Mechanical properties and electrical conductivity of ultrafine-grained aluminum consolidated by high-pressure sliding

Abstract

High-pressure sliding (HPS) was successfully applied for consolidation of aluminum powders at room temperature. A full densification was attained by the HPS processing under 2 GPa through 3 mm sliding (equivalent strain of 2.3). The consolidated samples showed ultrafine-grained structures with average grain sizes of ~0.85 μm and ~1.0 μm for the powder sizes of 45 μm and 75 μm, respectively. When the consolidated samples were annealed at a temperature in the range of 473–673 K, grain growth was significantly reduced by the presence of oxide particles originated from the surface layers on the powders. The hardness and tensile strength increased with increasing imposed strain and decreased with annealing but they remained higher in the consolidated samples than that in the bulk sample. The electrical conductivity increased with straining and saturated to a value of 50%IACS in a manner similar to the density. The strengthening mechanisms were evaluated in terms of particles dispersions as well as grain refinement. This study demonstrates that the HPS processing provides a useful approach to consolidate metallic powders into bulk form for application of electrical wires with higher tensile strength and enhanced thermal stability.