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Mechanical properties of sintered metals
between particles was assessed and the relevance for metal powder compaction discussed. The need for additional work is emphasized.
S E G R E G A T I O N OF BINARY C O M P R E S S I B L E POWDER M I X T U R E S S U B J E C T E D TO TAPPING
L.M. Popplewell and M. Peleg, (Univ of Masschusetts, A m h e r s t , Massachusetts, USA), Powder Technology, Vol 67, No 1, 1991, 21-26. Segregation patterns in p o w d e r mixtures subjected to tapping have been m o d e l l e d w i t h r e g a r d to p r e f e r e n t i a l settling of finer fractions, bed compaction and density of the powders. The calculation showed that a segregation index must take into account the concentration profile in order to distinguish between segregation of fines due to migration or as a result of volume reduction. Only extreme variations in powder density were found to contribute to the segregation.
IMPORTANCE OF R E S O L U T I O N LIMITS TO THE I N T E R P R E T A T I O N OF FRACTAL D E S C R I P T I O N S OF FINE PARTICLES
J.C. Graf, (NASA, Houston, Texas, USA), Powder Technology, Vol 67, No 1, 1991, 83-85. The utility of fractal descriptions of irregular particles such as sponge iron is discussed with respect to the limitation of the technique in particular the resolution limits of the instrumentation such as SEM. The need for an awareness of scale in order to show important textural elements is emphasized.
D I S T R I B U T I O N OF CONTACT F O R C E S IN LOADED POWDER BY M E A N S OF TWO-DIMENSIONAL M O D E L L I N G
is a continuous matrix and the other is u n i f o r m l y d i s t r i b u t e d i n c l u s i o n s . The porosity is a l s o a s s u m e d to be homogeneous. The deformation of matrix and inclusions are discussed in terms plastic flow theory. The theoretical results are c o m p a r e d with e x p e r i m e n t a l d a t a obtained from metal powder compaction.
STABILITY O F LIQUID METALLIC INTERLAYERS IN S I N T E R I N G HETEROPHASE COMPOSITIONS
H.F. Lisovsky, Poroshkovaya Metallurgiya, No 3, 1991, 20-22. (In Russian). A mathematical model is described for sintering a system consisting of two solid phases and a liquid phase. Liquid m i g r a t i o n , cavity size surface t e n s i o n effects and stability of liquid interlayers are considered. A critical cavity size, below w h i c h l i q u i d d o e s n o t p e n e t r a t e , is introduced.
MECHANICAL P R O P E R T I E S OF S I N T E R E D MATERIALS -- E F F E C T OF POROSITY IN PLASTICITY
e t al, P o r o s h k o v a y a MetaUurgiya, No 3, 1991, 93-100. (In
Y.V. M i l l m a n
Russian). The relationships between porosity and plasticity, under tensile loading, of sintered metals are critically reviewed. Expressions are given linking the reduction in plasticity and strength with the increase in porosity. Stress concentration at pores is discussed. It is shown that the working section is less than that determined solely from geometrical factors. Attention is drawn to the differences between face and body centered metals and alloys.
MECHANICAL P R O P E R T I E S OF S I N T E R E D METALS
Kovalchenko, Poroshkovaya Metallurgiya, No 3, 1991, 101-106. (In M.S.
Muzykantov, Poroshkovaya Metallurgiya, No 3, 1991, 11-15. (In Russian). A two-dimensional mathematical model of powder based on disks is described and used for analysis of elastic behaviour. P a r a m e t e r s r e l a t i n g e l a s t i c forces at contact points are d e t e r m i n e d and an estimate is made of strength concentrations in the loaded particles. A.V.
E Q U A T I O N S FOR PLASTIC D E F O R M A T I O N IN POROUS MATERIAL WITH RIGID INCLUSIONS
A.Y. Smyslov, Poroshkovaya MetaUurgiya, No 3, 1991, 15-19. (In Russian). The p l a s t i c d e f o r m a t i o n of p o r o u s material containing two rigid-plastic solid phases is discussed. One of the solid phases
Russian). The p a p e r d e v e l o p s t h e t h e o r y of mechanical properties of sintered material based on modern theory plasticity of porous solids with regard to rheological properties and relative density. The rheological model with parallel plastic and viscous elements is discussed. Problems arising from deformation hardening are also discussed. M O D E L S OF METAL POWDER ATOMIZATION
A.J. Aller and A~ Losada, (Univ of Leon, Spain). Powder Metallurgy Science and Technology, Vol 2, No 2, 1991, 13-37. The paper reviews and discusses models of the processes used for atomization of metal powders with consideration given to particle characterisitics.
MATHEMATICAL M O D E L OF FILM D I S I N T E G R A T I O N IN T H E ROTATINGELECTRODE PROCESS OF POWDER P R O D U C T I O N
I~ Chandramouli and A_V.R. Rao. (Regional E n g i n e e r i n g College, Warangal, I n d i a ) .
Powder Metallurgy Science and Technology, Vol 2, No 3, 1991, 21-24. The mechanisms of droplet formation in REO, d i r e c t drop formation, l i g a m e n t d i s i n t e g r a t i o n a n d film d i s i n t e g r a t i o n (FD) are discussed. A model of FD has been developed in order to be able to predict mean particle sizes.
PRODUCTS" Berylium ~.\:\L-_:............. . . . . . . . . . . . . . . . . . N E W P R O C E S S FOR IMPACT A T T R I T I O N OF BERYLIUM POWDER
S. Benshuang. (Ningxia Nonferrous Metals Research Inst, China), PM Technology, Vol 9, No 2, 1991, 112-115. (In Chinese). An impact attition mill is illustrated and its use for the processing of Be powder is described. The process is reported to yield Be p o w d e r of good quality w i t h high productivity and to minimize toxic hazards.
Cobalt INTERACTIONS B E T W E E N COBALT AND SILICON
L.S. Likhoded and L~A~ Dvorina, Poroshkovaya Metallurgiya, No 3, 1991, 74-77. (In Russian). Interactions between Co and Si powders, on heating in vacuum, were studied. Mutual diffusion is the principal mechanism. The formation of, firstly, a solid solution and then compounds were described. Temperature dependence of the interactions was established.
Copper TRIBOLOGICAL P R O P E R T I E S OF COPPER A G A I N S T CERAMIC MATERIALS
N.G. Baranov et al, PM Technology, Vol 9, No 1, 1991. (In Chinese). Poroshkovaya Metallurgiya, No 3, 1991, 6 8 - 7 3 . (In Russian). The w e a r behaviour of sintered Cu against ceramic materials was investigated. X-ray line broadening was u s e d to d e t e c t c h a n g e s in t h e w o r n surfaces of the Cu and ceramic. The dynamic equilibrium between formation and d e s t r u c t i o n of surface films was s h o w n to be t h e d o m i n a n t factor
MPR November 1991 53
S E G R E G A T I O N OF BINARY C O M P R E S S I B L E POWDER M I X T U R E S S U B J E C T E D TO TAPPING
L.M. Popplewell and M. Peleg, (Univ of Masschusetts, A m h e r s t , Massachusetts, USA), Powder Technology, Vol 67, No 1, 1991, 21-26. Segregation patterns in p o w d e r mixtures subjected to tapping have been m o d e l l e d w i t h r e g a r d to p r e f e r e n t i a l settling of finer fractions, bed compaction and density of the powders. The calculation showed that a segregation index must take into account the concentration profile in order to distinguish between segregation of fines due to migration or as a result of volume reduction. Only extreme variations in powder density were found to contribute to the segregation.
IMPORTANCE OF R E S O L U T I O N LIMITS TO THE I N T E R P R E T A T I O N OF FRACTAL D E S C R I P T I O N S OF FINE PARTICLES
J.C. Graf, (NASA, Houston, Texas, USA), Powder Technology, Vol 67, No 1, 1991, 83-85. The utility of fractal descriptions of irregular particles such as sponge iron is discussed with respect to the limitation of the technique in particular the resolution limits of the instrumentation such as SEM. The need for an awareness of scale in order to show important textural elements is emphasized.
D I S T R I B U T I O N OF CONTACT F O R C E S IN LOADED POWDER BY M E A N S OF TWO-DIMENSIONAL M O D E L L I N G
is a continuous matrix and the other is u n i f o r m l y d i s t r i b u t e d i n c l u s i o n s . The porosity is a l s o a s s u m e d to be homogeneous. The deformation of matrix and inclusions are discussed in terms plastic flow theory. The theoretical results are c o m p a r e d with e x p e r i m e n t a l d a t a obtained from metal powder compaction.
STABILITY O F LIQUID METALLIC INTERLAYERS IN S I N T E R I N G HETEROPHASE COMPOSITIONS
H.F. Lisovsky, Poroshkovaya Metallurgiya, No 3, 1991, 20-22. (In Russian). A mathematical model is described for sintering a system consisting of two solid phases and a liquid phase. Liquid m i g r a t i o n , cavity size surface t e n s i o n effects and stability of liquid interlayers are considered. A critical cavity size, below w h i c h l i q u i d d o e s n o t p e n e t r a t e , is introduced.
MECHANICAL P R O P E R T I E S OF S I N T E R E D MATERIALS -- E F F E C T OF POROSITY IN PLASTICITY
e t al, P o r o s h k o v a y a MetaUurgiya, No 3, 1991, 93-100. (In
Y.V. M i l l m a n
Russian). The relationships between porosity and plasticity, under tensile loading, of sintered metals are critically reviewed. Expressions are given linking the reduction in plasticity and strength with the increase in porosity. Stress concentration at pores is discussed. It is shown that the working section is less than that determined solely from geometrical factors. Attention is drawn to the differences between face and body centered metals and alloys.
MECHANICAL P R O P E R T I E S OF S I N T E R E D METALS
Kovalchenko, Poroshkovaya Metallurgiya, No 3, 1991, 101-106. (In M.S.
Muzykantov, Poroshkovaya Metallurgiya, No 3, 1991, 11-15. (In Russian). A two-dimensional mathematical model of powder based on disks is described and used for analysis of elastic behaviour. P a r a m e t e r s r e l a t i n g e l a s t i c forces at contact points are d e t e r m i n e d and an estimate is made of strength concentrations in the loaded particles. A.V.
E Q U A T I O N S FOR PLASTIC D E F O R M A T I O N IN POROUS MATERIAL WITH RIGID INCLUSIONS
A.Y. Smyslov, Poroshkovaya MetaUurgiya, No 3, 1991, 15-19. (In Russian). The p l a s t i c d e f o r m a t i o n of p o r o u s material containing two rigid-plastic solid phases is discussed. One of the solid phases
Russian). The p a p e r d e v e l o p s t h e t h e o r y of mechanical properties of sintered material based on modern theory plasticity of porous solids with regard to rheological properties and relative density. The rheological model with parallel plastic and viscous elements is discussed. Problems arising from deformation hardening are also discussed. M O D E L S OF METAL POWDER ATOMIZATION
A.J. Aller and A~ Losada, (Univ of Leon, Spain). Powder Metallurgy Science and Technology, Vol 2, No 2, 1991, 13-37. The paper reviews and discusses models of the processes used for atomization of metal powders with consideration given to particle characterisitics.
MATHEMATICAL M O D E L OF FILM D I S I N T E G R A T I O N IN T H E ROTATINGELECTRODE PROCESS OF POWDER P R O D U C T I O N
I~ Chandramouli and A_V.R. Rao. (Regional E n g i n e e r i n g College, Warangal, I n d i a ) .
Powder Metallurgy Science and Technology, Vol 2, No 3, 1991, 21-24. The mechanisms of droplet formation in REO, d i r e c t drop formation, l i g a m e n t d i s i n t e g r a t i o n a n d film d i s i n t e g r a t i o n (FD) are discussed. A model of FD has been developed in order to be able to predict mean particle sizes.
PRODUCTS" Berylium ~.\:\L-_:............. . . . . . . . . . . . . . . . . . N E W P R O C E S S FOR IMPACT A T T R I T I O N OF BERYLIUM POWDER
S. Benshuang. (Ningxia Nonferrous Metals Research Inst, China), PM Technology, Vol 9, No 2, 1991, 112-115. (In Chinese). An impact attition mill is illustrated and its use for the processing of Be powder is described. The process is reported to yield Be p o w d e r of good quality w i t h high productivity and to minimize toxic hazards.
Cobalt INTERACTIONS B E T W E E N COBALT AND SILICON
L.S. Likhoded and L~A~ Dvorina, Poroshkovaya Metallurgiya, No 3, 1991, 74-77. (In Russian). Interactions between Co and Si powders, on heating in vacuum, were studied. Mutual diffusion is the principal mechanism. The formation of, firstly, a solid solution and then compounds were described. Temperature dependence of the interactions was established.
Copper TRIBOLOGICAL P R O P E R T I E S OF COPPER A G A I N S T CERAMIC MATERIALS
N.G. Baranov et al, PM Technology, Vol 9, No 1, 1991. (In Chinese). Poroshkovaya Metallurgiya, No 3, 1991, 6 8 - 7 3 . (In Russian). The w e a r behaviour of sintered Cu against ceramic materials was investigated. X-ray line broadening was u s e d to d e t e c t c h a n g e s in t h e w o r n surfaces of the Cu and ceramic. The dynamic equilibrium between formation and d e s t r u c t i o n of surface films was s h o w n to be t h e d o m i n a n t factor
MPR November 1991 53