SIMULATION AND EXPERIMENTAL STUDIES ON GRAIN SELECTION BEHAVIOR OF SINGLE CRYSTAL SUPERALLOY II. Spiral Part

Abstract

The spiral selector is the key part for producing single crystal (SX) blades and ensures the integrity of crystal, which mainly includes starter block and spiral part. In this work, the influence of spiral part on the grain selection process was studied. Both of the metallography results and EBSD results proved that the prior location and the special orientation of the second dendrite arms were important for the grains competitive growth during the directional solidification process. Based on the experimental results, two geometrical restrict mechanisms of grain selection were proposed. They were the competitive stimulating effect on the second dendrite arms in horizontal direction, which was resulted from the spiral arc shape, and the growing blocking effect on the primary dendrites in vertical direction, which was resulted from the take-off angle of the spiral part. These models could successfully explain the grain selecting effects of the spiral part. The modified cellular automaton

Simulation and Experimental Studies on Grain Selection and Structure Design of the Spiral Selector for Casting Single Crystal Ni-Based Superalloy

“…Dai et al [ 19 ] emphasized that the efficiency of the spiral selector was significantly dependent on the corresponding geometry, whereas the spiral became quite efficient with (a) lower pitch length; (b) lower take-off angle; (c) lower wax wire diameter and (d) higher spiral rotation diameter at the same pitch length. Zhang et al [ 6 ] reported two grain selection effects, promoting the effect in the horizontal direction (Effect 1) and the primary dendrite growth restraint effect in the vertical direction (Effect 2) of the spiral part. In this study, to further present the relationship between the grain selection effects and the selector structure, proving a guide for the design of different spiral selectors, the simulation was utilized for further analysis and verification.…”

“…Therefore, this process is hard to control [ 3 , 4 , 5 ]. At present, the grain selection method is widely utilized [ 6 , 7 , 8 , 9 , 10 ]. Spiral grain selection is a common grain selection method, which has advantages such as simple processing, short production cycle and high operability [ 11 ].…”

“…The design of grain selectors also lacked corresponding theoretical guidance. In previous works, the grain selection simulation was executed and the spiral grain selection mechanism was proposed [ 6 , 24 ]. In this work, the heat radiation model and the grain growth model concerning solute equilibrium were added.…”

Large-scale simulation of dendrite growth in directional solidification castings

“…The transverse growth of the secondary dendritic arms in the [100] and [010] directions completely filled the spiral space, and this prevented the growth of other dendrites in the [001] direction. The results of the dendrite‐growth simulation, on a microscale, demonstrate the competitive growth of the grains in the spiral sections and verify the transverse grain‐selection mechanisms that occur during the single crystal selection process .…”

“…Within a spiral single crystal selector, the competitive grain growth behavior is complex and has attracted significant research attention . Figure (a) shows the structure of the columnar grains in a selector.…”