Thermally stable Al–Fe–Mn-based alloy prepared by centrifugal spraying and hot die forging

Abstract

An Al–8Fe–5Mn (wt%) alloy was prepared by a unique method combining centrifugal spraying with hot die forging. The rapidly solidified semi-product was prepared by pouring the melt onto a rapidly rotating graphite disc. The semi-product was then compacted by die forging at a temperature of 550°C. The structure, mechanical properties and thermal stability of the alloy were investigated. The investigated alloy was compared to a commercial casting Al–12Si–1Cu–1Mg–1Ni alloy (EN AC-48000), which is used in high temperature automotive applications. The preparation method produced a compact pore-free material. A very fine intermetallic phase Al6(Mn,Fe) was detected in the structure, which was found to primarily impact the thermal stability of the material. Thermal stability tests (400°C, 100h) showed that the hardness of the investigated alloy dropped from approximately 90 to 80 HV (11%) and the yield strength from 210 to 195MPa (7%). The hardness of the commercial alloy dropped from 110 to 55 HV (50%) and the yield strength from 330 to 150MPa (55%). At high temperatures, the yield strengths of the Al–8Fe–5Mn alloy and the commercial casting alloy were comparable – the yield strength at 400°C was 75MPa for the former and 78MPa for the latter. The combination of centrifugal spraying and die forging was also found to be a suitable processing route for aluminium alloys with high iron content.