Armored titanium alloy TC4, its nominal composition is ti-6al-4v, belongs to (+) two-phase titanium alloy, with the advantages of high specific strength, durable corrosion resistance, small thermal deformation resistance, good dynamic bearing performance, excellent elastic resistance and lower production cost. In recent years, with the development of low-cost preparation technology of titanium alloy, more and more attention has been paid to the field of armor titanium alloy.
It is well known that titanium alloy materials have a variety of microstructure, among which lamellar structure and basket structure are usually characterized by their high fracture toughness and fatigue performance, and isoaxial structure and bistate structure are often characterized by their good plasticity and strong plasticity matching. The heat treatment system plays a decisive role in the microstructure, dynamic mechanical properties and elastic resistance of bistate microstructure titanium alloy under the given thermal-mechanical processing technology. In general, annealing is often used to obtain lamellar and basket tissues, and the near annealing +(+) annealing process is used for the preparation of equiaxed and dimorphic tissues. In recent years, how to precisely control and control the phase structure, phase proportion and phase size of two-state microstructure by means of heat preservation temperature, heat preservation time and cooling rate in double annealing process has become a research hotspot.
The bistate structure of armored titanium alloy TC4 is generally composed of equiaxed phase (40%) and transition region, which is composed of residual phase and secondary phase. Given phase structure, the phase proportion and phase size strongly affect the dynamic mechanical properties and elastic resistance of the two-state microstructure titanium alloy. Titanium alloy material in the preparation of the double annealing process of binary organization, the general process includes: the first close beta annealing process, T beta (10 ~ 50 ℃, insulation 1 ~ 2 h, water or air cooling; The second (alpha + beta) annealing process, 500 ~ 600 ℃, insulation 4 ~ 8 h, air cooling. The ratio of primary equiaxed phase and transition zone in the bistate microstructure can be controlled by the temperature and time of heat preservation in the first near-annealing process, and the cooling rate can directly determine the width of secondary phase in the second (+) annealing process. However, the titanium alloy material to shift by controlling the beta, the proportion of precipitation and secondary lamella alpha beta zone phase morphology of dispersion strengthening classic double annealing heat treatment system, due to the aging heat treatment quenching and alloy steel, aluminum alloy solid solution aging heat treatment in quite a few similarities, make it has been difficult to be fully accurate application in the preparation of titanium alloy material binary organization.
