Microstructural evolution in a nanocrystalline Cu-Ta alloy: A combined in-situ TEM and atomistic study

Rajagopalan, M.; Darling, Kristopher A.; Turnage, S.; Koju, R.K.; Hornbuckle, B.C.; Mishin, Y.; Solanki, Kiran

doi:10.1016/j.matdes.2016.10.020

Cited by 71 publications

(14 citation statements)

References 43 publications

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“…In earlier works, the metastable phases in Ta-Cu system were investigated by Cullis et al [33] who observed the metastable substitutional solid solution in the form of thin films. Furthermore, amorphous phases were observed by Natasi et al [34] and Gong et al [35], whereas the nano-crystalline phases by Purja Pun et al [36] and Rajagopalan et al [37]. On the other hand, a Cu/stainless steel interface contains solidified melt zones that are exclusively composed of intermetallic phases of different chemical compositions and various morphology of grains, e.g., [16,19].…”

Section: Macro-/meso-scale Interfaces Overviewmentioning

confidence: 99%

“…The weak point of the mechanism proposed in [31] is that the matrix is not pure copper but is mostly a solid solution of Ta in the Cu (see Figure 8). However, aside from the limited information on the phase constitution in the Cu-Ta immiscible systems, the formation of metastable phases can be expected due to rapid cooling during solidification of melted volumes, as described for other processes in [33][34][35][36][37]41,42]. Due to the extremely high dynamic of the EXW process, there is no time for the diffusion in the solid state, hence the melting of Ta can be expected.…”

Section: Microstructural Changes Due To Formation Of the Solidified Mmentioning

confidence: 99%

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Structural Properties of Interfacial Layers in Tantalum to Stainless Steel Clad with Copper Interlayer Produced by Explosive Welding

Paul

Chulist

Mania

2020

Metals

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A systematic study of explosively welded tantalum and 304 L stainless steel clad with M1E copper interlayer was carried out to characterize the microstructure and mechanical properties of interfacial layers. Microstructures were examined using transmission and scanning (SEM) electron microscopy, whereas mechanical properties were evaluated using microhardness measurements and a bending test. The macroscale analyses showed that both interfaces between joined sheets were deformed to a wave-shape with solidified melt zones located preferentially at the crest of the wave and in the wave vortexes. The microscopic analyses showed that the solidified melt zones are composed of nano-/micro-crystalline phases of different chemical composition, incorporating elements from the joined sheets. SEM/electron backscattered diffraction (EBSD) measurements revealed the microstructure of layers of parent sheets that undergo severe plastic deformation causing refinement of the initial grains. It has been established that severely deformed areas can undergo recovery and recrystallization already during clad processing. This leads to the formation of new stress-free grains. The microhardness of welded sheets increases significantly as the joining interface is approaching excluding the volumes directly adhering to large melted zones, where a noticeable drop of microhardness, due to recrystallization, is observed. On lateral bending the integrity of the all clad components is conserved.

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Section: Macro-/meso-scale Interfaces Overviewmentioning

confidence: 99%

Section: Microstructural Changes Due To Formation Of the Solidified Mmentioning

confidence: 99%

Structural Properties of Interfacial Layers in Tantalum to Stainless Steel Clad with Copper Interlayer Produced by Explosive Welding

Paul

Chulist

Mania

2020

Metals

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“…3c ) implying that the higher temperatures increase thermal activation of dislocations and reduce activation barriers for thermal bypass of nanoclusters. Dislocation bypass is further enhanced by a reduction in the cluster-matrix-coherency strain 21 . Collectively, this loss of pinning efficiency leads to increasing the average dislocation velocity in a lattice environment whereby the drag coefficient is already increased as a result of elevated temperatures.…”

Section: Resultsmentioning

confidence: 99%

“…Further details related to the processing and impurity levels can be found in refs. 15 , 21 , 29 , 30 .…”

Section: Methodsmentioning

confidence: 99%

Anomalous mechanical behavior of nanocrystalline binary alloys under extreme conditions

et al. 2018

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Fundamentally, material flow stress increases exponentially at deformation rates exceeding, typically, ~103 s−1, resulting in brittle failure. The origin of such behavior derives from the dislocation motion causing non-Arrhenius deformation at higher strain rates due to drag forces from phonon interactions. Here, we discover that this assumption is prevented from manifesting when microstructural length is stabilized at an extremely fine size (nanoscale regime). This divergent strain-rate-insensitive behavior is attributed to a unique microstructure that alters the average dislocation velocity, and distance traveled, preventing/delaying dislocation interaction with phonons until higher strain rates than observed in known systems; thus enabling constant flow-stress response even at extreme conditions. Previously, these extreme loading conditions were unattainable in nanocrystalline materials due to thermal and mechanical instability of their microstructures; thus, these anomalies have never been observed in any other material. Finally, the unique stability leads to high-temperature strength maintained up to 80% of the melting point (~1356 K).

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“…Although there have been a lot of studies [13,14,15,16,17,18,19,20,21] on preparation methods and deformation mechanisms of the Cu–Ta alloy, few researchers pay any attention to analyzing some main factors influencing the mechanical properties of the Cu–Ta alloy quantitatively and systematically. According to Frolov’s work [12], the main purpose of this study is to quantitatively analyze the influence of grain size and strain rate on the mechanical properties of Cu–Ta (10 at %) alloy by molecular dynamics method and verify the rationality of the method of establishing the Cu–Ta alloy model.…”

Section: Introductionmentioning

confidence: 99%

Atomic Study on Tension Behaviors of Sub-10 nm NanoPolycrystalline Cu–Ta Alloy

Wang

Gao

et al. 2019

Materials

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Atomic simulations give a good explanation of the changes in the physical properties of a material. In this work, the tension behaviors of nanopolycrystalline Cu–Ta alloys are investigated through molecular dynamics (MD) simulations, and the influences of several important factors on the mechanical properties of the materials are studied. Firstly, nanopolycrystalline Cu–Ta (10 at %) alloy models with sub-10 nm grains are established by using the method of replacing the grain boundary atoms. Then, the effects of temperature, pressure, and strain rate on the mechanical properties of nanopolycrystalline Cu–Ta alloy are studied, and the elastic modulus and flow strength are obtained. The observations from the simulation results show that the elastic modulus and flow strength increase with the increasing of grain size for sub-10 nm nanopolycrystalline Cu–Ta alloys, and the elastic modulus increases firstly and then stabilizes as the strain rate increases. Finally, according to the evolution of dislocations and twin crystals, the plastic deformation mechanism of nanopolycrystalline Cu–Ta alloy during the stretching process is discussed in depth.

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Microstructural evolution in a nanocrystalline Cu-Ta alloy: A combined in-situ TEM and atomistic study

Cited by 71 publications

References 43 publications

Structural Properties of Interfacial Layers in Tantalum to Stainless Steel Clad with Copper Interlayer Produced by Explosive Welding

Structural Properties of Interfacial Layers in Tantalum to Stainless Steel Clad with Copper Interlayer Produced by Explosive Welding

Anomalous mechanical behavior of nanocrystalline binary alloys under extreme conditions

Atomic Study on Tension Behaviors of Sub-10 nm NanoPolycrystalline Cu–Ta Alloy

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