A new analytical approach to predict spacing selection in lamellar and rod eutectic systems

Abstract

The Jackson and Hunt (JH) theory has been modified to relax the assumption of isothermal solid/ liquid interface used in their treatment. Based on the predictions of this modified theory, the traditional definitions of regular and irregular eutectics are revised. For regular eutectics, the new model identifies a range of spacing within the limits defined by the minimum undercooling of the ␣ and ␤ phases. For the irregular Al-Si eutectic system, two different spacing selection mechanisms were identified:(1) for a particular growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing I ; (2) the average spacing ( av Ͼ I ) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model, a semiempirical expression has been developed to account for the influence of the temperature gradient, which is dominant in the irregular Al-Si system. The behavior of the Fe-Fe 3 C eutectic is also discussed. The theoretical calculations have been found to be in good agreement with the published experimental measurements.

The effect of Cu rejection in laser forming of AlCoCrCuFeNi/Mg composite coating

“…4d depicts that the smaller lamellar spacing is observed at a greater distance from the HEA particles because of a faster solidification velocity. In eutectic solidification, the eutectic spacing is approximately determined by [27,28] (…”

Modeling of Cast Iron Solidification—The Defining Moments

“…More recently, Catalina et al [30] proposed a modified JH model for eutectic growth applicable to both regular and irregular eutectics. The model accounts for the density difference between the liquid and the two solid phases, as suggested by Magnin and Trivedi.…”

“…For growth velocities higher than 10 mm/s, the experiments show that the spacing deviates from the relationship l 2 V 5 constant as austenite dendrites begin to appear in the microstructure and the graphite lamellae exhibit a relatively random orientation. [23,32] [30] For a complete discussion, as well as for a discussion on the Fe-Fe 3 C eutectic and the influence of the solidification gradient, the reader is referred to the original article. [30] The first analytical model to describe growth of the eutectic in SG iron was proposed in 1972 by Wetterfall et al [13] Calculations of diffusion-controlled steady-state growth of graphite through the austenite shell ( Figure 11) were made based on Zener's growth equation for an isolated spherical particle in a matrix of low supersaturation.…”

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