Intergranular Zn-assisted liquid metal embrittlement (LME) cracks have been frequently reported in steels, involving austenite grain boundary penetration of liquid Zn at high temperature. In the present study, a Zn-coated high strength steel was deformed at an intercritical temperature, and the characteristics of LME cracking were studied in a mixed microstructure composed of ferrite and austenite. Crack propagation was intergranular in austenite; in contrast, the ferrite exhibited both intergranular LME and transgranular LME. Trace analysis of the crack plane orientation was consistent with cracking along {100} cleavage planes in ferrite.
Keywords: Liquid metal embrittlement; Zn; ferrite; high strength steel; intercritical temperature; transgranular cracking.