Effect of the T6 Heat Treatment on Microhardness of a Directionally Solidified Aluminum-Based 319 Alloy

In this paper, the Al-5.5wt.%Si-3wt.%Cu alloy was elaborated and solidified in a water-cooled horizontal directional solidification device. The as-cast ingot was subjected to the precipitation hardening heat treatment (T6 heat treatment), which consisted of: solution for 5 h at 490°C±2°C, followed by quenching in water at 60°C±2°C and ageing for 3 h at 155°C±2°C, and cooling-air.

Secondary dendrite arm spacing (λ2) measurements were carried out before and after T6 heat treatment. The mechanical strength of the alloy was investigated by the microhardness test. It has been found that the heat treatment did not influence the λ2 values, however, highest HV values have been observed for the heat-treated samples.