The effect of the additive calcium on the rate of internal oxidation of silver-cadmium alloys
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(a)
1. C. A. Hoffmanand J. W.Weeton:NASATMX-68056, 1972. 2. R. W.Hoffman:in Thin Films, ASM,1964,p. 99. 3. J. W.Menterand D. W.Pashley:in Structure and Properties of Thin Films, p. 111,Wiley,NewYork, 1959.
The Effect of the Additive Calcium on the Rate of Internal Oxidation of Silver-Cadmium Alloys YUAN SHOUSHEN AND RICHARD H. KROCK The t h e o r y of oxidation as o r i g i n a l l y p r o p o s e d by C. Wagner 1 is d e s c r i b e d by the p a r a b o l i c r e l a t i o n s h i p : X = 27(Dot) ~/~
where X -- t h i c k n e s s of the i n t e r n a l l y oxidized zone D O = diffusion coefficient of oxygen in the s i l v e r c a d m i u m alloy t = time and y = dimensionless parameter
(b) Fig. 4--(a) Tungsten-tantalum laminar composite rolled 90:1 and exposed at 1093~ (2000~ for approximately 1 h. Magnification 10,O00 times. (b) Tungsten-tantalum laminar composite rolled 90:1 and exposed at 1093~ (Z000~ for approximately 1000 h. Magnification 10,000 times. 312-VOLUME 5, JANUARY 1974
The d i m e n s i o n l e s s p a r a m e t e r , y, is a function of (NoD 0/NcdDcd) where NO and NCd a r e the mole f r a c t i o n s of oxygen and c a d m i u m r e s p e c t i v e l y , and DCd is the diffusion coefficient of c a d m i u m in s i l v e r f i YUAN-SHOU SHEN and RICHARD H. KROCK are Staff Member and Group Manager,respectively, P. R. Mallory & Co., Inc. Burlington, Mass. 0 i 803. Manuscript submitted June 11, 1973. METALLURGICALTRANSACTIONS
Table 1, Alloy Compositions and Case Depths Composition Wt P c t Cd
1 Day AI. Pct
Ca
Cd
9.0
2 Days
Air Ca
Xmm
Oxygen Pct Inc
X
Air
Pctlnc
Xmm
4 Days Oxygen
X >1.1
-
>1.2
>1.2
-
>1.2
9.15
-
0.629
-
0.928
9.0
0.5
9.14
0.14
0.762
21
1.08I
17
0.882 1.002
14
12.5
-
12.06
-
0.496
-
0.738
-
0.705
-
Pct lnc
Air
Pct Inc
1.037
-
Xmm
8 Days Oxygen
Pct lnc .
X
Air
P c t Inc
.
.
Xmm
.
.
-
0.964
Pct l n c
-
>1.2
12.5
0.04
12.05
0.11
0.569
14
0.840
14
0.780
11
1.142
10
1.076
12
-
12.5
0.06
12.05
0.16
0.602
21
0.862
17
0.845
20
1.186
15
1.177
22
-
12.5
0.08
12.04
0.22
0.627
26
0.910
23
0.868
23
>1.2
-
>1.2
12.5
0.10
12.04
0.27
0.632
27
0.920
25
0.894
26
>1.2
-
>1.2
.
.
]9.0
-
18.38
-
-
-
0.539
-
0.480
-
0.710
-
0.681
-
19.0
0.06
18.36
0.16
-
-
0.661
23
0~552
15
0.830
17
0.795
17
.
.
1.174 >1.2
-
-
-
-
1.009
-
-
1.135
13
Notes." ( 1 ) X = O x i d i z e d case t h i c k n e s s . (2) >1.2 = The specimen was completely oxidized with only small depleted zone.
Thie equation leads one to conclude that when the factor t i m e r e m a i n s constant, the t h i c k n e s s of the oxidized c a s e depends p r i n c i p a l l y on the c o n c e n t r a t i o n s of the d i s s o l v e d oxygen and c a d m i u m as well as on t h e i r diffusion c o n s t a n t s . During a study of the i n t e r n a l oxidation of s i l v e r - c a d m i u m a l l o y s , it has b e e n found that in addition to the above f a c t o r s , the oxidation r a t
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