The influence of heat treatment on the stress-corrosion susceptibility of a ternary Al-5.3 Pct Zn-2.5 Pct Mg alloy
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, _2_2A r l _ aFe = N FeLp
-
1 1 PFeJ
2c (A s
-
A F e)
[2]
100Np
+
'
where
s l t y m e a s u r e m e n t s to o b t a i n the following " b e s t " v a l ues f o r the l a t t i c e p a r a m e t e r s of ~ - F e a l l o y e d with the following s o l u t e s Co, a = a F e + ( 1 + 0.5) • 10 "4 CCo ;
A Fe As N p
= a t o m i c weight of i r o n , = a t o m i c weight of s o l u t e , = Avogadro constant, = d e n s i t y of a l l o y ,
P Fe = density
Cr, a =aFe+(5•
I r , a = a F e + (38 • 1) • 10 -4 Cir ; Pt, a = a F e + (50+ 1) • 10 "~ Cpt ;
of iron.
We have c a l c u l a t e d the l a t t i c e p a r a m e t e r s of the s o l i d s o l u t i o n s f r o m Eq. [2] u s i n g the m e a s u r e d p, N = 6.0225 • 10 z~ tool -~, and a F e = 2.8664~. B e c a u s e of the p r e s ence of Ti c o m p o u n d s and o t h e r i m p u r i t i e s , a s m a l l c o r r e c t i o n to the d e n s i t y and A F e w a s n e c e s s a r y f o r the T i - g e t t e r e d i r o n . The v a l u e s of A a / A c w e r e then c a l c u l a t e d . T h e s e v a l u e s , t o g e t h e r with t h o s e d i r e c t l y m e a s u r e d b y us and by o t h e r s using x - r a y t e c h n i q u e s , a r e given in T a b l e I. The l a t t i c e p a r a m e t e r c h a n g e s m e a s u r e d in t h i s w o r k b y x - r a y s and b y d e n s i t y a r e in good a g r e e m e n t . Some d i f f e r e n c e s with p r e v i o u s w o r k e r s a r e a p p a r e n t . In p a r t i c u l a r , the v a l u e s of A a / A c r e p o r t e d b y A b r a h a m s o n and L o p a t a s f o r Pt, Re, and Cr a p p e a r to b e too high. A l s o the v a l u e of Aa/Ac r e p o r t e d b y Raub and P l a t t e s f o r Ru a p p e a r s to b e too low. The d a t a of K r a n z l e i n , Burton, and Smith 7 f o r Pt a g r e e with o u r s , a s do t h o s e of Sutton and H u m e - R o t h e r y f o r C r a n d Co s and P r e s t o n f o r C r . 9 E l i m i n a t i n g the d a t a of A b r a h a m s o n and L o p a t a f o r Pt, Re, and C r , and the d a t a of Raub and P l a t t e f o r Ru, we h a v e a v e r a g e d v a l u e s of A a / A c o b t a i n e d f r o m the X - r a y d e t e r m i n a t t o n s of t h i s w o r k and of Others and f r o m the d e n -
l
'
I
'
,. j I
PFe = 7.870 o l e m 3
)•
'
[3]
Re, a = a F e + (29 • 1) x 10 -4 CRe ; Rh, a = a F e + (36 9 2) x 10 -4 CRh ; Ru, a = a F e + (28 • 1) • 10 -4 CRu w h e r e a i s given in A, a F e = 2.8664A, and c i s in at. pct. 1. W. C. Leslie: Met. l)nns., 1972, vol. 3, pp. 5-36. 2. G. R. Speich, A. L Sehwoeble, andW. C. Leslie: Met. Trans., 1972, vol. 3, pp. 2031-37. 3. L. Zwell, J. T. Michalak, and H. A. Wriedt: s Appl. Cryst., 1970, vol. 3, pp. 357-60. 4. F. Garofalo and H. A. Wriedt: Aeta Met., 1962, vol. 10, pp. 1007-12. 5. E. P. Abrahamson II and S. L Lopata: Trans. TMS-AIME, 1966,vol. 236, pp. 76-87. 6. E. Raub and W. Platte: Z. Metallk., 1960, vol. 51, pp. 477-81. 7. H. H. Kranzlein, M. S. Burton, and G. V. Smith: Trans. TMS-AIME, 1965, vol. 233, pp. 64-70. 8. A. L.
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