Microstructure and mechanical properties of hierarchical multi-phase composites based on Al-Ni-type intermetallic compounds in the Al-Ni-Cu-Si alloy system

Systematic microstructural investigations of a series of Al81Ni13-xCuxSi6 alloys with x = 0, 3, 5, 8, and 10 at.% revealed that addition of Cu leads to a change of the primary intermetallic compound from Al3Ni to Al3Ni2. Moreover, Cu addition induces a multi-phase composite microstructure consisting of dual primary phases (Al3Ni2+ alpha-Al) and a eutectic matrix. The eutectic matrix is transformed from (alpha-Al+Si) eutectic to (alpha-Al+Al2Cu+Si) eutectic. In course of the microstructural evolution, the mechanical properties are enhanced, and the Al81Ni5Cu8Si6 alloy exhibits optimized room temperature mechanical properties such as an increased yield strength of similar to 600MPa and a remarkably improved fracture strain of similar to 15% due to similar lattice parameters and crystal structures of the constituent phases. The large macroscopic plastic strain is attributed to a combination of impeded crack growth and wavy propagation of shear bands in the intermetallic compounds. (C) 2018 Elsevier B.V. All rights reserved.