The mechanical behaviour of single crystals of metals, in particular copper

1957 ◽  
Vol 240 (1222) ◽  
pp. 304-320 ◽  
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Single Crystals ◽  
Mechanical Behaviour ◽  
Critical Shear Stress ◽  
Deformation Bands ◽  
Hexagonal Metals

With single crystals of copper, measurements have been made on the variation of the amount of easy glide with the orientation of the crystal axes relative to the direction of tension. At —180° C it has been shown that this variation can be quantitatively expressed by a specific hardening on the active glide planes, which does not exist for the latent glide planes, and a general hardening which applies to both active and latent glide planes. This is compared with the behaviour of hexagonal metals. The occurrence of double glide is analyzed. The variation of glide properties with temperature has been measured for one particular orientation, and the coefficient of specific hardening shown to be roughly independent of temperature. The critical shear stress is also very little affected by temperature, but depends somewhat on orientation. The glide behaviour at high temperature has been found to be influenced largely by the occurrence of deformation bands. A few measurements have been made on gold.

scholarly journals The critical shear stress of mercury single crystals

1937 ◽  
Vol 163 (912) ◽  
pp. 34-53 ◽  
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Melting Point ◽  
Single Crystal ◽  
Single Crystals ◽  
Critical Shear Stress ◽  
Impurity Content ◽  
Thermal Agitation ◽  
Plastic Yield ◽  
Metal Single Crystals

The influence of very small quantities of impurity on the critical shear stress of metal single crystals has an important bearing on the mechanism of their plastic deformation. For investigations in this field, mercury is a very suitable metal: its impurity content can easily be reduced to an extremely low level (Hulett 1911) and it contains no dissolved gases (Hulett 1911). Also, as first pointed out by Andrade (1914), single crystal wires of this metal can be prepared without difficulty. The low melting point of mercury (-38∙8° C.) is far from being a disadvantage. The crystals can be maintained at -60° C., and at a temperature so near the melting point the thermal agitation may be expected to accentuate phenomena not observable at lower temperatures, if such agitation plays the important part in the mechanism of glide ascribed to it (Taylor 1934; Polanyi 1934; Orowan 1934). As a possible instance of this, the experiments to be described have revealed the existence of a preliminary “set” preceding the true plastic yield. Widely differing forms of slip band have also been observed, and are described elsewhere (Greenland 1937). It is hoped that these results will throw further light on the mechanism of glide.

Influence of defects on the high temperature mechanical behaviour of yttria fully-stabilized zirconia single crystals

1999 ◽  
Vol 151 (1-4) ◽  
pp. 83-89
Author(s):  
D. Gómez-García ◽  
A. Gallardo-López ◽  
J. Martínez-Fernández ◽  
A. Domínguez-Rodríguez
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
Mechanical Behaviour ◽  
Stabilized Zirconia

Critical shear stress temperature and rate dependence in magnesium single crystals

1972 ◽  
Vol 4 (10) ◽  
pp. 1216-1220 ◽  
Author(s):  
F. F. Lavrent'ev ◽  
Yu. A. Pokhil ◽  
V. I. Startsev
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Critical Shear Stress ◽  
Rate Dependence

Orientation Dependence of High Temperature Creep Strength and Internal Stress in Ni3Al Alloy Single Crystals

1996 ◽  
Vol 460 ◽  
Author(s):  
Seiji Miura ◽  
Zhi-Lun Peng ◽  
Yoshinao Mishima
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Internal Stress ◽  
Single Crystals ◽  
Creep Behavior ◽  
Creep Strength ◽  
Orientation Dependence ◽  
Stress Axis ◽  
High Temperature Creep ◽  
Temperature Creep

ABSTRACTHigh temperature creep behavior of a nickel-rich Ni3(Al,Ta) with the L12 structure is investigated in order to clarify the influence of crystallographic orientation with respect to the stress axis. The single crystals with four different orientations are deformed in compressive creep at temperatures ranging from ‘M 23 to 1273 K under a constant load, initial shear stress being 35 to 120 MPa for (111)[101] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent of the orientation. It is shown, however, the internal stress, being measured by strain transient dip tests, is found to be orientation dependent and the creep behavior is independent on orientation if it is interpreted using the effective stress instead of the applied shear stress.

Precipitation of NiHfsi phase in NiAl single crystals containing Hf

1995 ◽  
Vol 53 ◽  
pp. 532-533
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
R. Darolia
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
High Temperature Strength ◽  
Bridgman Technique ◽  
Shell Mold ◽  
Third Phase ◽  
Unknown Phase ◽  
Transmission Electron ◽  
Two Phases ◽  
Nial Matrix

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.

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