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Hot deformation of 7050 aluminium alloy with coarse elongated grains has been investigated by tensile tests conducted at 340 and 460°C and the strain rate of 10 × 10–4–10 × 10–1 s–1. When the 7050 aluminium alloy was conducted at 460°C and 10 × 10–2 s–1, the maximum elongation of 273% is achieved and large plastic deformation was carried out at an almost constant stress. The microstructure evolution under the deformation condition is characterised using OM, SEM, EBSD and TEM in detail. The results show that the microstructure evolution is realised by continuous dynamic recrystallisation in coarse grains. The increase in misorientation is proportional to the increase in the true strain, and the k value, the increasing rate of average misorientation angle, is 157°. The primary hot deformation mechanisms of the 7050 aluminium alloy are localised grain boundary sliding and dislocation gliding, which can increase the grain boundary misorientation continuously. [ABSTRACT FROM AUTHOR]

Abstract: Both gravity casting and squeeze casting were carried out previously on an aluminium alloy (LM6) and a zinc alloy (ZA3) with different casting temperatures. Tensile, impact and density measurement were conducted. It was found that generally, samples taken from the bottom of the squeeze casting mould gave higher tensile strength, higher impact strength and higher density values. This study was carried out to determine the effect of solidification time on the mechanical properties of the castings. Two analytical methods were used: a steady-state heat flow model and Garcia''s virtual model. It was found that similar results were obtained with both analytical methods. Casting samples taken from the lower part of the squeeze casting mould were found to have a significantly shorter solidification time. For both types of alloys, it was found that generally the shorter the solidification time of the casting, the higher is its density, impact energy, yield strength and ultimate tensile strength (UTS). This study had therefore contributed to a better understanding of the mechanical properties obtained previously from different casting processes. [Copyright &y& Elsevier]