Effects of Solid Solution Treatments on the Microstructure and Mechanical Properties of a Nanoscale Precipitate-Strengthened Ferritic Steel

Abstract

Solid solution treatment (SST) and age hardening are the two main treatments used to produce nanoscale precipitation-strengthened steels. In this work, solution treatment and aging are employed to develop a nanoscale precipitation-strengthened steel displaying high degrees of strength, ductility, and toughness. The effects of SST on the microstructure and mechanical properties of the produced steel are investigated. The results show that the solution temperature strongly influences the matrix microstructure. Partial austenitization between $$ A_{{{\text{c}}1}} $$ and $$ A_{{{\text{c}}3}} $$ favors the formation of granular ferrite, while complete austenitization above $$ A_{{{\text{c}}3}} $$ leads to the formation of polygonal ferrite. Refined granular ferrite with a low dislocation density can effectively improve the plasticity and low-temperature toughness of steel. Precipitation strengthening is mainly related to the nature of the nano-precipitates, specifically their size and number density, independently of the matrix microstructure.