Bulk, polycrystalline (Co, Cu, Mg, Ni, Zn)O was synthesized using solid-state sintering. Micropillars were prepared and mechanically deformed along three crystallographic orientations: (001), (101), and (111). Pillars (001) and (111) cracked, while Pillar (101) remained intact. Pillars (001) and (101) exhibited activated slip systems, confirmed by a large stress drop, and the presence of slip bands, respectively. Schmid factor (SF) analysis was performed to examine the effect of grain orientations on dislocation activity and slip behavior. SF values range from 0 to 0.5, with non-zero values indicating potential for slip. Six slip systems exist in the (Co, Cu, Mg, Ni, Zn)O rock salt crystal structure: 1/2⟨110⟩11¯0. For the (001) orientation, four slip systems are potentially active (SF = 0.5). For the (101) orientation, there are four potentially active slip systems (SF = 0.25). For the (111) orientation, no potentially active slips systems exist (SF = 0). Dislocation structures, which were observed post-compression via transmission electron microscopy, demonstrated variations in size, number, and distribution across the pillar, depending on micropillar orientation. Entangled dislocations created misorientation in Pillar (001), which led to the possible formation of subgrains, while singular dislocations were observed in Pillar (101), and a lack of dislocations was observed in Pillar (111). Zener–Stroh type dislocation entanglement-mediated cracking is the proposed cause of the transgranular-type cracks in Pillar (001). The possible subgrain formation, or lack of formation, respectively, caused intergranular-type cracks to additionally form in Pillar (001), while Pillar (111) only exhibited transgranular-type brittle fracture. In combination, these findings highlight the importance of dislocation activity, without the need for elevated temperature, and grain orientation in controlling the mechanical deformation response in single-phase (Co, Cu, Mg, Ni, Zn)O.
The emerging class of multi-principal element alloy (MPEA) processes superior mechanical properties and has great potential for applications in extreme environments. In this work, the synergic effect of the Cr content and crystallographic orientation on the deformation behaviors of single-crystal CrCoFeNi MPEAs has been investigated by atomistic simulations. We have found distinct differences in dislocation activities, deformation microstructures, and mechanical behaviors in the model MPEAs, which depend on crystallographic orientations, Cr concentration, and the number of activated slip systems. When multiple slip systems are triggered along [100] and [111] orientations, Shockley partial activation and their interaction are predominant, leading to the formation of sessile dislocations and a dense dislocation network. When only two slip systems of Shockley partials are favored along the [110] direction, the influence of Cr concentration and planner defect energies emerges. At low Cr concentration, the double planar slip of Shockley partials results in deformation-induced nanotwins. At high Cr concentration, the partial dislocations of a single slip plane become dominant, attaining the highest volume fraction of deformation-induced phase transformation. The results provide a fundamental understanding of deformation mechanisms in MPEAs, elucidating the synergic effect of crystal orientation and composition on tunning the mechanical behaviors.
more » « less- NSF-PAR ID:
- 10522713
- Publisher / Repository:
- Journal of Applied Physics
- Date Published:
- Journal Name:
- Journal of Applied Physics
- Volume:
- 133
- Issue:
- 19
- ISSN:
- 0021-8979
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Dislocations, linear defects in a crystalline lattice characterized by their slip systems, can provide a record of grain internal deformation. Comprehensive examination of this record has been limited by intrinsic limitations of the observational methods. Transmission electron microscopy reveals individual dislocations, but images only a few square
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0146032
