LZ91镁锂合金热变形的本构模型及微观组织演变

In order to investigate the superplastic deformation characteristics of as rolled LZ91 magnesium lithium alloy, the uniaxial hot tensile test was carried out at different temperatures (513 K, 553 K, 593 K and 633 K) and different strain rates (9.06×10^-4 s^-1, 4. 53×10^-3 s^-1 and 2.26×10^-2 s^-1). The results show that the flow stress curve of the LZ91 alloy presents typical characteristics of dynamic recrystallization, and the peak stress decreases with the increase of deformation temperature (decrease of strain rate). The average hot deformation activation energy of the alloy is 89.74 kJ/mol in the range of test temperature and the strain rate sensitivity index m is 0.422 at 633 K, which indicates that the alloy has superplastic characteristics and the superplastic deformation mechanism is grain boundary slip controlled by grain boundary diffusion. The microstructure of the as rolled LZ91 alloy is composed of α-Mg and β-Li phases, the α-Mg phase is randomly distributed in the β-Li phase, and the dynamic recrystallization occurs during hot deformation.