Exploring the effects of austenitizing conditions on the heterogeneous microstructure and mechanical properties of 11Cr–11Ni–Ti–Mo maraging stainless steel: Breakthrough in the strength-ductility trade-off

Abstract

Based on the microstructure analysis, the present research investigated the influence of various austenitizing conditions on the transformation behavior of intermetallic compound particles, i.e. η-Ni3Ti, and the reversed austenite during ageing treatment in Ti–Mo maraging stainless steel, as well as the related mechanical properties. The results revealed numerous tiny rod-like intermetallic compound particles, i.e. η-Ni3Ti, having a Burgers orientation relationship, i.e., {101}α′//{0001}η ; α′//η, with the martensite matrix, as well as blocky, lath, and granular reversed austenite of various sizes distributed within the tempered martensite matrix. Regardless of the austenitizing treatment condition, more reversed austenite was found in the samples aged at 520 °C than in those aged at 640 °C. Although this finding was not consistent with the Thermo-Calc predictions, it should be associated with the thermal stability of reversed austenite at different ageing temperatures. In other words, the greater amount of reversed austenite that formed at 640 °C did not remain at room temperature due to secondary martensite transformation during cooling, as was verified by EBSD analysis.

Keywords

• Precipitation hardened stainless steel
• Microhardness
• Transmission electron microscopy
• Ni3Ti
• Reversed austenite
• EBSD