Softening-Hardening Mechanism in the Direct Hot-Extrusion of Aluminium Compacts
Powder compacts from two different commercial aluminium powder grades have been densified by direct hot extrusion. The extrusion runs have been carried out at 425 °C, with an extrusion ratio of 1:16 and a ram speed of 1.5 mm/s. Prior to extrusion, some green compacts were presintered (500 °C). The evolution of the extrusion load during the process and the hardness of the final products have been investigated. Additionally, microstructural characterization by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD) was carried out in order to understand the softening-hardnening mechanisms taking place during the process. The obtained results evidence grain refinement. Additionally, inter-metallic precipitation, dynamic recovery and geometric dynamic recrystallization take place depending on the composition of the powder, the heat treatment before extrusion and the strain involved in the process.
Duk Yong Yoon, Suk-Joong L. Kang, Kwang Yong Eun and Yong-Seog Kim
C. Zubizarreta et al., "Softening-Hardening Mechanism in the Direct Hot-Extrusion of Aluminium Compacts", Materials Science Forum, Vols. 534-536, pp. 837-840, 2007