基于等径通道挤压法的超细晶铜动态剪切变形行为实验研究

The thermal stability of ultra-fine-grained (UFG) copper microstructure prepared by equal channel angular pressing (ECAP) method and its influence on the mechanical properties of the material are studied. The Hopkinson pressure bar and MTS hydraulic servo testing machine are used to test ECAP ultrafine grained copper and annealed pure copper samples under strain controlled loading. The evolutions of its dynamic shear deformation behavior and microstructure are studied by digital image correlation method and the microscopic and XRD analysis of "frozen" recovered samples. The test shows that the ECAP UFG copper has strain hardening characteristics under quasi-static shear loading; the shear stress-strain curve presents strain softening characteristics at high strain rate; and the adiabatic shear dynamic recrystallization zone results in strain hardening rate being negative at high loading rate. The recrystallization temperature of ultrafine grained copper calculated by plastic work is only 325 K. Therefore, the adiabatic shear instability of ultrafine grained copper at high strain rate is easy to occur.