Tensile inhomogeneous deformation of stainless steel at elevated temperature

The material will emerge inhomogeneous deformation during deformation at elevated temperature,even cause surface defects.304 stainless steel surface morphology with various strain were analyzed through the elevated temperature tensile unloading tests at 1150℃.The results show that the surface roughness increase with strain.From the macro of sample,although samples have obviously inhomogeneous,it keep geometrical homogeneous at small strain.When the strain is large,it evolve bamboo-shaped.At the beginning of deformation sample surface forms a strain concentration zone and transfers to form hollows at elevated temperature.Transfer will concentrate at one zone to cause fracture when the strain is large.Analysis suggests that once strain concentration zone emerge,because of high strain rate hardening property of material make strain concentration region deformation resistance increased to prevent cross-sectional area from reducing and the strain concentration zone transferring.