μ Phase in a Nickel Base Directionally Solidified Alloy

Abstract

Scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) were employed to study the phase in a directionally solidified experimental nickel base alloy. It was observed that the phase distribute at interdendritic area and precipitate mainly from the 0 phase in this experimental alloy. Orientation relationship between the 0 and the phase was found as ð111Þ 0 k ð0001Þ and h " 1 110i 0 k h11 " 2 20i . Detrimental effect of the phase on oxidation resistance of the alloys was also found.

Precipitation behavior of a novel cobalt-based superalloy subjected to prior plastic deformations

“…In this study, two types of μ-phases were observed; they mainly consisted of Mo, Co, Cr, and Ni, as determined by EDX analysis. It has been reported that, of these elements, Mo has a stronger tendency to form the μ-phase than do the others such as W, Cr, Nb, and Co and that the μ-phase becomes the main TCP precipitate if the Mo and W contents are N3.5 (at%) [24]. This was also found to be the case in the present study.…”

“…The two nonequivalent orientation relationships between the μ-phase and the γ-matrix in the case of the investigated alloy were different from the ones mentioned above [24,[26][27][28]. This difference indicates that the nucleation and growth behaviors of the investigated alloy are little different with the normal one.…”

“…The structure of the μ-phase belongs to the D 5 3d −R 3m space group, with a = 0.476 nm and c = 2.56 nm [22]. In some superalloys, the precipitation of the μ-phase is unavoidable because of their high W or/and Mo content (W or/and Mo N 3.5 at.%) [24]. Normally, two types of μ-phases are observed: a primary μ-phase and a secondary μ-phase.…”

“…Normally, two types of μ-phases are observed: a primary μ-phase and a secondary μ-phase. The primary μ-phase precipitates at grain boundaries during solidification, while the secondary μ-phase forms during aging or at elevated temperatures [24]. Although it has been suggested that the precipitation of μ-phase has a detrimental effect on the mechanical properties at room temperature [23], Simonetti et al found no evidence of a needle-type μ-phase with a moderate volume fraction having a deleterious effect on the tensile properties of an MC-type single-crystal superalloy at room temperature [15].…”

Effect of Pt–aluminide bond coat on tensile and creep behavior of a nickel-base single crystal superalloy

“…14(a)-(b)). Therefore, they can cause premature crack initiation and the resultant deterioration in the stress rupture properties of the alloy [41,42]. Thus, the degradation of microstructure in and near the coating has also contributed to the lowering of the creep performance of the coated alloy.…”