Tensile Properties and Deformation-Induced Martensitic Transformation at Cryogenic Temperatures in Fe-Cr-Ni-Mn-N Alloys
The tensile properties and changes in microstructures during tensile deformation in Fe-Cr-Ni-Mn-N alloys with a variation of C and N contents have been investigated over the temperature range of 293–4.2 K. It was found that with decreasing temperature the deformation-induced martensitic transformation started at 173 K in the process of γ→ε→α′; the amount of α′ martensite formed with maximum uniform strain was greater at 77 K than at 173 or 4.2 K. For the formation of α′ martensite a critical strain was required, and the amount of α′ martensite increased with increasing deformation strain. With the increase in the contents of C and N, the critical strain and the tendency for the increase in the amount of α′ martensite with strain decreased. The results show that both C and N can lead to some increase in the yield and ultimate strengths and a decrease in the elongation, while the deformation-induced martensitic transformation is strongly restrained by the increase in C or N content.
KeywordsTensile Property Martensitic Transformation Ultimate Strength Austenitic Stainless Steel Austenitic Steel
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