Forming Properties and Microstructure of Copper-containing Austenitic Stainless Steel under Low Temperature Environment
The work aims to study and analyze the tensile and forming properties of copper-containing austenitic stainless steel at room temperature and low temperature,and understand the microstructure evolution of copper-containing austenitic stainless steel under the background of cupping experiments.Tensile and Erichsen cupping experiments were performed on copper-bearing austenitic stainless steel at room temperature and at-140 ℃ in a liquid nitrogen environment.The effects of room temperature and low temperature environments on the properties of copper-containing austenitic stainless steels were ana-lyzed by combining experiments with scanning electron microscopy and transmission electron microscopy characterization.The ultimate tensile strength of copper-containing austenitic stainless steel at-140 ℃ was increased by about 49.7％,the yield strength was increased by about 35.5％,and the elongation was reduced by about 27.3％.The mode of tensile fracture at room temperature was ductile fracture.At low temperature,the tensile fracture mode changed to a mixed brittle-tough fracture.In the cupping experiment,the protrusion value increased by 0.67 mm from 12.78 mm at room temperature to 13.45 mm at-140 ℃.In conclusion,the analysis of its internal microstructure by EBSD shows that the constant concentration of stress and changes in strain during the cupping experiment contribute to the slip of dislocations,the generation of twins and the martensitic phase transformation of austenite.The closer to the fracture crack region,the more obvious the stress concentration,the more obvious the transformation of austenite to martensite,and the more contents of martensite.Twinning-induced plasticity(TWIP)and phase transition-induced plasticity(TRIP)improve the strength and plasticity of stainless steel.The above provides a certain theoretical basis for solving the processing and preparation of copper-containing austenitic stainless steel in actual production.
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