An initial analysis of mechanisms leading to late stage abnormal grain growth in nanocrystalline Ni

Hibbard, G.D.; McCrea, J.L.; Palumbo, G.; Aust, K.T.; Erb, U.

doi:10.1016/s1359-6462(02)00098-2

Cited by 112 publications

(38 citation statements)

References 10 publications

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“…In addition, nano-crystalline Ni with a bimodal microstructure was recently known to exhibit the pronounced strain hardening. 23,24) Such concurrent strengthening and toughening, as also observed for the 4 ECA pressed AZ31 and AZ61 alloys when compared with asannealed one, could be attributed to the fine grains that reduce the size of nucleating defects and increase the resistance to crack propagation, leading to the higher fracture stress, 25) and the larger (softer) grains that might accommodate strains preferentially. 22) Consequently, the inhomogeneous mixed microstructure induces the strain hardening mechanisms that stabilize the tensile deformation accompanied with grain boundary sliding, leading to the high tensile ductility.…”

Section: Micro Hardness and Tensile Deformation Behaviorsupporting

confidence: 56%

Improvement of Mechanical Characteristics in Severely Plastic-deformed Mg Alloys

et al. 2004

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The commercial pure Mg, AZ31 and AZ61 alloys were severly plastic-deformed through equal channel angular pressing (ECAP). The grain size of pure Mg was decreased from 400 to 80 mm after ECAP and the 4 ECA pressed AZ31 alloy revealed the mixed microstructure of fine grains of less than 5 mm and coarser grains of approximately 5 $ 10 mm. Newly formed grains were attributed to dynamic recrystallization during ECAP at temperatures of higher than 1/2 T m , where T m is melting temperature. There was small increase of microhardness, yield stress and tensile strength in the ECA pressed pure Mg, while those of AZ31 and AZ61 alloys drastically increased after 1 pressing. The yield stress in the ECA pressed AZ31 and AZ61 alloys gradually decreased with increasing the number of pressings, but the tensile strength increased slightly. In particular, there was a typical tensile characteristic when compared with the other ECA pressed metals; a marked improvement in elongation was found concurrent with the pronounced strain hardening, without sacrificing the tensile strength, in the 4 ECA pressed AZ31 and AZ61 alloys. These tensile deformation characteristics were explained based on the observation of the deformed microstructure in the vicinity of fracture surface.

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Section: Micro Hardness and Tensile Deformation Behaviorsupporting

confidence: 56%

Improvement of Mechanical Characteristics in Severely Plastic-deformed Mg Alloys

et al. 2004

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“…12,13 A classic example of this phenomenon is found in nanocrystalline Ni where grain size increased by 20Â at only 30% of its melting point. 14 Similar behavior has been observed across a range of single-component nanocrystalline metals such as cobalt, 15 iron, 16 copper, 17 and silver 18 where microstructural evolution often prescribes to curvature-driven grain growth with the grain boundary velocity, m, proportional to the local mean curvature of the boundary, j:…”

Section: Introductionmentioning

confidence: 63%

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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“…The success of such technique to fabricate nanocrystalline materials has been addressed at length in several previous publications [6][7][8]. The electrodeposition process generally produces thin foils with a thickness of tens of micrometers.…”

Section: Methodsmentioning

confidence: 99%

Deformation of nanocrystalline materials at ultrahigh strain rates – microstructure perspective in nanocrystalline nickel

et al. 2006

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Nanocrystalline materials with grain sizes smaller than 100 nm have attracted extensive research in the past decade. Due to their high strength, these materials are good candidates for high pressure shock loading experiments. In this paper, we investigated the microstructural evolutions of nanocrystalline nickel with grain sizes of 10-50 nm, shock-loaded in a range of pressures (20-70 GPa). A laser-driven isentropic compression process was applied to achieve high shock-pressures in a timescale of nanoseconds and thus the high-strain-rate deformation of nanocrystalline nickel. Postmortem transmission electron microscopy (TEM) examinations reveal that the nanocrystalline structures survive the shock deformation and that dislocation activity is the prevalent deformation mechanism when the grain sizes are larger than 30 nm, without any twinning activity at twice the stress threshold for twin formation in micrometer-sized polycrystals. However, deformation twinning becomes an important deformation mode for 10-20 nm grain-sized samples.

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An initial analysis of mechanisms leading to late stage abnormal grain growth in nanocrystalline Ni

Cited by 112 publications

References 10 publications

Improvement of Mechanical Characteristics in Severely Plastic-deformed Mg Alloys

Improvement of Mechanical Characteristics in Severely Plastic-deformed Mg Alloys

Solute stabilization of nanocrystalline tungsten against abnormal grain growth

Deformation of nanocrystalline materials at ultrahigh strain rates – microstructure perspective in nanocrystalline nickel

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