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.