Development of Innovative Ti Alloy Compacts through Powder Metallurgy

Ti-6Al-4V is the most common Ti alloy and has been used in various industrial fields including aerospace and power plant because of their high tensile strength, high fatigue strength and light weight. However, their low thermal conductivity, high hardness and low Young’s modulus make them difficult to produce the complicated shapes via machining. On the other hand, metal injection molding process offers net shape production, high design flexibility, and high cost efficiency, which is useful for forming the materials with poor workability such as Ti alloys. In our previous studies, the injection molded Ti-6Al-4V alloy compacts were improved the properties by addition of third elements such as Cr and Mo, and they showed high tensile strength and high elongation comparable to wrought materials. However, the fatigue strength was significantly lower than that of wrought materials. In order to improve the fatigue strength of injection molded Ti-6Al-4V alloy compacts, refining of microstructure was treated by addition of 3rd & 4th elements including TiB2 powders and also heat treatment. Eventually, we obtained the same fatigue strength as that of wrought materials. In addition, the relationship of grain size and fatigue strength showed good agreement with Hall-Petch relations