Enabling the Double-C Curve in Pu-Ga Alloy Time-Temperature-Transformation Diagrams

2008 ◽  
Vol 1104 ◽  
Author(s):  
Jason R. Jeffries ◽  
Kerri J. M. Blobaum ◽  
Mark A. Wall ◽  
Adam J. Schwartz
Keyword(s):  
Transformation Products ◽  
Isothermal Hold ◽  
Face Centered Cubic ◽  
Ambient Conditions ◽  
Unusual Behavior ◽  
Ttt Diagram ◽  
Δ Phase ◽  
The Face ◽  
Temperature Transformation ◽  
Transformation Diagrams

AbstractUnder ambient conditions, a Pu-2.0 at.% Ga alloy is retained in the metastable δ phase. Upon cooling to approximately -120 °C, the face-centered-cubic δ phase partially transforms to the metastable monoclinic α′ phase via a martensitic transformation. The kinetics of the δ⟶α′ transformation are reported to have double-C curve kinetics in a time-temperature-transformation (TTT) diagram, but the mechanisms responsible for this unusual behavior are not understood. Our work focuses on determining the underlying cause of the two noses. Optical microscopy has been used to investigate the role of “conditioning”—an isothermal hold at sub-anneal temperatures—on the δ⟶α′ transformation and to illuminate any disparities in transformation products. Conditioning was found to affect substantially the amount of transformation that occurs at particular points corresponding to both the upper- and lower-C of the TTT diagram.

scholarly journals Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga

2008 ◽  
Vol 1104 ◽  
Author(s):  
Jason R Jeffries ◽  
Kerri J. M. Blobaum ◽  
Mark A. Wall ◽  
Adam J. Schwartz
Keyword(s):  
Ttt Diagram ◽  
Optimal Conditioning ◽  
High Temperature Anneal ◽  
Conditioning Treatment ◽  
Conditioning Temperature ◽  
Δ Phase ◽  
Transformation Mechanisms ◽  
Temperature Transformation ◽  
Underlying Mechanisms ◽  
Kinetics Of

AbstractThe gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable δ phase to the gallium-containing, monoclinic α′ phase near -100 °C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment—wherein, following an anneal at 375 °C, the sample is held at a sub-anneal temperature for a period of time—significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the δ⟶α′ transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of α′ formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of the conditioning treatment were destroyed, resulting in little or no transformation.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

Time-temperature-transformation (TTT) diagram of caustic calcined magnesia

CIM Journal ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 42-50 ◽  
Author(s):  
K. Ebrahimi-Nasrabadi ◽  
M. Barati ◽  
P. W. Scott
Keyword(s):  
Ttt Diagram ◽  
Temperature Transformation

MINIMAL KNOTTING NUMBERS

2009 ◽  
Vol 18 (08) ◽  
pp. 1159-1173 ◽  
Author(s):  
CASEY MANN ◽  
JENNIFER MCLOUD-MANN ◽  
RAMONA RANALLI ◽  
NATHAN SMITH ◽  
BENJAMIN MCCARTY
Keyword(s):  
The Body ◽  
Computer Algorithm ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Body Centered Cubic Lattice

This article concerns the minimal knotting number for several types of lattices, including the face-centered cubic lattice (fcc), two variations of the body-centered cubic lattice (bcc-14 and bcc-8), and simple-hexagonal lattices (sh). We find, through the use of a computer algorithm, that the minimal knotting number in sh is 20, in fcc is 15, in bcc-14 is 13, and bcc-8 is 18.

Poisson's Ratio for Central-Force Polycrystals

1976 ◽  
Vol 31 (12) ◽  
pp. 1539-1542 ◽  
Author(s):  
H. M. Ledbetter
Keyword(s):  
Electron Energy ◽  
Poisson Ratio ◽  
The Body ◽  
Central Force ◽  
Face Centered Cubic ◽  
Polycrystalline Aggregate ◽  
Body Centered Cubic ◽  
The Face ◽  
Predicted Values ◽  
Face Centered

Abstract The Poisson ratio υ of a polycrystalline aggregate was calculated for both the face-centered cubic and the body-centered cubic cases. A general two-body central-force interatomatic potential was used. Deviations of υ from 0.25 were verified. A lower value of υ is predicted for the f.c.c. case than for the b.c.c. case. Observed values of υ for twenty-three cubic elements are discussed in terms of the predicted values. Effects of including volume-dependent electron-energy terms in the inter-atomic potential are discussed.

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