Ductilization of a powder metallurgy Al-17 wt pct Cu by means of channel-die compression and extrusion

Metal powders always contain a surface oxide layer, which is particularly tenacious in aluminum alloys. After hot pressing, this oxide coats the particle boundaries and reduces the ductility. In this article, a study of the Al-17 wt pct Cu alloy densified from rapidly solidified powder is presented. Different thermomechanical treatments were investigated to improve the ductility of this material. Channel-die (CD) forging was performed at two temperatures (430 °C and 500 °C). Eight compression runs were applied to the samples in each CD treatment. At 430 °C, three strain values per run were investigated (35, 50 and 70 pct). A bar was also extruded with a 40:1 ratio. Because of the small size of the samples, the ductility was assessed by means of the ring expansion test and analyzed by post mortem (fracture surface and cross section) observations. No ductility was measured after CD compression at 430 °C, although it appears from the fracture surface observations that increasing the strain per run has a beneficial effect. The CD compression at 500 °C and extrusion were both successful at promoting ductility, extrusion being more effective.