High-temperature confocal laser scanning microscopy analysis of phase transformation of steels: a review

High-temperature confocal laser scanning microscopy (HT-CLSM) is considered as a powerful tool for in situ observation of the phase transformation of steels at elevated temperatures. It breaks the limitation that conventional approaches on this aspect can only post-mortem the microstructure at room temperature. The working principle and major functions of HT-CLSM in initial are introduced and the utilization in details with HT-CLSM is summarized, including the behaviors of melting-solidifying, austenite reversion, as well as the austenite decomposition (formation of Widmanstätten, pearlite, acicular ferrite, bainite and martensite) in steels. Moreover, a serie of HT-CLSM images are used to explore the growth kinetic of phase at elevated temperatures with additional theoretical calculation models. Finally, the in situ HT-CLSM observations of phase transformation, combined with post-mortem electron backscatter diffraction analysis, is also summarized to elucidate the crystallographic evolution.