Nanostructured martensite–austenite dual phase steels

Abstract

Nanostructured martensite–austenite microstructure was achieved by a quenching–partitioning–tempering (Q–P–T) treatment of high carbon low temperature bainitic steel. Microstructure observations showed that the nanostructured steel consisted of fine martensite (about 25 nm in thickness), retained austenite and carbides. X-ray diffraction analysis indicated that carbon was partitioned into austenite after martensite transformation. High hardness (about 655 HV1) and relatively high retained austenite fraction (0·36–0·41) was attained. The heat treatment times were greatly reduced, nearly equal or higher hardness and retained austensite fraction were achieved by Q–P–T treatment, compared with low temperature super bainite process.