Orientation Relationships in Al0.7CoCrFeNi High-Entropy Alloy

Prior research has shown that high-entropy alloys exhibit complex phase transformations and microstructural evolution during solidification. It was already known that the interplay between atomic size differences and chemical ordering can influence crystallographic texture and phase nucleation. However, no prior work had resolved the specific orientation relationships governing FCC phase nucleation in Al0.7CoCrFeNi alloys. This gap motivated a detailed investigation into the mechanisms of phase transformation and crystallographic orientation. The study aimed to clarify how atomic size mismatches and ordered phases affect the microstructure. Existing methods have not fully explained the deviations from expected orientation relationships. The need to understand these deviations led to the use of advanced characterization techniques. This paper's contribution lies in identifying the dominant orientation relationship and its deviations. The findings may help refine models of phase transformation in multi-element alloys.

The study aimed to investigate the mechanisms of phase transformation and crystallographic orientation in Al0.7CoCrFeNi high-entropy alloys. The specific problem addressed is the lack of clarity regarding how FCC phase nucleation occurs in alloys with atomic size mismatches. The motivation stems from the need to understand how ordered phases influence crystallographic texture. The research focused on identifying the dominant orientation relationship during phase transformation. The goal was to determine whether the Pitsch orientation relationship governs FCC nucleation. The study also sought to explain deviations from this relationship. The researchers used electron backscatter diffraction to analyze crystallographic orientations. The purpose was to provide a clearer picture of phase transformation mechanisms.

The study employed electron backscatter diffraction to characterize crystallographic orientations. Energy-dispersive X-ray spectroscopy was used to analyze chemical composition variations. The researchers examined the cast Al0.7CoCrFeNi alloy's microstructure. They focused on the transformation from BCC to FCC phases during solidification. The methods included detailed microstructural evaluation of nucleation mechanisms. The team analyzed the orientation relationships between parent and transformed phases. They identified the presence of FCC Widmanstätten plates in the dual-phase microstructure. The study combined microstructural and crystallographic data to explain transformation mechanisms.

The Pitsch orientation relationship was found to dominate FCC phase nucleation in the alloy. However, deviations from this relationship were observed in some regions. These deviations were attributed to lattice distortions caused by atomic size differences. The alloy's dual-phase microstructure included FCC Widmanstätten plates aligned with {110}BCC planes. The crystal orientation distribution after transformation was found to be confined. The study showed that the governing mechanisms limit the range of possible orientations. The FCC phase formed primarily through the Pitsch OR, with some exceptions. The ordered B2 phase contributed to the observed deviations in orientation relationships.

The authors propose that the Pitsch orientation relationship governs FCC phase nucleation in Al0.7CoCrFeNi alloys. Deviations from this relationship are explained by lattice distortions from atomic size mismatches. The study confirms the presence of FCC Widmanstätten plates aligned with parent BCC planes. The confined crystal orientation distribution is a result of the transformation mechanisms. The findings suggest that atomic ordering influences phase transformation pathways. The research highlights the role of atomic size differences in microstructural evolution. The results may inform future studies on phase transformation in high-entropy alloys. The study provides a clearer understanding of orientation relationships in multi-element systems.