Intermetallic compounds in equilibrium with aluminum in Al-Ca-Cu ternary alloying system
(National University of Science and Technology MISiS, 4 Leninsky pr., Moscow 119049, Russia)
Abstract: The structure and properties of the new (Al,Cu)4Ca, Al27Ca3Cu7, and Al8CaCu4 intermetallic compounds in equilibrium with aluminum solid solution in the ternary Al-Ca-Cu alloying system were comprehensively analyzed. The (Al,Cu)4Ca intermetallic compound is treated as a line phase based on the Al4Ca phase with Cu substituted by Al. The solubility of copper in the compound reaches 10 at.% (19 wt.%), which leads to marked changes in the crystal lattice structure, physical and mechanical properties of the compound. For instance, the density of the compound increases from 2.22 to 2.79 g/cm3 and the microhardness from HV 180 to HV 250. The Al27Ca3Cu7 phase is treated as a strict stoichiometric ternary compound with a primitive BaHg11 type crystal structure of the Pm3m space group. The lattice parameter is accepted to be 8.514 ？ corresponding to a density of 3.45 g/cm3. The Al8CaCu4 phase is also a strict stoichiometric ternary compound with a tetragonal crystal lattice structure of the Mn12Th type. The phase has the highest microhardness (HV 505) and density (4.57 g/cm3). The alloys pertaining to the binary (Al)+(Al,Cu)4Ca phase field and the quasi-binary (Al)+Al27Ca3Cu7 section can be considered promising as the base for new natural aluminum matrix composites.
Key words: intermetallics; Al-Ca alloys; microstructure; crystal structure; physical properties; mechanical properties