Deformation Twinning and Detwinning in Face‐Centered Cubic Metallic Materials

Nanotwinned (nt) metals exhibit excellent mechanical, electrical and thermal properties, and therefore attract much attentions. To fabricate large area nt surface, the fundamental mechanisms of deformation twinning induced by molecular dynamics (MD) are necessary to be explored. Nevertheless, MD of nt metals currently focus mainly on nt copper (Cu) and other single element metals with face-centered cubic (fcc) structure. In addition, MD simulations are usually performed on a built nt model, rather than from a single crystal, due to the difficulty of forming nanotwins. In this study, a single crystal is constructed in a ternary titanium (Ti) alloy with hexagonal closed-packed (hcp) lattice cell. Deformation twinning of MD simulation is performed in a ternary Ti alloy under nanoindentation from the built single crystal. Zonal structure is found during loading under nanoindentation, and nanograins transforms into nanotwins. Deformation twinning is significant to understanding the formation of nanotwins, as well as fabricating large area nt surface on a Ti alloy.

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Deformation Mechanisms of Nanocrystalline Hexagonal Close-Packed Metals

MRS Proceedings ◽

10.1557/proc-0924-z03-19 ◽

2006 ◽

Vol 924 ◽

Author(s):

Guangping Zheng

Keyword(s):

Deformation Twinning ◽

Dynamics Simulation ◽

Deformation Mechanisms ◽

Face Centered Cubic ◽

Transformation Mechanism ◽

Shockley Partial Dislocation ◽

Hexagonal Close Packed ◽

Simulation Results ◽

Face Centered ◽

Fcc Structure

ABSTRACTUsing molecular dynamics simulation of nanocrystalline (nc) samples with grain size of 10 nm, a reverse martensitic transformation from hexagonal close-packed (hcp) to face-centered cubic (fcc) structure is observed in nc-cobalt and nc-zirconium undergoing plastic deformation. In nc-cobalt hcp-to-fcc transformation is prevalent and deformation twinning is rarely observed. The transformation mechanism involves the motion of Shockley partial dislocation 1/3<1100> in every other (0001)hcp /(111)fcc plane. In nc-zirconium the hcp-to-fcc transformation competes with the deformation twinning. From the simulation results, it is suggested that the interaction among partials should be considered to understand the deformation mechanisms of hcp nc metals.

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Effect of Solid Solution Impurities on Dislocation Nucleation During Nanoindentation

Journal of Materials Research ◽

10.1557/jmr.2005.0244 ◽

2005 ◽

Vol 20 (8) ◽

pp. 1947-1951 ◽

Cited By ~ 32

Author(s):

D.F. Bahr ◽

G. Vasquez

Keyword(s):

Solid Solution ◽

Shear Stress ◽

Dislocation Nucleation ◽

Face Centered Cubic ◽

Metallic Materials ◽

Solid Solution Strengthening ◽

Free Region ◽

Solution Strengthening ◽

Face Centered ◽

Nucleation Of Dislocations

Dislocation nucleation in solid solutions of face-centered-cubic metallic materials was studied using nanoindentation. The effects of solute impurities in the copper–nickel system on the formation of dislocations in a previously dislocation-free region were demonstrated to be minimal. The shear stress required to nucleate dislocations in copper is approximately 1.6 GPa, while in nickel a 3.9 GPa shear stress is required. Changes in shear stress for nucleation track closely with changes in elastic modulus showing the nucleation stress is approximately 1/30 to 1/20 of the shear modulus. The expected solid-solution strengthening is identified within the same experimental method, demonstrating unambiguously the fact that solid-solution impurities in this system will impact the propagation of dislocations during plastic deformation but not alter the homogeneous nucleation of dislocations in these materials.

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DEFORMATION TWINNING IN FACE-CENTERED CUBIC METALS. Technical Report No. 1

10.2172/4159422 ◽

1963 ◽

Cited By ~ 1

Author(s):

J.A. Venables

Keyword(s):

Deformation Twinning ◽

Face Centered Cubic ◽

Cubic Metals ◽

Technical Report ◽

Face Centered

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