Effect of Grain Size on Quasi-static Mechanical Properties of Low StackingFault Energy Fe-Mn-Si-Al Austenitic Alloy Steel

The cold rolled Fe-29.8Mn-5.0Si-1.7Al austenitic steel with low stacking fault energy was annealed at different temperatures (700,730,800,900,1 000,1 100,1 200 ℃). The influence of original austenite grain size on quasic-static mechanical properties and phase transformation behavior during deformation of the steel was studied. With the annealing temperature (above 730 ℃) increasing, obvious static recrystallization occurred on the alloy steel, the grain size increased, and the microstructure was single austenite. Recrystallized annealed alloy steel underwent ε-martensitic transformation during tensile deformation, the fine-grained structure (austenite grain size was less than 21 μm) was conducive to the alloy steel to obtain high yield strength and high tensile strength, and the coarse-grained structure (austenite grain size was greater than 90 μm) was beneficial to improve the plasticity, because of evenly distributed and intersecting multiple variants ε-martensite formed in coarse austenite grains.