Is Segregation-induced Grain Boudary Embrittlement a Polymorphous Melting Process?

Nghi Q. Lam

Argonne National Laboratory, Argonne, IL 60439

Abstract

A number of important contributions to our understanding of solid-state amorphization and segregation-induced grain boundary embrittlement have been made in recent years. The two processes have traditionally been regarded as completely different phenomena belonging to different branches of materials science. However, recent systematic studies on Ni-S alloys have revealed striking similarities in the kinetics of S-implantation-induced amorphization and S-induced grain boundary embrittlement. In this presentation, we examine the underlying thermodynamics and show that both phenomena can be regarded as a polymorphous melting process. Disorder-induced melting of grain boundaries gives rise to low fracture resistance due to the ability of a crack to propagate readily through amorphous material.

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