Effect of Nd content and heat treatment on the thermal conductivity of MgNd alloys

Thermal conductivities of MgNd alloys in as-cast, T4 and T6 conditions with Nd content varying from 0 to 12 wt% were studied at room temperature, and corresponding microstructures observation and hardness tests were performed. The as-cast MgNd alloys consist of α-Mg and Mg12Nd phases, while Mg12Nd dissolves into α-Mg matrix or transforms to Mg41Nd5 after T4 treatment. T6 treated MgNd alloys are composed of α-Mg and Mg41Nd5 phases. With increasing Nd content, thermal conductivities of MgNd alloys all decrease gradually under as-cast, T4 and T6 conditions. The thermal conductivity of as-cast MgNd alloys is higher than that of T4 counterparts, while lower than that of corresponding T6 alloys. For T4 alloys, the changes in slopes of Nd content dependence of thermal diffusivity and hardness all occur around the saturated point 0.68 at.% (3.87 wt%), which result from no more Nd atoms dissolved into the Mg matrix with increasing Nd content. Quantitative studies about the influence of solution atoms and second phases on thermal diffusivity were made. The thermal diffusivity increment derived from one atom percentage of Nd addition into the Mg matrix is about 67.24 mm2/s while the increment derived from one atom percentage of Nd addition forming second phase is about 11.85 mm2/s.