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 Al2Cu (theta) for the 0.59% Mg alloy and Al(5)Cu(2)Mg(8)si(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 B 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. (c) 2006 Elsevier Inc. All rights reserved.