Effect of the misorientation angle and anisotropy strength on the initial planar instability dynamics during solidification in a molten pool. (March 2019)

• Record Type: Journal Article
• Authors: Yu, Fengyi; Ji, Yanzhou; Wei, Yanhong; Chen, Long-Qing
• Is Part Of: International journal of heat and mass transfer. Volume 130(2019)
• Page Start: 204
• Page End: 214
• Publication Date: 2019-03
• Subjects: Anisotropy strength -- Preferred crystalline orientation -- Morphology instability -- Transient analytic model -- Phase-field method; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2018.03.106
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: A transient analytic model considering the effects of anisotropy strength and preferred crystalline orientation is developed for the initial instability during welding. A quantitative phase-field model is developed to reproduce the initial instability with different surface tension anisotropies under transient conditions for welding. The model can represent directly the detailed interface morphology evolution. And the incubation time and average wavelength of initial instability with different surface tension anisotropies are investigated to reveal the effect of anisotropy strength and preferred crystalline orientation. Abstract: The initial planar instability will appear with the solute accumulation ahead of the solid/liquid (S/L) interface during solidification in a molten pool. The instability process is dominated by the misorientation angle and the surface tension anisotropy strength, where the misorientation angle is the angle between the preferred crystalline orientation of base metal and the thermal gradient direction in front of the S/L interface. In this study, their effects on the initial planar instability during gas tungsten arc welding of an Al -alloy are investigated using a modified analytic model and a quantitative phase-field model, respectively. Specifically, we apply the uniform fluctuation spectrum assumption, Aω (0) = kB TM /{ γ 0 [1 − 15 γ 4 cos(4 θ 0 )] ω 2 }, to represent the influence of thermal noise on S/L interface evolution. The incubation time, average wavelength and detailed interface morphology of the initial planar instability are investigated with varying surface tension anisotropies (determined by anisotropy strength γ 4 and misorientation angle θ 0 ). The results indicate that - γ 4 cos(4 θ 0 ) is a reasonable indicator for the effect of surface tension anisotropy on the initial planar instability. Moreover, rather than influencing solute diffusion, the surface tension anisotropy just affects the planar interface stability during the solidification. Finally, the experimental observations with the same welding parameters was carried out, which are in general agreement with the simulated results.