Reduced ductility of 6XXX series aluminium alloys at high-temperatures and intermediate strain rates

Abstract

The hot ductility of Al-1.00mol% Mg-0.86mol% Si alloy with an average grain size of approximately 50 μm was investigated. At temperatures of 773 K and above, the hot ductility shows a local maximum value in the low and high strain rate ranges and shows a local minimum value in the intermediate strain rate range. In the low strain rate range, a large elongation of over 300% is obtained owing to grain boundary sliding (GBS), and in the high strain rate region, a high ductility of over 200% is obtained by a deformation mechanism called solute drag creep (SDC). The local minimum value (of the hot ductility in the intermediate strain rate range) is observed in the transition region of the GBS and SDC. In this paper, the hot ductility loss in the intermediate strain-rate range is discussed from the viewpoint of the high-temperature deformation mechanism and observation of the microstructure.