STRUCTURE AND THERMAL OXIDATION PROPERTIES OF RuAl AND Ru-Al-Ti ALLOYS PREPARED BY MECHANICAL ALLOYING

In this study, RuAl, Ru(0.9)AlTi(0.1), Ru(0.75)AlTi(0.,25) and RuAlTi compounds were prepared by mechanical alloying. The structure of these compounds was studied by X-ray diffraction (XRD). Their oxidation behaviour at high temperature was investigated by thermogravimetric analysis (TGA). Mechanical alloying between Ru and Al was complete after 10 h of milling, leading to a B2-type RuAl structure. Upon prolonged milling, the lattice parameter of the RuAl phase decreased linearly with time, which is due to the incorporation of Fe atoms coming from the erosion of the steel milling tools. Single-phased Ru(0.9)AlTi(0.1), Ru(0.75)AlTi(0.25) and RuAlTi alloys with a B2-type structure were obtained after 15 h of milling. Comparative TGA experiments on as-milled RuAl and RuAlTi samples revealed that the addition of Ti in the B2 structure of RuAl reduces the onset oxidation temperature from 395 to 351 degrees C. After an annealing treatment at 1100 degrees C in Ar atmosphere, both samples exhibited almost similar oxidation behaviour with a onset oxidation temperature around 450 degrees C.