Thermal conductivity of Ni3(Si,Ti) single-phase alloys

Thermal conductivities of Ni3(Si,Ti) single-phase alloys with an L12 structure as functions of composition and temperature were measured to provide information for high-temperature structural applications. It was confirmed that the Ni3(Si,Ti) alloy has an extremely large single-phase region for the compositions Ni78(Si22-x,Tix) (x = 0-12 at.%), Ni89−y(Si11,Tiy) (y = 9.5-12 at.%), and Ni89−z(Siz,Ti11) (z = 9.5-12 at.%). The thermal conductivities at 293 K of all the Ni3(Si,Ti) single-phase alloys were estimated to be between 8 W/mK and 12 W/mK, which are lower than those of almost all other stoichiometric compounds. In the Ni3(Si,Ti) single-phase region, the thermal conductivity increased more significantly by increasing the Ni content than by varying the Si and Ti contents. The thermal conductivity of all the Ni3(Si,Ti) single-phase alloys increased monotonically with an increase in temperature. The temperature coefficient of thermal conductivity increased as the value of the thermal conductivity at 293 K was low, according to Mooij's relationship. Consequently, the thermal conductivity in the Ni3(Si,Ti) single-phase region became larger and less sensitive to the composition at higher temperatures above 1073 K, ranging between 22 W/mK and 24 W/mK.