Ingot structures in eutectic and monovariant eutectic Pb-Sn-Cd alloys
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F i g . 7 - - A n a l y s i s of the SAD p a t t e r n in Fig. 6(a) s h o w i n g the zone a x i s [0111 of the twin to be p a r a l l e l to the [0111 zone a x i s of the m a t r i x and the [111] T p a r a l l e l to [1111M.
r e f l e c t i o n s (see for example, Fig. 7(b), which is a d a r k field image of the twin r e f l e c t i o n m a r k e d as point A in Fig. 6(a)). A n a l y s i s of the diffraction p a t t e r n shown in F i g . 7 i n d i c a t e s that the twins lie along the (224) t r a c e d i r e c t i o n s of the {111} twin planes, where the zone axis [ 0 i l ] of the twin is p a r a l l e l to [011] of the m a t r i x . The twins a r e those of the favored twinning s y s t e m in copper, i.e. {111}(112). %~~ SAD p a t t e r n s in a r e a s next to the X M T r e g i o n show the t y p i c a l (100) zone axis of the o r i g i n a l clad c r y s t a l as viewed p e r p e n d i c u l a r to the d i r e c t i o n of detonation. This indicates that f u r t h e r away f r o m the X M T region the explosion cladding has not led to a r e o r i e n t a t i o n of the single c r y s t a l . The s t r u c t u r a l and morphological c h a r a c t e r i s t i c s of the bonding region in Cu/Cu e x p l o s i o n - c l a d single c r y s t a l s imply that the bonding is f o r m e d within a zone r a t h e r than at a s h a r p i n t e r f a c e . 1-3 This conclusion is f u r t h e r strengthened by the bond zones being f o r m e d in clad single c r y s t a l s , in which the effect of grain boundaries and i s o t r o p i c s u r f a c e s of p o l y c r y s t a l l i n e Cu/Cu s y s t e m s is e l i m i n a t e d . The qualitative a n a l y s i s of the s u b s t r u c t u r e s within the v a r i o u s regions of the bond zone should he app r o a c h e d in t e r m s of the t h e r m o m e c h a n i c a l p r o c e s s e s which produce them. The formation of a multiregion zone as a r e s u l t of the explosion cladding of single c r y s t a l s - s e e Fig. 2 - s u g g e s t s that the s t r u c t u r e of the m a t e r i a l in the vicinity of the c o l l i s i o n probably a r i s e s f r o m : i) a negative p r e s s u r e gradient p e r p e n d i c u l a r to the colliding s u r f a c e s ; 2 if) a turbulent p l a s tic flow in the d i r e c t i o n of the detonation coupled with the negative t e m p e r a t u r e gradient p e r p e n d i c u l a r to the detonation direction; 1,4,7 and iii) the fact that the v e l o c i t y of the advancing p r e s s u r e wave is subs t a n t i a l l y higher than that of the propagating heat. ~ In light of the above, the s t r u c t u r e s in the different regions a r e analyzed. Region XEA , which contains the r e c r y s t a l l i z e d equiaxed grains, and r e g i o n X E L , which contains the elongated grains, r e s u l t i n g f r o m the t e m p e r a t u r e r i s e in the collision zone and f r o m dynamic p l a s t i c deformation. Region XCS is c h
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