The effect of large thickness-reduction on microstructure evolution and tensile properties of Mg-9 Al-1 Zn alloy(AZ91)processed by hard-plate rolling(HPR)was investigated.Increasing rolling reduction from55%to 85%incr...The effect of large thickness-reduction on microstructure evolution and tensile properties of Mg-9 Al-1 Zn alloy(AZ91)processed by hard-plate rolling(HPR)was investigated.Increasing rolling reduction from55%to 85%increases the volume fraction and refines average size of fine grains(<3μm,FGs),leading to an optimized bimodal-grained structure consisting of coarse grains(CGs)uniformly embedded in FG regions.The sample with 85%reduction exhibits the highest yield strength of~314 MPa,ultimate tensile strength of~381 MPa and elongation of~11%.The high strength is primarily due to the contribution of grain boundaries(GBs)strengthening by FGs(accounting for~65%of strength),meanwhile the improved ductility originates from the optimized bimodal-grained structure and weakened basal texture that favor a higher ductility.The present findings successfully overcome the trade-off dilemma that the largereduction rolling processing on Mg alloys usually enhances strength at expense of ductility.In addition,the intensified heterogeneous deformation and favorable formation of a bimodal-grained microstructure during large-reduct ion HPR was addressed by tracing micro structure evolution details in grains of intere st via quasi-in-situ electron back scattering diffraction(EBSD).The present study can be instructive for further designing novel Mg alloys by tailoring bimodal-grained structures for superior combination of mechanical properties.展开更多
基金supported by the Natural Science Foundation of China(Nos.51922048,51625402,51871108 and 51671093)Partial financial support came from the Changjiang Scholars Program(No.T2017035)。
文摘The effect of large thickness-reduction on microstructure evolution and tensile properties of Mg-9 Al-1 Zn alloy(AZ91)processed by hard-plate rolling(HPR)was investigated.Increasing rolling reduction from55%to 85%increases the volume fraction and refines average size of fine grains(<3μm,FGs),leading to an optimized bimodal-grained structure consisting of coarse grains(CGs)uniformly embedded in FG regions.The sample with 85%reduction exhibits the highest yield strength of~314 MPa,ultimate tensile strength of~381 MPa and elongation of~11%.The high strength is primarily due to the contribution of grain boundaries(GBs)strengthening by FGs(accounting for~65%of strength),meanwhile the improved ductility originates from the optimized bimodal-grained structure and weakened basal texture that favor a higher ductility.The present findings successfully overcome the trade-off dilemma that the largereduction rolling processing on Mg alloys usually enhances strength at expense of ductility.In addition,the intensified heterogeneous deformation and favorable formation of a bimodal-grained microstructure during large-reduct ion HPR was addressed by tracing micro structure evolution details in grains of intere st via quasi-in-situ electron back scattering diffraction(EBSD).The present study can be instructive for further designing novel Mg alloys by tailoring bimodal-grained structures for superior combination of mechanical properties.
