Liquid-metal embrittlement of Type 316L stainless steel by gallium as measured by elastic-plastic fracture mechanics

In order to bound failure of austenitic stainless steel storage containers housing Ga-containing compounds, the liquid-metal embrittlement of Type 316L (UNS S31603) stainless steel (SS) by Ga was investigated. Type 316L SS compact tension specimens were exposed to liquid Ga using a depassivation technique to wet the specimen. Linear elastic and elastic-plastic fracture mechanics methods were used to compare the fatigue and fracture behavior. Mild liquid-metal embrittlement was observed, as indicated by increased fatigue crack growth rate, decreased number of fatigue cycles to failure, decreased crack initiation resistance, and increased crack growth rate. Stable cracking was observed for all test conditions. A small amount of intergranular cracking was observed following Ga exposure. No effect of test temperature on embrittlement was observed over the small temperature range examined (35degreesC to 75degreesC). Decreasing crosshead displacement rate promoted Ga embrittlement. Based on fractography, profilometry, and mechanics, it appears that both adsorption-induced decohesion and adsorption-enhanced plasticity mechanisms are operative in the Type 316L SS-Ga system.