Characterization of Screw Extruded Rapid Solidified AA6061

Abstract

By using rapid solidified aluminium as feedstock and a novel extrusion method, i.e. screw extrusion, it is possible to extrude aluminium continuously. Due to rapid solidification, the base material can have small grain size and super saturated solid solution in the as cast condition. Since consolidation of rapid solidified granules and particles is an inherent part of the screw extrusion process, conventional consolidation by compaction is redundant. This will give the possibility to extrude a high strength profile with less process steps than used commercially today.In this study commercially rapid solidified AA6061 is screw extruded at 530°C. The effects of post extrusion heat treatments are documented by microstructure analysis (OM, SEM) and strength (HV1, tensile tests) of the extruded profiles. Six different heat treatment procedures were conducted, e.g. two different T5 and four different T6 conditions.The results show that this process can give high strength even though the process is not fully optimized. The results from this work indicate that the age hardenability on T5 depends a lot on the quenching rate prior to extrusion. It is found that the solid solution heat treatment (SSHT) and age hardening both have positive and negative effect on microstructure and strength.