Prediction of Secondary Dendrite Arm Spacing in Directional Solidification of Aluminum Alloy by Casting Simulation and Micro-structural Inspection 2019-26-0166
KEYWORDS: Secondary Dendrite Arm Spacing, Cooling Rate, Solidification Time, Casting Simulation, Microstructural Inspection
In Automobile industry, many of the powertrain components (like engine head and cylinder block) are manufactured by a casting procedure. Secondary Dendrite Arm Spacing (SDAS) is one of the most important microstructural features in dendritic solidification of alloys during the casting process. SDAS has a significant influence on the mechanical behavior of the cast components. Mechanical behavior and fatigue life of a cast component can be improved by controlling the casting parameters to maintain a lower SDAS value. SDAS is dependent on various casting parameters like chemical composition of the alloy, solidification time/cooling rate and liquid melt treatment. During industrial casting of an alloy with predefined chemical composition, solidification time/ cooling rate during the mushy zone becomes the dominant parameter for controlling SDAS. The objective of this study is to predict the SDAS of die cast Al-Si alloy samples subjected to different solidification rates based on varying mold temperature. The SDAS is predicted from a casting simulation first using the empirical relations of its dependency on cooling rate and solidification time. The predicted SDAS values are then compared with the experimental results, obtained from the microstructural inspection of the cast samples. It is observed that the predicted SDAS are in good agreement with the inspected values. This study also shows an increasing trend of SDAS values with the reduction in cooling rate. The approach described in this study can be used to predict the fatigue property of a cast aluminum component based on the size of SDAS without any destructive fatigue failure testing.
Nilankan Karmakar, Pankaj Jha, Sudipto Ray, Neeraj Carpenter, Akshay A., Virupakshappa Lakkonavar, Michael Nienhuis
General Motors Technical Center India, General Motors Global Propulsion System
Symposium on International Automotive Technology 2019