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

ABSTRACT 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 _1.6 Mg _0.4 P ₂ O ₇ /Al composites through a strain engineering strategy. Under the Al matrix‐induced compressive strain, Zn _1.6 Mg _0.4 P ₂ O ₇ 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 _1.6 Mg _0.4 P ₂ O ₇ 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.