Nanoscale Twinned Ti-44Al-4Nb-1.5Mo-0.007Y Alloy Promoted by High Temperature Compression with High Strain Rate

In order to investigate the dynamic mechanical behavior of TiAl alloys and promote their application in the aerospace industry, uniaxial compression of Ti-44Al-4Nb-1.5Mo-0.007Y (at %) alloy was conducted at a temperature range from 25 to 400 °C with a strain rate of 2000 s‒1. Twinning is found to be the dominating deformation mechanism of the γ phase at all temperatures, and the addition of Nb and Mo has a chemical impact on the alloy and reduces the stacking fault energy of the γ phase. The decreased stacking fault energy increases the twinnability; thus, the deformation is dominated by twinning, which increases the dynamic strength of the alloy. With the temperature increasing from 25 to 400 °C, the average spacing of twins in the γ phase increases from 32.4 ± 2.9 to 88.1 ± 9.2 nm. The increased temperature impedes the continuous movement of partial dislocations and finally results in an increased twin spacing in the γ phase.

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Role of stacking fault energy (SFE) on the high strain rate deformation of cold sprayed Cu and Cu-Al alloy coatings

Materials Science and Engineering A ◽

10.1016/j.msea.2021.141242 ◽

2021 ◽

pp. 141242

Author(s):

Naveen Manhar Chavan ◽

P. Sudharshan Phani ◽

M. Ramakrishna ◽

L. Venkatesh ◽

Prita Pant ◽

...

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Stacking Fault ◽

Stacking Fault Energy ◽

Al Alloy ◽

High Strain Rate Deformation

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On effects of non-systematic reflections on weak-beam images of partial dislocations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087756 ◽

1991 ◽

Vol 49 ◽

pp. 688-689

Author(s):

K. Z. Botros ◽

S. S. Sheinin

Keyword(s):

High Precision ◽

Stacking Fault ◽

Important Application ◽

Stacking Fault Energy ◽

Sharp Peak ◽

Weak Beam ◽

Partial Dislocations ◽

Deviation Parameter ◽

Beam Diffraction

The main features of weak beam images of dislocations were first described by Cockayne et al. using calculations of intensity profiles based on the kinematical and two beam dynamical theories. The feature of weak beam images which is of particular interest in this investigation is that intensity profiles exhibit a sharp peak located at a position very close to the position of the dislocation in the crystal. This property of weak beam images of dislocations has an important application in the determination of stacking fault energy of crystals. This can easily be done since the separation of the partial dislocations bounding a stacking fault ribbon can be measured with high precision, assuming of course that the weak beam relationship between the positions of the image and the dislocation is valid. In order to carry out measurements such as these in practice the specimen must be tilted to "good" weak beam diffraction conditions, which implies utilizing high values of the deviation parameter Sg.

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Dislocations and stacking faults in stainless steel

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1957.0105 ◽

1957 ◽

Vol 240 (1223) ◽

pp. 524-538 ◽

Cited By ~ 124

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Stainless Steel ◽

Grain Boundaries ◽

Stacking Faults ◽

Stacking Fault ◽

Stacking Fault Energy ◽

Thin Sections ◽

Partial Dislocations ◽

Transmission Electron

Further experiments by transmission electron microscopy on thin sections of stainless steel deformed by small amounts have enabled extended dislocations to be observed directly. The arrangement and motion of whole and partial dislocations have been followed in detail. Many of the dislocations are found to have piled up against grain boundaries. Other observations include the formation of wide stacking faults, the interaction of dislocations with twin boundaries, and the formation of dislocations at thin edges of the foils. An estimate is made of the stacking-fault energy from a consideration of the stresses present, and the properties of the dislocations are found to be in agreement with those expected from a metal of low stacking-fault energy.

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Influence of the stacking fault energy surface on partial dislocations in fcc metals with a three-dimensional phase field dislocations dynamics model

Physical Review B ◽

10.1103/physrevb.84.144108 ◽

2011 ◽

Vol 84 (14) ◽

Cited By ~ 61

Author(s):

A. Hunter ◽

I. J. Beyerlein ◽

T. C. Germann ◽

M. Koslowski

Keyword(s):

Phase Field ◽

Energy Surface ◽

Three Dimensional ◽

Stacking Fault ◽

Stacking Fault Energy ◽

Dynamics Model ◽

Fcc Metals ◽

Partial Dislocations

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High Strain Rate Properties of Various Forms of Ti6Al4V(ELI) Produced by Direct Metal Laser Sintering

Applied Sciences ◽

10.3390/app11178005 ◽

2021 ◽

Vol 11 (17) ◽

pp. 8005

Author(s):

Amos Muiruri ◽

Maina Maringa ◽

Willie du Preez

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Electron Backscatter Diffraction ◽

Dynamic Strength ◽

Strain Rates ◽

Direct Metal Laser Sintering ◽

Heat Treated ◽

Electron Backscatter ◽

Backscatter Diffraction

For analysis of engineering structural materials to withstand harsh environmental conditions, accurate knowledge of properties such as flow stress and failure over conditions of high strain rate and temperature plays an essential role. Such properties of additively manufactured Ti6Al4V(ELI) are not adequately studied. This paper documents an investigation of the high strain rate and temperature properties of different forms of heat-treated Ti6Al4V(ELI) samples produced by the direct metal laser sintering (DMLS). The microstructure and texture of the heat-treated samples were analysed using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction detector for electron backscatter diffraction (EBSD) analysis. The split Hopkinson pressure bar (SHPB) equipment was used to carry out tests at strain rates of 750, 1500 and 2450 s−1, and temperatures of 25, 200 and 500 °C. The heat-treated samples of DMLS Ti6Al4V(ELI) alloys tested here were found to be sensitive to strain rate and temperature. At most strain rates and temperatures, the samples with finer microstructure exhibited higher dynamic strength and lower strain, while the dynamic strength and strain were lower and higher, respectively, for samples with coarse microstructure. The cut surfaces of the samples tested were characterised by a network of well-formed adiabatic shear bands (ASBs) with cracks propagating along them. The thickness of these ASBs varied with the strain rate, temperature, and various alloy forms.

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Stacking Faults in Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100998 ◽

1968 ◽

Vol 26 ◽

pp. 250-251

Author(s):

P. C. J. Gallagher

Keyword(s):

Stacking Faults ◽

Elastic Equilibrium ◽

Stacking Fault ◽

Stacking Fault Energy ◽

Major Influence ◽

Face Centered Cubic ◽

Degree Of Dissociation ◽

Partial Dislocations ◽

Layer Structures ◽

Face Centered

Stacking faults are an important substructural feature of many materials, and have been widely studied in layer structures (e.g. talc) and in crystals with hexagonal and face centered cubic structure. Particular emphasis has been placed on the study of faulted defects in f.c.c. alloys, since the width of the band of fault between dissociated partial dislocations has a major influence on mechanical properties.Under conditions of elastic equilibrium the degree of dissociation reflects the balance of the repulsive force between the partials bounding the fault, and the attractive force associated with the need to minimize the energy arising from the misfits in stacking sequence. Examples of two of the faulted defects which can be used to determine this stacking fault energy, Υ, are shown in Fig. 1. Intrinsically faulted extended nodes (as at A) have been widely used to determine Υ, and examples will be shown in several Cu and Ag base alloys of differing stacking fault energy. The defect at B contains both extrinsic and intrinsic faulting, and readily enables determination of both extrinsic and intrinsic fault energies.

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Localized Influence of Solute on the Stacking Fault Energy of Dilute Al-Based Solid Solutions

MRS Proceedings ◽

10.1557/proc-319-345 ◽

1993 ◽

Vol 319 ◽

Author(s):

C. Lane Rohrer

Keyword(s):

Solid Solutions ◽

Partial Dislocation ◽

Binary Systems ◽

Stacking Fault ◽

Stacking Fault Energy ◽

Dislocation Dipole ◽

Partial Dislocations ◽

Pure Metals ◽

Small Clusters ◽

Dislocation Spacing

AbstractThe stacking fault energy (SFE) is widely used to classify the mechanical behavior of pure metals. In alloys, however, the experimentally observed SFE is strongly influenced by localized solute effects. To further understand these effects on dislocation structure and on the observed SFE, solute segregation to an extended edge dislocation dipole, delineating two stacking faults, was studied in dilute Al:Cu, Al:Ag, and Al:Cu, Ag solid solutions. Cu and Ag were chosen to isolate solute size and modulus effects, Cu being smaller than Al, while Ag and Al are essentially the same size. Atomistic Monte Carlo results showed little change in the partial dislocation spacing in the binary systems as compared to the spacing in pure Al, even though Cu was observed to segregate to the compressive regions of the dislocation dipoles, forming widespread atmospheres, while Ag formed randomly distributed Ag-rich zones. However, in ternary Al:Cu,Ag simulations, the Ag apparently inhibited the Cu from distributing across the width of the extended dislocations, both Ag and Cu forming small clusters near or on the partial dislocations which increased the partial dislocation spacing. Results will be discussed in light of interpretations of experimental SFE determinations, emphasizing the importance of the localized solute distribution on the SFE.

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