Microstructure And Properties Of In-situ Tib Whisker Reinforced Ti60 Alloy Composites

TiBw/Ti60 composites with a uniform network microstructure were fabricated by in situ reactive hot processing by the system of Ti60 and TiB₂ powers. Thermodynamic analysis was used to predict the chemical reactions within the blended powders between Ti60 and TiB₂ during the sintering process. The microstructures of the composites were studied with XRD and SEM. The tensile properties of composites at both room and high temperatures were measured. The composites were rolled and heat treated, and the effect of rolling and heat treatment on microstructure and properties of the composites was investigated.Thermodynamic analysis results showed that TiB whisker reinforced TMCs could be prepared based on the in stitu chemical reaction between Ti and TiB₂.The volμme fraction could be changed by adjusting the content of TiB₂. Microstructure analysis results showed that TiB is rodlike whisker, which distributed around the boundaries of Ti60 matrix particles as-received. The TiB whisker subsequently formed into network structure. Furthermore, it can be clearly seen that TiB whiskers grew toward the inside of neighboring Ti60 powders like dowels pins inducing a strong bonding between neighboring Ti60 particles.It was believed to be beneficial to the strength and ductility of the composites.The research showed that sintering temperatures, the volμme fraction of TiBw and the heat treatment will have iMPact on the microstucture of TMCs. The sintered composite materials will get dense at 1300℃. The microstructure of matix contained equiaxedαphase and lamellarαphase, and it was also found that when the volμme fraction of TiBw increase,"sand-grey"layer was formed in the network microstructure, which is bad for the mechanical properties of the TMCs. When the TMCs was rolled and quenched at 950℃, the microstructure was typical tri-modal which includes equiaxedαand lamellarα, andβtramsforming phases. When the quenched TMCs was aged at 500℃for 2 hours, it had more equiaxedαphase, but when the quenched TMCs was aged at 600℃, it had just thick lamellarαphase without equiaxedαphase.Mechanical properties testing results showed that, coMPared to unreinforced Ti60 alloy, the tensile strength and especially the high temperature tensile strength of the TiBw/Ti60 composites were greatly improved, and even their elongations were improved. 5vol. % TiBw/Ti composites has a better room temperature mechanical properties. The room temperature ultimate tensile strength (UTS) of the quenched composites was increased by 25.6% than that of unreinforced Ti60 alloy and the elongation of composites was 12.8%, better than unreinforced Ti60 alloy which is 11%. 8vol. %TiBw/Ti60 has a better high temperature mechanical properties. At 600℃, The UTS reached 1124MPa, increased by 60.57% than that of alloy. The elongation reached 15.4%, a little better than that of alloy. At 700℃, The UTS reached 746MPa, increased by 30% than that of alloy, it means that the operating temperature of 8vol. %TiBw/Ti60 is 100℃higher than Ti60's.