Effect of Q&P parameters on microstructure development and mechanical behaviour of Q&P steels

Abstract

Steel with a nominal composition of 0.25C-1.5Si-3Mn-0.023Al (mass %) was subjected to Quenching and Partitioning (Q&P) with varying parameters (quenching temperature, partitioning temperature and partitioning time) resulting in formation of multi-phase microstructure, which was thoroughly studied using X-ray (XRD) and Electron Backscatter Diffraction (EBSD). Mechanical properties of the Q&P steel were measured by tensile tests. Plastic deformation of Q&P steel at micro-scale was investigated by in situ tensile testing and digital image correlation analysis. The effect of Q&P parameters on the microstructure (phase composition, size and volume fraction of micro constituents, texture and carbon content in retained austenite) is discussed. After analyzing the mechanical properties, plastic deformation at the micro-scale and the microstructure, it is shown that the strain partitioning between phases strongly depends on the microstructure of the Q&P steel, which, in turn, can be tuned via manipulation with Q&P parameters.