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

With an aim of obtaining aluminum PIM materials strengthened by solid solution of Mg and dispersion of transition metal compounds, Al-8mass%Fe, Al-8mass%Mn, and Al-8mass%Mn-2mass%Cr alloys were rapidly solidified with varied Mg additions of 0, 4 and 8 mass%. Rapid solidification (RS) was performed by gas atomizing the alloy melt and by subsequent splat-quenching on a rotating water-cooled copper roll. The RS flakes were consolidated to the PIM materials by 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 PIM materials were examined by tensile test at room and elevated temperatures. Uniform dispersion of intermetallic compounds was observed in all the extruded PIM 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 PIM materials containing Mg 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.