Zn Penetration in Liquid Metal Embrittled TWIP Steel

Abstract

Hot-dip Zn-coated high manganese twinning-induced plasticity (TWIP) steel is sensitive to liquid metal embrittlement (LME). The microstructure of Zn-coated TWIP steel after brittle fracture at 1123 K (850 A degrees C) was investigated. The grain boundaries at the tip of the Zn penetration were analyzed by electron microscopy and atom probe tomography. I"-(Fe,Mn)(3)Zn-10 was found at the tip of the Zn penetration in the TWIP steel, implying that liquid Fe- and Mn-saturated Zn-rich alloy had percolated along the grain boundaries to the tip of the Zn penetration. Evidence for extensive Zn grain boundary diffusion ahead of the Zn-rich alloy percolation path was also observed. Both the Stoloff-Johnson-Westwood-Kamdar model and the Krishtal-Gordon-An model for LME crack formation are compatible with the present in-depth microanalysis of the Zn penetration. (C) The Minerals, Metals & Materials Society and ASM International 2016