Phase transformation and grain refinement in hydrogenated metastable austenitic steel

The effect of hydrogen on strain-induced γ → α′ transformation in type 304 steel and on the microstructure of prestrained material was studied. Hydrogenation at 543 K under a pressure of 100 MPa prevents the formation of α′-phase during tensile straining. Such a treatment of pre-strained steel causes α′ → γ transformation and grain refinement. Ab initio calculations for the α- and γ-iron demonstrate that hydrogen decreases the equilibrium temperature of both phases. The reasons for the grain refinement and decrease in temperature of martensite reversion are discussed.