GRAIN-GROWTH IN THE 2-PHASE AL-CU ALLOYS

Grain and phase growth in the two-phase Al-Cu alloys containing 6, 11, 17, 24 and 33 wt% Cu were investigated by annealing at 535-degrees-C for 0.5-100 h. The grain and phase sizes of the kappa phase are seen to be larger than that of the theta phase. The size Of kappa phase decreases whereas the size of theta phase increases with increasing copper content in the alloy. As such, the kappa phase- and grain-size distributions are broader than the theta phase- and grain-size distributions, but the size range depends on annealing time and alloy composition. The grain sizes of the kappa, d(kappa), and theta, d(theta), phases can be related to the volume fraction of the theta phase, f(theta), according to the equation d(kappa) = 0.497 d(theta)/f(theta).