Abstract: The phenomena of Phase-hardening of soft phase (ferrite, austenite) and phase-softening of hard phase (martensite) in dual-phase steels were examined on steels with ferrite martensite and austenite-martensite structures. It was found that Phase-hardening and phase-softening are universal phenomena. The hardening of the soft phase is caused by he increase of dislocation density due to volumetric expansion of surrounding hard martensite Phase during transformation of the later. The softening of martensite phase is caused by the less constraining effect of the soft matrix resulting in the decrease of dislocation density in martensite and less density of twinned marten site. The existence of ferrite microareas within martensite islands is also a factor which decreases the microhardness values.

Key words: 马氏体, 双相钢, 铁素体, 相软化, 相硬化