Microstructure And Mechanical Properties Of In Situ TiB Reinforced Titanium Matrix Composites

In situ titanium matrix composites have being widely followed in the fie ld ofaerospace, aviation, automobile industry, etcdue to their excellent mechanicalproperties. So it is essentia l to make an in-depth research of the microstructure andmechanical properties of titanium matrix composites (TMCs). In thispaper,5vol.%TiB reinforced TMCs were prepared by the method of vacuumconsumable electrode arc smelting. Matrix nominal composition isTi-6Al-4Sn-10Zr-1Mo-1Nb-1W-0.25Si-0.3Y. The high temperature deformationbehavior and the organizationa l change rule of TMCs were investigated. Theas-cast microstructure and mechanics properties of the TMCs were analyzed. Theresearch of the microstructure and properties of rolled TMCs was carried out. Therelationships with the heat treatment process on the rolled TMCs and themicrostructures and properties in the room-temperature tens ile of TMCs werediscussed.The TiB reinforced TMCs as-cast ingot was prepared by three reme lting, andTiB was done by the reaction of TiB2with Ti. After high temperature deformation,the average hot deformation activation energy was224.54KJ/mol and the stressindex was3.81in β double phase region. The constitutive equation and Peak stressexpression of about the TMCs were builded, providing the theoretical basis forsubsequent hot working.The matrix structure of the ingot was consisted of the organization of slicelayer on top.with TiB exhibiting whisker morphology and hollow shaped, The top,middle, and low microstructure of the ingot was different with the matrix and themiddle had the best room-temperature tensile properties. The strength of theas-cast TMCs was decreased, but the plastic gradually was improved with theincreases of high tensib le temperature from550℃to750℃. The maximum tensilestrength was675.7MPa at the the temperature of550℃, and the plastic was20.4%at the the temperature of750℃. The typical cleavage fracture mechanism at roomtemperature was cleavage fracture as the same with550℃. When the temperatureincreased to600℃and650℃, the typical cleavage fracture mechanis m wereQuasi quasi cleavage, at higher temperatures for ductile fracture. Strengtheningmechanis ms of TMCs for fine-grain strengthening of second-phase particlesreinforced. The TMCs sheet was obtained by hot forging and β-rolling and themicrostructure was β phase and fine acicular phase. High length to diameter ratioof TiB was broken into short acicular and block. The room temperature strengthand the plastic ity of as-rolled TMCs were higher than the as-cast. The tensilestrength was increased by62%and the elongation was increased by five times.The mechanical properties of as-rolled TMCs was anisotropic after analys ing ofdifferent direction of high temperature mechanical properties of as-rolled TMCs.The TMCs with transverse rolling had higher strength but worse plastic itycompared with rolling direction at700℃. The fracture morphology at roomtemperature was full of a multitude of dimple and a sma ll amount of cleavage stepsand the fracture mechanis m at high temperature turned out to be ductile fracture.The room temperature strength and plasticity of TMCs could be improved byproper heat treatment and the best elongation of TMCs could reach6.2%. Themicrostructure of the second rolling sheet was analyzed.