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c r e e p , and also other p r o p e r t i e s , the c o m b i n e d effect of s e v e r a l s o l u t e s f r e q u e n t l y is not a s i m p l e a d dition of t h e i r s e p a r a t e effects, s i n c e i n t e r a c t i o n o c c u r s b e t w e e n s o l u t e s . This is an i m p o r t a n t point, but little s y s t e m a t i c i n f o r m a t i o n is a v a i l a b l e on it; its b a s i c study is s u r e l y the m o s t neglected p r o b l e m in m e t a l l u r g y . " This quote f r o m McLean I d e s c r i b e s the p r o b l e m to which this i n v e s t i g a t i o n was a d d r e s s e d - - t h e effect of solute i n t e r a c t i o n s on c r e e p s t r e n g t h . C o l u m b i u m - b a s e t e r n a r y alloys w e r e s e l e c t e d for study b e c a u s e c o m p r e h e n s i v e b i n a r y c r e e p s t r e n g t h data on this s y s t e m were a v a i l a b l e e and b e c a u s e c o l u m b i u m is the b a s e m e t a l for a f a m i l y of alloys with high p o t e n t i a l for s t r u c t u r a l use at elevated t e m p e r a t u r e s . Despite the effort put into d e v e l o p m e n t of c o l u m b i u m alloys, t h e r e has b e e n no s i g n i f i c a n t study of the effect of solute i n t e r a c t i o n s on t h e i r c r e e p s t r e n g t h . This p a p e r d e t a i l s the effect of solute i n t e r a c t i o n s on the c r e e p s t r e n g t h of four t e r n a r y c o l u m b i u m alloy s y s t e m s using a s p e c i a l technique to m e a s u r e a p p r o x i m a t e c r e e p s t r e n g t h s . A method to identify the effect of s o l ute i n t e r a c t i o n s on c r e e p s t r e n g t h is d e s c r i b e d , and the effect of t h e s e i n t e r a c t i o n s on c r e e p s t r e n g t h is a n a lyzed. In this study, solute i n t e r a c t i o n s t r e n g t h e n i n g is cons i d e r e d to be the c o m b i n e d effect of m u l t i p l e s o l u t e s on c r e e p s t r e n g t h without r e g a r d to s t r e n g t h e n i n g m e c h a n i s m or s t r u c t u r a l v a r i a t i o n . Thus, the o r i g i n of the s t r e n g t h change upon c o m b i n i n g s o l u t e s m a y be due to changes in bulk m a t r i x p r o p e r t i e s (e.g., diffusion r a t e s , m e l t i n g t e m p e r a t u r e , e l a s t i c p r o p e r t i e s ) , c h a n g e s in g r a i n size and s u b s t r u c t u r e , the p r e s e n c e of a second phase, or the i n t e r a c t i o n of the added s o l u t e s with the e v e r p r e s e n t i n t e r s t i t i a l a t o m s . This p h e n o m e n o l o g i c a l approach was adopted b e c a u s e it would have b e e n a l m o s t i m p o s s i b l e to study a r a n g e of a l l o y c o m p o s i t i o n s and t e s t t e m p e r a t u r e s in a r e a s o n a b l e t i m e if s t r u c t u r e s and m e c h a n i s m s were also analyzed. E X P E R I M E N T A L PROCEDURES The method of m e a s u r i n g c r e e p s t r e n g t h has b e e n d e s c r i b e d in detail p r e v i o u s l y , z In b r i e f , c