Effects of Al addition on the structure and mechanical properties of Zn alloys

Abstract

The noticeable improvement of hardness, elongation and yield stress in the cast zinc alloys was achieved using aluminium inoculation. Through varying the addition level of this eutectic-forming solute (aluminium), the mechanism of such property improvement of cast Zn alloys was investigated. The increase of hardness, elongation and yield stress was very sensitive to the aluminium content due to grain-refinement and solid-solution strengthening. Beyond the maximum solubility of aluminium in zinc, a three-dimensional eutectic network was developed to form a “eutectic-skeleton”, which produced further reinforcement in yield stress and elongation, but only marginal enhancement in hardness. These improved mechanical properties are found to be closely associated with significant microstructural refinement. The microstructural refinement, i.e. the columnar-to-equiaxed transition and the reduction in grain sizes, was mainly elucidated in terms of the Interdependence theory.