A Study of Grain Selection in Two-Dimensional (2D) Grain Selectors during the Investment Casting of Single-Crystal Superalloy

Abstract

In this study, a series of Bridgman casting experiments were conducted to study the physical processes occurring in 2D grain selectors with different geometric parameters. The corresponding effects of the geometric parameters on grain selection were quantified by using an optical microscopy (OM) and a scanning electronic microscopy (SEM) equipped with electron backscatter diffraction (EBSD) function. Based on the results, the influences of the geometric parameters of the grain selectors are discussed, and an underlying mechanism accounting for the experimental results is proposed. The critical nucleation undercooling in the 2D grain selectors during grain selection was also analyzed.

Effect of Initial Position and Crystallographic Orientation on Grain Selection Procedure in Z-Form Selector for Ni-Based Single-Crystal Superalloy

“…The grain selection behavior is mostly a competitive grain growth process within a specific component [9]. However, the grain selection process differs from the general process of competitive grain growth and exhibits distinctive characteristics [9,14,15,[23][24][25]. To begin, the structure of the selector is complex.…”

“…In order to improve the control accuracy of the crystallographic orientation of singlecrystal blades, the researchers paid in-depth attention to the grain selection process and its mechanism [9,[12][13][14][15][16][17]. The main role of the starter block in the grain selection process is widely considered to be the acquisition of <001> oriented grain clusters [18,19].…”

“…Meng et al studied the process of selecting grain in the selector with various geometries and sizes and showed that the crystallographic orientation of the surviving grain could be further optimized in the selector [22]. Using a two-dimensional grain selector, Zhu et al found that the grain selection efficiency largely depends on the selector wire diameter and the take-off angle [15]. According to research by Seo et al, the grain that is closest to the inner wall of the selector frequently develops high-branching dendrites to overgrow other grains and is subsequently chosen as the surviving grain [16].…”