SOLUTE-VACANCY CLUSTERING IN Al-Mg-Si ALLOYS STUDIED BY MUON SPIN RELAXATION TECHNIQUE

Zero-field muon spin relaxation experiments were carried out with Al-1.6% Mg2Si, Al-0.5% Mg, and Al-0.5% Si alloys. Observed relaxation spectra were compared with the calculated relaxation functions based on the Monte Carlo simulation to extract the dipolar width (Delta), trapping (nu(t)), and detrapping rates (nu(d)), with the initially trapped muon fraction (P-0). The fitting analysis has elucidated that the muon trapping rates depended on the heat treatment and solute concentrations. The dissolved Mg in Al dominated the nu(t) at lower temperatures below 120 K, therefore the similar temperature variations of nu(t) were observed with the samples mixed with Mg. The nu(t)around 200 K remarkably reflected the heat treatment effect on the samples, and the largest nu(t) value was found with the sample annealed at 100 degrees C among Al-1.6% Mg2Si alloys. The as-quenched Al-0.5% Si sample showed significant nu(t) values between 80 and 280 K relating with Si-vacancy clusters, but such clusters disappeared with the natural aged Al-0.5% Si sample.