Anomalous temperature dependence of the yield stress by secondary pyramidal slip in cadmium crystals—II. Mechanism

1994 ◽  
Vol 42 (8) ◽  
pp. 2853-2858 ◽  
Author(s):  
Hideki Tonda ◽  
Shinji Ando ◽  
Kazuki Takashima ◽  
Thad Vreeland
Keyword(s):  
Temperature Dependence ◽  
Yield Stress ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Pyramidal Slip

Yield Stress Reversibility and the Operation of Frank-Read Sources in Li2 Alloys in the Anomalous Regime For (111) Slip

1994 ◽  
Vol 364 ◽  
Author(s):  
S. S. Ezz ◽  
P. B. Hirsch
Keyword(s):  
Strain Rate ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Edge Dislocation ◽  
Anomalous Temperature Dependence ◽  
Successful Operation ◽  
Anomalous Temperature ◽  
Small Strains ◽  
Edge Dislocations ◽  
Is Strain

AbstractThe yield stress τy at small strains (≈ 0.01%) is strain rate independent, and has the same anomalous temperature dependence as that of the 0.2% strain. τy is considered to be the stress at which Frank-Read sources operate in a virgin crystal. For successful operation, τy must exceed the stress τs at which screws propagate dynamically through the crystal, and the source dislocation must pass rapidly through the unstable Frank - Read configuration. This can be achieved by the bowing edge dislocation overcoming local obstacles before reaching that configuration. Loops elongated along the screw direction are expected to be formed in the microstrain region. Under certain conditions such loops are unstable on unloading, thereby generating long edge dislocations which can operate successfully as sources at low but not at high temperatures, explaining the reversibility phenomenon.

Deformation Behavior of Magnesium Single Crystals in C-Axis Compression

2007 ◽  
Vol 345-346 ◽  
pp. 129-132 ◽  
Author(s):  
Takaaki Kitahara ◽  
Shinji Ando ◽  
Masayuki Tsushida ◽  
Hiromoto Kitahara ◽  
Hideki Tonda
Keyword(s):  
Fracture Surface ◽  
Single Crystals ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Pyramidal Slip ◽  
Axis Compression ◽  
General Deformation ◽  
Increasing Temperature

In general, deformation behavior of magnesium in compression is different from tensile. To investigate deformation behavior of magnesium single crystals, c-axis compression was performed. The crystals were yielded by second order pyramidal slip, and the yield stress shows anomalous temperature dependence (increased with increasing temperature) between 203K and 293K. Yield stress of c-axis compression is bigger than that of a-axis tensile. {10-13} twin and {11-24} twin occurred at 77293K and 77473K respectively. Fracture surface at 77293K was {11-24} and at 473K was {11-22}.

Anomalous Temperature Dependence of Yield Stress and Work Hardening Coefficient of B2-Stabilized NiTi Alloys

1996 ◽  
Vol 460 ◽  
Author(s):  
Hideki Hosoda ◽  
Yoshinao Mishima ◽  
Tomoo Suzuki
Keyword(s):  
Martensitic Transformation ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Test Temperature ◽  
Work Hardening ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Niti Alloys ◽  
Work Hardening Coefficient ◽  
Hardening Coefficient

ABSTRACTYield stress and work hardening coefficient of B2-stabilized NiTi alloys are investigated using compression tests. Compositions of NiTi alloys are based on Ni-49moJ.%Ti, to which Cr, Co and Al are chosen as ternary elements which reduce martensitic transformation temperatures of the B2 phase. Mechanical tests are carried out in liquid nitrogen at 77K, air at room temperature (R.T.) and in an argon atmosphere between 473K and 873K. Only at 77K, some alloys show characteristic stress-strain curves which indicate stress induced martensitic transformation (SIMT), but the others do not. Work hardening coefficient is found to be between 2 and 1 lGPa in all the test temperature range. The values are extremely high compared with Young's modulus of B2 NiTi. Yield stress and work hardening coefficient increase with test temperature between R.T. and about 650K in most alloys. The anomalous temperature dependence of mechanical properties is not related to SIMT but to precipitation hardening and/or anomalous dislocation motion similar to B2-type CoTi. Solution hardening by adding ternary elements is evaluated to be small for Cr and Co additions, and large for Al addition, depending on difference in atomic size of the ternary element with respect to Ni or Ti.

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