Effect of heat treatment on microstructure and mechanical property of ODS-CLAM-Zr steel

Abstract

Oxide dispersion strengthening (ODS) is one of the effective methods to improve the high temperature strength of many reduced activation ferritic/martensitic (RAFM) steels, alloys and even intermetallic compounds. This manuscript is focused on the ODS experiments for the improvement of China low activation martensitic (CLAM) steel with Zr addition. The tempered ODS-CLAM-Zr samples were prepared by mechanical alloying (MA) and hot isostatic pressing (HIP) followed with different heat treatments (HTs). The results showed that the samples after HT had a typical bimodal grain structure consisting of residual ferrite and martensite structures. The inhomogeneous structure of the samples may be caused by MA, and the ultrafine grains had good thermal stability at 1150°C. Higher tensile properties were obtained under normalizing at 1050°C and tempering at 750°C. The coarsening of the rod-shape ZrO2 phase at the grain boundaries with the increase of temperature was the main reason for the decrease of the strength of the samples. This work provides a reasonable HT for tempering ODS martensitic steels.