Characterization of a refractory Ti-Al-Si-Zr alloy

A novel refractory alloy produced in the Institute for Problems of Materials Science, Kiev, Ukraine, has been characterized. The composition of the alloy is Ti-6Si-SAl-7Zr (wt.%) with a specific density of 4.6 g/cm(3). The powder particles produced from this alloy by the plasma rotating electrode process (PREP) are spherical in shape with a very small variation in size (the average particle size was about 350 mu m). The particles have a dendritic microstructure and consist of three phases, disordered alpha-Ti, ordered Ti3Al and ordered Ti5Si3. The Ti5Si3 phase is stable on heating up to 1100 degrees C while disordering of the Ti3Al phase occurs near 1000 degrees C. Tensile properties of the cast alloy were studied at temperatures in the range of 20 degrees C to 800 degrees C. The yield strength and tensile strength of the cast alloy are higher than those of a gamma-TiAl-based alloy. The fracture toughness of the alloy is about 17-20 MPa root m within the temperature range of 20 degrees C to 600 degrees C. The oxidation resistance of the alloy was significantly superior to conventional titanium alloys, being similar to that of a silicon nitride ceramic at temperatures up to 950 degrees C. The results obtained suggest that the alloy could potentially be used in high-temperature engine applications up to 800 degrees C.