A study of high temperature dispersion strengthened titanium alloys by a PM process

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R e c e n t p r o g r e s s in p r o c e s s i n g Ti a l u m i n i d e s was reviewed with regard to microstructural and property evolution. E x a m p l e s of n e t s h a p e part, p r o d u c t i o n a n d e v a l u a t i o n w e r e given. REACTION-HOT ISOSTATIC PRESSING (RHIP) FOR TITANIUM ALUMINIDES M. D a h I n s et al, ( G K S S - F o r s c h u n g z e n t r u i n , Geesthact Germany. ) T h e u s e of RHIP for p r o d u c t i o n of Ti a l u m i n i d e s w a s d e s c r i b e d . E l e m e n t a l Ti a n d Al p o w d e r m i x t u r e s w e r e c o n s o l i d a t e d initially by e x t r u s i o n a n d t h e n by RttlP. t h e p o r o s i t y to be c l o s e d d u r i n g RHIP w a s f o u n d to be l e s s t h a n w h e n s i m p l e r e a c t i v e p r e s s i n g w a s u s e d . P r o d u c t i o n of r o d s a n d s h e e t w a s s h o w n to be possible. A r a n g e o f m i c r o s t r n c t u r e s w a s p r o d u c e d by v a r i a t i o n in p r o c e s s c o n d i t i o n s b u l t e n s i l e a n d f r a c t u r e p r o p e r t i e s w e r e h)wer t h a n in cast/forged materials. Oxygen content was foun(l to be high. A STUDY OF HIGH TEMPERATURE DISPERSION STRENGTHENED T I T A N I U M ALLOYS BY A PM P R O C E S S F. S c h w a r t z et al, (SNECA, Gennevilliers, France.) An i n v e s t i g a t i o n into l h e u s e of PM for t h e p r o d u c t i o n of d i s p e r s i o n s t r e n g t h e n e d Ti alloys w a s d e s c r i b e d . Two alloys, a n :x/fl alloy a n d a a l ) h a s e alloy, w e r e s t u d i e d a n d two m e a n s of i n c o r p o r a t i n g o x i d e s into t h e m a t r i x w e r e e m p l o y e d . T h e two alloys, w i t h and withoul oxide dispersant were atomised and lhe l)owder exlruded. Tensile and creet~ prot)erties were measured as a lunction of temperature w i t h r e g a r d to t h e effeel of t h e rare e a r t h oxide dispersions. Electron microscopy was u s e d to e v a l u a t e o x i d e p a r t i c l e sizes a n d d i s t r i b u t i o n in the m a t r i x . STRUCTURE AND HIGH TEMPERATURE DEFORMATION BEHAVIOUR OF TITANIUM-RICH TITANIUM ALUMINIDE M. T o k i z a n e el al, ( t ~ i t s u m e i k a n [~niversity, K.voto , J a p a n . ) T h e s t r u c t u r e an(I d e f o r m a t i o n of Ti47%A1 w e r e i n v e s t i g a t e d at 950 C. T h e compact showed a duplex slrueture with a g r a i n size on 2~tm in d i a m e t e r c o n s i s t i n g of e q u i a x e d 7 g r a i n s a n d a l a m e l l a r "//~e c u n s t i t u e n l , . T h e 47%A1 a l l o y s h o w e d h i g h e r s t r e n g t h t h a n t h e 5t)% AI alloy at r o o m t e m p e r a t u r e bul t h e flow s t r e s s at 9 5 0 ' C w a s lower. I .)ynamic r e c r y s t a l l i s a t i o n o c c u r s d u r i n g d e f o r m a t i o n at 9 5 ( ) C giving a refined grain size. Superplastic d e f o r m a t i o n w a s c o n s i d e r e d to h a v e t a k e n place. XD DEVELOPMENTS ALUMINIDES

IN TITANIUM

L. C h r i s t o d o u l o u , (Marl;in M a r r i e t l a L a b o r

;PM

EITERATURE

RiEVIE~

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atories, B a l t i m o r e , US.&) T h e p r o c e s s i n g o f Ti a l u m i n i d e s w a s outlined. The metallurgical phenomena w h i c h h a v e b e e n e x p l o i t e d to a t t a i n t h e o b s e r v e d p r o p e r t i e s in Ti a l u m i n i d e s w e r e reviewed. T h e s t a t u s o f t h e s e m a t e r i a l s w a s discussed.

A n Mg alloy, Mg-2, 5wt%Ag-2%R, E,0,6%Zr, w i t h a n d w i t h o u t p a r t i c u l a r SiC r e i n f o r c e m e n t w a s c o n s o l i d a t e d by s p r a y deposition. The structures, properties and i m p u r i t y , H a n d O, levels w e r e i n v e s t i g a t e d a n d f o u n d to be s a t i s f a c t o r y to p e r m i t u s e o f t h e alloys for a e r o s p a c e a p p l i c a t i o n s .

METAL INJECTION MOULDINGS (MIM) OF INTERMETALLIC MATERIALS)

COST EFFECTIVE HIGH PERFORMANCE ALUMINUM MATRIX COMPOSITED FOR AEROSPACE APPLICATIONS

W. Diehl et al, ( F o r s e h u n g z e n t r u m Jfilieh GmbH, Jdlich, Germany.) The application of MIM to the fabrication of intermetallie materials, w h i c h a r e n o t d e f o r m a b l e , w a s reviewed. A n o u t l i n e of t h e MIM p r o c e s s w a s given with due consideration to powder morphology and the production of injectable powder/binder mixtures. M o u l d i n g c r i t e r i a a n d p r o b l e m s of b i n d e r removal were discussed. Data concerning s i n t e r i n g , h e a t t r e a t m e n t a n d HIP w e r e given for TisSi a.

MICROSTRUCTURES AND PROPERTIES OF HIGH MELTING POINT TITANIUM SILICIDES G. F r o m m e y e r , R. R o s e n k r a n z , ( M a x - P l a n c k I n s t i t u t for E i s e n f o r s e h u n g , G e r m a n y . ) An i n v e s t i g a t i o n into t h e s t r u c t u r e a n d p r o p e r t i e s o f TisSia, a s a f u n c t i o n o f t e m p e r a t u r e u p I() 1300:C, w a s d e s c r i b e d . Measurements were made of Young's m o d u l u s a n d flow s t r e s s . F l o w s t r e s s w a s r e p o r t e d to d e c r e a s e e x p o n e n t i a l l y w i t h i n c r e a s e in t e m p e r a t u r e . At 1 0 0 0 C t h e flow s t r e s s of Ti~Si:~ w a s 1050 M P a a n d of TiSie, 230MPa. T h e m a t e r i a l s w e r e r e p o r t e d to h a v e l o w d e n s i t y a n d g o o d c r e e p resistance. REACTIVE SINTERING ALUMINIDES

OF TITANIUM

G. Leit, n e r et al, ( Z e n t r a l i n s t i t u t fOr Festk6rperphysik und Werkstofforschung, Dresden. ) T h e k i n e t i c s of p h a s e f o r m a t i o n d u r i n g reactive sintering of Ti-49atAl were investigated by calorimetry and dilatometry. The results and technological c o n c l u s i o n s w e r e d i s c u s s e d . It w a s d e d u c e d t h a t a t low h e a t i n g r a t e s TiAl 3 f o r m s o n l y by solid s t a t e r e a c t i o n b u t a t h i g h r a t e s a t r a n s i e n t A l - b a s e d liquid p h a s e is i n v o l v e d a n d w h i c h l e a d s to h i g h e r porosity. T h e need for optimised time/temperature regimes was emphasised.

SPRAY D E P O S I T E D M A G N E S I U M ALLOY A N D M E T A L M A T R I X COMPOSITES P.J. Vervoort, J. I)uszczyck, (Delft U n i v e r s i t y of T e c h n o l o g y , Delft, T h e N e t h e r l a n d s . )

W.H. H u n t , ( A l c o a h m o m e t a l x , USA.) The properties required of light weight materials for aerospace applications, current status and other commercial a p p l i c a t i o n s w e r e r e v i e w e d w i t h r e s p e c t to A L b a s e m e t a l m a t r i x c o m p o s i t e s (MMC). It was considered that t;he m a t e r i a l p r o p e r t i e d n e e d to be t a i l o r e d to m e e t t h e r e q u i r e m e n t s o f a given a p p l i c a t i o n if t h e s e r v i c e d e m a n d s a r e to be c o m p l i e d w i t h . The characteristics o f SiC p a r t i c u l a t e r e i n f o r c e d Al alloys, m a d e by PM, w e r e d i s c u s s e d w i t h r e s p e c t to a p p l i c a t i o n s a n d the current state of commercial readiness. MECHANICAL BEItAVIOUR OF A MECHANICALLY ALLOYED (MA) ALUMINIUM-TITANIUM ALLOY REINFORCED WITH SILICON CARBIDE PARTICLES G.J. H a c k et al, ( I n t o Alloys; Ltd., [tereford, England.) The paper discussed metal matrix c o m p o s i t e s (MMC) m a d e by c o m b i n i n g MA Ti a n d Al p o w d e r m i x t u r e s w i t h SiC p a r t i c l e s . T h e A l - b a s e m a t r i x w a s s h o w n to c o n t a i n a l a r g e p r o p o r t i o n of Al:~Ti a n d to have a high elastic modulus and elevated t e m p e r a t u r e strenglLh. Two alloys, w i t h 6 a n d 10% Ti a n d two levels o f r e i n f o r c e m e n t w e r e d i s c u s s e d . T h e MMCs w e r e r e p o r t e d to h a v e a very h i g h m o ( l u l u s a n d slrengl, h u p to 4 8 f f C . ALUMINIUM-BASE METAL MATRIX C O M P O S I T E S ( M M C ) P R O D U C E D BY SINTERING AND FORGING M.H. C a r v a l h o et al, (I,NETI, L i s b o n , Portugal.) T h e e f l ~ ( t s of c o m p o s i t i o n , %SiC of 10, 15 a n d 20'%,, a n d p r o c e s s v a r i a b l e s , compacting pressures, by ('IP and degassing/sintering cycles, on the p r o p e r t i e s o f SiC p a r t i c u l a t e r e i n f o r c e d 6061 AL alloys w e r e i n v e s l i g a t e d w i t h t h e objective of process Ol)timisation. C o n d i t i o n s w h i c h r e s u l t e d in d e n s i t i e s of 90% o r m o r e w e r e d e s c r i b e d , tlot s w a g i n g a n d f o r g i n g w e r e u s e d to a t t a i n full densifieation. Tensile strength up to 4 4 0 M P a for a 20%SIC MMC w e r e o b t a i n e d . E l o n g a t i o n w a s r e p o r t e d to d e c l i n e w i t h %SiC a n d v a l u e s of 6 to 7% e h m g a t i o n w e r e f o u n d for a 10% SiC m a t e r i a l at a t e n s i l e s t r e n g t h of 4 0 0 M P a

M P R F e b r u a r y 1992 6 3