PCT No. PCT/GB91/01286 Sec. 371 Date Mar. 8, 1993 Sec. 102(e) Date Mar. 8, 1993 PCT Filed Jul. 30, 1991 PCT Pub. No. WO92/02655 PCT Pub. Date Feb. 20, 1992.The mechanical properties of aluminium alloy extrusion in a specified transverse direction are improved by upsetting the extrusion billet in at least one direction chosen with reference to the specified transverse direction. For example, the extrusion billet may be of generally circular cross-section with one or two opposite segments arising. The extrusion may be subjected to thermomechanical treatment and/or vibration treatment. A preferred final thermomechanical treatment is also described.
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