High-temperature Dislocation-precipitate Interactions in Al Alloys: An in situ Transmission Electron Microscopy Deformation Study

2005 ◽  
Vol 20 (7) ◽  
pp. 1792-1801 ◽  
Author(s):  
B.G. Clark ◽  
I.M. Robertson ◽  
L.M. Dougherty ◽  
D.C. Ahn ◽  
P. Sofronis
Keyword(s):  
High Temperature ◽  
Al Alloys ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Rate Limiting Step ◽  
Transmission Electron ◽  
Deformation Processes ◽  
Temperature Interaction ◽  
Rate Limiting

The fundamental processes controlling the high-temperature interaction of dislocations with precipitates in Al-alloys were investigated in real time by deforming specimens in situ in the transmission electron microscope at elevated temperature. The observations support a bypass mechanism involving the interaction of lattice dislocations with the precipitate–matrix interface dislocations, where the rate-limiting step in the interaction is the release of the dislocation from the particle. These observations are discussed in relation to high-temperature deformation processes and models.

High-temperature deformation and fracture of Bi–Sr–Ca–Cu–O superconductors

1994 ◽  
Vol 9 (3) ◽  
pp. 541-547 ◽  
Author(s):  
K.C. Goretta ◽  
E.J. Zamirowski ◽  
J.M. Calderoñ-Moreno ◽  
D.J. Miller ◽  
Nan Chen ◽  
...  
Keyword(s):  
Dislocation Motion ◽  
Steady State Creep ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Creep Response ◽  
Transmission Electron ◽  
Deformation And Fracture ◽  
Deformation Processes ◽  
Apparent Activation Energies ◽  
Kinetics Of

Dense polycrystalline Bi2Sr2Cu2Ox (2201), Bi2Sr2CaCu2Ox (2212), and (Bi, Pb)2Sr2Ca2Cu3Ox (2223) specimens were compressed in air at 730–835 °C. All of the materials exhibited an apparent steady-state creep response. Strain rate was proportional to stress to the 3.1–3.8 power. Apparent activation energies for the deformation processes were 520 ± 50 kJ/mole for the 2201, 630 ± 210 kJ/mole for the 2212, and 960 ± 210 kJ/mole for the 2223. Transmission electron microscopy revealed substantial generation and propagation of basal-plane dislocations during deformation. Few nonbasal-plane dislocations were observed. Intergranular fracture was evident in all deformed samples, and intragianular fracture was evident along the basal planes of some grains. It is suggested that the kinetics of fracture were determined by dislocation motion within the grains.

Comparison of High-Temperature Compressive Deformation Characteristics of Differently Processed LY12 Aluminum Alloys

2010 ◽  
Vol 667-669 ◽  
pp. 845-849
Author(s):  
Yao Wang ◽  
Qing Wei Jiang ◽  
Ying Wu ◽  
Xiao Wu Li
Keyword(s):  
High Temperature ◽  
Surface Deformation ◽  
Testing Temperature ◽  
Al Alloys ◽  
Compressive Deformation ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Al Alloy ◽  
Damage Characteristics ◽  
Angular Pressing

The individual or joint effects of annealing and equal channel angular pressing (ECAP) treatments on the high-temperature compressive deformation and damage behavior of cast LY12 Al alloys were studied. The compressive deformation behavior and surface deformation and damage characteristics of differently treated LY12 Al alloy samples were examined at temperatures ranging from 25°C to 400°C. It is found that the LY12 Al alloy exhibits different compressive mechanical behavior depending on different treatments, and the compressive deformation and damage characteristics of LY12 Al alloys with different microstructural states are closely related with the testing temperature. As compared to other samples (e.g. as-cast, annealed, as-cast+2ECAPed), the sample annealed at 450°C for 3h followed by ECAPed for 2 passages (i.e. annealed+2ECAPed) shows a better high-temperature deformation stability.

The role of interphase boundary phenomena on mechanical behavior during high-temperature deformation

1991 ◽  
Vol 49 ◽  
pp. 594-595
Author(s):  
B. Hidalgo-Prada
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Interphase Boundary ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Metallographic Analysis ◽  
Two Phase ◽  
Transmission Electron ◽  
Phase Size

The influence of interphase boundary on the mechanical behavior of a two-phase (α/β) Ni-Modified Ti-6A1-4V alloy during superplastic deformation (SPD), has been investigated in the range of temperature and strain rate where maximum ductility is - attained.Uniaxial tests for constant and differential strain rates were performed over the - range of 5.0 x 10-5 s-1 to 5.0 x 10-3 s-1 and at temperature from 1023 to 1123 K. To optimize the initial microstructure, tensile specimens were static annealed in argon for 1 hour at 815 °C ( SA-1-815).Upon completion of the tests, specimens were quenched in pre-chilled argon to pre—serve the high temperature microstructure for metallographic analysis. The gage portion of the specimen was polished and etched in a solution of 2 ml HF, 3 ml HNO3 and 95 ml H2O. Subsequently, they were subjected to scanning and transmission electron - microscopy (SEM and TEM) examination. A Quantimet Image Analizer was used for determining the phase size, its distribution and volume fractions.

Effect of High Temperature Deformation on Grain Boundary Defects in Yba2Cu3O7-X

1989 ◽  
Vol 169 ◽  
Author(s):  
R. Garcia ◽  
W.Z. Misiolek ◽  
R.N. Wright ◽  
K. Rajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Ceramic Superconductors ◽  
Bulk Ceramic ◽  
Transmission Electron ◽  
Lattice Distortions

AbstractThe results of transmission electron microscopy studies on YBa2Cu3O7‐x subjected to high temperature extrusion are presented. Particular emphasis is put on high temperature accommodation processes of lattice dislocations into sub‐grain boundaries. It is suggested from the electron microscopy observations that stress induced climb mechanisms for dislocations are operative. Also presented is evidence of localized lattice distortions near twin boundaries due to isothermal high temperature deformation. Preliminary results on the structure of grain boundary facets and steps is described. The implications of these results for texture development in bulk ceramic superconductors is also discussed.

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