A novel rolling route to enhance strength-ductility balance in AISI 430 steel

Abstract

This study explored the microstructure and mechanical response of ferritic stainless steel subjected to asymmetric turned rolling (ATR). The asymmetric rolling path of the sheets changed after every 5 % strain by rotating 180° around the rolling direction (RD). As the rolling deformation level increased, grain width was decreased. At the highest deformation level (60 %), the microstructure exhibited highly elongated ferrite grains and the presence of deformation bands. Furthermore, with increasing strain, the intensity of shear and deformation textures was enhanced. The increase in dislocation density with increasing strain levels resulted in the enhancement of macrohardness and microhardness. It is noteworthy that the up and down surfaces revealed similar hardness values due to using the turned path. Microstructural changes, including grain refinement, deformation bands, increased dislocation density, and enhanced textures, directly influenced the mechanical properties. These features improved hardness and strength by hindering dislocation motion and enhancing crystallographic alignment, explaining the high yield (781.2 MPa) and tensile strength (795.7 MPa) of the 60 % ATR sample, along with its reduced ductility (11.3 %). Furthermore, while the number of deep and large dimples on the fracture surface diminished with increasing strain, a ductile fracture mode remained dominant in all ATR-processed samples.