On the mechanism of liquid copper penetration into iron grain boundaries

The penetration of liquid copper into iron grain boundaries has been experi mentally analysed. During the penetration, Cu diffuses into the iron grains . In this case, a Kirkendall effect is created, leading to vacancies which diffuse to the grain boundaries where they condense. A grain boundary crack is formed, which will be filled with liquid Cu. The driving force for pene tration of the Cu-liquid into the grain boundary is the condensation of vac ancies and the surface/interface free energy change. A theoretical model de scribing the penetration rate is derived and a good agreement between theor y and experiments was achieved. The model is general and can be used to exp lain liquid metal embrittlement.