MECHANICAL-PROPERTIES OF EXTRUDED RAPIDLY SOLIDIFIED AL-FE-CE - EFFECT OF ASPECT RATIO AND POST-EXTRUSION ROLLING

Recent advances in rapid solidification technology have resulted in th e development of aluminium alloys for elevated temperature application s as a suitable replacement for titanium based alloys. Processing of t hese alloys is an important step in developing optimal properties for elevated temperature use. One such approach is the study of the aspect ratio (width/thickness) effect in extrusion. In the present investiga tion, gas atomized Al-6.7w/oFe-5.9/oCe powder was extruded into rectan gular slabs of aspect ratio approximate to 5:1. For comparison, axisym metric extrusion (aspect ratio 1:1) was carried out under identical co nditions. The room temperature and elevated temperature mechanical pro perties were evaluated for both die geometry extrudates. The rectangul ar bars were 'straight' and 'cross' rolled in the ''hot'' condition. M icrostructural characterisation was performed using transmission elect ron microscopy and textures were quantified using X-ray diffraction. T he microstructure was homogeneous in the rectangular bar extrudates co mpared to the axisymmetric round bars due to an improved dispersoid di stribution. The straight rolled material exhibited a texture consistin g of the ''Copper'' and ''S'' components whereas the Gross rolled prod uct exhibited predominantly the ''Brass'' component with other compone nts such as {110}<2 $($) over bar$$ 23>. The observed texture differen ces were explained on the basis of the Dillamore and Roberts model. Th e rectangular bar extrudates do not show an improvement in mechanical properties because texture differences offset the advantage provided b y the improved dispersoid distribution.