A Viscoplastic Model for Single Crystals

1992 ◽  
Vol 114 (1) ◽  
pp. 19-26 ◽  
Author(s):  
E. H. Jordan ◽  
K. P. Walker
Keyword(s):  
Elevated Temperature ◽  
Constitutive Model ◽  
Single Crystals ◽  
Deformation Behavior ◽  
Slip Systems ◽  
Thermomechanical Loading ◽  
Straightforward Manner ◽  
Viscoplastic Model ◽  
Active Slip ◽  
Anisotropic Deformation

A viscoplastic constitutive model is described in which deformation behavior is postulated on representative slip systems and the behavior of the entire crystal is determined by summing the slip on the active slip systems. By building in the slip geometry known from the metallurgical literature, it is possible to predict the anisotropic deformation behavior and to model in a straightforward manner other phenomena which have been described by metallurgists in crystallographic terms. Elevated temperature tension-torsion tests were run and used to verify the model’s predictive abilities. Ratchetting behavior under thermomechanical loading conditions is specifically addressed.

Effects of Deviation from Stoichiometry on Deformation Behavior of Hard-Oriented NiAl Single Crystals

1998 ◽  
Vol 552 ◽  
Author(s):  
R. Srinivasan ◽  
M. F. Savage ◽  
R. D. Noebe ◽  
M. J. Mills
Keyword(s):  
Transition Temperature ◽  
Single Crystals ◽  
Deformation Behavior ◽  
Mechanical Response ◽  
Slip Systems ◽  
Alloying Additions ◽  
Strain And Strain Rate ◽  
Deviation From Stoichiometry ◽  
Slip Transition ◽  
Active Slip

ABSTRACTNi-44A1, Ni-50Al and NiAl-0.3 at.% Hf single crystals have been studied in compression to understand the effects that alloying additions and deviation from stoichiometry can have on the mechanical response of NiAl-based single crystals. While all three single crystals deform through a<111> slip at lower temperatures, the active slip systems differ at higher temperatures. Climb of a<010> dislocations contributes to deformation in Ni-50AI single crystals beyond the slip transition temperature, while Ni-44Al and NiAl-0.3Hf crystals deform through a<101> glide. But several microstructural differences have been observed in the mode of deformation between Ni-44Al and NiAl-0.3Hf crystals. In addition, significant strengthening is exhibited in the Hf-doped crystals at higher temperatures. The post-deformation microstructure is also observed to be sensitive to both strain and strain rate. A possible explanation is offered for some of the observed differences in deformation behavior between the three alloys.

Plastic Deformation of Mo(Si,Al)2 Single Crystals with the C40 Structure

1996 ◽  
Vol 460 ◽  
Author(s):  
M. Moriwaki ◽  
K. Ito ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Single Crystals ◽  
Deformation Behavior ◽  
Basal Slip ◽  
Room Temperature ◽  
Slip Systems ◽  
Temperature Range ◽  
Al Content ◽  
Partial Dislocations ◽  
Increasing Temperature ◽  
Critical Resolved Shear Stress

ABSTRACTThe deformation behavior of single crystals of Mo(Si,Al)2 with the C40 structure has been studied as a function of crystal orientation and Al content in the temperature range from room temperature to 1500°C in compression. Plastic flow is possible only above 1100°C for orientations where slip along <1120> on (0001) is operative and no other slip systems are observed over whole temperature range investigated. The critical resolved shear stress for basal slip decreases rapidly with increasing temperature and the Schmid law is valid. Basal slip appears to occur through a synchroshear mechanism, in which a-dislocations (b=1/3<1120>) dissociate into two synchro-partial dislocations with the identical Burgers vector(b*1/6<1120>) and each synchro-partial further dissociates into two partials on two adjacent planes.

Deformation behavior and slip systems of quenched β-CuZn single crystals

1979 ◽  
Vol 27 (7) ◽  
pp. 1219-1230 ◽  
Author(s):  
S. Hanada ◽  
H. Yamamoto ◽  
O. Izumi
Keyword(s):  
Single Crystals ◽  
Deformation Behavior ◽  
Slip Systems

Tensile Deformation of Magnesium and Magnesium Alloy Single Crystals

2014 ◽  
Vol 783-786 ◽  
pp. 341-345 ◽  
Author(s):  
Shinji Ando ◽  
Atsushi Kodera ◽  
Kazuki Fukushima ◽  
Masayuki Tsushida ◽  
Hiromoto Kitahara
Keyword(s):  
Single Crystals ◽  
Basal Slip ◽  
Tensile Deformation ◽  
Pure Magnesium ◽  
Slip Systems ◽  
Pyramidal Slip ◽  
Higher Temperature ◽  
Von Mises ◽  
Zn Alloy ◽  
Active Slip

According to von-Mises criterion, five kinds of independent slip systems are required for uniform deformation, so it is necessary to activate non-basal slip systems to show good ductility. However, it has not become clear the effect of Zn or Al for non-basal slip systems yet. To investigate deformation behavior of magnesium crystal by non-basal slip and alloying effect for the non-basal slip, pure magnesium and Mg-Al-Zn single crystals were stretched in the [110] direction. While {112}<23> second order pyramidal slip was activated at room temperature in pure magnesium, {101}<23> first order pyramidal slip became active slip at higher temperature. In Mg-Al-Zn alloy single crystal, {101} twin also activated by adding aluminum. These results indicate that active non-basal slip systems and twin in magnesium strongly depend on deformation temperature and alloying elements.

Investigation of Deformation Behavior of SS304 and Pure Copper Subjected to Electrically Assisted Forming Process

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Tianhao Jiang ◽  
Linfa Peng ◽  
Peiyun Yi ◽  
Xinmin Lai
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Constitutive Model ◽  
Electric Current ◽  
Deformation Behavior ◽  
Pure Copper ◽  
Annihilation Process ◽  
Forming Process ◽  
Electrically Assisted ◽  
Dislocation Movement

Both electrically assisted tension (EAT) and thermally assisted tension (TAT) tests were performed on SS304 and pure copper to decouple the influence of elevated temperature from electric current on flow stress and ductility. It is found that the reduction on flow stress and ductility of SS304 are more dependent on the elevated temperature than electric current, but electric current has a stronger effect by 10% on reducing flow stress and ductility of pure copper than the elevated temperature does. As the flow stress and ductility of two metals are related to the dislocation evolution, a constitutive model considering both storage and annihilation process of dislocation was established to describe the effect of electric current and temperature on dislocation movement. It is found that electric current accelerated the annihilation process of dislocation in pure copper up to 20% in EAT compared with that in TAT, but such phenomenon was rarely observed in SS304. Furthermore, attempts have also been made to distinguish the influence of elevated temperature with that of electric current on microstructure evolution and it is also found that the formation of [111] crystals in pure copper is nearly 10% less in EAT than that in TAT.

Room Temperature Deformation in “Soft” Orientation Nial Single Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
R.D. Field ◽  
D.F. Lahrman ◽  
R. Darolia
Keyword(s):  
Shear Stress ◽  
Elevated Temperature ◽  
Single Crystals ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Temperature Deformation ◽  
Slip Planes ◽  
Schmid Factor ◽  
Critical Resolved Shear Stress ◽  
Active Slip

ABSTRACTA detailed study of deformation of NiAl single crystals in two soft orientations, <110> and <111>, has been conducted. The Schmid factor favors {100} slip in the former and {110} slip in the latter. Detailed dislocation analysis, critical resolved shear stress measurements, and slip trace analysis have been performed to determine the nature of dislocation motion and interactions in this material. Particular attention is given to prismatic loops formed during deformation, since the shapes of these loops reveal the active slip planes. Similar loop morphologies observed in elevated temperature [001] oriented tensile specimens are also discussed.

Anisotropy in the hardness of single crystals

1971 ◽  
Vol 322 (1548) ◽  
pp. 73-88 ◽  
Keyword(s):  
Crystal Structure ◽  
Shear Stress ◽  
Single Crystals ◽  
Dislocation Motion ◽  
Slip Systems ◽  
Maximum Hardness ◽  
Indentation Process ◽  
Wide Range ◽  
Knoop Indentation ◽  
Active Slip

The results of this work, and those published by other researchers who have used Knoop indentation measurements, confirm that the nature of anisotropy in hardness is essentially determined by the crystal structure and the primary slip systems which accommodate dislocation motion during indentation. Materials belonging to the same class of crystal structure and having common slip systems possess similar anisotropic properties. The varying extent of work-hardening or fracture, associated with indentations, does not appear to influence the anisotropy— although twinning on the basal planes of hexagonal closepacked metals may have a significant effect. An analysis of the indentation process is presented which establishes a clear relationship between the ‘effective resolved shear stress’ (t 0 '), in the bulk of the crystal beneath the indenter, and the observed hardness. Directions which correspond to the minimum values of t' e , on specific crystallographic surfaces, are those of maximum hardness and conversely. The analysis is shown to be equally applicable to a wide range of crystalline solids including nonmetallic materials, of various crystal structure, and typical f.c.c., b.c.c. and c.p.h. metals. Finally, anisotropy in hardness can be used to identify active slip systems in those crystals where it is possible for dislocations to move on more than one system.

Soft and Hard Modes of Deformation in Mosi2 Single Crystals

1994 ◽  
Vol 364 ◽  
Author(s):  
K. Ito ◽  
T. Yano ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Single Crystals ◽  
Plastic Flow ◽  
Deformation Behavior ◽  
Crystal Orientation ◽  
Room Temperature ◽  
Intermediate Temperature ◽  
Slip Systems ◽  
Anomalous Increase ◽  
Temperature Range ◽  
Intermediate Temperature Range

AbstractThe deformation behavior of MoSi2 single crystals has been studied in the temperature range of -196<1500°C. While [001]-oriented crystals can be plastically deformed only above 1300°C, plastic flow is possible from temperatures as low as room temperature for single crystals with orientations other than [001]. Five slip systems, {110)<111], {011)<100], {010)<100], {023)<100] and {013)<331], are identified to be operative, depending on crystal orientation. An anomalous increase in CRSS is observed in the intermediate temperature range for the former three slip systems. Schmid’s law is generally valid for the soft modes, {110)<111], {011)<100] and {023)<100]. In contrast, the CRSS for the hard mode, {013)<331], strongly depends on crystal orientation with the higher values for orientations closer to [001].

Dislocation Boundaries and Slip Systems in Uniaxially Deformed Crystals

2001 ◽  
Vol 683 ◽  
Author(s):  
Grethe Winther ◽  
Xiaoxu Huang ◽  
Søren Fæster Nielsen ◽  
John Wert
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Crystal Orientation ◽  
Boundary Plane ◽  
Slip Systems ◽  
Crystal Boundary ◽  
Secondary Slip ◽  
Slip Planes ◽  
Planar Dislocation ◽  
Active Slip

ABSTRACTThe dislocations in the extended planar dislocation boundaries formed during deformation are generated by the active slip systems. Investigation of the boundaries is therefore a tool to obtain information on the active slip systems. Here, the orientation of the dislocation boundaries in uniaxially deformed aluminum poly- and single crystals are compared. It is found that the single crystal boundary planes are consistent with those found in polycrystals, indicating that the active slip systems in single and polycrystals are the same. However, boundaries are closer to the slip planes in the single crystals. This is taken as an indication that the secondary slip systems are more active in the polycrystal. The orientation of the boundary plane varies with the crystal orientation in a way that is consistent with activation of the five most stressed slip systems.

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