Mechanical Properties of Powder Metallurgy Extruded Al Based Composites Using Sheath

Abstract

The effects of extrusion and dispersed particles (SiC or SiO₂) on the mechanical properties are examined on aluminum (Al) based composites prepared from powder metallurgy. Extrusion is effective for i) grain refinement of the α-Al matrix and ii) producing high quality bulk specimens on a large scale. This is because of a high applied stress during hot-extrusion contributes to the degradation of oxide films covering the powder particles, leading to the creation of new real surfaces. Microstructural observations show that powder-based extruded Al and its composites have fine-grained structures, i.e., an average grain size of less than 5 μm in the α-Al matrix. Accordingly, associated to these microstructures, they show higher strength (~30 MPa) and hardness (~10 Hv) than those of cast Al and its composite. In addition to beneficial mechanical properties, the extrusion process does not give a negative impression as for wear property, i.e., the wear rate. Plasticity-controlled void growth mechanism is focused to consider the impact of extrusion on bonding quality. The time required to shrink voids is estimated, and this value is consistent with the actual processing duration.