A novel Al-Si-Ni-Fe near-eutectic alloy for elevated temperature applications

A novel near-eutectic Al-15.0Si-4.1Ni-1.9Fe (wt%) alloy with a ternary eutectic reaction of Liquid→α-Al+Si+(Al,Si)5(Fe,Ni) was investigated. Eutectic Si and (Al,Si)5(Fe,Ni) phases exhibit short nanoscale fibrous morphologies with volume fractions of 14.3 ± 1.6% and 15.1 ± 1.9%, respectively. The (Al,Si)5(Fe,Ni) phase has a tetragonal Al2.7FeSi2.3-type crystal structure with excellent thermal stability, which contributes to high mechanical properties at room and elevated temperatures. First-principles density-functional theory (DFT) calculations reveal its chemical composition of tetragonal (Al4.75Si0.25)(Fe0.5Ni0.5) having Si solution at the Al sites with two Fe neighbours contributes to the lowest solution energy. The newly developed alloy has superior mechanical properties at room and elevated temperatures compared with other typical heat-resistant aluminium alloys, which has great potential for industrial applications.