Grain structure and intermetallic evolution of Nb-containing FeCrAl alloy treated by cryogenic laser quenching

Thin-walled FeCrAl alloy tubes emerge as significant contenders for substituting zirconium alloy cladding tubes. Enhancing the surface strength and corrosion resistance of these tubes is essential for their industrial utilization. Cryogenic laser treatment emerges as a promising technique for enhancing the surface corrosion resistance of Nb-containing FeCrAl alloy. A comprehensive investigation was carried out to study the evolution of solidification structure in a Nb-containing FeCrAl alloy subsequent to cryogenic laser quenching, with the intention of augmenting the mechanical characteristics of the alloy surface. A refined composite structure, consisting of planar-columnar-equiaxed crystals, was identified on the surface of the sample. We have made observation of an amorphous precipitated phase, which is recognized as the intermediate phase found between the Laves phase and ferrite phase. The presence of amorphous precipitates exerts a beneficial influence on the surface hardness and strength of the alloy. Our study delves into the exploration of the causes for the amorphous phase and conducts an analysis of the structural evolution during its recrystallization.