Atomic-scale understanding of the structural evolution of TiN/AlN superlattice during nanoindentation—Part 1: Deformation
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In: Acta materialia, Vol. 234.2022, No. 1 August, 118008, 19.05.2022, p. 1-13.
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T1 - Atomic-scale understanding of the structural evolution of TiN/AlN superlattice during nanoindentation—Part 1: Deformation
AU - Chen, Zhuo
AU - Zheng, Yonghui
AU - Huang, Yong
AU - Gao, Zecui
AU - Sheng, Huaping
AU - Bartosik, Matthias
AU - Mayrhofer, Paul Heinz
AU - Zhang, Zaoli
PY - 2022/5/19
Y1 - 2022/5/19
N2 - At present, the theoretical predictions of the mechanical properties of transition-metal nitride (TMN) superlattices (SLs) are primarily based on the intrinsic properties of perfect epitaxial nanolayers. However, due to a lack of understanding of the specific strengthening mechanism, the experimentally determined strength, e.g., hardness, of TMN SLs often deviates significantly from the theoretical predictions. Here, by coupling FIB (focused ion beam) sectioning with TEM, we observe the structural evolution of two representatives TiN/AlN SL coatings, i.e., a single-crystalline and a polycrystalline SL, under identical loads. We found that in comparison with the polycrystalline SL, the indented single-crystalline SL forms a larger ‘intermixed’ region, within which the layer structure transforms into a solid solution under loads. Close TEM characterization demonstrates that the single-crystalline SL deformation is of variety, including the distortion of SL interfaces, polycrystalline deformation (grain rotation) in solid solution, and SL slip deformation. By contrast, columnar grain boundary sliding is the primary deformation mechanism in the polycrystalline SL. And, a relatively large solid-solution zone in single-crystalline SL is attributed to the severe interfacial deformation. The current research unravels TMN SL deformation behavior at the atomic scale.
AB - At present, the theoretical predictions of the mechanical properties of transition-metal nitride (TMN) superlattices (SLs) are primarily based on the intrinsic properties of perfect epitaxial nanolayers. However, due to a lack of understanding of the specific strengthening mechanism, the experimentally determined strength, e.g., hardness, of TMN SLs often deviates significantly from the theoretical predictions. Here, by coupling FIB (focused ion beam) sectioning with TEM, we observe the structural evolution of two representatives TiN/AlN SL coatings, i.e., a single-crystalline and a polycrystalline SL, under identical loads. We found that in comparison with the polycrystalline SL, the indented single-crystalline SL forms a larger ‘intermixed’ region, within which the layer structure transforms into a solid solution under loads. Close TEM characterization demonstrates that the single-crystalline SL deformation is of variety, including the distortion of SL interfaces, polycrystalline deformation (grain rotation) in solid solution, and SL slip deformation. By contrast, columnar grain boundary sliding is the primary deformation mechanism in the polycrystalline SL. And, a relatively large solid-solution zone in single-crystalline SL is attributed to the severe interfacial deformation. The current research unravels TMN SL deformation behavior at the atomic scale.
U2 - 10.1016/j.actamat.2022.118008
DO - 10.1016/j.actamat.2022.118008
M3 - Article
VL - 234.2022
SP - 1
EP - 13
JO - Acta materialia
JF - Acta materialia
SN - 1359-6454
IS - 1 August
M1 - 118008
ER -