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

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 in-compatibility at the NbC/gamma 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.

Automated summary

A Nb-stabilized cast austenitic stainless steel was subjected to homogenization treatments at different temperatures to investigate the influence of microstructure on deformation behavior and mechanical properties. Dissolution of primary NbC at temperatures above 1150 C led to the disruption of network connectivity and an increase in carbon and niobium content in the matrix, resulting in improved ultimate tensile strength and elongation.