Tensile properties of some zinc-based alloys comprising 27.5% Al: effects of alloy microstructure, composition and test conditions

This paper deals with tensile properties of a few zinc–27.5% Al based alloys under varying material composition (wherein copper has partially been replaced through nickel/silicon/nickel plus silicon) and microstructural features. The effects of: (i) strain rate at room temperature; and (ii) test temperature at a typical strain rate on the tensile (strength and elongation) properties of the alloys have also been studied. Tensile properties improved with strain rate irrespective of the alloy composition/microstructure. On the contrary, the tensile strength deteriorated with temperature while elongation followed a reverse trend. In general, the nickel/silicon-free alloy attained highest strength and elongation under all the test conditions except at the maximum test temperature. This was followed by those of the nickel containing alloy while the presence of silicon/silicon plus nickel also deteriorated the property at lower temperatures. However, alloying with nickel/silicon/nickel plus silicon caused the strength of the alloy system to become less temperature sensitive. The study suggests that it is quite possible to develop a variety of zinc-based alloys with different combinations of mechanical properties through compositional/microstructural modifications. The (partial) replacement of copper through nickel and/or silicon imparts thermal stability to the alloy system. The behaviour of the alloys has been discussed in terms of the specific nature of their constituent phases whose contribution towards governing the overall performance of the alloys greatly depends on the test conditions. The view has also been substantiated through the features of the fractured surfaces and subsurface regions of typical samples.