Microstructure and thermal-physical properties of hypereutectic Al-Ni alloys

Abstract

The microstructure and thermal-physical properties of Al-xNi (x = 6–25 wt.%) alloys were investigated by experiments first. With the increase of Ni content, the volume fraction and size of the Al3Ni increase significantly, while the morphology has no change. The thermal expansion coefficient (CTE) and the thermal conductivity (TC) decrease at the same time. The CTE of Al-6 wt.%Ni alloy is 20.2 × 10−6/K at 100 °C, decreasing to 15.4 × 10−6/K for Al-25 wt.%Ni, which demonstrates favorable thermal expansion performance. The TC changes from 202.8 W/(m·K) to 103.9 W/(m·K). Besides, the structure and thermal properties of Al3Ni were studied by the first-principles calculation to provide relevant thermodynamic data. The expansion performance was analyzed at the same time, the linear CTE of Al3Ni is 13.82 × 10−6/K at 100 °C. Based on the experiments and first-principles calculations, the modified Turner and general Effective Medium Theory (GEMT) models were used to explain the relationships between microstructure and thermal expansion coefficient, thermal conductivity of Al-xNi alloys.