Development of microstructure during extrusion of rapidly solidified Al–7Mg–2Cr powder alloy
作者:
DashwoodR. J.,
SheppardT.,
期刊:
Materials Science and Technology
(Taylor Available online 1992)
卷期:
Volume 8,
issue 5
页码: 455-467
ISSN:0267-0836
年代: 1992
DOI:10.1179/mst.1992.8.5.455
出版商: Taylor&Francis
数据来源: Taylor
摘要:
AbstractA study has been performed on an Al–7Mg–2Cr (wt-%) rapidly solidified alloy as a candidate for engineering applications requiring low density and high strength. The objective of the work was to investigate the development of microstructure during extrusion with respect to the consolidation conditions used and this was achieved by employing a combination of X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The rapidly solidified powder was found to be cellular in structure with drastic segregation of magnesium during solidification, which resulted in a heterogeneous distribution of magnesium rich intermetallics in the as atomised condition. However, it was observed that the atomisation process had successfully prevented the formation of coarse chromium containing intermetallics. Owing to the stability of a ternary chromium containing phase at the lower consolidation temperatures used (450°C) the severity of this inhomogeneity was reduced and the desired homogeneous distribution of chromium rich intermetallics in a magnesium rich solid solution was produced. The mean dispersoid diameter increased with extrusion temperature, as did the volume fraction of dispersoids, this being a result of the rapid increase in the diffusivity of chromium in aluminium over the temperature range employed for consolidation. Owing to a high dispersoid density, the substructure formed by dynamic recovery during deformation was refined, with the extruded material exhibiting subgrains of the order 0·4–1·0μm mean diameter. The consolidation temperature that yielded the optimum microstructure was found to be 500°C.MST/1488
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