Equal channel angular extrusion of high purity gold

Publication Type:
Journal Article
Citation:
Materials Forum, 2007, 31 pp. 31 - 35
Issue Date:
2007-12-01
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Equal channel angular extrusion (ECAE) has attracted significant research interest in recent years because of its capacity to produce submicron- and nano-grained bulk materials. A high purity (99.99%) gold billet of 10 mm diameter, was processed with up to 9 repeated extrusion passes, using the ECAE technique. Mechanical properties of the extruded gold were determined by microhardness and nanoindentation measurements. It was found that the gold sample was substantially hardened after the 1st extrusion pass, with a microhardness increase from ∼30 HV to ∼60 HV. The hardness continued to increase with further extrusions, but at a lower hardening rate. After 9 extrusion passes, a microhardness of ~80 HV was achieved. Grain refinement of the extruded gold was assessed after the 9 extrusion passes via electron backscattered diffraction (EBSD) analysis. Results of EBSD analysis showed substantial grain refinement in the extruded metal. Grain sizes of the extruded sample were found in the range of 50-350 nm, with an average value of ∼140 nm. A high volume of ∼80% of high angled grain boundaries (>15°), was identified in the extruded material. Orientation distribution of the grains was also investigated, showing no strong textures. Development of weak {110} components was however observed. © Institute of Materials Engineering Australasia Ltd.
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