Wide Temperature Zero Thermal Expansion in Al Matrix Composites with High Thermal Conductivity

Lightweight Al composites enhanced with negative thermal expansion (NTE) materials exhibit ultra-low temperature sensitivity, offering substantial promise for high-precision and aerospace applications. However, most strong NTE reinforcements driven by abrupt phase transitions tend to present a narrow operation window, limiting the realization of wide-range zero thermal expansion (ZTE) behavior in the composites. Herein, this critical challenge is addressed in the Zn_1.6Mg_0.4P₂O₇/Al composites through a strain engineering strategy. Under the Al matrix-induced compressive strain, Zn_1.6Mg_0.4P₂O₇ exhibits a broad uniform NTE response spanning 80°C, contrasting sharply with its inherent narrow NTE temperature window (20°C). As a result, the composite with 35 vol.% Zn_1.6Mg_0.4P₂O₇ achieves high-performance ZTE (0.90 ppm/°C) across 25-80°C. Meanwhile, due to the high content of the Al matrix with high thermal conductivity, this ZTE material exhibits excellent thermal conductivity (80.9 W·m^-1·K^-1) compared with the ZTE alloy Invar (12.8 W·m^-1·K^-1). In situ neutron powder diffraction, Raman spectroscopy, and X-ray diffraction characterizations demonstrate that the wide and gradual volume shrinkage in the NTE phase is attributable to strain-driven structural transformations. This work presents a simple yet effective approach for homogenizing the performance of NTE materials and holds great potential for facilitating the practical applications of specialized NTE materials.