Strain-induced ε-martensitic transformation and hydrogen embrittlement of SUS304 stainless steel

ABSTRACT

We examined the hydrogen embrittlement mechanism in SUS304 stainless steel by conducting synchrotron radiation diffraction experiments and high-resolution TEM observations. It was found that the strength of SUS304 was lowered by adding hydrogen and that brittle fracture occurred with elongation of approximately 20%. Synchrotron radiation diffraction experiments revealed that the formation of the ε phase having a hexagonal close-packed structure was promoted by hydrogen addition to SUS304. In addition, high-resolution TEM observations revealed the presence of the ε phase with a width of up to approximately 5 nm at the twin boundary in the twin structure due to the γ phase. Furthermore, a large number of stacking faults were formed in the ε phase. These results imply that the strain-induced martensitic phase transformation from the γ phase to the α′ one was suppressed by hydrogen addition to SUS304 and that the ε phase having a large number of stacking faults was stabilised as an intermediate phase during the α′ martensitic phase transformation. The formation of the ε phase having a large number of stacking faults should presumably originate in hydrogen embrittlement.

KEYWORDS:

• Austenitic stainless steel
• induced ε-martensite phase
• deformation structures
• stacking fault
• stacking-fault energy

Disclosure statement

No potential conflict of interest was reported by the authors.