Liquid metal embrittlement cracking behavior in iron-zinc (Fe/Zn) couple: Comparison of ferritic and austenitic microstructures

Abstract

• The liquid–metal-embrittlement (LME) was studied in ferritic and austenitic samples. • The ferritic sample showed higher sensitivity to LME crack initiation. • The austenitic specimen displayed higher LME crack propagation rate. • Crack propagation was accelerated by phase transformation and segregation. Liquid metal embrittlement (LME) has emerged as a major concern when developing high-strength automotive steels. However, information regarding the impact of initial microstructure on LME severity is limited in the Fe/Zn couple. Specifically, there is no consensus as to which ferritic and austenitic microstructures are more susceptible to LME cracking. The present study aims to examine the LME cracking behavior of fully ferritic and austenitic microstructures under the same thermomechanical conditions. It was shown that the ferritic microstructure has a higher sensitivity to LME crack initiation, whereas the austenitic specimen displayed a much longer average crack length, which indicates higher crack propagation rate than the ferritic specimen. It has been determined that in-situ austenite to ferrite transformations during Zn diffusion, as well as grain boundary segregation of alloying elements such as Cr and Ti, contribute to the LME propagation rate.