Description of the New Eutectic Al-Ca-Cu System in the Aluminum Corner

Abstract

The structure of the new ternary eutectic Al-Ca-Cu system considered as a replacement for the ternary eutectic system Al-Ce-Cu widely used for additive manufacturing has been studied using experimental techniques. The liquidus projection of the Al-Ca-Cu system in the aluminum corner has been suggested based on experiential studies of the microstructure and phase composition of model alloys. The suggested structure of the diagram has two quasi-binary sections: (Al)-Al27Ca3Cu7 and (Al)-Al8CaCu4 and three invariant eutectic transformations: L→(Al) + (Al,Cu)4Ca + Al27Ca3Cu7 (at 5.6 wt.% Ca, 4.5 wt.% Cu, 595 °C), L→(Al) + Al27Ca3Cu7 + Al8CaCu4 (at 2.2 wt.% Ca, 13.5 wt.% Cu, 594 °C) and L→(Al) + Al8CaCu4 + Al2Cu (at 0.5 wt.% Ca, 34 wt.% Cu, 544 °C). The limit solubility of copper in aluminum solid solution (Al) at 530 °C reaches ~5.1 wt.% in the ternary phase field (Al) + Al8CaCu4 + Al2Cu and drops to ~2.4 wt.% in the (Al) + Al8CaCu4 + Al27Ca3Cu7 ternary phase field. For the example of the model ternary hypoeutectic alloys with a predominant content of the eutectic (Al,Cu)4Ca phase, it has been shown that the system is promising for designing new eutectic-type alloys with a natural composite structure.