Grain size refinement and effect on the tensile properties of a novel low-cost stainless steel

Abstract

In this study, a novel 20LH5 austenitic stainless steel (AUSS) with various grain sizes was produced. The purpose of this paper is to analyse the effect of the grain size on the tensile fracture morphology and mechanical properties. After a phase reversion process (large ductility cold rolling and annealing), stainless steels with different microstructures comprising coarse grains (CGs) (~9.2 μm) to fine grains (FGs) (~2.1 μm) to ultrafine grains (UFGs) (~1.4 μm) were observed. Tensile tests were then carried out to verify the grain refinement strengthening mechanism. The results show that the mechanical properties in materials that possess UFGs reached a tensile strength of ~1090 MPa, a yield strength of ~530 MPa and an elongation rate of ~47%, which is much better than those of materials with FGs, CGs, and most 300 series AUSSs. Furthermore, the voids in UFG AUSSs were densely distributed and finer than those in the other two counterparts. This indicates that a decreased grain size contributed to a decreased dimple size; that is, the ductility and strength were increased.