Evaluation of the thixoformability of 318.1 aluminum alloy

Abstract

Abstract The objective of this study was to evaluate the thixoformability of 318.1 aluminum alloy in terms of its thermodynamic, metallurgical and rheological characteristics. The influence of processing parameters on the microstructural evolution of the alloy in the semisolid state and, consequently, its rheological behavior and thixoformability, were studied. The processing parameters investigated were temperature, heating rate and duration of heat treatment. The study was motivated by the dearth of articles in the literature on the thixoformability of this material in industrial environments. The alloy was first subjected to heat treatment to spheroidize its microstructure and observe the microstructural evolution. Hot-pressing tests were then performed to observe the rheological behavior. Micrographs were used to determine average primary-phase grain size, globule size and shape factor. The results confirmed the material to be suitable for semisolid processing from a metallurgical perspective because of its good morphological consistency. Heat treatment successfully spheroidized the microstructure, giving shape factors as high as 0.62 and primary-phase globule and grain sizes as high as 70 μm and 110 μm, respectively. The apparent viscosity was of the order of 105 Pa · s, which is similar to that of liquid glass according to the literature, indicating very good formability. Little variation in the results was observed, showing the suitability of the material for thixoforming from a rheological perspective.