Microstructure And Properties Of Austenitic Steels After High Pressure Torsion And High Pressure Annealing

In this paper,two kinds of austenitic steels were subjected to high pressure torsion and high pressure annealing,and the microstructure changes of two austenitic steels were characterized by optical metallographic microscope,X-ray diffraction and electron backscatter diffraction analyzer.The mechanical properties of TWIP?Twinning induced plasticity steel?steel and 301 austenitic steel were measured by microhardness tester and universal tensile tester.TWIP and 301 stainless steel are all austenitic steels,but they have different deformation mechanisms.TWIP steel is mainly twinning induced plasticity,while301 stainless steel is transformed from austenite to martensite by phase transformation.The experimental results are as follows:The two austenitic steels were subjected to high-pressure torsion treatment with different turns.TWIP steel has little change in austenite content with the increase of the number of torsion turns,and the microstructure is remarkably refined.The hardness increases with the increase of the number of torsion turns,the maximum value is 580HV_0.5,the yield strength and tensile strength increase,and the plasticity decreases significantly,from 65.8%to 5.5%.However,the austenite content of 301 stainless steel increases sharply with the increase of the number of torsion turns,and the martensite content increases significantly.The maximum hardness increase was 570 HV_0.3,the yield strength and tensile strength were increased to a maximum of 1534 MPa and 1698 MPa,respectively,and the plasticity decreased significantly from 95%to 4.6%.High-pressure annealing of austenitic steel after high-pressure torsion is carried out under the conditions of 550 to 850?and 5 GPa anealing for one hour.TWIP steel begins to recrystallize at 550?annealing,producing a large number of annealed twins with uniform grains.When the temperature rises,the hardness of TWIP steel decreases,from503HV_0.5 to 350HV_0.5,the yield strength and tensile strength decrease,and the plasticity increases.301 stainless steel under the same pressure and holding time,with the increase of annealing temperature,the microstructure change process of 301 stainless steel is the reverse transformation process of martensite structure to austenite structure,accompanied by grain growth.The hardness of 301 stainless steel decreased from 551HV_0.3 to 375HV_0.3.The yield strength and tensile strength are reduced and the plasticity is enhanced.