Mechanical properties and thermal stability of Al-23Si-8Fe-1Cr and Al-23Si-8Fe-5Mn alloys prepared by powder metallurgy

Al–23Si–8Fe–1Cr and Al–23Si–8Fe–5Mn (in wt%) alloys were prepared via melt centrifugal atomization following powder compaction by uni-axial pressing at 6 GPa and 450 °C for 60 min. The obtained materials were porosity-free with good particle-to-particle contact. The “composite-like” microstructures were very fine, showing silicon particles distributed in an α-Al matrix and displaying nearly equiaxed intermetallic phases. The intermetallic phases were identified as β-Al5FeSi and α-Al9.3FeMn1.4Si1.8 in the Al–23Si–8Fe–1Cr and Al–23Si–8Fe–5Mn alloys, respectively. The Vickers hardness and compressive yield strength were 182 HV5 and 540 MPa, respectively, for the Al–23Si–8Fe–1Cr alloy and 197 HV5 and 650 MPa, respectively, for the Al–23Si–8Fe–5Mn alloy. The thermal stability of the alloys was studied by mechanical testing after long-term annealing at 300–400 °C, by compressive testing at 200–300 °C and by creep testing at 300 °C and 250 MPa. The thermal stability of both alloys was significantly better when compared to the “thermally stable” casting Al–12Si–1Cu–1Mg–1Ni alloy that is commonly utilized in the automotive industry for thermally loaded components such as pistons for combustion or diesel engines.