The Heat Treatability of High Conductivity, Moderate Strength Al-Fe-Ni-Mg-Si Alloys

The Al-Ni-Fe-Mg-Si system has castability, electrical and thermal conductivity, and mechanical properties that are suited to modern aerospace and transportation applications. The heat treatability of Mg and Si alloying additions have been well documented due to their high solubility (17.4 wt.% and 1.65 wt.%, respectively), favourable intermetallic phases, and improved castability. The low solubility of Fe and Ni in solid state Al (0.052 wt.% and 0.04 wt.%, respectively), result in alloys with Fe and Ni intermetallic phases that minimally reduce electrical and thermal conductivity. The addition of elements with high and low solubility creates a dynamic alloying system that responds well to heat treatment. Three compositions were heat treated using solutionizing (530-620 °C for 2-8 hours) only, aging (150-300 °C for 1-4 hours) only, and solutionizing (530-620 °C for 2-8 hours) and aging (150-300 °C for 4 hours) treatments. Microhardness and electrical conductivity were assessed to determine changes in microstructure. Additionally, statistical analysis was used to determine the statistical significance of each heat treatment step. Heat treatments with significant and positive results were used for tensile samples to determine their effect on strength and elongation. The Al-Ni-Fe-Mg-Si alloys demonstrated good response to heat treatment, microhardness values ranging from 55-75 HV, and electrical conductivity ranging from 42-52 IACS%.