The effect of Fe content and alloy composition on the mechanical properties and electrical conductivity of Al—Fe system alloys

Анотація

The effect of Fe content (0,6 and 1,5% (wt.)) on the microstructure, electrical conductivity, and mechanical properties of aluminum conductor alloys was investigated. The ingots of Al—0,6Fe—0,2Si—0,15Zr—0,2Ce and Al—1,5Fe—0,6Si—0,15Zr— 0,4Mn alloys were produced using a water-cooled copper mold, which ensures an increased cooling rate of the melt and promotes the formation of a fine-grained ingot structure. Wires were fabricated from the ingots via hot extrusion followed by drawing at room temperature. The resulting wires were annealed at 250 °C for 12 hours (heat treatment, HT). In both the as-cast state and after heat treatment, hardness measurements, electrical resistivity testing, tensile tests, and microstructural analysis using optical and scanning electron microscopy (SEM) were performed. In the as-cast condition, the experimental alloys exhibit a grain structure of an aluminum solid solution with eutectic-origin AlFeSi intermetallics. The distribution, size, and morphology of these intermetallics depend on the alloy composition. The wires produced from the experimental alloys exhibit a fibrous structure. After annealing, no signs of recrystallization were observed. According to SEM analysis, annealing of the Al—0,6Fe—0,2Si—0,15Zr—0,2Ce alloy promotes the formation of rounded AlFeSi(Ce) and AlFeSi particles and increases their quantity. In the Al—1,5Fe—0,6Si—0,15Zr—0,4Mn alloy, the number and morphology of AlFeSi particles remain largely unchanged, with a small amount of Al(FeMn)Si particles detected in the wire. The tensile strength of the Al—0,6Fe—0,2Si—0,15Zr—0,2Ce alloy wire is 150 MPa with 21% elongation, while the Al—1,5Fe—0,6Si— 0,15Zr—0,4Mn alloy wire reaches 170 MPa tensile strength with 22% elongation. The electrical conductivity of the obtained wires, relative to annealed copper (IACS), ranges from 51% to 56%. It was demonstrated that increasing the Fe content to eutectic in Al—Fe alloys enables to obtain a satisfactory level of strength without the addition of costly Ce.

Keywords: Al—Fe conductive alloys, microstructure, mechanical properties, electrical conductivity, intermetallics.