Effects of phase transitions upon some physical properties of the compound Ti3Al and its alloys

Abstract

1 At 150°C and in the temperature ranges 250–350 and 500–650°C the physicomechanical properties of the compound Ti3Al and its alloys vary with temperature in an irregular manner. In view of the fact that these anomalies exhibit no hysteresis on heating and cooling and also that the high-temperature modification cannot be preserved in an overcooled condition, the phenomena observed may be regarded as manifestations of isomorphic tr ans for mations. 2 The nature of the isomorphic transformations taking place in the compound Ti3Al and its alloys in the temperature ranges 250–350 and 500–650°C is linked with changes in the SWASC in the titanium and aluminum sublattices and s(p)⇄d electron exchange between the atoms in the aluminum and titanium sublattices during the thermal excitation of their outer electron subshells. 3 The variation of the physical properties of the compound at temperatures above 800°C is attributable to the nucleation of regions with a degree of long-range orderη<1, which ends at a temperature close to 1080°C with the polymorphic transformationα2 phase→β solid solution.