Deformation behavior of a high strength multiphase steel at macro- and micro-scales

Advanced high strength steels via quenching and partitioning (Q&P) process are a mainstream trend in modern steel research. This work contributes to a better understanding of their local mechanical properties and local deformation behavior at the micro-scale in relation to their local microstructure. A low alloyed steel was subjected to Q&P heat treatments leading to the formation of complex multiphase microstructures. Nanoindentation tests were performed to measure nanohardness of individual phases and to generate 2D maps showing nanohardness distribution on the surface of the material. To study local in-plane plastic strain distribution during deformation, in situ tensile tests were carried out using the digital image correlation technique. Significant partitioning of plastic strain between phase microconstituents during tensile deformation is shown. The effect of the microstructure on the mechanical behavior of the Q&P processed steel is analyzed. The local plastic deformation behavior of individual phases is discussed with respect to their strength and their spatial orientation.