Van den Beukel_1976_Inhomogeneous plastic deformation in a Au-Cu alloy

The v a l u e m 147 is in good agreement w i t h the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: f W i j l e f a t a! [ 6 ] : m = 1,5 in a AuCu 7.5 a l l o y . From (9) and the e x p e r i m e n t a l v a l u e o f K^ an e s t i m a t e o f AC can be made Takin 0 = 1 ,5 10 -2 cm2sec, E = 0 , 7 e V , W = 0 ~ e V u = ~ , . - 8 _ c r . . . . _~ • g v ,~ ,u .).,u ~m, ~ = IU i t is f ound t h a t A c t r = 0 , 3 cm. The main emrror comes from the u n c e r t a i n t v : ~ i n E which a c c o r d i n g t o E o r e v a a r [~/] i s 0,03 eV, y i e l d i n g an e r r o r in ACcr o f ' a f a c t o r o f ; . T h e r e f o r e the p r o b a b l e v a ] u e o f ACcr is between 0 , l c_ and c o . This does n o t d i s a g r e e w i t h van den B e u k e l ' s [ 4 ] e s t i m a t e ACcr -- o , Y c o from a model o f the onset of serrated yielding. 5 36 INHOMOGENEOUS DEFORMATION IN A u - C u ALLOY Vol. i0, The c o n d i t i o n (8) can a l s o be a p p l i e d to the case o f f i r s t y i e l d i n g . I t was f ound ( f i g . 1) t h a t a t 0°C f o r t a = 30 sec a l ~ d e r s band was o b s e r v e d f o r E ~ 10%, w hereas i t was n o t f o r ¢ = 6 and 8%. Taking a g a i n E = 0 , 7 eV, the c o n s t a n t K~ a t 0 C c an be calculated from Jts room temperature value, yleldlng Ko = 0,7 sec. Then f rom (8) it is found that for inhomogeneous deformation to occur ~ = 47,31 and 2 2 sec respectively for ~ = 6,8 and 10%. It is seen that only in t~e latter case an aging time of 30 sec is sufficient to start inhomogeneous deformation, in a ccordance with the experimental result. F inally equation (8) also applies to the start of the PL effect. In this case the aging of dislocations occurs during the deformation-'(dynamic strain aging) in contrast to the cases of first and repeated yielding where static strain aging t akes place. Diffusion of solute atoms to moving dislocations occurs during the time t the dislocations are waiting in front of obstacles to be surmounted (Mc. Co~mick [3]). The condition for the start of the PL effect follows from (8) b y p u t t i n g t a = tw: ECm " w here E C t W = K2 (10) is the s t r a i n where the PL e f f e c t starts. Further is = ½ bp¢ d = ½bp L__ t (11) W p a nd / , b e i n g the d e n...
View Full Document

This document was uploaded on 01/23/2014.

Ask a homework question - tutors are online