Numerical simulation of microstructure evolution during directional solidification of Ti-45at.%Al alloy

Kuangfei, Wang; Guo, Jifeng; Guofa, MI; Li, Bangsheng; Fu, Hengzhi

doi:10.7498/aps.57.3048

Cited by 3 publications

(1 citation statement)

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“…Numerical simulations make it possible to trace the formation and development of first and higher order arms in dendrites or the coupled phase growth during eutectic solidification, taking the interaction of growing crystallites into account. Information on the topology of the modelled structures and on the microsegregation of alloy components in the liquid and solid phases is obtained [ 3 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

Section: Introductionmentioning

confidence: 99%

CA Modeling of Microsegregation and Growth of Equiaxed Dendrites in the Binary Al-Mg Alloy

Zyska

2021

Materials

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A two-dimensional model based on the Cellular Automaton (CA) technique for simulating free dendritic growth in the binary Al + 5 wt.% alloy was presented. In the model, the local increment of the solid fraction was calculated using a methodology that takes into account changes in the concentration of the liquid and solid phase component in the interface cells during the solidification transition. The procedure of discarding the alloy component to the cells in the immediate vicinity was used to describe the initial, unstable dendrite growth phase under transient diffusion conditions. Numerical simulations of solidification were performed for a single dendrite using cooling rates of 5, 25 and 45 K/s and for many crystals assuming the boundary condition of the third kind (Newton). The formation and growth of primary and secondary branches as well as the development of component microsegregation in the liquid and solid phase during solidification of the investigated alloy were analysed. It was found that with an increase in the cooling rate, the dendrite morphology changes, its cross-section and the distance between the secondary arms decrease, while the degree of component microsegregation and temperature recalescence in the initial stage of solidification increase. In order to determine the potential of the numerical model, the simulation results were compared with the predictions of the Lipton–Glicksman–Kurz (LGK) analytical model and the experimental solidification tests. It was demonstrated that the variability of the dendrite tip diameter and the growth rate determined in the Cellular Automaton (CA) model are similar to the values obtained in the LGK model. As part of the solidification tests carried out using the Derivative Differential Thermal Analysis (DDTA) method, a good fit of the CA model was established in terms of the shape of the solidification curves as well as the location of the characteristic phase transition temperatures and transformation time. Comparative tests of the real structure of the Al + 5 wt.% Mg alloy with the simulated structure were also carried out, and the compliance of the Secondary Dendrite Arm Spacing (SDAS) parameter and magnesium concentration profiles on the cross-section of the secondary dendrites arms was assessed.

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Section: Introductionmentioning

confidence: 99%

CA Modeling of Microsegregation and Growth of Equiaxed Dendrites in the Binary Al-Mg Alloy

Zyska

2021

Materials

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Phase constitution and microstructure evolution of rapidly solidified Ti-Cu-Fe alloy

鲁晓宇¹,

廖霜²,

阮莹³

et al. 2012

Acta Phys. Sin.

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Ternary Ti61.2Cu32.5Fe6.3 quasiperitectic alloy is rapidly solidified in drop tube. The diameter of the obtained droplets varies from 80 to 1120 m. The theoretical analysis indicates that the range of undercooling is from 34 to 293 K (0.23TL). Due to the influences of containerless, microgravity, ultrahigh vacuum, etc, the microstructure of solidified alloy is composed of Cu0.8Fe0.2Ti phase, CuTi2 phase and CuTi3 phase. This result deviates appreciably from the equilibrium state. CuTi3 phase exhibits a conspicuous solute trapping effect during rapid solidification. The microstructure of alloy consists chiefly of eutectic (Cu0.8Fe0.2Ti and CuTi2 phases) and dendrites (Cu0.8Fe0.2Ti, CuTi3) structure. With the increase of undercooling, the microstructure of eutectic experiences a transition from strip eutectic cell to ellipsoidal eutectic cell to spherical eutectic cell; the morphology of Cu0.8Fe0.2Ti dendrite experiences a transition from coarse dendrites to broken dendrites to anomalous grain; while the morphology of CuTi3 dendrite changes from small block to coarse dendrite.

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Three-dimensional modelling and numerical simulation on segregation during Fe-Pb alloy solidification in a multiphase system

Wang¹,

Wang²,

Wang³

et al. 2014

Acta Phys. Sin.

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The three-dimensional mathematical model for a three-phase flow during its horizontai solidification is studied using fluid dynamics method based on Eulerian-Eulerian and volume of fraction methods, in which the mass, momentum, species, and enthalpy conservation equations of the Fe-Pb alloy solidification process are solved simultaneously. Effects of Pb area quadratic gradient (∇ (∇SPb)) and Pb concentration quadratic gradient (∇ (∇CPb)) on the segregation formation are investigated. Results show that the segregation mode is manifested as X-segregates in the upper and V-segregates in the lower part during flow-solidification of liquid phase and gas phase. The X-segregates result from the phase transformation driving force of gas phase and “scattering” is due to the orientation of phase transition. When t >tc the lower ∇ (∇SPb) and ∇ (∇CPb) curves cause a larger yielding rate of Pb with a larger down angle of X-segregates and a smaller up angle of X-segregates and V-segregates. All these are favorable for the formation of a well-dispersed microstructure. In addition, the gas-liquid two-phase flow interaction term has an effect on channel segregation, showing that channels occur only in the region where the flow-phase transition interaction term (ul·∇cl and ug·∇cg) is negative. With a negative flow-phase transition interaction term the increase in flow velocity due to the flow perturbation and flow-phase transition interaction becomes more negative, thus the channel continues to grow and tends to be stable. Calculated results show good agreement with experimental data.

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Numerical simulation of microstructure evolution during directional solidification of Ti-45at.%Al alloy

Cited by 3 publications

References 0 publications

CA Modeling of Microsegregation and Growth of Equiaxed Dendrites in the Binary Al-Mg Alloy

CA Modeling of Microsegregation and Growth of Equiaxed Dendrites in the Binary Al-Mg Alloy

Phase constitution and microstructure evolution of rapidly solidified Ti-Cu-Fe alloy

Three-dimensional modelling and numerical simulation on segregation during Fe-Pb alloy solidification in a multiphase system

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