Experimental And Numerical Investigations On The Plastic Deformation Behavior Of ZK60 Magnesium Alloy

In order to examine the effect of heat treatment on tensile and compressive properties of ZK60 alloys, solutionized and aged samples were prepared to be subjected to tension and compression tested along various directions. The microstructure of the fabricated samples were examined by optical microscopy and by electron backscattered diffraction(EBSD).Polycrystal model based on plasticity theory is also used to help determine the deformation mechanisms that cause different alloys to exhibit distinct deformation behavior. Several conclusions can be made as follows::① It reveals that basal texture intensity can be well retained after aging at 175 o C for 10 h. In addition, the precipitates from aging treatment contributes significantly to the strength of ZK60 magnesium alloy. Using a visco-plastic self-consistent model can perfectly fit the experimental stress-strain response in various deformation modes.② The dominated deformation mechanisms of solutionized and aged ZK60 during tension along RD direction are basal slip and prismatic slip. The modeling results reveal that precipitates strongly impede prismatic slip while facilitate the activation of basal slip. This change will cause a different rotation of c-axis, thus may lead to an increase of the relative activity of pyramidal slip, which would result in the low r-value during the in-plane tension.③ The relative activity of various deformation mechanisms has great effects on both texture evolution and mechanical anisotropy of ZK60 magnesium alloy. Aging treatment doesn’t change the dominated deformation modes during tension and compression, thus the texture evolution of aged and solutionized ZK60 samples follow the same pattern. The modeling results show that aging treatment can increase the activity of compression twin, thus lead to a slight difference of texture between aged and solutionized samples during 90°and 0°compression.④ Aging treatment enhances both tension and compression yield strengths.{10-12} twinning is more strengthened by the presence of precipitates than prismatic slip, which will lead to an increase of yield asymmetry.⑤ The dominated deformation mechanisms of aging ZK60 magnesium alloy are{10-12} twinning and basal slip during compression along RD direction. It is considered that the aging treatment raises the twinning stress or onset of twinning, but might not affect the twin growth with plastic strain. The large yield asymmetry of the ZK60 sheet is attributed to the fact that the critical resolved shear stress(CRSS) for {10-12} extension twinning is far less than that for prismatic slip.