Effect of pre-solution treatment on deformation behavior of AZ80-Ag magnesium alloy

Abstract

To improve the deformation uniformity and plasticity of AZ80-Ag magnesium alloy, solid solution treatment was introduced before deformation. Isothermal compression tests for both as-homogenized specimens and pre-solution treated specimens were carried out and compared systematically. The results show that the coarse discontinuous precipitates (CDP) of β-Mg17Al12 were fully dissolved by the pre-solution pre-treatment, and the flow stresses were decreased greatly by 12.4–26.3MPa. Moreover, the unstable region with the local plastic flow and cracking defects was significantly reduced. Eventually, uniform deformation is achieved for AZ80-Ag magnesium alloy by the pre-solution treatment, which shows great potential for magnesium alloy engineering application. Then, microstructure observations such as OM and EBSD were carried out and analyzed. Abundant lamellar {10–12} extension twinning appear 86.3° <11–20> relationship occurs after pre-solution treatment, rather than few needle-like {10–12} extension twinning appear 7.4° <1–210> relationship in as-homogenized specimen, is found out to be responsible for deformation plasticity improvement and defects eliminating. On the one hand, stress concentration along deformation twins are released by {10–12} extension twinning appear 86.3° <11–20> effectively, which is verified by Kernel Average Misorientation (KAM) of the as-homogenized and pre-solution treated specimen. In the other hand, twinning induced dynamic recrystallization (TDRX) inside high dense lamellar twins is the main DRX mechanism for the pre-solution treated specimen, which accelerates DRX and further releases stress concentration.