Effects of C Content on the Microstructures and Mechanical Properties of CMnSiAlCu TRIP-Aided Cold-Rolled Steel Sheets

摘要

The effects of carbon content on the microstructures and mechanical properties of 1.5Mn-0.3Si-1.5Al-0.5Cu TRIP-aided cold-rolled steel sheets with different C contents (0.1, 0.12 and 0.15 wt%) were investigated. The cold-rolled TRIP-aided steel sheets were fabricated via two-step heat treatment route composed of intercritical annealing and isothermal heat treatment. The triple phase microstructures generated during heat treatment, focusing on the retained austenite, were assessed using optical microscopy and X-ray diffraction. The tensile and yield strengths obtained from uniaxial tensile test were increased but elongation was decreased with increasing carbon content, which were attributed to the remarkable increase in the volume fraction of second phases mainly consisted of bainite and retained austenite. The tensile strength and ductility balance has a good correlation with the amount of retained austenite and its characteristic can be explained by means of strain dependency of incremental strain hardening exponent.