The yield stress of single crystals of α-phase copper-aluminium alloys

1981 ◽  
Vol 376 (1766) ◽  
pp. 343-359 ◽  
Keyword(s):  
Standard Deviation ◽  
Single Crystals ◽  
Yield Stress ◽  
Aluminium Alloys ◽  
Composition Dependence ◽  
Experimental Conditions ◽  
Α Phase

The composition dependence of the yield stress, σ , of single crystals of α-phase copper-aluminium alloys has been measured at 293 and 4.2 K under precisely defined experimental conditions to determine whether the Friedel relation with σ ∝ c 1/2 or the Mott-Labusch relation with σ ∝ c 2/3 applies. The best statistical fit gives a dependence of σ on c 1/2 for values of c between 0 and 0.15. A curve with σ ∝ c 2/3 can be fitted to the results for 0.003 ≤ c ≤ 0.15 with a small increase in the standard deviation, but a segment with σ ∝ c 1/2 must be introduced for 0 ≤ c ≤ 0.003. On the basis of these measurements it is not possible to decide between the validity of Friedel and of Mott-Labusch statistics for the concentrated alloys.

THE NATURE AND FORMATION OF BANDS OF DEFORMATION IN SINGLE CRYSTALS OF α-PHASE COPPER–ALUMINIUM ALLOYS

1967 ◽  
Vol 45 (2) ◽  
pp. 453-479 ◽  
Author(s):  
J. W. Mitchell ◽  
J. C. Chevrier ◽  
B. J. Hockey ◽  
J. P. Monaghan Jr.
Keyword(s):  
Surface Topography ◽  
Single Crystals ◽  
Aluminium Alloys ◽  
Optical Microscope ◽  
Step Height ◽  
Interference Microscopy ◽  
Slip Lines ◽  
Α Phase ◽  
Transmission Electron ◽  
Characteristic Features

The mechanism of the deformation in tension of [321] axis square-sectioned single crystals of α-phase copper–aluminium alloys with [Formula: see text] and [Formula: see text] surfaces has been studied. Extensive use has been made of interference microscopy and carbon replicas for the determination of the surface topography of the bands of deformation. It has been shown that, in addition to the discrete slip lines which are seen with the optical microscope and in replicas, there is a background of plastic deformation on a much finer scale which is not resolved. The integrated step height across bands of deformation corresponding with this fine slip can be measured on the interferograms. The integrated step height between corresponding points on the opposite [Formula: see text] surfaces was found to be equal. The studies of surface topography were supplemented by work on the nature of the distributions of dislocations within the crystals by etching and transmission electron microscopy. It was found that the dislocations are largely present as interleaved pileups of parallel positive and parallel negative dislocations in near-edge orientations and as closely spaced multipolar distributions. Large pileups of several hundred dislocations have been observed and correlated with surface slip lines. They appear to be introduced as avalanches from surface sources. Characteristic features of this previously unrecognized type of band of deformation have been established and the mechanism proposed for the formation of the bands recalls many of the features of the dynamical model for the multiplication of dislocations discussed by Frank in 1947. The background on which the slip lines are superimposed appears to be due to the limited activation by the shear stress within the band of deformation of a uniform distribution of sources.

The yield stress of single crystals of α-phase Cu-Ni-Pd and Cu-Pd alloys

1989 ◽  
Vol 423 (1865) ◽  
pp. 267-278 ◽  
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Yield Stress ◽  
Yield Point ◽  
Concentration Dependence ◽  
Atomic Concentration ◽  
Α Phase ◽  
Alloy Series ◽  
Pd Alloy ◽  
Critical Resolved Shear Stress

Single crystals of Cu- x at. % Ni- x at. % Pd [ x ═ 1 to 6] and Cu- x at. % Pd alloys [ x ═ 1, 2, 4 and 6] were deformed in tension at 293 K and 4.2 K. The crystals had the [331] {͞110} {͞1͞16} orientation which has two equivalent {͞1͞11} <011> and {͞1͞11} <101> primary glide systems. The concentration dependence of the critical resolved shear stress σ at the yield point for both alloy series was given by σ T ═ σ 0 ( T )+ A ( T ) c α , where σ 0 ( T ) and A ( T ) are constants for one alloy series at T K and c is the atomic concentration of the solute. The exponent α is 0.72 or 0.73 for the Cu-Ni-Pd and 0.61 or 0.62 for the Cu-Pd alloy series at 293 or 4.2 K. The data for both alloy series could be fitted to the relation σ 4.2K -σ 293K ═ 1.046+0.526σ 4.2K [MPa]. This establishes the stress equivalence behaviour of single crystals of these alloys.

Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent

1982 ◽  
Vol 47 (7) ◽  
pp. 1973-1978 ◽  
Author(s):  
Jiří Karhan ◽  
Zbyněk Ksandr ◽  
Jiřina Vlková ◽  
Věra Špatná
Keyword(s):  
Standard Deviation ◽  
Nmr Spectroscopy ◽  
Standard Method ◽  
Internal Standard ◽  
Internal Standard Method ◽  
Concentration Region ◽  
Experimental Conditions ◽  
Curve Method ◽  
Sample Preparation Procedure

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.

Features of forming the α-phase in zirconium pseudo single crystals during their polymorphic transformation

2010 ◽  
Vol 1 (3) ◽  
pp. 238-244
Author(s):  
Yu. V. Khlebnikova ◽  
D. P. Rodionov ◽  
Yu. V. Kaletina ◽  
V. A. Sazonova ◽  
I. L. Solodova
Keyword(s):  
Single Crystals ◽  
Polymorphic Transformation ◽  
Α Phase

Orientation dependence of yield stress in 4.4% silicon iron single crystals

1967 ◽  
Vol 15 (7) ◽  
pp. 1179-1191 ◽  
Author(s):  
S Takeuchi ◽  
E Furubayashi ◽  
T Taoka
Keyword(s):  
Single Crystals ◽  
Yield Stress ◽  
Orientation Dependence ◽  
Silicon Iron

Anomaly of the Work Hardening of Zn-Cu Single Crystals Oriented for Slip in Secondary Systems

2011 ◽  
Vol 56 (4) ◽  
pp. 1021-1027
Author(s):  
K. Pieła
Keyword(s):  
Strain Hardening ◽  
Single Crystals ◽  
Yield Stress ◽  
Work Hardening ◽  
Temperature Anomaly ◽  
Strain Hardening Exponent ◽  
Plastic Behavior ◽  
Thermal Dependence ◽  
Copper Addition ◽  
Secondary Systems

Anomaly of the Work Hardening of Zn-Cu Single Crystals Oriented for Slip in Secondary SystemsThe copper alloyed (up to 1.5%) zinc single crystals oriented for slip in non-basal systems (orientation close to < 1120 >) were subjected to compression test within a range of temperatures of 77-293K. It has been stated, that Zn-Cu crystals exhibit characteristic anomalies of the thermal dependence of yield stress and of the strain hardening exponent. Both of them are related to the change in type and sequence of active non-basal slip systems: pyramidal of the 1storder {1011} < 1123 > (Py-1) and pyramidal of the 2ndorder {1122} < 1123 > (Py-2). The temperature anomaly of the yield stress results from the change of the slip from Py-2 systems to simultaneous slip in the Py-2 and Py-1 (Py-2 + Py-1) systems, occurring in the preyielding stage. On the other hand, sequential activation of pyramidal systems taking place in advanced plastic stage (i.e. the first Py-2 and next Py-2 + Py-1 systems) is responsible for temperature anomaly of strain hardening exponent. Increase in copper addition favors the activity of Py-2 systems at the expense of Py-1 slip, what leads to a drastic differences in plastic behavior of zinc single crystals.

Annealing and Yield Stress of NaCl Single Crystals

1964 ◽  
Vol 47 (11) ◽  
pp. 585-587 ◽  
Author(s):  
W. S. ROTHWELL ◽  
R. G. GREENLER
Keyword(s):  
Single Crystals ◽  
Yield Stress

GRAIN-SIZE DEPENDENCE OF FRACTURE IN COPPER–ALUMINIUM ALLOYS EMBRITTLED BY MERCURY

1967 ◽  
Vol 45 (2) ◽  
pp. 1235-1249 ◽  
Author(s):  
F. W. J. Pargeter ◽  
M. B. Ives
Keyword(s):  
Aluminium Alloys ◽  
Cellular Network ◽  
Size Dependence ◽  
Network Formation ◽  
Pure Copper ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Aluminium Content ◽  
Α Phase ◽  
Stacking Fault Energies

Polycrystalline specimens of α-phase copper–aluminium alloys of varying composition, amalgamated with mercury, have been deformed in tension in a soft tensile machine. In all cases, brittle intergranular failure occurred at stresses and strains below those required for fracture in air, the degree of embrittlement increasing with increasing aluminium content. The alloys having stacking-fault energies less than '~8 erg/cm2 were found to obey quite well the Petch–Stroh relation:[Formula: see text]The other alloys showed deviations from this relation which became more marked with increasing stacking-fault energy. Values of the fracture energy, varying from ~48 erg/cm2 for pure copper to ~470 erg/cm2 for Cu −8 wt.% Al, have been obtained for all of the alloys. These values are only applicable for relatively small grain sizes.The deviation from the Petch–Stroh relation in the high stacking-fault energy alloys is thought to be due to their tendency to show cross-slip and cellular-network formation, rather than coplanar arrays of dislocations as required by the Stroh model. The low stacking-fault energy alloys typically show well-defined pileups and so obey the Petch–Stroh relations, as expected.

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