Microstructure and Mechanical Properties of 7075 Al Alloy Consolidated from a Premixed Al-Zn-Mg-Cu Powder by Hot Extrusion

摘要

This study examined the processing of 7075 Al alloy by hot extrusion of a premixed powder. To this end, a premixed Al-Zn-Mg-Cu powder, Alumix 431D, was uniaxially cold pressed at 600 MPa into cylindrical compacts 25 mm in diameter and 15 mm thick. Subsequently, the green compacts were subjected to a presintering heat treatment (heating to 400 °C and holding at 400 °C for 20 min, followed by heating to 525 °C and soaking at this temperature for 45 min). Extrusion of the powder compacts was performed at deformation temperatures of 370 °C, 425 °C, and 490 °C using an extrusion ratio of 25:1. The presintering heat treatment resulted in a high degree of alloy development prior to extrusion. No porosity was present in the microstructures of the extruded alloys. The extrusion temperature had significant effects on the mechanical properties of the consolidated materials. The optimum temperature for the extrusion of presintered Alumix 431D powder compacts was determined to be 425 °C, which resulted in a superior combination of mechanical properties for the extruded alloy.