Abstract
Research and /or Engineering Questions/Objective:
The elastic property of lightweight structural materials is very important because their elastic modulus determines stiffness and NVH properties of structural parts. Especially, the elastic modulus of aluminum is much lower than modulus of steels and cast irons, so we must modify the design and the weight reduction effect from material replacement is limited. In this point of view, it would be beneficial to develop the aluminum alloys with higher elastic modulus which has both advantageous properties; lightweight and high strength. Therefore, the objective of this study was to develop high elastic aluminum alloy for casting using elastic prediction and in-situ reaction.
Methodology:
High elastic alloys can be designed by distributing or precipitating reinforcements with higher stiffness. Because their stiffness will be determined mainly by the volume fraction and elastic constants of each reinforcement phase, the prediction of these principal parameters enables “smart design” to tailor elastic properties with minimized experimental effort. Computational materials science can provide a solution to predict the intrinsic physical property as like elastic modulus. In this study, a methodology was proposed to predict the elastic properties of high elastic aluminum alloys by combining the CALPHAD method, first-principles calculation, and elasticity models. The in-situ process was used to ensure good matrix-to-reinforcement compatibility and microstructure homogeneity. The effect of this alloy design concept was verified by the experimental method as like phase analysis and resonant ultra sound spectroscopy. And the various properties and formability of the developed alloy were evaluated.
Results:
The computational methodology in this study could obviously provide a reliable way to design the elastic properties of candidate alloys in the development of Al alloys and Al-based composites. In order to design for high elastic aluminum cast alloy, the following things were considered such as the elastic property of reinforced phases, the wettability and the dispersion in molten Al, and the control of microstructure and fluidity for casting. The final design concept for high elastic aluminum cast alloys was proposed using the effects of TiB2, Al3Ti, and Si. The chemical composition was optimized for increasing the amounts of TiB2 and Al3Ti, and the in-situ process was used to ensure good matrix-to-reinforcement compatibility and microstructure homogeneity. The young’s modulus of proposed alloy was improved to 20% than commercial aluminum cast alloys. In the casting of automotive part, the fluidity of developed alloys was equal to commercial alloy and the enhanced and uniform elastic property was confirmed.
Limitations of this study:
In order to apply for the automotive parts, the high elastic Al alloys should have the applicability to the current casting process. So this developed alloy should be equal with commercial alloy in the fields of fludity, uniformity and scale-up. What does the paper offer that is new in the field in comparison to other works of the author: In the view points of parts, this is new approach to overcome the limitations of current Al alloys focused on only their low density and mechanical properties. The high elastic alloy design was considered using computational science and the in-situ reaction was considered with current manufacturing process. Conclusion: New aluminum alloys having 20% enhanced elastic modulus, equal mechanical properties and applicability for current casting process could be developed. These characteristics can improve the stiffness and NVH properties of parts, minimize the design modification and enhance the weight reduction effect.
KEYWORDS – Elastic modulus, Casting, In-situ process, Computational material science, Aluminum