Research On Microstructure And Mechanical Properties And Hot Deformation Behavior Of As-forged Beta Titanium Alloy

Beta titanium alloys form one of the most versatile classes of materials with respect to processing, microstructure, and mechanical properties, due to their increased heat treatability, deep hardening potential, and excellent ability of deformation, These alloys can be used in aerospace, power plant, sporting good, automotive, orthopedic implant, and downhole service applications.In the present study, a self-designed Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy as the research material. Effects of solution and aging heat treatment process of the alloy were studied systemly. High temperature deformation behavior of the alloy was investigated by Gleeblel500, and according to the results of Gleeble1500, rolling high quality plate.The heat treatment of the forging alloy Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe study showed that:the primary alpha meet dissolved into the beta matrix after solution; then after aging treatment, it precipitated a large number of acicular secondary alpha phase which width at the nm level and can significantly improve the mechanical properties from the grain boundaries to the inside of the grain, the best comprehensive mechanical properties is the tensile strength is 1460MPa, and the plasticity is 6% at 800℃ /1h/AC+440℃/8h/AC. Due to a small amount of TiC and TiB particles situ autogenous, it can absorb most of the impact energy, change the crack propagation path and the crack growth rate slowing down seriously in fracture, so the alloy have a high fracture toughness.Thermal simulation results show that:there was no dynamic recrystallization at 740℃ 0.001s-1; there was a numble of dynamic recrystallization at 770-900℃ 0.001s-1. The grain size and volume fraction of the dynamic recrystallization grain continue to rise with the riseing temperatures. A large number of small angle grain boundaries appeared in the thermal deformation process, and the dynamic recrystallization in the nucleation and growth of the small angle grain boundaries from EBSD. Calculated the deformation activation energy Q=219.266KJ/mol, alloy constitutive equation for e= e19.44[sinh(0.00784σ)]3.13exP(-219.3/RT), and make hot processing map, and 770-800℃ and 850-880℃ interval with the maximum dissipation efficacy at 8=0.5.According to the hot working map, the surface quality of the sheet material in the (α+β) phase region and the beta phase region are rolled out. In the (α+β) phase rolling, the grains are finer, and the alpha phase is in the shape of the axial grain. In the β phase rolling, the grains are mainly composed of the grains with dynamic recrystallization. After 800℃ /1h/AC solution+520/8h/AC aging heat treatment, the tensile strength of the sheet material is more than 1400MPa. In addition to the rolling of the dual phase region, the deformation textures are distributed in the{001}.