Nonuniform twin-boundary motion in Ni–Mn–Ga single crystals

2004 ◽  
Vol 84 (20) ◽  
pp. 4071-4073 ◽  
Author(s):  
Miguel A. Marioni ◽  
Samuel M. Allen ◽  
Robert C. O’Handley
Keyword(s):  
Single Crystals ◽  
Twin Boundary ◽  
Boundary Motion

In-situ observation of stress-induced stochastic twin boundary motion in off stoichiometric NiMnGa single crystals

2013 ◽  
Vol 103 (2) ◽  
pp. 021909 ◽  
Author(s):  
Rozaliya I. Barabash ◽  
Christoph Kirchlechner ◽  
Odile Robach ◽  
Olivier Ulrich ◽  
Jean-Sébastien Micha ◽  
...  
Keyword(s):  
Single Crystals ◽  
Twin Boundary ◽  
In Situ Observation ◽  
Boundary Motion

Acoustic-Assisted, Magnetic-Field-Induced Actuation of Ni-Mn-Ga Single Crystals

2008 ◽  
Vol 583 ◽  
pp. 147-168
Author(s):  
Ratchat Techapiesancharoenkij ◽  
Samuel M. Allen ◽  
Robert C. O'Handley
Keyword(s):  
Magnetic Field ◽  
Single Crystals ◽  
Yield Stress ◽  
Twin Boundary ◽  
Magnetic Energy ◽  
Large Strain ◽  
Threshold Field ◽  
Stress And Strain ◽  
Boundary Motion ◽  
Reversible Strain

Ni–Mn–Ga based ferromagnetic shape memory alloys (FSMAs) have emerged as a promising class of active materials capable of producing a large (up to 10%) magnetic-field-induced strain (MFIS). This large strain is not the familiar anisotropic magnetostriction; it results from field-induced twin-boundary motion and has appropriately been referred to as magnetoplasticity. FSMAs still have several characteristic shortcomings that may limit their potential applications. A threshold field of 150 to 300 kA/m must be overcome to initiate twin-boundary motion and a larger field is required to achieve full strain. The operating window of the stress output from FSMA actuators is limited to the range between 1 and 1.5 MPa. Outside this operating range, the strain output diminishes significantly. This paper addresses these performance limitations and describes an acoustic-assist technique that has been shown to decrease the required threshold field and increase the stress and strain output of FSMA actuation. The application of an acoustic assistance from a 33-mode piezoelectric stack is shown to improve MFIS of Ni–Mn–Ga single crystals by reducing the required threshold field and twinning-yield stress. Threshold field reductions of up to 80 kA/m are observed, and the twinning-yield stress can be reduced by up to 0.5 MPa. The effect of acoustic assistance on FSMA actuation can be understood as a form of time varying stress waves that facilitate twin-boundary motion. A stress wave analysis is shown to give a quantitative understanding of the measured reduction in the twinning-yield stress. For FSMA cyclic actuation, both operating stress and strain outputs of the FSMA actuation are significantly enhanced by acoustic assistance. Without the acoustic assistance, the maximum reversible strain of the sample used here is 3% and appears only in the limited external stress range between 0.7 and 1 MPa. With the acoustic assistance, the maximum reversible strain increases to 4.5% and appears in a broader range of stress output between 0.4 and 1.2 MPa. The reduction in the twinning-yield stress due to the acoustic assistance significantly improves the FSMA cyclic actuation performance; magnetic energy not used to drive twin-boundary motion can be utilized to work against a larger external load.

Anisotropy of the flux creep in the motion of vortices along twin-boundary planes in YBa2Cu3O7−x single crystals

2001 ◽  
Vol 27 (5) ◽  
pp. 339-344 ◽  
Author(s):  
A. V. Bondarenko ◽  
A. A. Prodan ◽  
M. A. Obolenskiı̆ ◽  
R. V. Vovk ◽  
T. R. Arouri
Keyword(s):  
Single Crystals ◽  
Twin Boundary ◽  
Flux Creep

scholarly journals Effect of Twin Boundary Motion and Dislocation-Twin Interaction on Mechanical Behavior in Fcc Metals

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2238
Author(s):  
Jaber Rezaei Mianroodi ◽  
Bob Svendsen
Keyword(s):  
Twin Boundary ◽  
Partial Dislocation ◽  
Shear Loading ◽  
Dislocation Nucleation ◽  
The Other ◽  
Boundary Motion ◽  
Normal Loading ◽  
Fcc Metals ◽  
Boundary Orientation ◽  
Normal Twin

The interplay of interface and bulk dislocation nucleation and glide in determining the motion of twin boundaries, slip-twin interaction, and the mechanical (i.e., stress-strain) behavior of fcc metals is investigated in the current work with the help of molecular dynamics simulations. To this end, simulation cells containing twin boundaries are subject to loading in different directions relative to the twin boundary orientation. In particular, shear loading of the twin boundary results in significantly different behavior than in the other loading cases, and in particular to jerky stress flow. For example, twin boundary shear loading along ⟨ 112 ⟩ results in translational normal twin boundary motion, twinning or detwinning, and net hardening. On the other hand, such loading along ⟨ 110 ⟩ results in oscillatory normal twin boundary motion and no hardening. As shown here, this difference results from the different effect each type of loading has on lattice stacking order perpendicular to the twin boundary, and so on interface partial dislocation nucleation. In both cases, however, the observed stress fluctuation and “jerky flow” is due to fast partial dislocation nucleation and glide on the twin boundary. This is supported by the determination of the velocity and energy barriers to glide for twin boundary partials. In particular, twin boundary partial edge dislocations are significantly faster than corresponding screws as well as their bulk counterparts. In the last part of the work, the effect of variable twin boundary orientation in relation to the loading direction is investigated. In particular, a change away from pure normal loading to the twin plane toward mixed shear-normal loading results in a transition of dominant deformation mechanism from bulk dislocation nucleation/slip, to twin boundary motion.

Kinetics of twin boundary migration in YBa2Cu3O7−x single crystals

1992 ◽  
Vol 203 (3-4) ◽  
pp. 342-346 ◽  
Author(s):  
L.A. Dorosinskii ◽  
V.I. Nikitenko ◽  
A.A. Polyanski ◽  
V.K. Vlasko-Vlasov ◽  
A. Roytburd ◽  
...  
Keyword(s):  
Single Crystals ◽  
Twin Boundary ◽  
Boundary Migration ◽  
Kinetics Of

Real-time observation of twin boundary motion in organic crystal (TMTSF)2X

2001 ◽  
Vol 251 (1) ◽  
pp. 199-205 ◽  
Author(s):  
Kazushige Kawabata ◽  
Yasuyoshi Hosokawa ◽  
Takashi Kawauchi ◽  
Takashi Sambongi
Keyword(s):  
Real Time ◽  
Twin Boundary ◽  
Organic Crystal ◽  
Boundary Motion ◽  
Time Observation ◽  
Real Time Observation

Theoretical Study of Twin Boundary Motion in Heusler Ni-Mn-Ga Alloys Using Monte Carlo Method

2012 ◽  
Vol 190 ◽  
pp. 327-330
Author(s):  
K.I. Kostromitin ◽  
Vasiliy D. Buchelnikov ◽  
V.V. Sokolovskiy ◽  
P. Entel
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Monte Carlo Simulations ◽  
Twin Boundary ◽  
Constant Temperature ◽  
Theoretical Study ◽  
Heusler Alloys ◽  
Boundary Motion ◽  
Different Temperatures

The twin boundary motion in Ni-Mn-Ga Heusler alloys has been investigated using Monte Carlo simulations. The Hamiltonian of system includes magnetic and elastic parts and two magnetoelastic terms. It is shown that the twin boundary shifts in a magnetic field at the constant temperature. The spin and strain volume fractions have been obtained at different temperatures.

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