The relationship between resistivity and temperature in ordered alpha(2)-Ti3Al and gamma-TiAl intermetallic compounds single crystals

The temperature dependence of the resistivity of ordered alpha(2)-Ti3Al and gamma-TiAl intermetallic compounds single crystals with various compositio ns have been measured from 4.5 to 1120 K. The changes of resistivity and te mperature coefficient of resistivity with the composition in Ti-Al system a re investigated. It has been found that the ordered alpha(2)-Ti3Al intermet allic compounds single crystals have a large resistivity and show a negativ e temperature coefficient of resistivity with small absolute value, while t he ordered gamma-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 sy stematically. There is a local maximum value near alpha(2)-Ti75Al25 composi tion and a minimum value near gamma-Ti50Al50. In the composition range of 1 0 similar to 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 v ery small electron mean free path and the ratio of the number of total cova lence electrons to the number of total valence electrons. This kind of allo y, with a large resistivity (larger than 200 mu Omega . cm), a small temper ature coefficient of resistivity in a wide temperature range (4.5 similar t o 1120 K) and good linearity in resistivity-temperature curve, can be devel oped into precision resistance alloys used in the environment of high tempe rature, oxidation or corrosion. (C) 1999 Elsevier Science S.A. All rights r eserved.