Synthesis of TiAl from Sponge Ti and Chip Al through a Mechanical Alloying-Pulse Discharge Sintering Process

摘要

In order to realize the practical application of TiAl alloys in automobile industry, the possibility of decreasing cost of engine components by applying low-cost and recycled raw materials, in place of expensive elemental powders, was investigated. The TiAl exhaust valves with a relative density of 99 percent were made from chip Al and sponge Ti/Titanium Hydride (TiH_2) through the Mechanical Allying-Pulse Discharge Sintering technique (MA-PDS). The sintered specimens from the sponge TiH_2/cbip-Al system have the same level of fracture strength as those sintered from the powdered Ti/Al system, although the commercial price of TiH_2 is only one third that of Ti powder and the price of chip Al is one sixteenth that of Al powder. XRD results showed that specimens from the TiH2/chip-AI system consisted of duplex phases of TiAl and Ti3 Al, which is identical with that of specimens from the Ti/Al powder system. On the other hand, the specimens from sponge-Ti/chip-Al system with the lowest cost have slightly lower mechanical properties caused by the unexpected coarse Al-rich phase.