Prediction on flow behaviors of individual grains in DP600 steel with grain features

摘要

In describing the flow behaviors of ferrite and martensite phases in dual phase steels, a dislocation-based flow model without considering microstructure features was discussed and developed. The model indicates that the flow stress of individual phase was influenced by contents of chemical elements (e.g. Mn, P, Si, Cu, Ni, Cr, Mo, N_(ss) and C) and ferrite grain size (d_a). To verify the inhomogeneous flow behavior in microstructure, the flow curves of ferrite and martensite phases in multiple regions of DP600 steel were predicted. It was found that the flow behavior of individual phase varied significantly in microstructure and the difference was attributed to various microstructure variables (e.g. martensite volume fraction, carbon content and grain size). To achieve a precise description of the inhomogeneous flow behavior in microstructure, flow models of ferrite and martensite grains were proposed by considering microstructure variables. According to measured indentation yield strengths of different ferrite grains, their flow curves were obtained from the proposed model. The results indicate that different grains differed significantly in the flow curve and the difference was associated with grain features referring to grain size, grain shape and martensite distribution around ferrite grain.