Additives and thermal treatment influence on microstructure of nonferrous alloys

Abstract

Although Zn alloys are a very widely used material, there is a need for investigations concerning the influence of thermal conditions on its microstructure and its properties, which makes it useful for the specific tasks it has to fulfil for mass-produced items manufactured by the metalworking industry, in the automotive industry, as well as in countless electronic components. One of the possibilities is to create finer microstructures and enhance their properties, to change their chemical composition by adding alloying additives, and inoculation using modifiers. So in this paper, investigation results are presented concerning the influence of chosen alloying additives, such as Sr, Ce and Ti-B on the measured and calculated thermal characteristics and microstructure of zinc alloys with the addition of aluminium and copper. Based on the results on the phase and chemical composition of the cast Zn-Al-Cu alloys, inoculated with Sr and Ti-B, no differences were detected in the phase composition of the investigated alloys, owing to changes in cooling rates, which were chosen for the sample cooling process. A small amount of added cerium caused the occurrence of new phases present in the microstructure. Modification of the Zn-Al-Cu alloy precipitates changes in the thermomorphology of the phase and the 'tweed' type changes in the microstructure. Moreover, the addition of cerium causes a decrease in the temperature at the beginning (T L) and the end of the solidification, as well as the occurrence of a multicomponent eutectic, which can be detected on the derivative curve.