1340 Effect of deformation temperatures on microstructure and mechanical properties in an Al containing low Si TRIP steel

Abstract

An Al containing low Si TRIP steel was subjected to different deformation temperatures in austenite non-recrystallization region during thermo-mechanical processes. The microstructural characteristics were analyzed by means of optical microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron back scattered diffraction (EBSD), and its effects on mechanical properties were investigated. The results show that lower deformation temperature strongly promotes the proeutectoid ferrite formation at the expense of bainite, which causes an increase in the amount of retained austenite (RA). Compared with the case of higher deformation temperature in austenite non-recrystallization region, the steel processed by lower deformation temperature exhibits higher elongation and excellent combination of strength and ductility because of higher fractions of polygonal ferrite and RA particles with different size that provide sustained transformation induced plasticity (TRIP) effect over a significantly wide strain range. The un-transformed RA in fractured tensile specimen has much smaller grain size and higher carbon content in comparison to the case before fracture.