The forming of Zr 3 Al-base alloys
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containing 7.6, 8.6 and 9.0 wt pet A1 w e r e p r e p a r e d as d e s c r i b e d e l s e w h e r e . 2 T r a n s f o r m e d (Zr3A1) and u n t r a n s f o r m e d (Zr/Zr2A1) s a m p l e s w e r e p r e p a r e d for rolling, cam p l a s t o m e t e r and tube e x t r u s i o n e x p e r i ments as d e s c r i b e d in Table I. B e c a u s e of the high h a r d n e s s of the ingots (380 VHN), the e x t r u s i o n b i l l e t s w e r e machined using a c a r b i d e bit* having a negative
s t r a i n r a t e . 4 The tools and l u b r i c a n t s used in the ext r u s i o n e x p e r i m e n t s w e r e chosen on the b a s i s of i m m e d i a t e a v a i l a b i l i t y r a t h e r than s u i t a b i l i t y for the t e m p e r a t u r e in mind and, while adequate for the p r e s ent p u r p o s e , a r e not n e c e s s a r i l y the b e s t choice f o r high-temperature forming. M i c r o s t r u c t u r e s w e r e examined o p t i c a l l y . The s u r f a c e s w e r e p r e p a r e d using the a t t a c k p o l i s h i n g / c o l o r etching technique 5 and the phase content was d e t e r mined f r o m a r e a f r a c t i o n m e a s u r e m e n t s using quantitative television microscopy. 2. RESULTS 2.1 Rolling Rolling t r i a l s r e v e a l e d that the t r a n s f o r m e d alloy when soaked at 1175 K could not be r e d u c e d by m o r e than 2 to 3 pct in t h i c k n e s s b e f o r e s u r f a c e c r a c k s app e a r e d . With f u r t h e r r e d u c t i o n s the existing c r a c k s p r o p a g a t e d and new ones f o r m e d . Eventually the s a m p l e s d i s i n t e g r a t e d . A t t e m p t s to i m p a r t g r e a t e r p l a s t i c i t y by lowering the reduction in t h i c k n e s s p e r p a s s to 0.5 pct o r by i n c r e a s i n g it to 10 pct w e r e not successful.* (These p a r t i c u l a r r e d u c t i o n s a r e not *In terms of process mechanics A05 pct = 5.8, A1 pet = 4.1 and AIO pet = 1.3 in the present case (see Table I for defintion of A).
meant to i m p l y that a light r e d u c t i o n p e r p a s s is a c o n s e r v a t i v e a p p r o a c h when rolling.) S i m i l a r l y , r a i s ing the soaking t e m p e r a t u r e to 1225 K had a negligible effect, while l o w e r i n g it to 1075 K i m p r o v e d the w o r k a b i l i t y only s l i g h t l y . M a c r o s c o p i c a l l y , the c r a c k s a p p e a r e d to begin at the edges of the work p i e c e and then p r o p a g a t e a c r o s s the top and bottom s u r f a c e s , g e n e r a l l y running p e r -
*G. E. Carbaloy 883.
r a k e . To f o r m an oxide diffusional b a r r i e r between the alloy and the container, the b i l l e t s w e r e oxidized in a i r f o r 2 h at 775 K. They w e r e then canned in m i l d s t e e l c o n t a i n e r s which w e r e closed by welding. The cam p l a s t o m e t e r used in this work is a comp r e s s i o n t e s t i n g machine that d e f o r m s the s p e c i m e n s up to a m a x i m u m s t r a i n of 0.8 at a constant t r u e E. M. SCHULSON is Resea
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