Thixoforging of Al-3.8% Si alloy recycled from aluminum cans

Thixoforging is an offshoot of the thixoforming process and consists of shaping a partially molten alloy into a die similarly as in a conventional forging process. However, thixoforging is carried out in solid fractions higher than 0.5 (1>fs>0.5). The aim of this work was to develop a new Al-Si alloy suitable for forming processes in the semi-solid state (SS) from recycled aluminum cans with the addition of commercially pure silicon. In this study, a new recycled aluminum alloy was created from aluminum cans with 3.8% of Si. An important aspect in the SS process is the globular microstructure, which confers relevant mechanical properties when compared to the same alloy with a dendritic morphology. The new alloy was preconditioned by thermomechanical heat treatment (THT) similar to a well-known thermomechanical method, the strain-induced melt-activation (SIMA). Samples were solution heat-treated at 530 °C for 4 h, quenched in water, and rolled at 350 °C. The influence of the solid fraction and of the soaking time in semi solid state before thixoforging on the strength behavior of the thixoforged parts was evaluated. For all thixoforged specimens, solution heat-treatment followed by artificial aging (T6) was performed. The technique allowed us to obtain parts with tensile strength up to 334 MPa and maximum elongation of 14%. These results are consistent with other thixoformed alloys obtained from processes that use raw materials with higher purity and they show, in a practical way, that it is possible to create recyclable alloys for applications in the automotive industry.