Effect of strain-induced martensitic phase transformation on the formability of nitrogen-alloyed metastable austenitic stainless steels

Strain-induced martensitic phase transformation and its influence on the formability of newly developed nitrogen-alloyed metastable austenitic stainless steels were systematically investigated. Yield strength for the asreceived steels bearing lownickel content was around 300 MPa and their elongation ratios varied from 55. 2% to61. 7%. Erichsen numbers of these samples differed from 13. 82 to 14. 57 mm. Although its Cu content was lower than that of other samples,steel D2 exhibited better plasticity and formability,which was attributed to γ→α’martensitic phase transformation. EBSD,XRD,and magnetism tests showed that increases in deformation ratio gradually increased the α’ martensite phase of a sample,thereby contributing to its strain and inducing the optimal transformation-induced plasticity effect. An M;temperature of around 20 ℃,which is close to the deformation temperature,provided the austenite with adequate stability and gradually transformed it into martensite,thereby endowing lean ASS with better formability.