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Item type:Publication, Access status: without files , Nickel-rhenium compound sheds light on the potency of rhenium as a strengthener in high-temperature nickel alloys(American Physical Society (APS), 2014-09-16); ; ; ; For many decades, it has been known that rhenium imparts a tremendous resistance to creep to the nickel-based high-temperature alloys colloquially known as superalloys. This effect is so pronounced that is has been dubbed "the rhenium effect." Its origins are ill-understood, even though it is so critical to the performance of these high-temperature alloys. In this paper we show that the currently known phase diagram is inaccurate, and neglects a stoichiometric compound at 20 at.% Re (Ni4Re). The presence of this precipitate at low temperatures and the short-range ordering of Re in fcc-Ni observed at higher temperatures have important ramifications for the Ni-based superalloys. The Ni4Re compound is shown to be stable by quantum mechanical high-throughput calculations at 0 K. Monte Carlo simulations show that it is thermally persistent up to ≈930 K when considering configurational entropy. The existence of this compound is investigated using extended x-ray absorption fine spectroscopy on a Ni96.62Re3.38 alloy.Publicationtype: Journal Article34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , An accidental visualization of the Brillouin zone in an Ni-W alloy via diffuse scattering(Munksgaard, 2013); ; ; ; Solid state physics is built on the concept of reciprocal space. The physics of any given periodic crystal is fully defined within the Wigner-Seitz cell in reciprocal space, also known as the first Brillouin zone. It is a purely symmetry-based concept and usually does not have any eye-catching signature in the experimental data, in contrast with some other geometrical constructions like the Fermi surface. However, the particular shape of the Fermi surface of nickel allowed the visualization of the system of edges (skeleton) of the Wigner-Seitz cell of the face-centred cubic lattice in reciprocal space in three dimensions by the diffuse scattering of X-rays from Ni1-x W x (x = 0.03, 0.05, 0.08) single crystals. Employing a cluster-expansion method with first-principles input, it is possible to show that the observed scattering is inherent to the given nickel alloys and the crystal structures they form. This peculiar feature can be understood by considering the shape of the Fermi surface of pure nickel.Publicationtype: Journal Article75