• PDF / 513,534 Bytes
• 6 Pages / 612 x 792 pts (letter) Page_size
• 71 Downloads / 208 Views

DOWNLOAD

REPORT

---

ALTHOUGH

r e c o v e r y a r i s i n g f r o m the m i g r a t i o n of quenched-in point defects has been studied extensively in p u r e m e t a l s and in a few s i m p l e a l l o y s , ~ a l m o s t no e x p e r i m e n t s a r e r e p o r t e d on m a t e r i a l s of e n g i n e e r i n g i m p o r t a n c e . This p a p e r d e s c r i b e s a d i s l o c a t i o n d a m p ing i n v e s t i g a t i o n of r e c o v e r y in high p u r i t y F e - 1 8 C r Ni a l l o y s ( a u s t e n i t i c s t a i n l e s s s t e e l s ) , a c l a s s of a l l o y s c o m m o n l y u s e d a s s t r u c t u r a l m a t e r i a l s in n u c l e a r r e a c t o r s . W h e n e v e r t h e s e m a t e r i a l s a r e u s e d in t h i s a p p l i c a t i o n , the l a r g e n u m b e r s of p o i n t d e f e c t s c r e a t e d b y i r r a d i a t i o n can m i g r a t e , b r i n g i n g about m a r k e d c h a n g e s in m e c h a n i c a l b e h a v i o r . One of the two o b j e c t i v e s of t h i s w o r k is to m e a s u r e and e x p l a i n the k i n e t i c l a w s d e s c r i b i n g the m i g r a t i o n of p o i n t d e f e c t s d u r i n g r e c o v e r y in t h e s e m a t e r i a l s , s o that t h e i r m e c h a n i c a l b e h a v i o r d u r i n g and a f t e r i r r a d i a t i o n m i g h t be b e t t e r understood. In a d d i t i o n to t h i s e n g i n e e r i n g - o r i e n t e d o b j e c t i v e , the w o r k p r o v i d e s b a s i c i n f o r m a t i o n about the f u n d a m e n t a l m e c h a n i s m s of r e c o v e r y in fcc a l l o y s . It i s known t h a t d i s l o c a t i o n s s e r v e a s s i n k s for p o i n t d e f e c t s d u r i n g the r e c o v e r y p r o c e s s , and the r o l e of the one d i m e n s i o n a l o r t o t a l d i s l o c a t i o n a s a sink h a s b e e n s t u d i e d , a On the o t h e r hand, the d i s l o c a t i o n s in t h e s e a l l o y s a r e e x t e n d e d (two d i m e n s i o n a l ) , and the width of the e x t e n d e d d i s l o c a t i o n i s a s t r o n g function of s t a c k i n g f a u l t e n e r g y , 7, which in t u r n d e p e n d s s e n s i t i v e l y upon n i c k e l content, s The i n v e s t i g a t i o n h a s b e e n c o n d u c t e d on t h r e e F e - 1 8 C r a l l o y s containing 10 (7 = 10 e r g p e r s q cm), 15 (7 = 18 e r g p e r sq cm), a n d 20 (7 = 24 e r g p e r sq cm) wt p c t Ni. Since w, the width of the e x t e n d e d d i s l o c a t i o n , i s i n v e r s e l y prooportional to 7, w ~ 150A for the 10 p c t a l l o y , w ~ 90A f o r the 15 p c t a l l o y , and w ~ 60/~ f o r the 20 p c t a l l o y . The s t u d y of r e c o v e r y in t h i s s y s t e m then, i s in f a c t the s t u d y of N. F. FIORE is Associate Professor and Chairman, Department of Metallurgical Engineering and Materials Science, University of Notre Dame, Notre Dame, Ind. D. C. STEWART, formerly with the Department of Metallurgical Engineering and Materials Science, University of Notre Dame, is with Florida Research and Developme