Creep-induced heterogeneous precipitation of Laves phase with two morphologies in tempered martensite ferritic steels

We report two typical morphologies (elongated- and blocky-shaped) of the Laves phase in tempered martensite ferritic steels during creep process, originating from the two independent formation paths, i.e. along grain boundaries (GBs) and neighboring M₂₃C₆. This is attributed to the multi-element segregation (Cr, Mn, Si and W) at GBs and adjacent M₂₃C₆ that serves as suppliers of Laves phase formers. Furthermore, the subsequent different growth mechanisms play crucial roles in the two typical morphologies. Our findings improve the understanding of Laves phase heterogeneous precipitation and provide new insights for the innovation of novel heat-resistant steels with superior creep strength.