Effects of iron precipitation and novel metal screw extrusion on electrical conductivity and properties of AA1370 aluminium

Abstract

In order to develop well-performing aluminium electrical conductors, the role of iron and processing method on electrical and mechanical properties was studied for an AA1370 alloy. Firstly, Ø3 mm cold drawn wires were subjected to a solid solution heat treatment (640 °C/1 h) followed by artificial aging at various temperatures in order to reveal the representative time-temperature-transformation (TTT)-diagram for Fe-rich precipitates. The highest precipitation rate occurred at 450 °C. Secondly, an identical AA1370 alloy was produced by the novel metal continuous screw extruder (MCSE) process into a new Ø3 mm wire. The as produced wire had a recrystallised outer layer and an elongated fibrous structure having a typical 〈0 0 1〉 texture in the center region. TEM investigations revealed Fe-rich precipitates at grain boundaries thus impeding grain growth to some extent. The screw extruded wire processed at 450 °C had a high conductivity (64.2%IACS) while being softer (UTS 65 MPa) than the cold drawn wire (UTS 164 MPa, 61.9%IACS). The correspondence between strength and electrical conductivity for cold drawn and screw extruded wires was compared to literature data for pure and dilute alloys. The screw extruded wire outperformed other alloys as to electrical conductivity, while being among the materials having lowest strength.