Thermal Analysis, Barothermal Treatment, Microstructure, and Properties of an Al–2.5 at % Ca Binary Alloy

An Al–2.5 at % Ca binary alloy is thermographically studied by differential scanning calorimetry at atmospheric pressure and by differential barothermal analysis at a moderately high argon pressure of ~100 MPa. The baric coefficients of the solidus and liquidus temperatures of the alloy (7.5 × 10–2 and 11 × 10–2 K/MPa, respectively) exceeding the baric coefficient of the melting temperature of pure aluminum (6 × 10–2 K/MPa) are found. Barothermal treatment of the alloy is carried out at a subsolidus temperature of 615°C and a pressure of 100 MPa for 180 min. The alloy microstructure is studied. The size distribution of Al4Ca intermetallic particles with an average equivalent diameter of ~2.9 μm is established. High porosity of the alloy is revealed. Data on an exponential pore size distribution and on the average pore diameter (~220 nm) are obtained. A model of pore formation as a result of severe generation of dislocations and their subsequent coagulation is proposed. The mechanical properties of the binary alloy are found to be low due to the significant pore density in the material.