Abstract
The goal of this research was to investigate the influence of zinc and magnesium on the fluidity of Al-Zn-Mg alloy. The fluidity test was carried out using a serpentine-shape sand mould. The length of the serpentine-shape pattern was 180 cm. The experiment was designed by varying the compositions of zinc from 1 to 5 wt%, and magnesium from 0.5 wt% to 2.5 wt%. Variation in compositions of the two elements was done separately, and later a combined variation in compositions of zinc and magnesium was investigated. The superheat temperature was placed at 70ºC above the liquidus temperature. From the results obtained, it was observed that there was general increase in fluidity when the percentage weight composition of magnesium was increased. Alloy with 2.3 wt% Mg was found to have the highest fluidity, followed by alloy with 2.85 wt % Mg. When the percentage weight compositions of zinc were increased, there was a general decrease in fluidity of the Al-Zn-Mg alloy, in which alloy with 5.14 wt % zinc recorded the lowest fluidity of 57.1 cm as compared to the as-cast alloy. Also for the combined variation in compositions of zinc and magnesium, it was discovered that there was decrease in the flow length of the alloy, where alloy with 5.14 wt% Zn and 2.85 wt% Mg combined has flow length of 59.8 cm. But the reduction in fluidity length when the composition of zinc was varied was more drastic as compared to that of the combined alloying elements.
Highlights
The increasing demand of light weight, high strength cast alloys has triggered a substantial increase in the world production of aluminium alloy castings in the past two decades [1]
3 Results and discussion 3.1 Effect of Zinc on the Fluidity of Al-Zn-Mg Alloy The result in Fig. 1(a) shows the percentage variation of the weight of Zinc from 1.54 wt% to 2.85 wt% Zn in the Al-Zn-Mg alloy and it was observed to have a flow length of 62.8 cm, which indicates a decrease in fluidity length by 3.2 % as compared to sample A (1.54 wt % Zn) which has a fluidity length of 64.9 cm
This decrease in fluidity when the percentage weight of zinc was increased could be as a result of change in solidification mode that occurred in the Al-Zn- Mg alloy
Summary
The increasing demand of light weight, high strength cast alloys has triggered a substantial increase in the world production of aluminium alloy castings in the past two decades [1]. The industrial demand of thin-wall castings in aluminum alloys is of great importance in order to produce light components. The production of thin wall castings is limited by the fluidity of the molten metal. The castability/fluidity is an important feature since it limits the wall thickness that can be successfully filled [2]. In addition to properties and part performance, castability has become an important parameter in the development of aluminium cast alloys. Melt fluidity is one of the critical properties influencing castability of an alloy and is affected by many variables [3].
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