粗大化した結晶粒より成るＡｌ‐４ｗｔ％Ｃｕ合金の機械的性質に及ぼす溶質偏析の影響

Abstract

Al-4wt% Cu alloy ingots with solute segregation were produced by iterative casting with seed, and their structures and mechanical properties were measured. The grain size increased with the iterative casting, and the ingot after the 4th iterative casting consisted of almost one grain. The primary arm spacing λp and the secondary arm spacing λs had relations with the cooling rate V and the local solidification time θ; λp[mm]=0.17·υ-0.56[K/S], and λs[mm]=0.015·θ0.29[S]. These agreed well with the previous results for alloys consisting of columnar grains or equiaxed grains. The yield strength σy, the ultimate tensile strength UTS and the elongation of 4th ingot decreased with primary arm spacing λp. After heat treatment, there was no dependence of σy and UTSL (parallel to primary arms) on the spacing λp, but UTST (perpendicular to primary arms and parallel to secondary arms) and the elongation varied with λp. These results imply that σy and UTSL are largely affected by the solute segregation, and UTST and the elongation are largely affected by cavities and micro-cracks created during solidification.