Effect of particle size on the microstructure and tensile property of the Al-28.5Si alloy prepared by continuous powder extrusion

Abstract

Continuous powder extrusion, a new powder consolidation technology, is used to process alloy powders that are difficult to form. In the paper, Al-28.5Si alloys were successfully prepared by continuous powder extrusion, and the influences of particle size on the microstructure and tensile property have been investigated. In the as-extruded rods, the primary Si phase is dispersed in the α-Al matrix. As the powder size reduces from more than 75 μm to less than 25 μm, the equivalent diameter of the primary Si particles consecutively decreases, but the shape factor increases. Comparing the Si particles in the alloy rod and the powder, it is found that the eutectic Si phase disappears during continuous extrusion. Primary Si particles change from coarse and irregular to round. Specifically, the ultimate tensile strength and elongation at break of the powder-extruded alloy further increase from 211 MPa to 266 MPa and 0.99% to 2.21%. Moreover, the fracture mechanism of alloy rods is the brittle fracture.