The crystallography of ferrous martensites

  • PDF / 2,889,857 Bytes
  • 15 Pages / 612 x 792 pts (letter) Page_size
  • 98 Downloads / 221 Views

DOWNLOAD

REPORT


P, D U N N E A N D

C. M. W A Y M A N

T h e a p p l i c a b i l i t y o f t h e p h e n o m e n o l o g i c a l c r y s t a l l o g r a p h i c t h e o r y to m a r t e n s i t i c t r a n s f o r m a t i o n s i n f e r r o u s a l l o y s i s d i s c u s s e d , a n d i t i s c o n c l u d e d that o n l y f o r t h e { 3 , 1 5 , 10}F a n d {252}F transformations a r e experimental data sufficiently c o m p l e t e for d e t a i l e d comparisons with predictions o f t h e t h e o r y . S i n c e crystallographic m e a s u r e m e n t s have p r o v e d m o r e diffic u l t t o o b t a i n i n t h e {252 } F c a s e a d e t a i l e d a s s e s s m e n t o f e l e c t r o n m i c r o s c o p y o b s e r v a t i o n s a n d of r e p o r t e d m e a s u r e m e n t s o f t h e s h a p e s t r a i n a n d o r i e n t a t i o n r e l a t i o n s h i p i s g i v e n f o r t h i s t r a n s f o r m a t i o n . T h e b a s i c t h e o r y i n t r o d u c e d in t h e 1 9 5 0 ' s a c c o u n t s s a t i s f a c t o r i l y f o r t h e { 3 , 1 5 , 10}F t r a n s f o r m a t i o n but not f o r t h e { 2 5 2 } F c a s e . R e c e n t m o d i f i c a t i o n s o f t h e t h e o r y b a s e d on m u l t i p l e l a t t i c e i n v a r i a n t s h e a r s a r e a l s o r e v i e w e d a n d a r e e x a m i n e d i n t h e l i g h t o f t h e c r y s t a l l o g r a p h i c m e a s u r e m e n t s . T h e u s e of e x p e r i m e n t a l i n f o r m a t i o n t o i n f e r p o s s i b l e i n h o m o g e n e o u s d e f o r m a t i o n m o d e s is e m p h a s i z e d .

THE

phenomenological

crystallographic theories* of

*Although the plural is used here, it should be emphasized that only one theory of variousformulations is really under consideration. The equivalence of the various formulations by Bowles andMackenzie, Bullough and Bilby, andWechsler, et al. has been demonstrated many times, and the invariant plane strain shape deformation and inhomogeneous or complementary shear are central in all cases. m a r t e n s i t e f o r m a t i o n w e r e i n t r o d u c e d i n the 1 9 5 0 ' s a n d a r e b a s e d o n t h e c o n c e p t that t h e i n t e r f a c e p l a n e b e t w e e n t h e m a r t e n s i t e a n d p a r e n t p h a s e s is e s s e n tially macroscopically invariant-/, e., undistorted a n d u n r o t a t e d . 1-~ T h e s e t h e o r i e s h a v e g a i n e d g e n e r a l a c ceptance b e c a u s e of the a g r e e m e n t b e t w e e n theory and e x p e r i m e n t in a n u m b e r o f c a s e s . H o w e v e r , w h e n t h e s e t h e o r i e s a r e a p p l i e d to v a r i o u s m a r t e n s i t i c t r a n s f o r m a t i o n s in i r o n a l l o y s a n d s t e e l s , o n e must conclude that o n l y a f e w s p e c i f i c t r a n s f o r m a t i o n s a r e a d e q u a t e l y a c c o u n t e d f o r . O n the o t h e r h a n d , t h e u n d e n i a b l e s u c cess o f t h e i n v a r i a n t p l a n e t h e o r y in t h o s e " w o r k a b l e " c a s e s s e r v e s to v a l i d a t e i

Data Loading...