Simulation of microporosity formation in modified and unmodified A356 alloy castings |
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Authors: | Julie Huang James G Conley T Mori |
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Affiliation: | (1) Department of Mechanical Engineering and Material Science and Engineering, Northwestern University, 60208 Evanston, IL |
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Abstract: | In order to comprehensively model both the performance and inspectability of early design stage safety critical aluminum castings,
the size, shape, and location of defects such as pores should be determined by simulation. In this article, a two-dimensional
(2-D) model to predict grain size, pore size, pore morphology, and location is presented. The proposed model couples hydrogen
gas evolution and microshrinkage pore formation mechanisms with a grain growth simulation model. The nucleation and growth
of grains are modeled with a probabilistic method that uses the information from a macroscale heat transfer simulation to
determine the rules of transition for grain evolution. Microshrinkage pores and the combination of microshrinkage and gas
pores are addressed. The proposed model and postprocessing can provide direct simulated views of the microstructure of the
solidifying casting. In the present work, the effect of Sr modifier and hydrogen content on pore size and morphology for equiaxed
aluminum alloy A356 is modeled. The simulation results correlate well with the experimental observation of cast structures
and other published data. In addition, Sievert’s law and the conditions for spontaneous growth of a gas pore are derived from
first principles in the Appendix. |
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Keywords: | |
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