The relationship between resistivity and temperature in ordered α2-Ti3Al and γ-TiAl intermetallic compounds single crystals

The temperature dependence of the resistivity of ordered α2-Ti3Al and γ-TiAl intermetallic compounds single crystals with various compositions have been measured from 4.5 to 1120 K. The changes of resistivity and temperature coefficient of resistivity with the composition in Ti–Al system are investigated. It has been found that the ordered α2-Ti3Al intermetallic compounds single crystals have a large resistivity and show a negative temperature coefficient of resistivity with small absolute value, while the ordered γ-TiAl intermetallic compounds single crystals have a large value of resistivity too, but show a positive small temperature coefficient of resistivity. The resistivity in Ti–Al system changes with Al content systematically. There is a local maximum value near α2-Ti75Al25 composition and a minimum value near γ-Ti50Al50. In the composition range of 10∼80 at.% Al, the temperature coefficient of resistivity of the system is less than 10−3 K−1. The above phenomena may be related to the very small electron mean free path and the ratio of the number of total covalence electrons to the number of total valence electrons. This kind of alloy, with a large resistivity (larger than 200 μΩ · cm), a small temperature coefficient of resistivity in a wide temperature range (4.5∼1120 K) and good linearity in resistivity-temperature curve, can be developed into precision resistance alloys used in the environment of high temperature, oxidation or corrosion.