Accelerated evolution of hydrogen from metals during plastic deformation
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o c c u r r e d d u r i n g cooling. T a b l e I l i s t s the m e a s u r e d o r c a l c u l a t e d t r i t i u m c o n c e n t r a t i o n in the s p e c i m e n s and t h e i r r e l a t i v e s u p e r s a t u r a t i o n at r o o m t e m p e r a ture. The a s - c h a r g e d i r o n and n i c k e l s p e c i m e n s w e r e s t o r e d at 77 K u n t i l t e s t i n g to m i n i m i z e diffusion l o s s e s of hydrogen. The s t a i n l e s s s t e e l was s t o r e d at 233 K b e c a u s e s t o r a g e at 77 K would have caused s o m e t r a n s f o r m a t i o n to m a r t e n s i t e . T h e a l u m i n u m and Inconel 718 s p e c i m e n s were also s t o r e d at 233 K. T e n s i l e t e s t s were r u n at c o n s t a n t c r o s s h e a d speeds with i n i t i a l s t r a i n r a t e s r a n g i n g f r o m 3 x 10-~ to 8 x 10-2 s-L An e n v i r o n m e n t a l c h a m b e r c o n t r o l l e d the t e s t t e m p e r a t u r e to within • K. S p e c i m e n t e m p e r a t u r e s were m e a s u r e d with a t h e r m o c o u p l e in contact with the s p e c i m e n s d u r i n g the i s o t h e r m a l t e s t s , which r a n g e d f r o m 123 K to 373 K. The t r i t i u m o f f - g a s s i n g r a t e s f r o m the t e n s i l e s p e c i m e n s w e r e d e t e r m i n e d by s w e e p i n g a c a r r i e r gas a r o u n d the gage length of each s p e c i m e n (Fig. 1), and then p a s s i n g the c a r r i e r gas and d e s o r b e d t r i t i u m through an i o n i z a t i o n c h a m b e r . The gas flow r a t e s were m e a s u r e d with a n i n - l i n e flow m e t e r . The s y s t e m was c a l i b r a t e d with a s t a n d a r d t r i t i u m leak so that the a b s o l u t e r e l e a s e r a t e was known within a factor of two. RESULTS Strength Properties Charged and u n c h a r g e d s p e c i m e n s w e r e t e s t e d u n d e r s i m i l a r conditions so that effects of c h a r g i n g could be e v a l u a t e d . The s t r e n g t h p r o p e r t i e s of nickel,
Table I. Concentration of Tritium in Materials and Relative Supersaturation
Material
Concentration mole/m3
ArmcoIron* Nickel* Type 304LStainlessSteelt 5086 Aluminumtt Inconel71882
9 X 10-1 1.3 13.0 1.3 X 1 0 -9 13.0
Relative Supersaturation at
298 K
500 3 3 3.5 X 10a 3
*Measuredby liquidscintillationcounting. t Estimatedfrom Ref. 9. ttEstimated fromRef. 10. 82Analogywith stainlesssteels.
VOLUME 7A, NOVEMBER 1976-1677
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1
9
I Flow Meter
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Off-Gas Exhaust System Ionization Gage
8
r'_o ~ I
X
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20"
E
Specimen
600
F i g . 1 - - S c h e m a t i c of a p p a r a t u s to m e a s u r e t r i t i u m r e l e a s e s from tensile specimens.
500 4oo Z
i r o n , 304L s t a i n l e s s s t e e l , and 5086 a l u m i n u m w e r e u n c h a n g e d by the h y d r o g e n charging; however, I n c o n e l 718 was e m b r i t t l e d . T h e effects of hydrogen on the s t r e n g t h p r o p e r t i e s of m o s t of these m a t e r i a l s was d i s c u s s e d in an e a r l i e r r e p
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