Mechanical behavior of CrMo steel with tempered martensite and ferrite–bainite–martensite microstructure

This study is concerned with a correlation between the microstructure and mechanical properties of 42CrMo4 steel, with two different microstructures. Quench tempering and step quenching heat treatments produced tempered martensite and ferrite–bainite–martensite (FBM) microstructures, respectively. Tensile test results indicated a yield-drop effect in FBM microstructure with ferritic matrix. This was attributed to dislocation generation in ferrite phase during bainitic and martensitic transformations. Fractographic investigations indicated transgranular cleavage and microvoid in FBM and tempered martensite microstructures, respectively. This can be attributed to high density of interphase boundary in FBM microstructure and carbide formation in tempered martensite microstructure.