Effect of thermomechanical treatment on the microstructure and mechanical properties of Si-containing oxide dispersion strengthened reduced activation ferritic steel synthesized via mechanical alloying and spark plasma sintering

Abstract

The present work describes the effect of thermo-mechanical treatment on the microstructure, and its subsequent effect on the mechanical properties of Si-containing oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel. ODS-RAF steel powder mixture with a nominal composition of Fe-14Cr-2W-0.3Ti-1Si-0.3Y2O3 was mechanically alloyed up to 50 h and subsequently consolidated via spark plasma sintering (SPS) at 900 °C followed by thermo-mechanical treatment (TMT) at 850 °C. Microstructural study revealed that the sintered sample consisted of ultrafine grains (0.35 µm) along with nano-size particles (Cr2TiO4, SiO2, and Y2Ti2O7) distributed in the matrix. This sintered sample exhibited excellent mechanical properties such as Vickers hardness (600 VHN), compressive strength (1795 MPa), and total elongation (21%), which is ascribed to the presence of ultrafine grains and nano-size particles. The thermo-mechanically treated sample exhibited an increase in the density by 2.7% and a reduction in the grain size by 23%. Consequently, the Vickers microhardness, compressive strength, and failure elongation of the sintered sample improved by 13%, 37%, and 19%, respectively, upon thermo-mechanical treatment.

Keywords

• Oxide dispersion strengthened reduced activation ferritic steel
• Silicon, Spark plasma sintering
• Thermo-mechanical treatment
• Microstructure
• Mechanical property