Hydrogen-induced increase in phase stability in metastable austenite of various grain sizes under strain

Martensitic transformation is a pressing issue in austenitic steels in the context of hydrogen embrittlement; strain-induced martensite formation may increase the level of hydrogen embrittlement in metastable austenite. Therefore, the effect of hydrogen on phase stability was investigated. An austenitic stainless steel with several grain sizes was charged with various hydrogen contents, and the mechanical stability of austenite under cold-rolling was studied. Grain size did not affect the amount of martensite formed in the material for any condition. Increasing hydrogen contents decreased the amount of strain-induced martensite at each tested strain. The results were confirmed with magnetization saturation, X-ray diffraction, and electron backscattered diffraction measurements. Hydrogen appears to both change the deformation mechanism and the martensite forming rate. The stabilization is caused by a lower population of martensite nucleation locations.