Aluminum-Matrix Natural Composite Material Based on the Al–Ca–Ni–La–Fe System

Abstract

The primary crystallization concentration region of the aluminum solid solution (Al) is refined using computational analysis in the Thermo-Calc program, including the construction of liquidus surfaces and polythermal sections of the Al–Ca–Ni–La–Fe system, as well as experimental microstructural analysis using scanning electron microscopy. This region can be considered promising for the formation of new aluminum-matrix natural eutectic-type composite materials containing above 20 vol % of intermetallic particles in the structure. The investigation into the microstructure of a promising composition with the formula, wt %, Al–4Ca–2Ni–1La–0.6Fe revealed that it contains up to 23 vol % of Al4Ca and Al9FeNi intermetallic phases of a eutectic nature according to the calculation. Separate crystals of these phases in the eutectic composition have submicron sizes, notably, a length of 250–400 nm and a thickness of 100–200 nm. It is also established that no formation of the Al4La intermetallic phase predicted by the thermodynamic calculation is observed, while lanthanum itself is completely dissolved in the Al4Ca calcium-containing phase. An analysis of the microstructure and hardness during stepped annealing has shown that codoping of the Al–4Ca–2Ni–1La–0.6Fe alloy by zirconium and scandium (0.2% Zr and 0.1% Sc) leads to precipitation hardening due to the decomposition of the (Al) solid solution and further formation of coherent nanoparticles of the L12 phase—Al3(Zr, Sc) up to 20 nm in size. The results of studying the mechanical properties under uniaxial tension testing of cylindrical castings of the Al–4Ca–2Ni–1La–0.6Fe–0.2Zr–0.1Sc alloy show a relatively high level of strength characteristics (σв of 265 MPa and σ0.2 of 177 MPa) with the conservation of the elongation acceptable for the composite material (~2%). Thus, it is shown based on these results that the Al–Ca–Ni–La–Fe system is promising for the fabrication of new aluminum-matrix natural composite materials.