Sputtered Hf–Ti nanostructures: A segregation and high-temperature stability study

Polyakov, Mikhail N.; Chookajorn, Tongjai; Mecklenburg, Matthew; Schuh, Christopher A.; Hodge, Andrea M.

doi:10.1016/j.actamat.2016.01.073

Cited by 36 publications

(19 citation statements)

References 42 publications

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“…In contrast, samples that were annealed at 550 °C or 750 °C only contained ordered grain boundaries. Similar reports of segregation and amorphous film formation in other materials have also be reported in the literature (see, e.g., [14,26,37]).…”

Section: (B) Is the Corresponding Eds Line Profile Scan Showing That supporting

confidence: 88%

Identifying interatomic potentials for the accurate modeling of interfacial segregation and structural transitions

Schuler

Rupert

2018

Computational Materials Science

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Chemical segregation and structural transitions at interfaces are important nanoscale phenomena, making them natural targets for atomistic modeling, yet interatomic potentials must be fit to secondary physical properties. To isolate the important factors that interatomic potentials must capture in order to accurately model such behavior, the performance of four interatomic potentials was evaluated for the Cu-Zr system, with experimental observations used to provide validation. While experimental results show strong Zr segregation to grain boundary regions and the formation of nanoscale amorphous complexions at high temperatures and/or dopant compositions, a variety of disparate behaviors can be observed in hybrid Monte Carlo/molecular dynamics simulations of doping, depending on the chosen potential. The potentials that are able to recreate the correct behavior accurately reproduce the enthalpy of mixing as well as the bond energies, providing a roadmap for the exploration of interfacial phenomena with atomistic modeling. Finally, we use our observations to find a reliable potential for the Ni-Zr system and show that this alloy should also be able to sustain amorphous complexions.

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Section: (B) Is the Corresponding Eds Line Profile Scan Showing That supporting

confidence: 88%

Identifying interatomic potentials for the accurate modeling of interfacial segregation and structural transitions

Schuler

Rupert

2018

Computational Materials Science

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“…An alloy of W-20 at.% Ti synthesized via high energy ball milling exhibited an as-milled grain size of approximately 20 nm that remained stable at 1100°C for one week 43 ; unalloyed nanocrystalline tungsten coarsened by over an order of magnitude to a grain size of .0.5 lm under identical conditions. Similar behavior has been observed in a range of other alloy systems including W-Cr 44 and HfTi 45 as well as in nanocrystalline ceramic materials such as La-doped yttria-stabilized zirconia (YSZ). 46 In this study, thermal stability of magnetron sputtered nanocrystalline tungsten and tungsten alloy thin films is explored through in situ transmission electron microscopy (TEM) annealing experiments up to 1000°C.…”

Section: Introductionmentioning

confidence: 48%

Solute stabilization of nanocrystalline tungsten against abnormal grain growth

et al. 2017

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Microstructure and phase evolution in magnetron sputtered nanocrystalline tungsten and tungsten alloy thin films are explored through in situ TEM annealing experiments at temperatures up to 1000°C. Grain growth in unalloyed nanocrystalline tungsten transpires through a discontinuous process at temperatures up to 550°C, which is coupled to an allotropic phase transformation of metastable b-tungsten with the A-15 cubic structure to stable body centered cubic (BCC) a-tungsten. Complete transformation to the BCC a-phase is accompanied by the convergence to a unimodal nanocrystalline structure at 650°C, signaling a transition to continuous grain growth. Alloy films synthesized with compositions of W-20 at.% Ti and W-15 at.% Cr exhibit only the BCC a-phase in the as-deposited state, which indicate the addition of solute stabilizes the films against the formation of metastable b-tungsten. Thermal stability of the alloy films is significantly improved over their unalloyed counterpart up to 1000°C, and grain coarsening occurs solely through a continuous growth process. The contrasting thermal stability between W-Ti and W-Cr is attributed to different grain boundary segregation states, thus demonstrating the critical role of grain boundary chemistry in the design of solute-stabilized nanocrystalline alloys. transition with a focus on harsh environment sensors produced by additive manufacturing processes. Professor Trelewicz's research is on the science of interface engineered alloys with particular emphasis on high-strength and radiation-tolerant nanomaterials for extreme environment applications. His group couples in situ and analytical characterization tools with large-scale atomistic simulations to explore the thermal stability, mechanical behavior, and radiation tolerance of solute-stabilized nanocrystalline alloys, crystalline-amorphous nanolaminates, metallic glass matrix composites, and other unique hierarchical metallic structures. Professor Trelewicz is a recipient of the 2017 DOE Early Career

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“…Such grain size stability, at temperatures as high as 0.92Tsolidus, has been documented for Cu-Zr [18] but is a new observation for the Cu-Hf and Cu-Mo systems. While stabilization through doping has been reported in systems such as Ni-W [73], Hf-Ti [74], and W-Ti [75], the annealing temperatures used were significantly lower than 0.90Tmelting in these studies. Darling et al [72] did report on a very stable nanocrystalline Fe-Zr alloy, with the stability attributed to Zr segregation.…”

Section: Characterization Of Cu-rich Alloysmentioning

confidence: 75%

Materials selection rules for amorphous complexion formation in binary metallic alloys

Schuler

Rupert

2017

Acta Materialia

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Complexions are phase-like interfacial features that can influence a wide variety of properties, but the ability to predict which material systems can sustain these features remains limited. Amorphous complexions are of particular interest due to their ability to enhance diffusion and damage tolerance mechanisms, as a result of the excess free volume present in these structures.In this paper, we propose a set of materials selection rules aimed at predicting the formation of amorphous complexions, with an emphasis on (1) encouraging the segregation of dopants to the interfaces and (2) lowering the formation energy for a glassy structure. To validate these predictions, binary Cu-rich metallic alloys encompassing a range of thermodynamic parameter values were created using sputter deposition and subsequently heat treated to allow for segregation and transformation of the boundary structure. All of the alloys studied here experienced dopant segregation to the grain boundary, but exhibited different interfacial structures. Cu-Zr and Cu-Hf formed nanoscale amorphous intergranular complexions while Cu-Nb and Cu-Mo retained crystalline order at their grain boundaries, which can mainly be attributed to differences in the enthalpy of mixing. Finally, using our newly formed materials selection rules, we extend our scope to a Ni-based alloy to further validate our hypothesis, as well as make predictions for a wide variety of transition metal alloys.

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Sputtered Hf–Ti nanostructures: A segregation and high-temperature stability study

Cited by 36 publications

References 42 publications

Identifying interatomic potentials for the accurate modeling of interfacial segregation and structural transitions

Identifying interatomic potentials for the accurate modeling of interfacial segregation and structural transitions

Solute stabilization of nanocrystalline tungsten against abnormal grain growth

Materials selection rules for amorphous complexion formation in binary metallic alloys

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