Study On Mechanical Properties And Fracture Behavior Of New Lightweight TWIP Steel Under Different Temperature Condition

The new lightweight Fe-Mn-C-Al TWIP steel,known for its excellent strength and toughness,is considered a highly promising material.In this study,mechanical properties and fracture behavior of Fe-Mn-C-Al TWIP steel were investigated through mechanical testing under different temperatures and various states.The research focused on the thermal deformation behavior of Fe-15.3Mn-0.58C-2.3Al TWIP steel,the influence of trace rare earth Ce on the low-temperature toughness of Fe-18Mn-0.6C-1.8Al TWIP steel,and the improvement of room temperature comprehensive mechanical properties of heterogeneous Fe-18Mn-0.6C-1.8Al TWIP steel prepared by ultrasonic surface rolling.The experimental results show that Fe-15.3Mn-0.58C-2.3Al TWIP steel exhibits excellent hot plasticity within the temperature range of 600℃to 1310℃,with no traditional brittle zone.The section shrinkage rate reaches a maximum value of 89.4%at 1275℃.Dislocation slip was the main deformation mechanism during high-temperature tensile process,and dynamic recrystallization caused by plastic deformation is an important reason for improving its plasticity.The inclusions in Fe-18Mn-0.6C-1.8Al TWIP steel can be successfully modified by Ce.When 0.0048wt.%Ce was added,the liquid nitrogen temperature impact toughness was 103.6 J/cm~2,with an increase of 87.3%.The irregular large-sized inclusions in the steel transform into fine rare earth inclusions with an elliptical shape,which greatly reduces the proportion of large-sized inclusions.The average inclusion size decreases and disperses,which alleviates stress concentration in the steel matrix,increases the path of crack propagation,enhances the impact absorption energy,and changes the fracture mode from cleavage to toughness.By successfully preparing heterogeneous Fe-18Mn-0.6C-1.8Al TWIP steel using ultrasonic surface rolling,the surface exhibits gradient nanocrystals,high-density dislocation clusters,and gradient deformation twinning.The 4 passes and 750 N rolling pressure have optimal room temperature mechanical properties,with a yield strength of 790 MPa,an increase of 152.4%,and an elongation of 36.6%.Excessive rolling pressure can cause the sample surface to peel off,reducing the overall hardness and ductility of the sample.This method maximizes the strength while minimizing the loss of ductility.This study provides a new way to improve the mechanical properties of TWIP steel under various service temperature conditions and lays a good foundation for its future industrial-scale application.