Computer-Aided Analysis of Solidification Time and its Effect on Hardness for Aluminium Copper Alloy

Abstract

Aluminium alloys are known for their very good strength to weight ratio. Aluminium alloy finds its applications depending upon the alloying agent/agents added. Among other alloying materials Copper, Silicon, Magnesium are some of the alloying agents which are largely used with Aluminium, as they improve the strength of the alloy without affecting the density when compared to pure Aluminium. Addition of Silicon to pure Aluminium improves the strength of the resulting alloy at room temperature. But at higher temperatures (above 150 ℃) strength of Aluminium–Silicon (Al–Si) alloy is very poor. It is a preferred alloying agent when it comes to casting as the Al–Si alloy shows good casting ability compared to other (alloy without having silicon). But in the present study Copper is used with Aluminium as the major alloying material and silicon is either absent or present only as impurity. Copper addition to the Aluminium improves the alloy strength at room as well as at high temperatures, but at the cost of quality of the cast component. To get good quality, defect-free castings and to improve yield ‘casting simulation software’ can be used which can predict the casting defects virtually. So in the present study effect of adding Copper in the absence of silicon is studied where casting simulation software helped to predict the solidification time and quality of final cast component. Prediction of solidification time for different compositions of alloy gives an idea about the hardness of the alloy. Simulation results from two types of sand castings (spiral shape, step) are compared for their solidification time. The variation in solidification time with variation of copper weight percentage which is 4, 8, 12% for this experiment is studied. It was found that for a fixed composition the solidification results from both types of sand casting (spiral shape and five-step component) are of similar nature. The shop floor casting of the five step component is done and Rockwall hardness for all three compositions tested. Prediction of solidification time and shrinkage defects results obtained through virtual casting process helps in improving process parameters which eventually can help in improving the yield of the component production. Hardness results obtained for different compositions goes well with the type of predicted solidification nature (time) for different shapes of casting for this study.