Effects of intercritical annealing treatment on the phase transformation and mechanical properties of 0.15C-1.5Mn-1.5Al TRIP-aided cold-rolled steel sheets

The effects of intercritical annealing temperature on the phase transformation,retained austenite characters and mechanical properties of 0.15C-1.5Mn-1.5Al TRIP-aided cold-rolled steel sheets were investigated by means of dilatometric measurements,heat treatment testing,tensile testing and X-ray diffraction analysis.Similar transformation processes were found at different intercritical annealing temperatures,while the austenite fraction increases and its carbon content decreases with increasing the intercritial annealing temperature;intercritical annealing temperature affects the mechanical properties of the TRIP steel and the volume fraction and carbon content of retained austenite.When the temperature is 820 ℃,the specimens have excellent mechanical properties with the tensile strength and elongation product of 25 400 MPa·%,and the volume fraction and carbon content of retained austenite reach the highest values of 14% and 1.36%,respectively.This retained austenite shows fine mechanical stability and gradually transforms to martensite during deformation,showing a higher instantaneous work-hardening index n than other specimens.