Analysis of bending behavior of TiN particle-reinforced martensitic steel using micro-digital image correlation

Abstract

Martensitic steels are widely used for safety parts in automobiles due to their high strength and excellent energy absorption, in particular, under high strain-rate service conditions. Precipitation in the martensite matrix increases strength but reduces ductility, limiting the application of martensitic steels for parts with complex shapes. In this study, the bending behavior of TiN particle-reinforced martensitic steel was investigated using a microdigital image-correlation technique. The strain distribution of deformed martensitic steel induces deformation localization in lath martensite and crack initiation in the TiN particles. Cracks in TiN particles occurred within local strain ranges of 0.2-5.7% in particles of diverse size. Such cracked particles act as sites of void nucleation and growth, and the cracks generated, then propagate in the martensite packets. This result shows that TiN-particle cracking is the critical factor affecting the ductility and bendability of martensitic steel.