Ordering and structural transformations in Ni3Al alloys

Abstract

X-ray diffraction profile studies on the filings of stoichiometric and off-stoichiometric compositions of Ni3AI alloys, with and without boron additions, were conducted to clarify some of the significant anomalies noticed in the literature. The long-range order parameter was estimated as a function of temperature in all the four alloys from (1 00)/(200) and (1 1 0)/(2 2 0) pairs of reflections. The L 12 structure appears to attain a maximum stability at about 600 ~ around which temperature its order parameter was close to the theoretical value. Above 600 ~ this structure becomes less stable and there appears to be formation of an additional structure of a lower symmetry.~.

Yield strength of Ni–Al–Cr superalloy under pressure

“…Diffraction patterns were found to be consistent with cubic Pm-3m(g 0 ) and Fm3m(g) structures. Lebail fitting using GSAS [24] resulted in a ¼ 3.567 ± 0.005 Å and v ¼ 45.38 ± 0.05 Å 3 in agreement with literature values [25,26]. In-situ X-ray diffraction studies were carried out on NieAleCr using diamond anvil cell at beamline 12.2.2, of Advanced Light Source (ALS), LBNL employing angle dispersive geometry using wavelength of 0.4959 Å.…”

Deformation-induced structural transformation in boron-doped Ni76Al24

“…It has been shown by Sato and Toth [28] and Beattie [29], that by creating an APB of 1/2h110i on every alternate (001) plane, L1 2 structure can be transformed to DO 22 structure. The stability of DO 22 structure of Ni 76 Al 24 (B) can also be inferred from the work of Ramesh et al [5]. They observed that high temperature annealing of filed powders of a Ni 76 Al 24 alloy led to changes in the relative intensities of {200} and {220} peaks as a function of the temperature of annealing.…”

“…However, there are inconsistent reports regarding the stability of ordered Ni 3 Al. Kornilov and Mints [4] first reported from their dilatometric study that there is a solid-state phase transformation at about 600 C. Ramesh et al [5,6] reported about the presence of such transformation by X-ray analysis. They hypothetically proposed that the transformed structure is another ordered tetragonal structure.…”

Changes in order and texture during annealing of heavily cold-rolled Ni3Al(B,Zr) alloy

“…The following relationship was used for the calculation of S: [16] of the same alloy, which was previously subjected to heavy 2 } amounts of cold deformation. Specifically, the changes in order and crystallographic texture, consequent upon anneal-…”