Analysis of the properties of 0.2C-4Al-1.2Mn TRIP-assisted Steel subjected to Mo micro-alloy and isothermal bainitic transformation (IBT) time

Abstract

In this investigation, the results of the experiment in which two samples of TRIP-assisted steel were micro-alloyed with 0.05 and 0.30 wt.% Mo addition in combination with isothermal bainitic transformation (IBT) time parameters was analyzed and evaluated. Microstructures were studied using optical microscope (OM) and field emission scanning electron microscope (FE-SEM) equipped with an energy dispersive X-ray spectrometer (EDX). Using X-ray diffraction (XRD), the retained austenite (RA) phase volume percentage was calculated. The studied steels had a multi-phased structure including δ-ferrite as the matrix phase and α-ferrite, bainite, and RA along with some martensite. The quantity of RA and its morphology in the microstructure of the samples are key factors in achieving desirable combinations of mechanical characteristics (high strength and acceptable ductility). Yield stresses of 400-440 MPa, tensile strengths of 790-870 MPa, and elongations to failure of 24-34% were observed in TRIP-assisted steels containing 0.05 and 0.30 wt.% Mo-alloy. It was determined that the best UTS×TE was (850MPa×32%) 27200 MPa.%, with 0.30 wt.% Mo addition and IBT temperature and time of 450 ℃ and 10 minutes.