average absolute relative error(AARE),and relative error were examined for comparative predictability of the model.Results show that flow stresses for different initial grain sizes calculated by the new proposed model perfectly correlate with experimental ones,with a mean relative error of 1.19%,which confirms that the new modified Johnson−Cook relation can give a precise estimation of the hot flow stress of AA1070 aluminum by considering the initial grain size.
基金support from Rio Tinto AluminiumNSERC are gratefully acknowledged
文摘Microstructure evolution during the homogenization heat treatment of an Al?Mg?Si?Fe?Mn(AA6xxx)alloy wasinvestigated using a combination of modelling and experimental studies.The model is based on the CALPHAD-coupledhomogenization heat treatment model originally developed for AA3xxx alloys(i.e.,Al?Mn?Fe?Si).In this work,the model wasadapted to the more complex AA6xxx system(Al?Mg?Si?Mn?Fe)to predict the evolution of critical microstructural features suchas the spatial distribution of solute,the type and fraction of constituent particles and dispersoid number density and size distribution.Experiments were also conducted using three direct chill(DC)cast AA6xxx alloys with different Mn levels subjected to varioushomogenization treatments.The resulting microstructures were characterized using a range of techniques including scanning electronmicroscopy,electron microprobe analysis(EPMA),XRD,and electrical resistivity measurements.The model predictions werecompared with the experimental measurements,and reasonable agreement was found.
文摘Aluminum alloy 5083(AA5083)processed by large-scale Equal-channel angular pressing(ECAP)is an excellent engineering material with great prospects for industrial applications.An accurate assessment of the underlying constitutive relationships with easily determined material constants is critical for the predictive design and informed processing of such structural materials.To develop such a design framework,uniaxial dynamic compressive tests over a wide range of temperatures(293-573 K)were carried out for an ECAP-processed AA5083 alloy.Additionally,the microstructure before and after dynamic loading was characterized by SEM and TEM.Based on the experimental results,a new dynamic constitutive model,based on thermal activation theory,was established to describe the plastic flow behavior of the AA5083 alloy that incorporates the effects of plastic strain,temperature,and strain rate.The input parameters of the new model were determined using a particle swarm optimization(PSO)method.The model predictions show excellent agreement with experimental results,which suggests that the current predictive constitutive model is highly effective in reproducing the dynamic deformation behavior of the large-scale ECAP-processed AA5083.
基金Project(51301209) supported by the National Natural Science Foundation of China
文摘The hot deformation behavior of AA2014forging aluminum alloy was investigated by isothermal compression tests attemperatures of350-480°C and strain rates of0.001-1s-1on a Gleeble-3180simulator.The corresponding microstructures of thealloys under different deformation conditions were studied using optical microscopy(OM),electron back scattered diffraction(EBSD)and transmission electron microscopy(TEM).The processing maps were constructed with strains of0.1,0.3,0.5and0.7.The results showed that the instability domain was more inclined to occur at strain rates higher than0.1s-1and manifested in theform of local non-uniform deformation.At the strain of0.7,the processing map showed two stability domains:domain I(350-430°C,0.005-0.1s-1)and domain II(450-480°C,0.001-0.05s-1).The predominant softening mechanisms in both of the twodomains were dynamic recovery.Uniform microstructures were obtained in domain I,and an extended recovery occurred in domainII,which would lead to the potential sub-grain boundaries progressively transforming into new high-angle grain boundaries.Theoptimum hot working parameters for the AA2014forging aluminum alloy were determined to be370-420°C and0.008-0.08s-1.
基金Project(P2014-15)supported by the State Key Laboratory of Materials Processing and Die and Mould Technology,Huazhong University of Science and Technology,ChinaProject(20120006110017)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China+1 种基金Project(2015M580977)supported by China Postdoctoral Science FoundationProject supported by Beijing Laboratory of Metallic Materials and Processing for Modern Transportation,China
文摘The influences of process parameters on mechanical properties of AA6082in the hot forming and cold-die quenching(HFQ)process were analysed experimentally.Transmission electron microscopy was used to observe the precipitate distribution and to thus clarify strengthening mechanism.A new model was established to describe the strengthening of AA6082by HFQ process in this novel forming technique.The material constants in the model were determined using a genetic algorithm tool.This strengthening model for AA6082can precisely describe the relationship between the strengths of formed workpieces and process parameters.The predicted results agree well with the experimental ones.The Pearson correlation coefficient,average absolute relative error,and root-mean-square error between the calculated and experimental hardness values are0.99402,2.0054%,and2.045,respectively.The model is further developed into an FE code ABAQUS via VUMAT to predict the mechanical property variation of a hot-stamped cup in various ageing conditions.
