Effect of hafnium addition on wear resistance of zinc-aluminum 5 alloy: A three-dimensional presentation
Advanced Materials Letters,
2017, Volume 8, Issue 9, Pages 910-915
AbstractZAMAK 5 alloy is known to solidify in a large grain dendritic structure, which negatively affects its mechanical properties and surface quality. It is therefore of prime importance to reduce its grain size in order to overcome these drawbacks. In this paper, the effect of addition of hafnium (Hf) on the microstructural and mechanical characteristics of ZAMAK 5 alloy has been investigated. An amount of 0.10 wt.% Hf was introduced to the starting alloy using the well-established microalloying technique. The microstructural examination revealed that addition of Hf transformed the large grained dendrites into fine grains, which turned to increase its hardness number by 2.5% and slightly enhance its both yield and fracture stresses. The wear resistance was determined using a pin-on-disc test at different loads, speeds and time periods and the mass loss results of both alloys, before and after Hf addition, were compared with each other. The results indicated that ZAMAK 5 possesses better performance against wear at minimum speed, load and time (23.4m/min., 5N and 15min). Whereas, the Hf-containing alloy showed 42% improved performance against wear at severe experimental conditions of 153.5 m/min., 20N and 60min. The cumulative mass loss results were presented by three dimensional graphs in terms of speed, time and load, which indicated that the mass loss is a function of the three parameters. However, the graphs did not specify the most influential factor on the wear behaviour of both alloys. Full factorial design of experiments was used to identify the effect of parametric interaction on the cumulative mass loss of tested specimens and accordingly the speed was considered to be the main factor. The grain refined alloy is recommended to work under reduced speed and load conditions for prolonged service life.
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