The Morphology and Solute Segregation of Dendrite Growth in Ti-4.5% Al Alloy: A Phase-Field Study

Abstract

Ti-Al alloys have excellent high-temperature performance and are often used in the manufacture of high-pressure compressors and low-pressure turbine blades for military aircraft engines. However, solute segregation is easy to occur in the solidification process of Ti-Al alloys, which will affect their properties. In this study, we used the quantitative phase-field model developed by Karma to study the equiaxed dendrite growth of Ti-4.5% Al alloy. The effects of supersaturation, undercooling and thermal disturbance on the dendrite morphology and solute segregation were studied. The results showed that the increase of supersaturation and undercooling will promote the growth of secondary dendrite arms and aggravate the solute segregation. When the undercooling is large, the solute in the root of the primary dendrite arms is seriously enriched, and when the supersaturation is large, the time for the dendrite tips to reach a steady-state will be shortened. The thermal disturbance mainly affects the morphology and distribution of the secondary dendrite arms but has almost no effect on the steady-state of the primary dendrite tips. This is helpful to understand the cause of solute segregation in Ti-Al alloy theoretically.

Modeling Segregation of Fe–C Alloy in Solidification by Phase-Field Method Coupled with Thermodynamics

“…Although previous studies have clarified several factors affecting the precipitation of primary carbides in steels, the underlying mechanism was not clear due to the limitations of traditional experimental methods, particularly for an in-depth understanding of the solidification of high temperature steel melt. In the last few decades, the phase-field method has been developed to become one of the most powerful tools to investigate the dynamics of microstructure evolution during the solidification of metallic alloys [17][18][19][20][21], which has been widely used in the study of complex phase transitions in multi-component and multi-phase alloys [22][23][24][25]. The advantage of the phase-field method is to introduce the concept of a diffusive interface to represent different phases by uniform order parameters, which avoids the intractable problem of explicitly tracking the solid-liquid interface.…”