Tempering treatments T4, T5 and T6 have been applied after thixoforming to investigate the effects of heat treatment on microstructure and mechanical properties of thixoformed wrought aluminium alloy 2014, a 'modified' 2014 and high strength casting aluminium alloy 201. The 'modified' 2014 was a simplified version of 2014 with composition (wt%) Cu 3.87, Mg 0.6 and Si 0.14. The results showed that standard solution time for conventional wrought alloy 2014 (1 h at 500degreesC) gave incomplete homogenisation of thixoformed material. Longer times (5 and 17 h) at 500degreesC are required for complete solutionisation of CuAl2. Low hardness values in the as-thixoformed 2014 were increased by subsequent heat treatment. After 18 h ageing at 160degreesC, the hardness of material solutionised for 5 and 17 h is higher than that for the standard 1 h. The tensile properties of the thixoformed 2014 were improved and close to those of forged 2014 using optimised post-forming heat treatment (solution treatment for 17 h at 500degreesC followed by water quenching and then ageing for 24 h at 160degreesC). Thixoformed alloy 201 in the standard T6 condition (2 h at 513degreesC followed by 17 h at 527degreesC and water quenching and then ageing 20 h at 153degreesC) showed a significant improvement over permanent mould casting. Good elongation to fracture (19.6%) was found for thixoformed 'modified' 2014 in the T6 condition. (C) 2004 Kluwer Academic Publishers.