Nickel, with symbol Ni, is a silvery-white lustrous metal with a slight golden tinge. It is a ductile and highly corrosion resistant transition metal and is used in alloys that have properties that include high temperature resistance, strength and toughness.
The melting point of a metal is the maximum temperature at which it can be heated without losing its physical integrity. This temperature is governed by the way in which the solid absorbs kinetic energy (as it expands and contracts) and by the attractive forces that operate between its atoms.
Melting temperatures for copper-nickel alloys vary widely from a few hundred degrees Celsius to a few thousand degrees. It is important for engineers and scientists working with these alloys to understand their melting points as the failure of the material at its melting temperature can have severe consequences.
A common approach for identifying the melting point of an alloy is to examine the X-ray diffraction pattern. As the sample is heated the X-ray diffraction (XRD) patterns are collected continuously and the onset of melting is observed by the first appearance of liquid diffuse scattering (LDS) in the spectra.
X-ray absorption near edge structure (XANES) analysis is another technique that can be used to confirm the melting of a material. This method is used to identify the onset of melting by observing the change in the XANES region of the XRD spectra.
In this study the XANES technique was applied to extend the knowledge of the phase diagram of nickel and to validate it by ex situ post analysis of laser-heated samples using focused ion beam (FIB) milling on heated spots and combined scanning electron microscope (SEM) to observe the shape of the molten material. The results show that the XANES method is reliable for the identification of melting in nickel under pressure and temperature.