Coordinated deformation and high formability mechanisms of 7A36 aluminum alloy by Sc micro-alloying and low-frequency electromagnetic casting

Abstract

The influence of low-frequency electromagnetic casting (LFEC) and Sc addition as variables on the microstructure, properties, and deformation behavior of 7A36 aluminum alloy has been systematically examined. The results have predicted that the LFEC could make the grains of the as-cast alloy finer by electromagnetic stirring and forced convection. By the addition of Sc, the average diameters of the equiaxed grains have been reduced and the intensity of the fiber texture has become weakened. The fine and continuous η′ precipitates on the grain boundaries (GBs) instead of the coarse large-sized discontinuous η′ precipitates, which results in a more uniform distribution of plastic deformation and which is beneficial for improving plasticity. By adding Sc and applying LFEC, the large size η′ internal grain precipitated phase decreased slightly. The fine nano-sized Al3(Sc, Zr) phase particles were dispersed in the matrix. As the dislocation movement had to travel less distance, that's why this process consumed less energy. These features also reduced the strain difference within the grain and near the grain boundary, which result in the increase of EL. The excellent mechanical properties of 7A36 aluminum as extruded plates were obtained when it was aged at 120 °C for 8 h by Sc micro-alloying and applying LFEC. The yield strength (YS) and ultimate tensile strength (UTS) remained at 738.3 MPa and 767.0 MPa, respectively, while the elongation (EL) to failure 6.5% is increased by 160% than the value of direct chill casting.

Keywords

• Micro-alloying Sc
• LFEC
• Microstructure
• Properties
• 7A36 aluminum alloy