X‐ray photoelectron spectroscopy studies of Ti–Al and Ti–Al–V alloys using Cr K_β radiation

Abstract

NTRODUCTIONAlloy development and design require a better understanding of alloying behaviour at the electronic level.1 Auger parameter 2,3 differences between pure metals and alloys have been used in various studies to probe electronic changes, such as charge transfer (or charge redistribution), that accompany alloy or compound formation. 4 -12 The metallurgical importance of charge transfer between solvent and solute(s) can be appreciated when considering issues such as the nature of the metallic bond, crystal structure variations and order/disorder phenomena in various alloys. 4 -6 Alloy formation involves the co-existence of atoms of two or more elements in the same lattice accompanied by electronic changes in the valence configurations, which lead to the formation of new bonds or modification of the existing ones. Thus, the crystal structure may be modified or altered completely and these modifications may trigger microstructural changes with significant impact on the properties and performance of the alloys formed. This interplay between atomic structure crystal structure microstructure material performance justifies the emphasis of current research to understand better the alloying behaviour at electronic level. High-energy XPS with Cr Kˇradiation (h D 5946.7 eV) in combination with thermodynamic predictions and microstructural studies has been proved to be useful to probe the nature of atomic bonding, crystal structure modifications and microstructural evolution. 5,6 In this paper an attempt has been made to understand the phenomena taking place at the atomic and sub-atomic level upon alloying using Auger parameter values and plasmon energies and intensities obtained by high-energy and conventional (h D 1486.6 eV with Al K˛radiation) XPS and to relate these to thermodynamic modelling and the microstructures of Ti-Al-(V) alloys. EXPERIMENTALAlloys of nominal compositions 20,30at.%Al,.%V, Ti-25at.% Al-25at.%V, V-50at.%Al and Ti-50at.%V were prepared by clean melting using high-purity Ti, V and Al. Special care was taken to ensure chemical homogeneity and very low levels of interstitials (O 2 < 500 ppm, H 2 < 20 ppm, C < 20 ppm and N 2 < 30 ppm). Prior to XPS analysis the surface of the alloy was polished down to 1 µm followed by ultrasonic cleaning with inhibisol.Acquisition of deep, well-localized 1s KLL transitions lead to optimum results in Auger parameter studies.

Calculations for displacive ω-phase transformations in Ti–Al alloys with Nb additions at finite temperature

“…Pair-potential modeling for the Ti 3 Al 2 Nb system [32] and first-principles studies of transition metal aluminides [33,34] indicate the existence of a strong covalent bonding component, which makes the bonding between Ti-Al atoms significantly stronger than between Ti-Nb or Al-Al atoms. This statement is in agreement with the results of the x-ray photoelectron spectroscopy (XPS) studies of Ti-Al and Ti-Al-V alloys [35] that indicate charge transfer from the Al sites towards the transition metal sites. The Ti-Al bond is stronger at shorter distances, relative to their positions in BOT structure.…”

Capturing the Dynamics of Ti Diffusion Across TixW1−x/Cu Heterostructures using X‐Ray Photoelectron Spectroscopy

“…As the Ti 1 s core level is not as widely studied as Ti 2 p due to the need for hard X‐ray sources, only a handful of publications exist, with reported BEs varying considerably. [ 36,49–56 ] The BE positions of the Ti(0) 1 s peak observed in the present work fall within the literature range of metallic Ti, and the asymmetric line shape of the peak, which can be clearly observed in Figure 5b,c, is commensurate with this assignment. An asymmetric line shape is a hallmark of the core level spectra of many transition metals.…”

New books on physics and related sciences

“…The MOPA results are also in agreement with the results of the x-ray photoelectron spectroscopy (XPS) studies of Ti-Al and Ti-Al-V alloys [30] which indicate charge transfer from the Al sites toward the transition metal sites. Therefore, the instability of the BOT structure with respect to the ω -type displacement is a consequence of the strong bonding between the Ti d electrons and Al p electrons.…”