scholarly journals The Increase in a Brittle-to-ductile Transition Temperature in Fe–Al Single Crystals

2011 ◽  
Vol 51 (6) ◽  
pp. 999-1004 ◽  
Author(s):  
Masaki Tanaka ◽  
Keiki Maeno ◽  
Kenji Higashida ◽  
Masahiro Fujikura ◽  
Kohsaku Ushioda
Keyword(s):  
Transition Temperature ◽  
Single Crystals ◽  
Brittle To Ductile Transition

Dislocation Activity in 4H-SiC in the Brittle Domain

2010 ◽  
Vol 645-648 ◽  
pp. 335-338
Author(s):  
Jean Luc Demenet ◽  
Madyan Amer ◽  
Alexandre Mussi ◽  
Jacques Rabier
Keyword(s):  
Transition Temperature ◽  
Single Crystals ◽  
Basal Plane ◽  
High Stress ◽  
Previous Literature ◽  
Dislocation Activity ◽  
Brittle To Ductile Transition ◽  
Crystallographic Planes

Results of deformation experiments on 4H-SiC single crystals below the usual brittle to ductile transition temperature are reported and discussed in comparison of previous literature data. Si-core and C-core partials are evidenced in the basal plane, and perfect dislocations are also observed on other crystallographic planes. These results could indicate that dislocation activity under high stress is more complex than expected.

Effect of Prestraining on the Brittle-To-Ductile Transition of NiAl Single Crystals

1996 ◽  
Vol 460 ◽  
Author(s):  
S. Shrivastava ◽  
F. Ebrahimi
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Crack Initiation ◽  
Single Crystals ◽  
Low Temperatures ◽  
Crack Initiation And Propagation ◽  
Brittle To Ductile Transition ◽  
Initiation And Propagation ◽  
Toughness Testing ◽  
Dislocation Sources

ABSTRACTThe brittle-to-ductile transition (BDT) has been established for NiAl single crystals as evaluated by fracture toughness testing and also the effects of prestraining on the brittle-to-ductile transition temperature (BDTT) have been investigated. Specimens were prestrained to a 10% plastic strain level at 200°C under tension prior to toughness testing. The BDT of the prestrained specimens was compared to that of the as homogenized specimens. The results have revealed the occurrence of two competing effects upon prestraining: (1) an increase in dislocation sources causing a difficulty in micro-crack initiation and resulting in an increase in toughness at low temperatures, and (2) an increase in the flow stress resulting in an increase in BDT temperature. The crack initiation and propagation mechanisms were also analyzed and have been discussed.

Deformation mechanisms in MoSi2at temperatures above the brittle-to-ductile transition temperature

1997 ◽  
Vol 75 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Daniel J. Evans ◽  
Frank J. Scheltens ◽  
John B. Woodhouse ◽  
Hamish L. Fraser
Keyword(s):  
Transition Temperature ◽  
Deformation Mechanisms ◽  
Brittle To Ductile Transition

Predicting the Brittle-to-Ductile Transition Temperatures for Surface Cracks in Pipeline Girth Welds: It’s Better Than You Thought

2008 ◽  
Author(s):  
Gery Wilkowski ◽  
David Rudland ◽  
Do-Jun Shim ◽  
David Horsley
Keyword(s):  
Transition Temperature ◽  
Surface Crack ◽  
Master Curve ◽  
Crack Depth ◽  
Temperature Shift ◽  
Transition Temperatures ◽  
Surface Cracks ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Girth Welds

A methodology to predict the brittle-to-ductile transition temperature for sharp or blunt surface-breaking defects in base metals was developed and presented at IPC 2006. The method involved applying a series of transition temperature shifts due to loading rate, thickness, and constraint differences between bending versus tension loading, as well as a function of surface-crack depth. The result was a master curve of transition temperatures that could predict dynamic or static transition temperatures of through-wall cracks or surface cracks in pipes. The surface-crack brittle-to-ductile transition temperature could be predicted from either Charpy or CTOD bend-bar specimen transition temperature information. The surface crack in the pipe has much lower crack-tip constraint, and therefore a much lower brittle-to-ductile transition temperature than either the Charpy or CTOD bend-bar specimen transition temperature. This paper extends the prior work by presenting past and recent data on cracks in line-pipe girth welds. The data developed for one X100 weld metal shows that the same base-metal master curve for transition temperatures works well for line-pipe girth welds. The experimental results show that the transition temperature shift for the surface-crack constraint condition in the weld was about 30C lower than the transition temperature from standard CTOD bend-bar tests, and that transition temperature difference was predicted well. Hence surface cracks in girth welds may exhibit higher fracture resistance in full-scale behavior than might be predicted from CTOD bend-bar specimen testing. These limited tests show that with additional validation efforts the FITT Master Curve is appropriate for implementation to codes and standards for girth-weld defect stress-based criteria. For strain-based criteria or leak-before-break behavior, the pipeline would have to operate at some additional temperature above the FITT of the surface crack to ensure sufficient ductile fracture behavior.

scholarly journals Research Progress on Ni-Based Antiperovskite Compounds

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
P. Tong ◽  
Y. P. Sun
Keyword(s):  
Phase Diagram ◽  
Transition Temperature ◽  
Single Crystals ◽  
Superconducting Transition Temperature ◽  
Spin Fluctuations ◽  
Research Progress ◽  
Future Research ◽  
Magnetic Element ◽  
Superconducting Transition ◽  
Cubic Structure

The superconductivity in antiperovskite compound MgCNi3was discovered in 2001 following the discovery of the superconducting MgB2. In spite of its lower superconducting transition temperature (8 K) than MgB2(39 K), MgCNi3has attracted considerable attention due to its high content of magnetic element Ni and the cubic structure analogous to the perovskite cuprates. After years of extensive investigations both theoretically and experimentally, however, it is still not clear whether the mechanism for superconductivity is conventional or not. The central issue is if and how the ferromagnetic spin fluctuations contribute to the cooper paring. Recently, the experimental results on the single crystals firstly reported in 2007 trend to indicate a conventionals-wave mechanism. Meanwhile many compounds neighboring to MgCNi3were synthesized and the physical properties were investigated, which enriches the physics of the Ni-based antiperovskite compounds and help understand the superconductivity in MgCNi3. In this paper, we summarize the research progress in these two aspects. Moreover, a universal phase diagram of these compounds is presented, which suggests a phonon-mediated mechanism for the superconductivity, as well as a clue for searching new superconductors with the antiperovskite structure. Finally, a few possible scopes for future research are proposed.

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