Revealing the deformation behavior and microstructure evolution in Mg-12Y–1Al alloy during hot compression

Abstract

In this study, the hot uniaxial compression of the heat-treated Mg-12Y–1Al alloy containing long-period stacking ordered (LPSO) phase was conducted by a Gleeble-3500 simulator. Compressive mechanical properties at elevated temperatures and the effects of deformation temperature (300–450 ℃) and strain rate (0.001–1 s−1) on the hot deformation behavior of the alloy were systematically investigated. Combining with an optical microscope (OM), electron backscatter diffraction (EBSD), and in-grain misorientation axes (IGMA) analysis, the microstructure and texture evolution, dislocation slip, and dynamic recrystallization (DRX) mechanism of the alloy was studied in detail. The results showed that the flow stress decreased with the increase in temperature and the decrease in strain rate. At a strain rate of 1 s−1, the compressive strength at 300 ℃ and 350 ℃ was basically the same. After deformation, the morphology of Al2Y had almost no change, while the LPSO underwent apparent kinking deformation. The increase in temperature was conducive to DRX. The DRX mechanism of the alloy mainly included discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), and DDRX was dominant. The dense lamellar LPSO at the grain boundary was detrimental to the occurrence of DDRX. In addition, the deformed microstructure presented a typical [0001]//CD (compression direction) texture. With the increase in temperature, the texture intensity decreased progressively due to the activation of multiple slip systems and the increased DRX fraction. At a strain rate of 0.01 s−1, when the temperature increased to 450 ℃, the number of deformed grains dominated by pyramidal Ⅱ<c+a> slip increased substantially.