Nanoscale Clustering in an Additively Manufactured Zr-Based Metallic Glass Evaluated by Atom Probe Tomography

Abstract

Composition analysis at the nm-scale, marking the onset of clustering in bulk metallic glasses, can aid the understanding and further optimization of additive manufacturing processes. By atom probe tomography, it is challenging to differentiate nm-scale segregations from random fluctuations. This ambiguity is due to the limited spatial resolution and detection efficiency. Cu and Zr were selected as model systems since the spatial distributions of the isotopes therein constitute ideal solid solutions, as the mixing enthalpy is, by definition, zero. Close agreement is observed between the simulated and measured spatial distributions of the isotopes. Having established the signature of a random distribution of atoms, the elemental distribution in amorphous Zr59.3Cu28.8Al10.4Nb1.5 samples fabricated by laser powder bed fusion is analyzed. By comparison with the length scales of spatial isotope distributions, the probed volume of the bulk metallic glass shows a random distribution of all constitutional elements, and no evidence for clustering is observed. However, heat-treated metallic glass samples clearly exhibit elemental segregation which increases in size with annealing time. Segregations in Zr59.3Cu28.8Al10.4Nb1.5 > 1 nm can be observed and separated from random fluctuations, while accurate determination of segregations < 1 nm in size are limited by spatial resolution and detection efficiency.

Hard Magnetic Properties and the Features of Nanostructure of High-Temperature Sm-Co-Fe-Cu-Zr Magnet with Abnormal Temperature Dependence of Coercivity

“…The needle-shaped APT specimens were prepared using FEI Helios G4 UX dual-beam focused ion beam/scanning electron microscope (FIB/SEM) (FEI Company, part of Thermo Fisher Scientific, Hillsboro, OR, USA). APT measurements [ 30 , 31 , 32 , 33 , 34 ] were performed using the CAMECA LEAP 5000 XR system in the laser mode with a pulse frequency of 200 kHz and an applied laser energy of 30 pJ, while the tip was maintained at 60 K. The data reconstruction and analysis were performed with the Integrated Visualization and Analysis Software (IVAS 3.8.10) of CAMECA Instruments Inc (Fitchburg, WI, USA).…”