Aluminum/Calcium Deformation Metal-Metal Composites After Conversion to Al2Ca Intermetallic Reinforcement

Deformation-processed metal-metal composites (DMMCs) provide an appealing approach for producing lightweight materials with high strength and high conductivity. DMMCs can be produced by powder metallurgy and severe plastic deformation resulting in nano-filamentary reinforcement. Al/Ca composites with monolithic construction have shown promise as next-generation overhead transmission conductors. Previous research has shown that these materials tend to form various intermetallic species when exposed to elevated temperatures resulting in the degradation of properties. This study examines the effect of using a reduced loading of Ca and intentionally converting the reinforcement to an intermetallic species to produce a material with enhanced high-temperature stability while retaining superior performance properties. Al/Ca (11.5 vol.%) composites were produced and converted to Al/Al2Ca (18 vol.%) by heat-treatment at 260°C. In addition to the effect of reinforcement material, the influence of filament spacing was studied. The transformation to Al2Ca was analyzed by differential-scanning calorimetry and scanning electron microscopy. Tensile strength and electrical conductivity were investigated for unconverted and converted materials as well as samples that had undergone extended heat treatment. The measured material properties were used in line sizing calculations to determine the benefits of using these composites for high-voltage direct-current transmission.