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

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, 100 h) showed that the hardness of the investigated alloy dropped from approximately 90 to 80 HV (11%) and the yield strength from 210 to 195 MPa (7%). The hardness of the commercial alloy dropped from 110 to 55 HV (50%) and the yield strength from 330 to 150 MPa (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 75 MPa for the former and 78 MPa 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.