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Mechanisms of full densification in tungsten-copper compacts
Modelling
HIP MODELLING SHAPED PARTS
A UNIT PROBLEM APPROACH TO MODELLING OF POWDER CONSOLIDATION I I. Li et al. ( C a r n e g i e M e l l o n U n i v e r s i t y , l)ittsburg, U S A ) . D(.velopment of models of powder c o m p a c t i o n w a s d i s c u s s e d . A s t u d y of a 2l)arti('le m o d e l , u n d e r c o m p r e s s i o n w a s d e s c r i b e d a n d u s e d to d e v e l o p a n i n t e r n a l :tare variable model to incorporate t,arti(le/particle interaction. The model w a s m o d i f i e d in t h e l i g h t of r e s u l t s f r o m , . x p e l - i m e n t s o n two c o n t a c t i n g Al s p h e r e s . T h e r e l a t i o n s h i p s d e d u c e d w e r e u s e d to :epre,,ent interaction at large and small o n t a c t a r e a s . T h e m o d e l w a s v a l i d a t e d over , ran~,e of s t r a i n rates. NUMERICAL MODELLING OF NEAR NET SHAPE HIP OF TITANIUMALUM INIUM-VANADIUM POWDER I~. A b q , n d a n c e et al. C E A / C E R A M , G r e n o b l e , !.ran(~,). It w a s r e p o r t e d t h a t HIP to n e a r n e t > h a p c of a Ti-AI-V alloy p a r t h a s b e e n m o d e l l e d in o r d e r to p r e d i c t final d e n s i t y :rod d i m e n s i o n s . U s e w a s m a d e o f p o w e r i)rop(,rties a n d f i n i t e e l e m e n t m e t h o d s , a p p l i e d in 2- a n d 3 - d i m e n s i o n s . The difference between predicted and m e a s ~ l r e d d i m e n s i o n s w a s r e p o r t e d to b e b~'ss t h a n 0.2 ram. A THREE-DIMENSIONAL FINITE ELEMENT SIMULATION OF HOT POWDER FORGING OF A PART _LG.K J i n k a et al. (Ecole Nat. S u p e r i e u r e des Mines de Paris, Sophia Antipolis, l.'rance). D~'velopment of a finite element algorithm for modelling of powder deformation, based on use of volume preserving and dilatation parameters, was d e s c r i b e d . T h e m a i n u n k n o w n s in t h e ,,quations are velocity, pressure and \ o l u m e s t r a i n r a t e s . A m o d u l e allows for n o n - i s o t h e r m a l d e f o r m a t i o n . U s e is m a d e o f a m o d i f i e d yield c r i t e r i o n w h i c h is p r e s s u r e sensil:ive. A1 p o w d e r w a s u s e d to d e t e r m i n e ,,xperimental parameters. The model was a p p l i , ' d to a n a u t o m o t i v e c o n n e c t i n g rod. ROLE OF CONTACT-CONTACT INTERACTION IN DENSIFICATION POWDERS
OF
N.A. Fleck et al. ( U n i v e r s i t y o f C a m b r i d g e , Cambridge, UK). A study of interfacial contact and pore g e o m e t r y in h y d r o s t a t i c c o m p a c t i o n w a s d e s c r i b e d for a 2 - d i m e n s i o n a l a r r a y o f (Tlindrical p a r t i c l e s . Slip-line field t h e o r y a n d finite e l e m e n t m e t h o d s w e r e u s e d . It was shown that contact-contact interaction h a s a s t r o n g effect o n c o m p a c t i o n a f t e r t h e initial stage.
OF COMPLEX
MECHANISMS OF FULL DENSIFICATION IN TUNGSTENCOPPER COMPACTS
D.G. S e l i v e r s t o v , V.N. S a m a r o v . (VILS, Moscow, R u s s i a ) . A n e w c o n c e p t of m o d e l l i n g o f H I P a n d capsule design, based on special classification of parts and a choice of q u a l i t a t i v e m e t h o d in 2- a n d 3 - d i m e n s i o n s w a s d e s c r i b e d . It is r e p o r t e d t h a t u s e of t h e t e c h n i q u e l e a d s to c o s t s a v i n g s a n d r e d u c e d m a t e r i a l losses.
J.S. Lee et al. ( H a n y a n g University, A n s a n , Korea). Sintering of nano-composite W-Cu p o w d e r s , 3 0 - 5 0 n m , w a s d i s c u s s e d a n d it w a s r e p o r t e d t h a t t h e r e is e n h a n c e d s i n t e r i n g to full d e n s i t y d u r i n g h e a t i n g . The correlation between densification and microstructural evolution was illustrated.
DENSIFICATION MECHANISMS IN THE INITIAL STAGE OF SOLID PHASE SINTERING
HOMOGENIZATION AND DENSIFICATION DURING SOLID STATE SINTERING
W. S c h a t t et al. ( M a x P l a n c k Inst. for M a t e r i a l s Science, S t u t t g a r t , G e r m a n y ) . T h e role o f l a t t i c e d e f e c t s in e n h a n c i n g mass transport and densification during solid s t a t e s i n t e r i n g w a s d i s c u s s e d w i t h respect to formation, interaction and r e l a x a t i o n o f d e f e c t s a n d t h e i r r e l a t i o n to sintering mechanisms. It w a s s h o w n t h a t s h r i n k a g e c a n n o t be e x p l a i n e d solely by d i f f u s i o n , d i s l o c a t i o n flow m u s t also be c o n s i d e r e d .
1C B r a n d , W. S c h a t t ( T e c h n i c a l U n i v e r s i t y o f Dresden, Dresden, Germany). An investigation of solid state d e n s i f i c a t i o n a n d h o m o g e n i z a t i o n o f Ni-Cu a n d Ni-Co c o m p a c t s w a s d e s c r i b e d . It w a s d e d u c e d t h a t d e n s i f i c a t i o n of 2 - c o m p o n e n t s y s t e m s , w i t h t o t a l s o l i d s o l u b i l i t y , is c o n t r o l l e d by t h e s a m e d e f e c t a c t i v a t e d mechanisms as 1 component systems and t h a t h o m o g e n i z a t i o n h a s little effect o n densification where the diffusion coefficients a r e n e a r e q u a l , a s in Ni-Co. In Ni-Cu t h e effect of i n t e r d i f f u s i o n is g r e a t e r and depends on the element which predominates.
THREE-DIMENSIONAL SIMULATION OF MICROSTRUCTURAL EVOLUTION OF A COMPRESSED POWDER J.P. J e r n o t et al. (LERMAT, U R A / C R N S , Caen, France). A computer simulation of random s t a c k i n g of u n i f o r m s p h e r e s , w h i c h a r e then densified, was described. For each densification step stereological and topological parameters were deduced. The m o d e l w a s s h o w n to c o r r e s p o n d closely with powder compression. DIFFUSION IN NICKEL-ALUMINIUM AND MATHEMATICAL MODELLING OF REACTION SINTERING S. D o m s a et al. ( M a x P l a n c k I n s t . for M a t e r i a l s Science, S t u t t g a r t , G e r m a n y ) . By m o d e l l i n g a n d e x p e r i m e n t d i f f u s i o n and dissolution coefficients were d e t e r m i n e d for t h e Ni-Ni2A13-Alliq s y s t e m . A continuum model of sintering, taking phase transformation into account, was developed. SOLID STATE SINTERING OF TUNGSTEN CARBIDE-COBALT B. U h r e n i u s et al. (Royal Inst. o f T e c h n o l ogy, S t o c k h o l m , S w e d e n ) . Solid state sintering of WC-Co was d i s c u s s e d w i t h r e g a r d to t h e d e v e l o p m e n t o f m o d e l s . It w a s s h o w n e x p e r i m e n t a l l y t h a t 70% o f t h e v o l u m e s h r i n k a g e t a k e s p l a c e in t h e s o l i d s t a t e . A s t u d y o f microstructural evolution was described. T h e r e s u l t s w e r e d i s c u s s e d in t e r m s o f mechanisms. Mathematical simulations were presented.
SYNTHESIS OF NICKEL ALUMINIDE FROM ULTRAFINE POWDERS M. B o s h m a n n et al. ( M a x P l a n c k Inst. for M a t e r i a l s Science, S t u t t g a r t , G e r m a n y ) . A s t u d y of t h e s y n t h e s i s of NiAl f r o m a d e n s e h o m o g e n e o u s b l e n d of u l t r a f i n e Ni a n d A1 p o w d e r s by reactive s i n t e r i n g , self p r o p a g a t i n g h i g h t e m p e r a t u r e s 3 ~ t h e s i s or d i f f u s i o n c o n t r o l l e d solid s t a t e r e a c t i o n is d e s c r i b e d . Kinetics, m i c r o s t r u c t u r e s a n d p h a s e c o m p o s i t i o n s w e r e d e t e r m i n e d . It w a s r e p o r t e d t h a t NiAl c a n be s y n t h e s i z e d in t h e solid s t a t e by a two s t a g e h e a t t r e a t m e n t , 15 m i n u t e s a t 550°C, to NiAl:3, a n d 1 h o u r a t 800°C. ALTERNATIVE METHODS OF MICROSTRUCTURAL ANALYSIS M.M.R.M. H e n d r i x et al. ( E i n d h o v e n University of Technology, Eindhoven, The Netherlands). Stereology, for q u a n t i t a t i v e a n a l y s i s o f m i c r o s t r u c t u r e s , w a s d i s c u s s e d . It w a s n o t e d t h a t t h i s m a y u s e o n l y a singleparticle model whereas a multi-particle model is required for sintering. Correlation and coordination analyses, which deal with spatial distribution of matter and coordination of pores and p a r t i c l e s , respectively, a r e d e s c r i b e d . T h e c o n c e p t o f a ' m e s o cell' is i n t r o d u c e d a s a microstructural parameter a n d is s h o w n to be a b o u t t e n t i m e s g r e a t e r t h a n t h e m e a n g r a i n i n t e r c e p t size for p a r t i a l l y s i n t e r e d AI203.
M P R D e c e m b e r 1995 53
HIP MODELLING SHAPED PARTS
A UNIT PROBLEM APPROACH TO MODELLING OF POWDER CONSOLIDATION I I. Li et al. ( C a r n e g i e M e l l o n U n i v e r s i t y , l)ittsburg, U S A ) . D(.velopment of models of powder c o m p a c t i o n w a s d i s c u s s e d . A s t u d y of a 2l)arti('le m o d e l , u n d e r c o m p r e s s i o n w a s d e s c r i b e d a n d u s e d to d e v e l o p a n i n t e r n a l :tare variable model to incorporate t,arti(le/particle interaction. The model w a s m o d i f i e d in t h e l i g h t of r e s u l t s f r o m , . x p e l - i m e n t s o n two c o n t a c t i n g Al s p h e r e s . T h e r e l a t i o n s h i p s d e d u c e d w e r e u s e d to :epre,,ent interaction at large and small o n t a c t a r e a s . T h e m o d e l w a s v a l i d a t e d over , ran~,e of s t r a i n rates. NUMERICAL MODELLING OF NEAR NET SHAPE HIP OF TITANIUMALUM INIUM-VANADIUM POWDER I~. A b q , n d a n c e et al. C E A / C E R A M , G r e n o b l e , !.ran(~,). It w a s r e p o r t e d t h a t HIP to n e a r n e t > h a p c of a Ti-AI-V alloy p a r t h a s b e e n m o d e l l e d in o r d e r to p r e d i c t final d e n s i t y :rod d i m e n s i o n s . U s e w a s m a d e o f p o w e r i)rop(,rties a n d f i n i t e e l e m e n t m e t h o d s , a p p l i e d in 2- a n d 3 - d i m e n s i o n s . The difference between predicted and m e a s ~ l r e d d i m e n s i o n s w a s r e p o r t e d to b e b~'ss t h a n 0.2 ram. A THREE-DIMENSIONAL FINITE ELEMENT SIMULATION OF HOT POWDER FORGING OF A PART _LG.K J i n k a et al. (Ecole Nat. S u p e r i e u r e des Mines de Paris, Sophia Antipolis, l.'rance). D~'velopment of a finite element algorithm for modelling of powder deformation, based on use of volume preserving and dilatation parameters, was d e s c r i b e d . T h e m a i n u n k n o w n s in t h e ,,quations are velocity, pressure and \ o l u m e s t r a i n r a t e s . A m o d u l e allows for n o n - i s o t h e r m a l d e f o r m a t i o n . U s e is m a d e o f a m o d i f i e d yield c r i t e r i o n w h i c h is p r e s s u r e sensil:ive. A1 p o w d e r w a s u s e d to d e t e r m i n e ,,xperimental parameters. The model was a p p l i , ' d to a n a u t o m o t i v e c o n n e c t i n g rod. ROLE OF CONTACT-CONTACT INTERACTION IN DENSIFICATION POWDERS
OF
N.A. Fleck et al. ( U n i v e r s i t y o f C a m b r i d g e , Cambridge, UK). A study of interfacial contact and pore g e o m e t r y in h y d r o s t a t i c c o m p a c t i o n w a s d e s c r i b e d for a 2 - d i m e n s i o n a l a r r a y o f (Tlindrical p a r t i c l e s . Slip-line field t h e o r y a n d finite e l e m e n t m e t h o d s w e r e u s e d . It was shown that contact-contact interaction h a s a s t r o n g effect o n c o m p a c t i o n a f t e r t h e initial stage.
OF COMPLEX
MECHANISMS OF FULL DENSIFICATION IN TUNGSTENCOPPER COMPACTS
D.G. S e l i v e r s t o v , V.N. S a m a r o v . (VILS, Moscow, R u s s i a ) . A n e w c o n c e p t of m o d e l l i n g o f H I P a n d capsule design, based on special classification of parts and a choice of q u a l i t a t i v e m e t h o d in 2- a n d 3 - d i m e n s i o n s w a s d e s c r i b e d . It is r e p o r t e d t h a t u s e of t h e t e c h n i q u e l e a d s to c o s t s a v i n g s a n d r e d u c e d m a t e r i a l losses.
J.S. Lee et al. ( H a n y a n g University, A n s a n , Korea). Sintering of nano-composite W-Cu p o w d e r s , 3 0 - 5 0 n m , w a s d i s c u s s e d a n d it w a s r e p o r t e d t h a t t h e r e is e n h a n c e d s i n t e r i n g to full d e n s i t y d u r i n g h e a t i n g . The correlation between densification and microstructural evolution was illustrated.
DENSIFICATION MECHANISMS IN THE INITIAL STAGE OF SOLID PHASE SINTERING
HOMOGENIZATION AND DENSIFICATION DURING SOLID STATE SINTERING
W. S c h a t t et al. ( M a x P l a n c k Inst. for M a t e r i a l s Science, S t u t t g a r t , G e r m a n y ) . T h e role o f l a t t i c e d e f e c t s in e n h a n c i n g mass transport and densification during solid s t a t e s i n t e r i n g w a s d i s c u s s e d w i t h respect to formation, interaction and r e l a x a t i o n o f d e f e c t s a n d t h e i r r e l a t i o n to sintering mechanisms. It w a s s h o w n t h a t s h r i n k a g e c a n n o t be e x p l a i n e d solely by d i f f u s i o n , d i s l o c a t i o n flow m u s t also be c o n s i d e r e d .
1C B r a n d , W. S c h a t t ( T e c h n i c a l U n i v e r s i t y o f Dresden, Dresden, Germany). An investigation of solid state d e n s i f i c a t i o n a n d h o m o g e n i z a t i o n o f Ni-Cu a n d Ni-Co c o m p a c t s w a s d e s c r i b e d . It w a s d e d u c e d t h a t d e n s i f i c a t i o n of 2 - c o m p o n e n t s y s t e m s , w i t h t o t a l s o l i d s o l u b i l i t y , is c o n t r o l l e d by t h e s a m e d e f e c t a c t i v a t e d mechanisms as 1 component systems and t h a t h o m o g e n i z a t i o n h a s little effect o n densification where the diffusion coefficients a r e n e a r e q u a l , a s in Ni-Co. In Ni-Cu t h e effect of i n t e r d i f f u s i o n is g r e a t e r and depends on the element which predominates.
THREE-DIMENSIONAL SIMULATION OF MICROSTRUCTURAL EVOLUTION OF A COMPRESSED POWDER J.P. J e r n o t et al. (LERMAT, U R A / C R N S , Caen, France). A computer simulation of random s t a c k i n g of u n i f o r m s p h e r e s , w h i c h a r e then densified, was described. For each densification step stereological and topological parameters were deduced. The m o d e l w a s s h o w n to c o r r e s p o n d closely with powder compression. DIFFUSION IN NICKEL-ALUMINIUM AND MATHEMATICAL MODELLING OF REACTION SINTERING S. D o m s a et al. ( M a x P l a n c k I n s t . for M a t e r i a l s Science, S t u t t g a r t , G e r m a n y ) . By m o d e l l i n g a n d e x p e r i m e n t d i f f u s i o n and dissolution coefficients were d e t e r m i n e d for t h e Ni-Ni2A13-Alliq s y s t e m . A continuum model of sintering, taking phase transformation into account, was developed. SOLID STATE SINTERING OF TUNGSTEN CARBIDE-COBALT B. U h r e n i u s et al. (Royal Inst. o f T e c h n o l ogy, S t o c k h o l m , S w e d e n ) . Solid state sintering of WC-Co was d i s c u s s e d w i t h r e g a r d to t h e d e v e l o p m e n t o f m o d e l s . It w a s s h o w n e x p e r i m e n t a l l y t h a t 70% o f t h e v o l u m e s h r i n k a g e t a k e s p l a c e in t h e s o l i d s t a t e . A s t u d y o f microstructural evolution was described. T h e r e s u l t s w e r e d i s c u s s e d in t e r m s o f mechanisms. Mathematical simulations were presented.
SYNTHESIS OF NICKEL ALUMINIDE FROM ULTRAFINE POWDERS M. B o s h m a n n et al. ( M a x P l a n c k Inst. for M a t e r i a l s Science, S t u t t g a r t , G e r m a n y ) . A s t u d y of t h e s y n t h e s i s of NiAl f r o m a d e n s e h o m o g e n e o u s b l e n d of u l t r a f i n e Ni a n d A1 p o w d e r s by reactive s i n t e r i n g , self p r o p a g a t i n g h i g h t e m p e r a t u r e s 3 ~ t h e s i s or d i f f u s i o n c o n t r o l l e d solid s t a t e r e a c t i o n is d e s c r i b e d . Kinetics, m i c r o s t r u c t u r e s a n d p h a s e c o m p o s i t i o n s w e r e d e t e r m i n e d . It w a s r e p o r t e d t h a t NiAl c a n be s y n t h e s i z e d in t h e solid s t a t e by a two s t a g e h e a t t r e a t m e n t , 15 m i n u t e s a t 550°C, to NiAl:3, a n d 1 h o u r a t 800°C. ALTERNATIVE METHODS OF MICROSTRUCTURAL ANALYSIS M.M.R.M. H e n d r i x et al. ( E i n d h o v e n University of Technology, Eindhoven, The Netherlands). Stereology, for q u a n t i t a t i v e a n a l y s i s o f m i c r o s t r u c t u r e s , w a s d i s c u s s e d . It w a s n o t e d t h a t t h i s m a y u s e o n l y a singleparticle model whereas a multi-particle model is required for sintering. Correlation and coordination analyses, which deal with spatial distribution of matter and coordination of pores and p a r t i c l e s , respectively, a r e d e s c r i b e d . T h e c o n c e p t o f a ' m e s o cell' is i n t r o d u c e d a s a microstructural parameter a n d is s h o w n to be a b o u t t e n t i m e s g r e a t e r t h a n t h e m e a n g r a i n i n t e r c e p t size for p a r t i a l l y s i n t e r e d AI203.
M P R D e c e m b e r 1995 53