Development of Low Expansion and High Strength Aluminum Matrix Hybrid Composite

An aluminum (Al) matrix hybrid composite reinforced with yttrium tungstate (Y₂W₃O₁₂) and aluminum nitride (AlN) is synthesized by high energy ball milling followed by compaction and sintering. Y₂W₃O₁₂, a negative thermal expansion material (−7.1 × 10⁻⁶/K), is chosen as one of the reinforcements to lower the coefficient of thermal expansion (CTE) of the composite. AlN is added to the composite in order to improve the strength and thermal conductivity of the composite. X-ray diffraction patterns of the milled powders as well as sintered composites reveal the presence of only Al, AlN and Y₂W₃O₁₂ peaks indicating no chemical reaction between the matrix and reinforcement during milling and sintering. The scanning electron micrograph shows fairly uniform dispersion of reinforcement in the matrix. Hardness, elastic modulus and CTE are measured by Vickers hardness test, nanoindentation test, and dilatometry, respectively. It is observed that a composite with high hardness, high Young’s modulus and low CTE can be obtained by adding 15 wt% AlN and 30 wt% Y₂W₃O₁₂ into the Al matrix.