For any time of solution heat treatment and artificial aging up to 8 h at 160 1C and 170 1C, the Brinell hardness values are low (Fig. 10). This is attributed to the slow speed of coherent precipitate formation [17]. Higher temperatures promote the diffusion mechanisms and the precipitates formation, causing the alloy hardening (Fig. 10). Fig.10 shows that samples heat treated at 540 1C and later aged at 180 1C, presented the highest hardness values. The maximum hardness value obtained in this work (125 HBW) corresponds to the sample solution heat treated at 540 1C through 15 min. This value does not differ significantly to which performed by Möller [5] on the A356 alloy, performed in semisolid state, with longer times of solution heat treatment. From Fig. 10 it may be observed that the hardness values decrease slightly increasing the time of solution heat treatment. Furthermore, the aging temperature decrease involves longer times of aging heat treatment.