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Effects of presintering parameters on double pressed and sintered steels
Composites EVOLUTION OF MICROSTRUCTURES DURING IN-SITU PROCESSING OF ALUMINIUM-TITANIUM ALUMINIDE
P.Bhargava et al (University of Alabama, Alabama, USA). The p r o d u c t i o n of a n A1/TiA13 composite by liquid p h a s e sintering from elemental powders was reported. The evolution of t h e m i c r o s t r u c t u r e was described which was shown to be a fine dispersion of TiA13 particles a n d larger Ti particles. The TiA13 was found to coarsen at higher temperatures. Structure/property relationships were discussed. LOW COST PRODUCTION OF TITANIUM MATRIX COMPOSITES WITH CERAMIC AND INTERMETALLIC PARTICLES
S.Abkowitz et al (Dynamet Technology Inc, Burlington, USA). It was r e p o r t e d t h a t a c o m b i n a t i o n of CIP a n d HIP h a d b e e n u s e d in t h e fabrication of a Ti alloy reinforced with ceramic particles. The resulting composites w e r e s a i d to e x h i b i t p o t e n t i a l . T h e manufacture and properties of t h e composite were described a n d significant increase in strength at ambient t e m p e r a t u r e s were reported. D E S I G N AND PROCESSING OF ALLOY AND COMPOSITES FROM ULTRAFINE POWDERS
A. Lawley et al (Drexel University, USA). The processing of p a r t i c u l a t e materials was reviewed with regard to t h e use of r a p i d solidification a n d m e c h a n i c a l alloying. The use of ~ m / n m e l e m e n t a l m e t a l / c e r a m i c powder m i x t u r e s to produce full density c o m p a c t s was discussed w i t h reference to solid state reactions a n d t h e f o r m a t i o n of new phases. E l e m e n t a l powders were said to be highly compressible a n d required lower t e m p e r a t u r e s for sintering, t h u s avoiding t h e decomposition of desirable c o n s t i t u e n t phases. The use of t h e m e t h o d s for Co-W, WC-Co, Co-Ti, Co-Ti-C, Ni-Ti a n d Ni-Ti-C w a s r e p o r t e d . S t r u c t u r e a n d properties were given to show t h e viability of this m e t h o d of powder processing. PRODUCTION OF PARTICLE R E I N F O R C E D ALUMINIUM F I B R E S BY MELT EXTRACTION
G. Lotze et al ( F r a u n h o f e r Inst for Applied Materials Research, Germany). It was r e p o r t e d t h a t fibres of A1 alloys containing 15% SiC or 10% A1203 particles h a d been p r e p a r e d by melt extraction. The fibres were subsequently consolidated by extrusion. The s t r u c t u r e a n d properties of the composites were determined and c o m p a r e d with composite materials m a d e by o t h e r methods. Increased s t r e n g t h of t h e SiC reinforced composite was reported.
44 MPR November 1993
PARTICLE CRACKING IN PM P R O C E S S E D SiC REINFORCED AI MATRIX COMPOSITES
B. Wang et al (University of Alabama, USA). Cracking of t h e SiC reinforcements in a n A1 alloy m a t r i x composite was described. It was shown that there was a linear relationship between applied s t r a i n a n d t h e p r o p o r t i o n of cracked particles.
Dimensional control and sintaring E F F E C T S OF P R E S l N T E R I N G PARAMETERS ON DOUBLE P R E S S E D AND S I N T E R E D S T E E L S
I. D o n a l d s o n (PresMet Corp, Worcester, USA). The r e q u i r e m e n t for i m p r o v e m e n t in properties of high p e r f o r m a n c e PM steels, b r o u g h t a b o u t by d o u b l e - p r e s s i n g a n d d o u b l e - s i n t e r i n g to a t t a i n high density, was discussed. An i n v e s t i g a t i o n of t h e effects of p r e s i n t e r i n g p a r a m e t e r s o n p r o p e r t y d e v e l o p m e n t was described. It was suggested that by control of presintering conditions mechanical properties could be optimized while m a i n t a i n i n g close d i m e n s i o n a l tolerances. DIMENSIONAL CHANGES IN A SINTER H A R D E N I N G ALLOY STEEL
R.W. Kiefer et al ( P i t n e y B o w e s Inc, Stamford, Connecticut, USA). Dimensional changes in s i n t e r h a r d e n e d alloy steels were discussed as a function of mechanical properties/composition r e l a t i o n s h i p . A s t u d y of d i m e n s i o n a l changes in s i n t e r h a r d e n i n g alloy steels was described. Structure a n d properties were m e a s u r e d in order to e s t a b l i s h t h e relationships between cooling rates, dimensional changes and properties. A p p l i c a t i o n s to p a r t p r o d u c t i o n w e r e outlined. E F F E C T S OF A T M O S P H E R E ON DIMENSIONAL CONTROL IN IRONCOPPER-CARBON COMPACTS
R.W. Kiefer et al ( P i t n e y Bowes Inc, Stamford, Connecticut, USA). A n i n v e s t i g a t i o n of t h e e f f e c t s of a t m o s p h e r e composition on d i m e n s i o n a l changes in a Fe-5% Cu-0.9% C steel was described. N, N - H , a n d N-H-CO a t m o s p h e r e s were studied. The sintered materials were characterized for microstructure, properties and d i m e n s i o n s . It w a s r e p o r t e d t h a t t h e composition of t h e sintering a t m o s p h e r e had significant influence on final dimensions. Atmospheres containing H a n d CO reduced d i m e n s i o n a l growth more t h a t N or N-H mixtures. This was a t t r i b u t e d to diffusion of Cu into Fe, wetting of Fe by Cu, the effectiveness of oxide reduction a n d the amount of carburization/de-
c a r b u r i z a t i o n . The i m p l i c a t i o n s of t h e results were discussed.
Modelling and computational methods IMPROVEMENT OF N E T SHAPE DIMENSIONAL CAPABILITY OF PM P R O C E S S BY USE OF EXPERIMENTAL DESIGN
T. C a m p b e l l a n d T.M. C a d l e ( Z e n i t h Sintered Products Inc, C-ermantown, Wisconsin, USA). A n i n v e s t i g a t i o n to d e t e r m i n e t h e factors with the greatest effects on sintered dimensional precision was described. These i n c l u d e d c o m p o s i t i o n a l accuracy, p r e s s / f e e d system, green density a n d sintering conditions. A t e c h n i q u e was devised to d e t e r m i n e t h e c o n t r i b u t i o n of each factor to d i m e n s i o n a l precision. The s o u r c e s of d i m e n s i o n a l v a r i a t i o n were r a n k e d in order. The investigation was e x t e n d e d to d e t e r m i n e t h e c a u s e s of variation a n d reduce them. E x p e r i m e n t a l techniques, quantified effect of variables and the improvement attained were described. FINITE E L E M E N T MODELLING OF COLD POWDER COMPACTION
T. McCabe et al ( C o n c u r r e n t Technologies Corp, USA). The paper reported the use of a finite e l e m e n t p r o g r a m in t h e s t u d y of p r o b l e m s of cold compaction. An elastic/ plastic model with the Kuhn-Shima yield criterion was used to describe d e f o r m a t i o n d u r i n g die compaction. The simulation results were said to provide d a t a which could be used for improving process design. C O N S I S T E N T MODELLING A N D CONTROL OF COMPACTINGSINTERING P R O C E S S
K.Z. Korczak (KZK Powder Technologies Corp, USA). A m e t h o d for t h e i d e n t i f i c a t i o n of p a r a m e t e r s w h i c h will allow p r e d i c t i o n a n d control of d i m e n s i o n a l changes during pressing a n d sintering was described. The critical steps were control of powders, die design a n d set-up p a r a m e t e r s a n d were said to result in effective i m p l e m e n t a t i o n of process d e v e l o p m e n t a n d direct p r o d u c t i o n control. E F F E C T S OF POWDER CHARACTERISTICS ON SIMULATION OF DENSITY DISTRIBUTION VARIATIONS
S. S h i m a a n d M.A.E. Saleh (Kyoto University, Kyoto, J a p a n ) . A finite e l e m e n t simulation of density d i s t r i b u t i o n in closed die c o m p a c t s was described. It was shown t h a t for accuracy of
P.Bhargava et al (University of Alabama, Alabama, USA). The p r o d u c t i o n of a n A1/TiA13 composite by liquid p h a s e sintering from elemental powders was reported. The evolution of t h e m i c r o s t r u c t u r e was described which was shown to be a fine dispersion of TiA13 particles a n d larger Ti particles. The TiA13 was found to coarsen at higher temperatures. Structure/property relationships were discussed. LOW COST PRODUCTION OF TITANIUM MATRIX COMPOSITES WITH CERAMIC AND INTERMETALLIC PARTICLES
S.Abkowitz et al (Dynamet Technology Inc, Burlington, USA). It was r e p o r t e d t h a t a c o m b i n a t i o n of CIP a n d HIP h a d b e e n u s e d in t h e fabrication of a Ti alloy reinforced with ceramic particles. The resulting composites w e r e s a i d to e x h i b i t p o t e n t i a l . T h e manufacture and properties of t h e composite were described a n d significant increase in strength at ambient t e m p e r a t u r e s were reported. D E S I G N AND PROCESSING OF ALLOY AND COMPOSITES FROM ULTRAFINE POWDERS
A. Lawley et al (Drexel University, USA). The processing of p a r t i c u l a t e materials was reviewed with regard to t h e use of r a p i d solidification a n d m e c h a n i c a l alloying. The use of ~ m / n m e l e m e n t a l m e t a l / c e r a m i c powder m i x t u r e s to produce full density c o m p a c t s was discussed w i t h reference to solid state reactions a n d t h e f o r m a t i o n of new phases. E l e m e n t a l powders were said to be highly compressible a n d required lower t e m p e r a t u r e s for sintering, t h u s avoiding t h e decomposition of desirable c o n s t i t u e n t phases. The use of t h e m e t h o d s for Co-W, WC-Co, Co-Ti, Co-Ti-C, Ni-Ti a n d Ni-Ti-C w a s r e p o r t e d . S t r u c t u r e a n d properties were given to show t h e viability of this m e t h o d of powder processing. PRODUCTION OF PARTICLE R E I N F O R C E D ALUMINIUM F I B R E S BY MELT EXTRACTION
G. Lotze et al ( F r a u n h o f e r Inst for Applied Materials Research, Germany). It was r e p o r t e d t h a t fibres of A1 alloys containing 15% SiC or 10% A1203 particles h a d been p r e p a r e d by melt extraction. The fibres were subsequently consolidated by extrusion. The s t r u c t u r e a n d properties of the composites were determined and c o m p a r e d with composite materials m a d e by o t h e r methods. Increased s t r e n g t h of t h e SiC reinforced composite was reported.
44 MPR November 1993
PARTICLE CRACKING IN PM P R O C E S S E D SiC REINFORCED AI MATRIX COMPOSITES
B. Wang et al (University of Alabama, USA). Cracking of t h e SiC reinforcements in a n A1 alloy m a t r i x composite was described. It was shown that there was a linear relationship between applied s t r a i n a n d t h e p r o p o r t i o n of cracked particles.
Dimensional control and sintaring E F F E C T S OF P R E S l N T E R I N G PARAMETERS ON DOUBLE P R E S S E D AND S I N T E R E D S T E E L S
I. D o n a l d s o n (PresMet Corp, Worcester, USA). The r e q u i r e m e n t for i m p r o v e m e n t in properties of high p e r f o r m a n c e PM steels, b r o u g h t a b o u t by d o u b l e - p r e s s i n g a n d d o u b l e - s i n t e r i n g to a t t a i n high density, was discussed. An i n v e s t i g a t i o n of t h e effects of p r e s i n t e r i n g p a r a m e t e r s o n p r o p e r t y d e v e l o p m e n t was described. It was suggested that by control of presintering conditions mechanical properties could be optimized while m a i n t a i n i n g close d i m e n s i o n a l tolerances. DIMENSIONAL CHANGES IN A SINTER H A R D E N I N G ALLOY STEEL
R.W. Kiefer et al ( P i t n e y B o w e s Inc, Stamford, Connecticut, USA). Dimensional changes in s i n t e r h a r d e n e d alloy steels were discussed as a function of mechanical properties/composition r e l a t i o n s h i p . A s t u d y of d i m e n s i o n a l changes in s i n t e r h a r d e n i n g alloy steels was described. Structure a n d properties were m e a s u r e d in order to e s t a b l i s h t h e relationships between cooling rates, dimensional changes and properties. A p p l i c a t i o n s to p a r t p r o d u c t i o n w e r e outlined. E F F E C T S OF A T M O S P H E R E ON DIMENSIONAL CONTROL IN IRONCOPPER-CARBON COMPACTS
R.W. Kiefer et al ( P i t n e y Bowes Inc, Stamford, Connecticut, USA). A n i n v e s t i g a t i o n of t h e e f f e c t s of a t m o s p h e r e composition on d i m e n s i o n a l changes in a Fe-5% Cu-0.9% C steel was described. N, N - H , a n d N-H-CO a t m o s p h e r e s were studied. The sintered materials were characterized for microstructure, properties and d i m e n s i o n s . It w a s r e p o r t e d t h a t t h e composition of t h e sintering a t m o s p h e r e had significant influence on final dimensions. Atmospheres containing H a n d CO reduced d i m e n s i o n a l growth more t h a t N or N-H mixtures. This was a t t r i b u t e d to diffusion of Cu into Fe, wetting of Fe by Cu, the effectiveness of oxide reduction a n d the amount of carburization/de-
c a r b u r i z a t i o n . The i m p l i c a t i o n s of t h e results were discussed.
Modelling and computational methods IMPROVEMENT OF N E T SHAPE DIMENSIONAL CAPABILITY OF PM P R O C E S S BY USE OF EXPERIMENTAL DESIGN
T. C a m p b e l l a n d T.M. C a d l e ( Z e n i t h Sintered Products Inc, C-ermantown, Wisconsin, USA). A n i n v e s t i g a t i o n to d e t e r m i n e t h e factors with the greatest effects on sintered dimensional precision was described. These i n c l u d e d c o m p o s i t i o n a l accuracy, p r e s s / f e e d system, green density a n d sintering conditions. A t e c h n i q u e was devised to d e t e r m i n e t h e c o n t r i b u t i o n of each factor to d i m e n s i o n a l precision. The s o u r c e s of d i m e n s i o n a l v a r i a t i o n were r a n k e d in order. The investigation was e x t e n d e d to d e t e r m i n e t h e c a u s e s of variation a n d reduce them. E x p e r i m e n t a l techniques, quantified effect of variables and the improvement attained were described. FINITE E L E M E N T MODELLING OF COLD POWDER COMPACTION
T. McCabe et al ( C o n c u r r e n t Technologies Corp, USA). The paper reported the use of a finite e l e m e n t p r o g r a m in t h e s t u d y of p r o b l e m s of cold compaction. An elastic/ plastic model with the Kuhn-Shima yield criterion was used to describe d e f o r m a t i o n d u r i n g die compaction. The simulation results were said to provide d a t a which could be used for improving process design. C O N S I S T E N T MODELLING A N D CONTROL OF COMPACTINGSINTERING P R O C E S S
K.Z. Korczak (KZK Powder Technologies Corp, USA). A m e t h o d for t h e i d e n t i f i c a t i o n of p a r a m e t e r s w h i c h will allow p r e d i c t i o n a n d control of d i m e n s i o n a l changes during pressing a n d sintering was described. The critical steps were control of powders, die design a n d set-up p a r a m e t e r s a n d were said to result in effective i m p l e m e n t a t i o n of process d e v e l o p m e n t a n d direct p r o d u c t i o n control. E F F E C T S OF POWDER CHARACTERISTICS ON SIMULATION OF DENSITY DISTRIBUTION VARIATIONS
S. S h i m a a n d M.A.E. Saleh (Kyoto University, Kyoto, J a p a n ) . A finite e l e m e n t simulation of density d i s t r i b u t i o n in closed die c o m p a c t s was described. It was shown t h a t for accuracy of