Effects of cryogenic treatment on mechanical properties and crystal orientation of 0.25C-0.80Si-1.6Mn steel with extraordinary strength-toughness

Abstract

Deep cryogenic treatment (DCT) in the phase transition region of austenite (A) to ferrite (F) is a novel process that can efficiently improve the content of martensite (M) and F of dual phase (DP) steel. In this work, microstructure transformation in DP structural steel treated by DCT was investigated in detail. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to characterize the microstructure, alloy distribution, grain size, and orientation for the DP structural steel. The results demonstrated that DCT could effectively improve the yield ratio and mechanical properties of the tested steel. F and its large-angle significantly reduced the influence of fine-grain strengthening on the reduction of yield ratio. This research offered innovative technical support and theory guidelines for producing and studying such extraordinary strength-toughness DP steel with high strength and low yield ratio.

Keywords

• dual phase steel
• deep cryogenic treatment
• crystal orientation
• yield ratio
• retained austenite
• microstructure and mechanical properties