Anomalous strain rate dependence of tensile ductility in moisture-embrittled Co₃Ti alloys

The effect of strain rate on tensile ductility of moisture-induced embrittlement of Co₃Ti alloys was investigated at ambient temperatures (298–353 K) by tensile test and scanning electron microscope fractography. The anomalous increase of tensile elongation and ultimate tensile stress was observed in a very low strain rate region and also at high temperatures, accompanied by an increase of area fraction in ductile transgranular fracture pattern. The anomalous strain rate dependence of tensile ductility was shown to become more evident with decreasing grain size and also with deviation from alloy stoichiometry. Oxidation on the alloy surface was suggested as a process counteractive to the hydrogen decomposition process from moisture in air.