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Carolina R. Barbosa,Gabriel H. Machado,Hugo M. Azevedo,Fernando S. Rocha,José C. Filho,Arielly A. Pereira,Otávio L. Rocha 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.3
In this work, solidification and T6-heat treatment experiments were performed with the Al7Si0.3Mg alloy in order to investigatethe effect of processes parameters on the microstructure and microhardness (HV). A directional solidification devicewas used, and the solidification thermal parameters investigated were the growth and cooling rates (VL and TR). The heattreatment applied was the T6 (T6-HT), under the following conditions: solution treatment for 3 h at 520 ± 2 °C, followed byquenching in warm water (70 ± 20 °C), aging for 1, 2, 3 and 4 h at 155 ± 2 °C and air-cooling. The microstructure observedin both as-cast and T6-heat treated samples is composed of a primary phase consisting of an Al-rich dendritic network andsecondary eutectic phases, located within the interdendritic regions, formed by Si and Mg2Siparticles and Fe-intermetallicphases. The dendritic microstructure was characterized by secondary dendritic spacing (λ2) and, for both investigated samples,a single mathematical expression was proposed on the λ2 dependence with the position in the ingot. Spheroidized-likeeutectic Si particles have been found in both analyzed samples for finer microstructures. Elements quantitative and qualitativemicroanalysis by SEM/EDS as well as HV measurement at the dendritic and interdendritic regions attest to the effectivenessof the T6-heat treatment. It is highlighted in this work that mathematical expressions have been proposed to characterizethe HV dependence on aging time.