Thermal conductivity in yttria dispersed copper

The impact of yttria particles incorporated by Friction Stir Processing (FSP) on the thermal conductivity (TC) and Coefficient of Thermal Expansion (CTE) of copper is reported. Thermal properties of samples with or without powder were investigated for the temperature ranges between 40 and 240 C as a function of the number of FSP passes. The reduction of CTE in the samples without powder is attributed to the decrease of the grain size during FSP. CTE values are rather close at the lower temperatures i.e., 40–80 C, but, as the temperature rises to higher values there is a clear distinction between pure copper and samples with a modified microstructure. An impressive 27% reduction in the CTE was observed for a sample with uniformly distributed yttria particles in copper (i.e.; 9 passes with yttria) in comparison to pure copper. Thermal conductivity at 240 C are slightly higher for the copper modified 3 passes and 9 passes with yttria powder when compared to pure copper. It was found that distribution of yttria particles in the copper matrix play a significant role in stabilizing the microstructure and hence reduce the CTE with no loss in thermal conducting ability of copper.