Microstructure and Mechanical Properties of TRIP-Aided Steels with Different Heat Treatments

Abstract

The microstructures, mechanical properties and retained austenite characteristics of TRIP-aided steels with three different heat treatments were studied in this paper. The results indicated that the designed annealing treatments resulted in completely different matrices and the morphologies of second phase, and a significant difference in mechanical properties. The TAM steel was found to have fine annealed martensite lath matrix and inter lath acicular retained austenite, and possessed an excellent combination of strength and elongation which attributed to the highest retained austenite volume fraction and carbon concentration. For TPF steel, the higher instability and lower carbon content of retained austenite and the soft matrix resulted in the lowest ultimate tensile strength and total elongation. While in TBF steel, the stability of retained austenite was lower than that in TAM steel but higher than that in TPF steel. The ultimate tensile strength of TBF was significantly higher than the TAM and TPF steels, but the ductility of TBF steel was lower than TAM steel.