A study of as-cast and heat-treated uranium-uranium carbide alloys by optical and electron microscopy

About: The article was published on 1966-02-01 and is currently open access. It has received 2 citations till now. The article focuses on the topics: Uranium carbide & Uranium.

Summary

DISCLAIMER

• Portions of this document may be illegible in electronic image products.
• Images are produced from the best available original document.
• A review of this literature indicates that the presence of finely dispersed particles in uranium fuel cores may show a restraining effect on the irradiation swelling of the elements.
• Observations made in postirradiation annealing studies indicate that the "halo" of gas porosity surrounding fine uranium carbide particles is much finer than the area of porosity a few microns distant from the particle.
• First, t h e carbides, in combination with other inclusions, form seams and striations on the surface of the core that interfere with proper bonding of the core with i t s aluminum jacket.

2. SUMMARY

• Thereafter, aging caused a decrease in hardness indicated by the climb of dislocations into subboundaries.
• Matrix precipitation occurred after approximately 2 hours and increased the hardness slightly.

3.4 SPECIAL MELTING STUDY

• The samples were then heated from llOO°C to 113OOC in 5" increments allowing 30 minutes before each increase; above 113OoC, 1 t o 2" increases were used to the melting point.
• Since the samples were mounted beam fashion, they would sag suddenly when their melting temperatures were reached.
• When a sample sagged, i t s temperature was recorded, and the power was turned off.

4.2 GAMMA SOLUTION TREATMENT

• The samples were held in a Vycor tube a t 950°C under argon atmosphere for 3 hours and then quenched in an ice-brine bath held at -2OOC.
• Quenching was accomplished by upending the Vycor tube, which allowed the samples to plunge into the quenching bath within 2 seconds.

6.4.2 Seven Minutes

• Figure 17b also shows some large irregular loops and jogging.
• Electron diffraction indicated no coherent zones of precipitation.

6.4.4 Fifteen Minutes

• Further precipitation along substructures can b e observed ; most of the particles are rod shaped.
• Figure 17d also shows the growth of some of the particles over those of the 11 minute anneal.

6.4.5 Two Hours

• Electron micrographs show that the rod -like precipitates along the substructures have shown some growth .
• Neither optical nor electron microscopy revealed any evidence of matrix precipitation.

6.4.6 Six Hours

• Further growth or coalescence of precipitates along the boundaries can be seen in the opticlrl micrograph, Figure 18b , and the electron micrograph, Figure 17f .
• Figures 18b and 17f showed that precipitation within the matrix h a s been initiated.

7.1.1 Identification

• Alloys with lower carbon content a l s o showed some primary carbides, and these were attributed to either the graphite crucible or the derby feed stock.
• 1.1.2 T h e nature of diffraction contrast effects between the primary carbides and the networkphase particles.

7.1.2 Etchina Characteristics of Hiah -Purity Samples

• Observations of the carbon -alloyed samples and high -purity samples showed a difference in types of structures when etched in a 1 :1 aqueous -nitric acid solution.
• From this and their own studies, it wasconcluded that high-purity uranium etched in nitric acid tends to be attacked at dislocation structures having associated, condensed, solute atom atmospheres.).

FIGURE 24

• Papapetrou stated that dendrites started from an ' 'idiomorphic" form and preferentially grew dendritic arms from the corners of the idiomorph.
• Conversely, a low diffusion rate would promote the dendritic type of formation.
• Figure 27 shows the primary carbide dendritic growth as predictEd above.
• Others include the heterogeneous nuclecrtion of uranium carbide on foreign particles and further growth on the crystal faces.
• Similar formations produce seams if they occur on the surface of the core, and these seams may adversely affect the bond between the uranium fuel core and i t s aluminum jacket or "can".

Full text

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NLCO
-
968
Metals, Ceramics, and Materials
(TID
-
4500, 47th
Ed.)
A
STUDY
OF
AS
-
CAST
AND
HEAT
-
TREATED URANIUM
-
URANIUM CARBIDE
ALLOYS BY
OPTICAL
AND ELECTRON MICROSCOPY
William A. Althaus
Marlin
M.
Cook
Richard
J.
Bieker
of
\
TECHNICAL DIVISION
NATIONAL LEAD COMPANY
OF
OHIO
\
Date
of
Issuance: February,
1966
Approved
By:
Approved
By;
Technical Director Head, Metallurgical Department
NATIONAL
LEAD
COMPANY
OF
OHIO
Box
39158,
Cincinnati, Ohio
45239
Contract
No.
AT(30-
1)-1156
1
,

TABLE
OF CONTENTS
Page
No
.
LIST
OF
FIGURES
...............
iii
ABSTRACT
.................
1
1
.
INTRODUCTION
...............
1
2
.
SUMMARY
................
2
3
.
SAMPLE PREPARATION
....
,
.........
3
3.1 Alloy Preparation
..............
3
3.2 Metallographic Preparation
............
4
3.3 Electron Microscopy Technique
...........
4
3.4 Special Melting Study
.............
4
4
.
HEAT TREATMENT
..............
4
4.1 Homogenization
..............
4
4.2 Gamma Solution Treatment
............
5
4.3 Beta Solution Treatment
............
5
4.4 Alpha Anneal
...............
5
5
.
RESULTS: AS-CAST STRUCTURES
..........
5
5.1 Second
-
Phase Structures
............
5
5.2 Phase Distribution and Interactions
..........
7
6
.
RESULTS: HEAT -TREATED STRUCTURES
........
12
6.1 Homogenization
..............
12
6.2 Gamma Solution Treatment
............
12
6.3 Beta Solution Treatment
............
13
6.4 Alpha Anneal
...............
13
7
.
DISCUSSION
................
23
7.1
As
-Cast Structures
.............
23
7.1.1 Identification
.............
23
7.1.2 Etching Characteristics
of
High-Purity Samples
......
24
7.1.3 Formation of Structures
...........
24
7 1.4 Growth Characteristics of UC
in
the
UC
+
Liquid Phase Field
...
28
7.1.5 Changes produced
in
As-Cast Structures
During
Fabrication
...
29
7.2
Heat
-
Treated Structures
............
30
7.2.1 Homogenization Treatments
..........
30
7.2.2
Alpha
Anneal
.............
32
8
.
ACKNOWLEDGEMENTS
.............
33
9
.
REFERENCES
...............
34
10
.
APPENDIX:
Preparation
of
Samples
for
Electron Microscopy
.....
35
10.1 Thin Foils
...............
35
10.2 Replicas
...............
37
b
11