SEM and XRD Characterization of Ni-Hf Alloys at Low Hf Concentration

Abstract

Abstract. The alloying and phase formation in Ni-Hf samples with 0.2-, 2-, and 5-at.% Hf were studied by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Both characterization methods, XRD and SEM, reveal the presence of the HfNi 5 phase (fcc structure) where the excess Ni atoms are present in the form of Ni or Ni-rich segregations in the sample containing 5-at.% Hf. The sample with 2-at.% Hf is characterized by the presence of the two phases present in the 5-at.% sample and by Hf atoms, which occupy substitutional lattice positions in the Ni lattice. Finally, in the third sample with 0.2-at.% Hf, the Hf atoms mainly substitute the Ni atoms in the lattice. This analysis is being complemented with additional information on the local structure around Hf by extended X-ray absorption fine structure spectroscopy (EXAFS).

Magnetic dipole and electric quadrupole interactions of 181Ta probe in Ni–Hf alloy

“…The rather large frequency distribution parameter ı 2 (18-51%) indicates a defect associated 181 Ta site. As seen from the previous experiments [11], distortions are present in the fcc HfNi 5 phase. Therefore, this EQI could be ascribed to Ta probe substituting in irregular HfNi 5 phase.…”

“…To achieve a homogenous distribution of Hf, the sample was turned over and remelted several times. Our previous X-ray diffraction and scanning electron microscopy measurements confirmed alloying and phase formation in the Ni-Hf sample according to the Ni-Hf phase diagram [11]. Hf atoms occupy two different sites: substitutional lattice positions in Ni and in the HfNi5 phase with defective lattice structure relative to that of the equilibrium phase.…”

The time differential perturbed angular correlation study of the Ni–5at.% Hf alloy

“…1. Previous SEM and XRD analysis of the nickel-5 at.% hafnium alloy revealed the presence of two phases: the Ni(Hf) solid solution and the defective HfNi 5 phases [1]. The majority of Hf atoms appeared to be incorporated in the HfNi 5 phase as demonstrated by EXAFS investigation on this alloy [1,2].…”

“…[1,2]. These earlier investigations on structural properties and alloy formation in the Ni-5 at.% Hf alloy showed that the composition of this alloy is in accordance with the Ni-Hf phase diagram [3].…”

Experimental and theoretical study of lattice relaxation around refractory atoms in nickel

“…The solid solubility of Hf in Ni is limited, and its maximum solubility below the eutectic temperature is estimated to be around 1.3 at.% [17]. In our earlier paper [18], we have performed comparative X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. Fig.…”