Homogenization temperature dependent microstructural evolution and mechanical properties in a Nb-stabilized cast austenitic stainless steel

Abstract

A Nb-stabilized cast austenitic stainless steel is processed by homogenization treatments at 1050 °C, 1150 °C, and 1250 °C respectively to investigate microstructure dependent deformation behaviors and mechanical properties. Homogenization treatment at 1050 °C could not change the size of primary NbC, while significant dissolution of primary NbC destroys the network connectivity after homogenization treatments at temperatures above 1150 °C. Meanwhile, dissolution of NbC will increase C and Nb content in austenite matrix, leading to an increase in SFE. Nucleation of microcracks within NbC at the initial stage of deformation is caused by plastic strain incompatibility at the NbC/γ interface. Fast crack propagation along the continuous network of primary NbC leads to premature fracture at a lower stress level, and resultant lower ultimate tensile strength and elongation in as-cast and 1050-H samples. A higher SFE reduces the susceptibility to localization of deformation and crack propagation along the discrete primary NbC is suppressed, resulting in an obvious improvement in the ultimate tensile strength and elongation in 1150-H and 1250-H samples. • The dissolution and precipitation of NbC during homogenization treatments by different temperatures were revealed. • A higher SFE is responsible for the lower rate of deformation-induced α'-martensitic transformation by suppressing the planar slip. • A higher SFE reduces the susceptibility to localization deformation and the crack propagation along the primary NbC is suppressed. • A noticeable improvement in the ultimate tensile strength and elongation after homogenization treatment at temperatures above 1150 °C.