Time Dependence of Muon Spin Relaxation Rate in Aluminum and Al-1.6%Mg₂Si Alloy

Abstract

Zero-field muon spin relaxation experiments were carried out for Al-1.6%Mg2Si and a pure aluminum in isothermal conditions between 260 and 300 K. Observed relaxation spectra were analyzed to extract the dipole width (D) values which were found to decrease with time after solution heat treatment and quenching. Time variations of D appeared to take place two stages in both samples. The stage transition times (tII) deduced for Al-1.6%Mg2Si were comparable to those for the Si-rich clustering stage reported for Al-Mg-Si alloys. The estimated activation energy of Si-rich clustering was 0.62 (±0.04) eV. The stage transition times (tM) for the pure aluminum were 255, 110 and 82 min after quenching at the measuring temperatures of 260, 280 and 300 K, respectively. An Arrhenius plot of logarithmic tM against reciprocal temperature resulted in an activation energy of 0.19 (±0.06) eV.