Solute-Vacancy Clustering In Al-Mg-Si Alloys Studied By Muon Spin Relaxation Technique

Abstract

Zero-field muon spin relaxation experiments were carried out with Al-1.6%Mg[2]Si, 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 (Δ), trapping ([ν[t]]), and detrapping rates ([ν[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 [ν[t]] at lower temperatures below 120 K, therefore the similar temperature variations of [ν[t]] were observed with the samples mixed with Mg. The [ν[t]] around 200 K remarkably reflected the heat treatment effect on the samples, and the largest [ν[t]] value was found with the sample annealed at 100°C among Al-1.6%Mg[2]Si alloys. The as-quenched Al-0.5%Si sample showed significant [ν[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.