Microstructure-mechanical properties evaluation of AISI 304 steel during back-annealing

Abstract

ABSTRACT In this research, the effect of back-annealing on the microstructure and mechanical properties of deformed austenitic stainless steel was studied. After the annealing treatment, the density of defects including mechanical twins and strain-induced martensite (SIM) were reduced in the microstructure. At 700°C both diffusional and shear reversion mechanisms (DRM and SRM) were active, while at higher temperatures (800 and 900°C) the SRM was dominant. After the annealing at 700°C for 60 min, the microstructure changed significantly and new grains were widely observed which resulted from the reversion of γ through the DRM and SRM. The results showed a decrease in yield (940 MPa) and ultimate tensile (978 MPa) strengths in annealed sample at 700°C for 10 min with respect to the deformed steel, while the total elongation has not changed significantly and remains around 20%. By increasing the annealing time to 60 min, the yield and ultimate tensile strengths of steel decreased to 640 and 830.4 MPa, respectively, and the total elongation increased significantly to 40.5%. The fracture surface of annealed sample at 700°C for 10 min was heterogeneous. After 60 min, the fracture surface became homogeneous and fine dimples were uniformly observed throughout the surface.