A Model Describing Solidification Microstructure Evolution in an Inoculated Aluminum Alloys
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A Model Describing Solidification Microstructure Evolution in an Inoculated Aluminum Alloys Yan Song1,2 · Hongxiang Jiang1,2 · Lili Zhang1 · Shixin Li1,2 · Jiuzhou Zhao1,2 · Jie He1,2 Received: 18 May 2020 / Revised: 18 August 2020 / Accepted: 30 August 2020 © The Chinese Society for Metals (CSM) and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A population dynamics-cellular automaton (PD-CA) model is developed to describe the microstructure formation in an inoculated Al alloys. The model involves the dynamics behaviors of the inoculated particles and the nucleation, initial spherical growth of nuclei as well as the subsequent dendritic growth. The model was validated by using the experimental results for the Al-Cu alloys inoculated by Al–Ti–C refiner first, and then used to simulate the detailed solidification process in an inoculated Al–Cu alloy. The results indicate that the TiC is not stable in Al melt. The heterogeneous nucleation process consists of two stages: a very short initial stage dominated by the cooling rate and the later stage dominated by the number of the active TiC. It stops at the very moment the recalescence occurs. The average grains size d of the aluminum alloys a⋅exp(t∕60⋅ln(C0 ∕w)) inoculated by the Al–Ti–C refiner can be calculated by d(μm) = (𝜈 ⋅t)1∕3 w1∕3 + b⋅ln1∕2t where Q is the growth restriction cool
Q⋅vcool
factor, C0 (%) is the initial solutes composition, w (%) is the additive amount of Al–Ti–C refiner. t (min) is the holding temperature time since the Al–Ti–C refiner is added into the melt. a and b are the constants. Keywords Grain refinement · Nucleation · Dendritic growth · Simulation · Solidification
1 Introduction Grains refinement of alloys promotes the formation of the equiaxed solidification microstructure with the low casting defects and thus endows the castings with good mechanical properties [1–3]. Chemical inoculation by using Al–Ti–B or Al–Ti–C refiner has been widely applied in improving the solidification microstructure [4–7]. Efforts have been made since the 1970s to achieve an in–depth understanding of the solidification microstructure formation process in the inoculated aluminum alloys. Maxwell and Hellawell [8] proposed a model about the heterogeneous nucleation of α–Al nuclei Yan Song and Hongxiang Jiang are contributed equally to this work. * Jiuzhou Zhao [email protected] 1
Shi‑changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China
2
based on the classical nucleation theory. Greer et al. [9] proposed a free-growth theory to calculate the heterogeneous nucleation rate of α-Al in an aluminum alloy inoculated by TiB2 particles. Easton and St. John [10, 11] developed the empirical formulas to predict the grains size of inoculated aluminum alloys. In 2010, Qian et al. [12] proposed a model to calculate the constitutional supercooling-drive
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