Novel insights on the near atomic scale spatial distributions of substitutional alloying and interstitial impurity elements in Ti-6Al-4V alloy

The present study explores the near atomic scale spatial distributions of substitutional alloying elements (aluminium and vanadium) and interstitial impurities (oxygen and carbon) in the microstructures of Ti-6Al4V and its boron modified counterpart (Ti-6Al-4V-0.1B) alloys using transmission electron microscopy (TEM) and atom probe tomography (APT) techniques. The latter alloy possesses zero solubility of boron in alpha-Ti and high oxygen concentration around TiB particles. The results suggest that aluminium and vanadium atoms enrich alpha and beta phases, respectively due to strong elemental partitioning between these phases, to an extent that the atomic scale concentrations of various elements considerably differ from the bulk compositions of the two alloys. Furthermore, oxygen atoms are preferentially distributed within the alpha phase where other interstitial impurities (carbon) also segregate. Substitutional aluminium atoms share an inverse interrelation with interstitial oxygen atoms while vanadium atoms reside besides the impurity-rich regions for both the alloys. The size differences for these elements (substitutional vs. interstitial) with host titanium atoms and related lattice distortion is (partially) held responsible for the atomic scale elemental distributions and the observed interrelations within the alpha phase. These arguments are further substantiated from DFT results previously obtained for Ti-6Al-4V alloy.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the spatial distributions of substitutional alloying elements and interstitial impurities in Ti-6Al4V and Ti-6Al-4V-0.1B alloys on a near atomic scale. The results reveal that aluminum and vanadium atoms enrich alpha and beta phases, respectively, due to partitioning effects between these phases. Oxygen atoms preferentially distribute within the alpha phase alongside other interstitial impurities, while vanadium atoms reside near impurity-rich regions in both alloys. Size differences and lattice distortions are held responsible for the observed atomic scale elemental distributions and interrelations within the alpha phase.