In Situ X-ray Diffraction Investigation of Hydrogen Effects on Deformation-Induced Phase Transformation in Forged and Additively Manufactured 304L Stainless Steels

This study utilized high energy synchrotron x-ray diffraction to probe microstructural evolution during uniaxial deformation of conventionally manufactured and additively manufactured (AM) 304L stainless steel with and without internal hydrogen. The objective of this effort is to highlight the effect of hydrogen on deformation-induced martensite phase transformations in austenitic stainless steels. Solute hydrogen depresses the required applied strain to initiate austenite transformation to epsilon-martensite and alpha'-martensite in both forged and AM stainless steel. Similarly, the total fraction of transformation product is larger when the microstructure is saturated with hydrogen. Deformation induced phase transformations also lead to a variation in strain partitioning behavior, which is linked to the chemical composition and stacking fault energy of the starting and hydrogen-charged materials.

Automated summary

This study used high energy synchrotron x-ray diffraction to investigate the microstructural evolution during uniaxial deformation of conventionally manufactured and additively manufactured (AM) 304L stainless steel, as well as the effect of internal hydrogen. It was found that solute hydrogen can reduce the required applied strain for austenite transformation to epsilon-martensite and alpha'-martensite in both forged and AM stainless steel. Similarly, a higher fraction of transformation product was observed when the microstructure was saturated with hydrogen. Deformation-induced phase transformations also resulted in a change in strain partitioning behavior, which was influenced by the chemical composition and stacking fault energy of the starting and hydrogen-charged materials.