Effect of cold deformation on microstructure and mechanical properties of S32101 duplex stainless steel
Lean duplex stainless steels(LDSS)have the characteristics of low cost and high performance.They can realize reduction in material weight and full life cycle costs as structural materials.The substitution of LDSS for car-bon steels in urban transportation vehicle body structure requires that Rp0.2 reaches over 630 MPa and A50 be above 20％,thus S32101 needs to further increase its strength.Different cold rolling deformation amounts(5％-20％)were applied to S32101,and the cold deformation microstructure was analyzed and characterized using scanning elec-tron microscopy(SEM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM),and the effects of cold rolling deformation on mechanical properties were studied.The results showed that after 5％cold deformation,S32101 austenite formed layer faults and dislocations.With increasing cold deformation,mechani-cal twinning and strain-induced martensitic phase transformation gradually formed.The critical deformation amount required to produce deformation-induced martensite was 15％.The orientation relationship between the austenitic phase and martensitic phase conformed to the N-W relationship,i.e.,(110)α'//(111)γ 且[001]α'//[011]γ.The strengthening mechanisms of austenite phase during different stages of cold deformation were dislocation strengthen-ing,twinning strengthening and phase transformation strengthening.During cold deformation,the dislocation density in the ferrite phase gradually increased,and the mechanism was dislocation strengthening.LDSS S32101 was sensi-tive to cold deformation,and even small deformation amounts significantly improved its strength.When the cold deformation amount was 5％,the yield strength of economical duplex stainless steel S32101 reached 720 MPa,and the elongation was 22％,meeting the requirements of urban transportation vehicle body structural materials.With further increasing the cold deformation amount to 20％,the strength of S32101 gradually increased,the yield strength increased to 950 MPa,the tensile strength increased to 1 130 MPa,but the elongation decreased to 12％.
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