Anna Radecka

Insights into microstructural interfaces in aerospace alloys characterised by atom probe tomography

Atom probe tomography (APT) is becoming increasingly applied to understand the relationship between the structure and composition of new alloys at the micro- and nanoscale and their physical properties. Here, we use APT datasets from two modern aerospace alloys to highlight the detailed information available from APT analysis, along with potential pitfalls that can affect data interpretation. The interface between two phases in a Ti–6Al–4V alloy is used to illustrate the importance of parameter choice when using proximity histograms or concentration profiles to characterise interfacial chemistry. The higher number density of precipitates and large number of constituent elements in a maraging steel (F1E) present additional challenges such as peak overlaps that vary across the dataset, along with inhomogeneous interface chemistries.

Isothermal omega formation and evolution in the Beta-Ti alloy Ti-5Al-5Mo-5V-3Cr

Abstract The isothermal phase of Ti-5Al-5Mo-5V-3Cr wt.% is formed within a heat treatment at and identified by atom probe tomography as Ti-rich/solute lean precipitates. The composition and size remain essentially constant during ageing, although the volume fraction increases to 9.5% after ageing for 8 h. This is consistent with an ongoing transformation process of athermal to isothermal . The / interface becomes enriched with oxygen. This may be of significance as oxygen strongly stabilizes the phase, and the / interface has previously been suggested as the nucleation site for subsequent formation.

Characterizing solute hydrogen and hydrides in pure and alloyed titanium at the atomic scale

Abstract Ti and its alloys have a high affinity for hydrogen and are typical hydride formers. Ti-hydride are brittle phases which probably cause premature failure of Ti-alloys. Here, we used atom probe tomography and electron microscopy to investigate the hydrogen distribution in a set of specimens of commercially pure Ti, model and commercial Ti-alloys. Although likely partly introduced during specimen preparation with the focused-ion beam, we show formation of Ti-hydrides along α grain boundaries and α/β phase boundaries in commercial pure Ti and α+β binary model alloys. No hydrides are observed in the α phase in alloys with Al addition or quenched-in Mo supersaturation.

Atom-Probe Tomography: Detection Efficiency and Resolution of Nanometer-Scale Precipitates in a Ti-5553 Alloy

1 Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA 2 Center for Atom-Probe Tomography (NUCAPT), Northwestern University, Evanston, IL, USA 3 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, England 4 Department of Materials, Imperial College, South Kensington, London, England 5 Rolls Royce Plc, Elton Road, Derby, England 6 CAMECA Instruments, Inc., Madison, WI, USA 7 Department of Materials, University of Oxford, Oxford, England