A technique for characterizing microsegregation in multicomponent alloys and its application to single-crystal superalloy castings

Abstract

Instrumental errors in microsegregation measurements in multicomponent alloys complicate the treatment of randomly sampled data. In this article, two new alloy-independent data treatment algorithms are presented that are capable of separating the effects of scatter in the data from the underlying segregation trends, assigning each measurement location a unique fraction solid. These new methods are physically reasonable and result in improved estimates of segregation parameters, particularly the solute partitioning at the dendrite tip. This is demonstrated by determining the microsegregation in four successive generations of single-crystal (SX) nickel-based superalloys. Artificial, noise-induced, tails commonly seen in the microsegregation profiles are also minimized. A methodology for evaluating sorting schemes is introduced that does not depend upon a priori knowledge of the partitioning direction. Comparison is made to both other sorting methods and CALPHAD predicted partition coefficients. Implications for alloy design are reported, illustrating the interaction between solute species such as Ru, Re, Co, and W.

Solute Redistribution during Planar and Dendritic Growth of Directionally Solidified Ni-Base Superalloy CMSX-10

“…Of all solute elements that were presented in Table II, Ti and heavy refractory elements such as Re, Ta, and W exhibited particularly strong segregation tendency. This segregation tendency was found to be comparable with those reported for dendritically solidified commercial single crystal superalloys [3,4,7,11] and model single crystal superalloys [6,23]. (Table II).…”

“…Of the techniques available, random sampling approach, which is commonly known as point matrix scan technique, is widely used for characterizing microsegregation in Ni-base superalloys [3,4,7,[11][12][13][14]. This technique has become prevalent because it allows characterizing microsegregation with no dependence on the plane of examination and simply provides a continuous profile with respect to the fraction of solid ( s ).…”

Computation of Phase Transformation Paths in Steels by a Combination of the Partial- and Para-equilibrium Thermodynamic Approximations

“…The analyzed area was 10 mm × 5 mm with a total number of probed points reaching 20 000. Sorting methods proposed in literature were used, 11) namely the Flemings-Gungor (FG) sort and the Weighted Interval Rank Sort (WIRS). FG is the simplest approach, in which all solutes are sorted independently as ascending order of the concentration.…”

“…Under LR, the total solid Table 2. Liquidus temperature (°C) and onset temperature for the peritectic transformation (°C) deduced from DTA measurement and from the TCFE6 database 11) for alloy S-1 using various approximations. ].…”

Effect of rare earth for solute distribution of Cr-Mn-N stainless steel by directional solidification

“…As shown in Fig. 1, each sample was hit a number of points from the initial interface to the solid-liquid interface in the longitudinal cross-section to get its solute distribution measured by EDS [3] . the ratio of the measured distance from the initial interface to the total length of the fully solidified specimen is the solidification fraction (f s ) and to measure solute content (c s * ) in solid phase and the solute content (c l * ) in the liquid phase on both sides of the solid-liquid interface less than 1 microns distance.…”