アルミニウム中のＭｇの５２３Ｋ以下での平衡固溶度

Abstract

By annealing at 423 K for more than 10 Ms, the resistivity at 77 K, ρ77, in 92% cold rolled Al-3.18 at%Mg alloy decreased beyond a calculated value based on 2.5 at%Mg, the previously reported equilibrium solubility. Therefore, it is obvious that this 60 years old solubility data was overestimated. Aluminum alloys containing 3.18 to 8.91 at%Mg were isothermally annealed at temperatures of 423 to 523 K for longer than 864 ks with measuring ρ77. Through plotting the resistivity values versus annealing time t to the power of – 1/3 and extrapolating to the t−1/3=0, the resistivity after infinite period annealing, ρ77∞, in equilibrium state was estimated. Because the ρ77∞ increased with Mg content, the ρ77∞ values were plotted versus total Mg content and were regressed linearly. Equilibrium solid solubility at each temperature was estimated on the plots as intersections of the regression lines and the formerly determined relation between solute Mg concentration and ρ77. The obtained equilibrium solid solubility of Mg below 473 K is lesser than the previous values. Temperature dependence of the solubility is expressed as ln(X⁄0.385)⁄1−2X=1.948−2230⁄T, where X is atomic fraction of equilibrium solute Mg concentration. The equilibrium solubilities obtained from the above equation are 0.73 at% at 373 K, 1.54 at% at 423 K, 2.83 at% at 473 K and 4.73 at% at 523 K.