Effect of Mg additions on the structures and mechanical properties of rapidly solidified Al-transition metal alloys

For the purpose of obtaining aluminum P/M materials strengthened by solid solution of Mg and dispersion of transition metal compounds, Al-transition metal alloys with or without addition of Mg were rapidly solidified. Al-8 mass%Fe, Al-8 mass%Mn, and Al-8 mass%Mn-2 mass%Cr alloys were rapidly solidified with 0, 4 and 8 mass%Mg. Rapid solidification (RS) was performed by gas atomizing the alloy melt and subsequent splat-quenching on a rotating water-cooled copper roll under an argon atmosphere. The RS flakes were consolidated to the P/M materials by cold pressing and hot extrusion. Metallographic structures and constituent phases were studied for both RS flakes and P/M materials by optical microscope, TEM and X-ray diffraction. Mechanical properties of as-extruded P/M materials were examined by tensile test at room and elevated temperatures. Uniform dispersion of intermetallic compounds was observed in all the extruded P/M materials. Added Mg was present as the solute in all the P/M materials except for Al-Mg-Mn-Cr alloy in which solute Mg content decreased due to formation of the ternary compound Cr2Mg3Al18. The P/M materials containing Mg generally exhibited higher hardness and strength at room temperature, than those without Mg. It was considered that both solid solution of Mg and dispersion of intermetallic compounds were contributing the hardness and strength increase in the rapidly solidified Al-Mg-transition metal alloys.