Improved dimensional stability of zero-thermal-expansion Cu2P2O7/ZL101 composite by thermal treatment

Abstract

Compositing negative-thermal-expansion materials with Al is an effective strategy for obtaining light zero-thermal-expansion (ZTE) materials. However, the dimensional stability of those composites is not guaranteed due to the residual stress generated during fabrication and the microstructure instability of the matrix. Here, we studied the effects of heat treatments on the dimensional stability of ZTE Cu2P2O7/ZL101 composite (with 32 vol. % of ZL101) prepared using the pressure infiltration method. Compared with the as-cast case, after a certain heat treatment (water quenching after holding at 773 K for 1 h, then aging at 463 K for 8 h, and finally thermal-cold cycling between 463 and 77 K for three times), the dimensional stability was improved by a factor of 20 and the coefficient of thermal expansion (CTE) was highly reproducible in the subsequent temperature cycles test. The treated composite exhibits a CTE of −0.028 ppm/K at 240–305 K and a relatively high thermal conductivity of 29.5 W m−1 K−1 at room temperature, leading to a thermal distortion parameter well less than those of other ZTE materials. The improved dimensional stability and the CTE reproducibility can be attributed to the stabilization of matrix microstructure and the greatly relaxed residual stress as revealed by the analysis of 2θ-sin2ψ based on x-ray diffraction.