HIGH-TEMPERATURE THERMAL-DIFFUSIVITY OF NICKEL-BASED SUPERALLOYS AND INTERMETALLIC COMPOUNDS

By means of an installation developed in our laboratory, we measured t he thermal diffusivity (a) as a function of temperature for several si ngle and polycrystal nickel-based superalloys as well as for different intermetallic compounds with a Ll(2) (Ni3Al, Ni3Si, Ni3Ge, Ni3Fe, Zr3 Al, Co3Ti), Ll(0) (TiAl) or B2 (NiAl) structure. In the case of nickel -based superalloys, the experiments pointed out an unexpected but repr oductible slope change in the alpha=f(T) curves at about 750 degrees C , which is not explained at this time. It was shown that the initial m icrostructure, the crystal orientation and the grain size seem to have no noticeable influence on the thermal behaviour. slight variations b etween different alloys were rather attributed to a chemical compositi on effect. In the case of intermetallic compounds the temperature depe ndence of the thermal diffusivity appeared to drastically change from an alloy to an other. Thus, no clear relation could be found between t hermal behaviour, crystallographic structure and strength temperature dependence of these alloys.