TEM microstructural characterization of melt-spun aged Al–6Si–3Cu– xMg alloys

Three Al–6Si–3Cu– xMg alloys ( x = 0.59, 3.80 and 6.78 wt.%) were produced using melt-spinning. As-melt-spun ribbons were aged at 150, 180 and 210 °C for times between 0.05 and 100 h. Microstructural changes were examined using transmission electron microscopy (TEM) and microhardness was measured. TEM analysis of the as-melt-spun alloys revealed 5 nm nanoparticles and larger particles (50 nm) composed of Al 2Cu ( θ) for the 0.59% Mg alloy and Al 5Cu 2Mg 8Si 6 (Q) for 3.80% and 6.78% Mg alloys. Silicon solid solubility was extended to 9.0 at.% and Mg in solid solution reached 6.7 at.%. After aging treatments the 6.78% Mg alloy exhibited the most significant increase in microhardness, reaching 260 kg/mm 2. TEM analysis of aged specimens also showed θ and Q phase (5–20 nm nanoparticles and 35–40 nm particles). The combination of the volume fraction and size of the particles plays an important role in microhardness variation.