Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films

• DOI: 10.1017/s1431927618016264
• Publication Date: 2019-02-04T09:54:01Z
• Authors: Deodatta Shinde; Stefan Fritze; Mattias Thuvander; Paulius Malinovskis; Lars Riekehr; Ulf Jansson; Krystyna Stiller
• Keywords: 0103 physical sciences; 02 engineering and technology; 0210 nano-technology; 01 natural sciences

AbstractThe microstructure and distribution of the elements have been studied in thin films of a near-equimolar CrNbTaTiW high entropy alloy (HEA) and films with 8 at.% carbon added to the alloy. The films were deposited by magnetron sputtering at 300°C. X-ray diffraction shows that the near-equimolar metallic film crystallizes in a single-phase body centered cubic (bcc) structure with a strong (110) texture. However, more detailed analyses with transmission electron microscopy (TEM) and atom probe tomography (APT) show a strong segregation of Ti to the grain boundaries forming a very thin Ti–Cr rich interfacial layer. The effect can be explained by the large negative formation enthalpy of Ti–Cr compounds and shows that CrNbTaTiW is not a true HEA at lower temperatures. The addition of 8 at.% carbon leads to the formation of an amorphous structure, which can be explained by the limited solubility of carbon in bcc alloys. TEM energy-dispersive X-ray spectroscopy indicated that all metallic elements are randomly distributed in the film. The APT investigation, however, revealed that carbide-like clusters are present in the amorphous film.