Effect Of Heat Treatment And Hot Deformation Parameters On Microstructure And Mechanical Property Of Ti-20Zr-6.5Al-4V Alloy

Titanium and titanium alloys are of great importance in aerospace, energy, metallurgy,military, medical, chemical, offshore oil exploration and other aspects because of exceptional strength-to-weight ratio, high harden-ability, adequate ductility, excellent corrosion resistance and high-temperature resistance. However, the wear resistant property of Titanium alloy is poor, which greatly limits the further development of titanium alloys in the aerospace aviation. Adding Zr elements to design a series of new Ti Zr Al V alloys,these alloys exhibit excellent mechanical properties. Ti-20Zr-6.5Al-4V alloy was the optimal composition. In this dissertation, investigating effect of heat treatment and hot deformation parameters on microstructure evolution and mechanical properties of Ti-20Zr-6.5Al-4V alloy, which in order to obtain the appropriate properties of the alloy by controlling the heat treatment and hot deformation parameters.The results showed that, Ti-20Zr-6.5Al-4V alloy consisted of a duplex phase α? + βmicrostructure after solution treatment. With decreasing solution treatment temperature from 850 to 1000?C, the amount and size of α? phase gradually decreased, the size of βphase increased. After aging treatment, Ti-20Zr-6.5Al-4V alloy was composed of a large amount of α phase and a small quantity of β phase. With increasing solution treatment temperature from 850 to 1000?C, the amount of α phase and the bulk β phase decreased,while the amount and the size of acicular α phase increased. The solution-treated specimens had the excellent ultimate compressive strength and elongation, while the yield strength was slightly low. When the solution treated alloy was subjected to aging, the yield strength and ultimate compressive strength significantly increased, while the elongation obviously decreased compared with that of the solution-treated specimens.The Ti-20Zr-6.5Al-4V alloy was deformed at different deformation parameters to obtain different weight percentages of α and β phase. With increasing deformation temperature, the size of α phase increase. With increasing cooling rate, the content of αphase gradually decreased. The deformation can inhibit β â†' α phase transformation. With increasing cooling rate and deformation degree, the hardness of alloys increased.