Effects of ferrite grain characteristics on strain distribution of dual-phase steel

Abstract

Because of the multi-constituent microstructure of dual-phase (DP) steel and its inhomogeneous deformation, various parameters have been utilised to describe its microstructure and strain distribution features. In this study, Image-Pro Plus metallographic processing software was used to obtain the grain size, ferrite–martensite (F–M) phase boundary percentage, grain shape factor, and fractal dimension of ferrite boundaries. The effects of the F–M phase boundary percentage on the grain shape factor and fractal dimension were studied, and functional relations were established. Local strain analyses of DP600 steel were performed using a micro-scale digital image correlation (DIC) method. The strain range and strain standard deviation within ferrite grains were introduced to assess the non-uniformity of the ferrite strain distribution. The effects of the ferrite grain shape factor and fractal dimension on the strain distribution characteristics were researched. In addition, the grain size and F–M boundary percentage were selected as two independent parameters to analyse the impacts on the strain distribution features.