Research On Composite Structure And Properties Of High Strength Martensitic Steel-High Plasticity Austenitic Steel

High-strength and high-plasticity metal materials have broad application prospects.In order to obtain high-strength and high-plasticity metal materials at the same time,this topic selects high-strength martensitic steel and high-plasticity austenitic steel as the matrix materials,respectively.The martensitic steel and austenitic steel were compounded by vacuum hot rolling and spark plasma sintering respectively to obtain a high strength-high plastic composite steel.Using scanning electron microscopy,transmission electron microscopy,XRD,electron probe,microhardness and stretching machine and other equipment,the microstructure of the composite steel was characterized,and the corresponding strengthening and toughening mechanism was clarified.The plate-shaped martensitic steel and austenitic steel are composited by vacuum hot rolling.Because the composite material itself has a cooperative deformation,a transformation-induced plasticity mechanism,and a large number of geometrically necessary dislocations,the composite material has a higher uniform elongation,but the tensile strength is lower.By introducing the warm rolling process,the cooperative deformation mechanism is optimized,the work hardening ability of the composite material is improved,and the strength and plasticity of the composite material are improved at the same time.Among them,the composite material with a 10% warm rolling deformation has a tensile strength of 1546 MPa and a uniform elongation of 14.2%,which is attributed to a more excellent collaborative deformation ability.When the warm rolling deformation is30%,the strength increases but the plasticity decreases,and the tensile strength and uniform elongation are 1657 MPa and 10.5%,respectively.The powdery martensitic steel and austenitic steel are compounded by spark plasma sintering.The optimized sintering parameters are 1050°C for 10 min,and the sintering pressure is 50 MPa.The quality of the sintered sample was improved by hot rolling,and then introduced cold rolling and high temperature tempering experiment.Among them,martensitic steel: austenitic steel = 2:1(mass ratio)composite material,after cold rolling deformation of 30%,and 450°C tempering for 5 min,it has a tensile strength of 2177 MPa and 9.2 % of elongation at break.After the original sintering,the density of the sample was increased by hot rolling,so that the strength and plasticity of the composite material were improved at the same time.Through the cold rolling and high temperature tempering process,high-density dislocations are introduced.At the same time,repeated cold rolling operations make the pores continue to be squeezed and deformed,so that the pores are further optimized,so that the powder metallurgy composite steel has excellent tensile properties.