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Pore formation in PM iron-based ferritic oxide dispersion strengthened (ODS) superalloys during high temperature heat treatment
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STUDY OF YIELD SURFACE FOR UNI - CELLULAR POROUS BODY STRUCTURE V.T. Golovchan a n d V.I. Kuschch, Poroshkovaya MetaUurgiya, No.2, 1991, 8-12, (In Russian). A hollow ball model h a s been used to analyse, by finite e l e m e n t methods, plastic yield during deformation of particles. The a p p r o a c h h a s allowed consideration of t h e effect of elastic p r o p e r t i e s a n d s t r a i n h a r d e n i n g of t h e base m a t e r i a l on t h e plasticity surface. Significant differences were n o t e d for uniaxial compression a n d s h e a r deformation. GEOMETRICAL A N D FORCE P A R A M E T E R S IN METAL POWDER ROLLING A.V. S t e p a n e n k o et al, Poroshkovaya MetaUurgiya, No. 2, 1991, 13-17, (In Russian). The forces involved in t h e rolling of metal powders have b e e n e s t i m a t e d a n d t h e distribution of density in the rolledmaterials measured. The d e p e n d e n c e of stress fields a n d density on e x t e r n a l friction, roll d i a m e t e r a n d strip thickness were considered.
PRODUCTS: Aluminium E F F E C T S O F P R O C E S S VARIABLES ON T H E MECHANICAL P R O P E R T I E S OF MECHANICALLY ALLOYED ( M A ) ALUMINIUM ALLOY Y. Tada et al, J. Japan Soc. Powder and
Powder Metallurgy, Vol 38, No 2, 1991, 182-188, (In Japanese). 2024 A1 alloy p o w d e r was m i x e d with 2wt% Ni a n d subjected to MA in a vibratory ball mill to evaluate t h e effects of process variables on t h e p r o p e r t i e s of consolidated materials. Ball a n d powder charge were found to have significant effects a n d t h e user of small charges was beneficial to t e n s i l e p r o p e r t i e s . P r o p e r t i e s of l a r g e r charges could be improved by heat t r e a t m e n t . Ball size a n d mill capacity h a d minimal effect on properties. The use of g r a p h i t e as a process control a g e n t resulted in improved properties. HEATING S E Q U E N C E AND HYDROGEN EVOLUTION IN A L U M I N I U M ALLOY POWDERS J.L. E s t r a d a et al, (Delft Univ of Technology, Delft, The N e t h e r l a n d s ) , J. Materials Science, Vol 26, 1991, 1631-1634. The n o n - c o n t i n u o u s evolution of H fi'om A1-20wt%Si-3%Cu-l%Mg alloy powders was studied. The powders were h e a t e d at 2.5°C/ minute, in vacuum, to t e m p e r a t u r e s in t h e range 20 to 550°C. The evolved gases were analysed and water and H were the p r o d u c t s of degassing. Complete degassing could only be a t t a i n e d if a high t e m p e r a t u r e was reached. It was found that
66 MPR September 1991
LITERATURE
REVtEVt
t h e r m o d y n a m i c s alone were i n a d e q u a t e in explaining t h e kinetics of degassing a n d it was suggested t h a t diffusion of A1 t h r o u g h t h e oxide film on t h e powder was a rate d e t e r m i n i n g factor.
c o m p r i s e void c o a g u l a t i o n , c a u s e d by stress induced vacancy migration, and oxide shell growth r o u n d pore walls. The m o d e l is s u p p o r t e d by e x p e r i m e n t a l observations.
Copper
MAGNETOINDUCTIVE T E S T I N G OF PM PARTS
ELECTROLTYTIC P R O D U C T I O N OF NANO - - CRYSTALLINE COPPER POWDERS
M. Seidel a n d R. Natzke, (Technical Univ of Zwickau, Zwickau, Germany), Powder Me-
G.E. Folmanis a n d V ~ Uglov, Poroshkovaya Metallurgiya, No 2, 1991, 5-7, (In Russian). An improved m e t h o d for t h e p r o d u c t i o n of nanocrystalline electrolytic Cu powders is described. The p o w d e r was shown to consist of d e n d r i t e s composed of sub-micron Cu particles. M e a s u r e m e n t of p a r t i c l e size d i s t r i b u t i o n s h o w e d t h a t 70% of t h e p o w d e r s w e r e b e l o w 80 nm. P r o c e s s parameters studied were electrolyte c o m p o s i t i o n , cell v o l t a g e a n d c a t h o d e c u r r e n t density.
E F F E C T S OF A D D I T I O N S O F ALUMINIUM, CHROMIUM AND SILICON ON D E N S I F I C A T I O N CHARACTERISTICS OF S I N T E R E D FINE COPPER POWDER T-W. Lim a n d K. Hayashi, J. Japan Soc. Powder and Powder Metallurgy, Vol 38, No 2, 1991, 114-120, (In J a p a n e s e ) . The effects of a d d i t i o n s of Si, Cr or Cr (4%) on thedensification during sintering of 5 ~ m Cu powder was investigated at green densities of 52 a n d 92%. Sintering was e i t h e r in H or vacuum. It was found t h a t in general the alloy additions had a d e t r i m e n t a l effect on a t t a i n m e n t of full density for green densities of 52%. For green densities of 92% t h e alloy compacts r e a c h e d full density e x c e p t for t h e Cu-Si alloy a n d this was a t t r i b u t e d to gas p r e s s u r e within t h e compacts.
Iron and steel PORE FORMATION IN PM IRON-BASED FERRITIC OXIDE D I S P E R S I O N STRENGTHENED (ODS) SUPERALLOYS D U R I N G HIGH T E M P E R A T U R E HEAT T R E A T M E N T D. Sporer et al, (Metallwerk Plansee, Reutte, Austria), Powder Metall. Int., Vol 23, No 2, 1991, 162-165. Mechanisms of pore formation in Febase ferritic superalloys have been studied. From thermodynamic and other considerations it was deduced t h a t gases, H, 0 a n d N, were n o t responsible for pore formation. A model for pore initiation a n d g r o w t h is p r o p o s e d . T h e m e c h a n i s m s
tall. Int., Vol 23, No3, 1991, 166-168. Non-destructive quality control testing of ferrous PM p a r t s by m a g n e t i c induction techniques is discussed. The e x t e n s i o n of t h e m e t h o d to s t r u c t u r e d e t e r m i n a t i o n h a s been investigated. The m e t h o d h a s been applied to powder forged steel, h a r d m e t a l s a n d bronze parts. RECRYSTALLIZATION O F ELECTROLYTIC IRON POWDERS Petrov et al, Poroshkovaya Metallurgiya, No 2, 1991, 4-5, (In Russian)
A.S.
Diffusion of Cr a n d Cu in Fe-base alloys has been studied by radiochemical m e t h o d s . It was e s t a b l i s h e d t h a t m a s s t r a n s f e r of a t o m s is by v o l u m e a n d b o u n d a r y diffusion. The i n t r o d u c t i o n of volatile a n d fusible c o n s t i t u e n t s intensifies diffusion by enhancing the diffusion coefficients and results in a more homogenous s t r u c t u r e . V a r i a t i o n of diffusion coefficients with t e m p e r a t u r e h a s been d e t e r m i n e d for powder steels alloyed with Cu a n d brass. E F F E C T S OF PULSE LASER RADIATION ON THE P R O P E R T I E S OF ELECTROSPARK HARD METAL COATINGS ON PM STEEL A.V. Paustovsky a n d V.P. Botvinko, Poroshkovaya Metallurgiya, No 2, 1991, 55-57, (In Russian). Hard metal coatings have been applied to PM steel by m e a n s of a l a s e r / e l e c t r o s p a r k t e c h n i q u e . Use of t h e l a s e r r e s u l t s in melting of t h e coating a n d t h e s u b s t r a t e a n d new p h a s e s were d e t e c t e d in t h e c o m p o s i t e c o a t i n g . T h e u s e of l a s e r / e l e c t r o s p a r k m e t h o d s results in closure of pores a n d microcracks a n d increases wear life by a factor of t h r e e to four. TRIBOLOGICAL P R O P E R T I E S OF C E R M E T S BASED ON N I T R I D E / S T E E L MIXTURES A.D. Panasyuk et al, Poroshkovaya Metallurgiya, No 2, 1991, 65-68, (In Russian). The effect of oxide films on t h e friction a n d wear of powder steels with additions of e i t h e r Al nitride or A1 a n d Si nitrides h a s been investigated. Where t h e oxide films were found to be strongly a d h e r e n t to the s u b s t r a t e t h e r e was a reduction in friction a n d a n increase in wear resistance. Weakly a d h e r e n t films did not favour i m p r o v e m e n t in friction a n d wear properties.
STUDY OF YIELD SURFACE FOR UNI - CELLULAR POROUS BODY STRUCTURE V.T. Golovchan a n d V.I. Kuschch, Poroshkovaya MetaUurgiya, No.2, 1991, 8-12, (In Russian). A hollow ball model h a s been used to analyse, by finite e l e m e n t methods, plastic yield during deformation of particles. The a p p r o a c h h a s allowed consideration of t h e effect of elastic p r o p e r t i e s a n d s t r a i n h a r d e n i n g of t h e base m a t e r i a l on t h e plasticity surface. Significant differences were n o t e d for uniaxial compression a n d s h e a r deformation. GEOMETRICAL A N D FORCE P A R A M E T E R S IN METAL POWDER ROLLING A.V. S t e p a n e n k o et al, Poroshkovaya MetaUurgiya, No. 2, 1991, 13-17, (In Russian). The forces involved in t h e rolling of metal powders have b e e n e s t i m a t e d a n d t h e distribution of density in the rolledmaterials measured. The d e p e n d e n c e of stress fields a n d density on e x t e r n a l friction, roll d i a m e t e r a n d strip thickness were considered.
PRODUCTS: Aluminium E F F E C T S O F P R O C E S S VARIABLES ON T H E MECHANICAL P R O P E R T I E S OF MECHANICALLY ALLOYED ( M A ) ALUMINIUM ALLOY Y. Tada et al, J. Japan Soc. Powder and
Powder Metallurgy, Vol 38, No 2, 1991, 182-188, (In Japanese). 2024 A1 alloy p o w d e r was m i x e d with 2wt% Ni a n d subjected to MA in a vibratory ball mill to evaluate t h e effects of process variables on t h e p r o p e r t i e s of consolidated materials. Ball a n d powder charge were found to have significant effects a n d t h e user of small charges was beneficial to t e n s i l e p r o p e r t i e s . P r o p e r t i e s of l a r g e r charges could be improved by heat t r e a t m e n t . Ball size a n d mill capacity h a d minimal effect on properties. The use of g r a p h i t e as a process control a g e n t resulted in improved properties. HEATING S E Q U E N C E AND HYDROGEN EVOLUTION IN A L U M I N I U M ALLOY POWDERS J.L. E s t r a d a et al, (Delft Univ of Technology, Delft, The N e t h e r l a n d s ) , J. Materials Science, Vol 26, 1991, 1631-1634. The n o n - c o n t i n u o u s evolution of H fi'om A1-20wt%Si-3%Cu-l%Mg alloy powders was studied. The powders were h e a t e d at 2.5°C/ minute, in vacuum, to t e m p e r a t u r e s in t h e range 20 to 550°C. The evolved gases were analysed and water and H were the p r o d u c t s of degassing. Complete degassing could only be a t t a i n e d if a high t e m p e r a t u r e was reached. It was found that
66 MPR September 1991
LITERATURE
REVtEVt
t h e r m o d y n a m i c s alone were i n a d e q u a t e in explaining t h e kinetics of degassing a n d it was suggested t h a t diffusion of A1 t h r o u g h t h e oxide film on t h e powder was a rate d e t e r m i n i n g factor.
c o m p r i s e void c o a g u l a t i o n , c a u s e d by stress induced vacancy migration, and oxide shell growth r o u n d pore walls. The m o d e l is s u p p o r t e d by e x p e r i m e n t a l observations.
Copper
MAGNETOINDUCTIVE T E S T I N G OF PM PARTS
ELECTROLTYTIC P R O D U C T I O N OF NANO - - CRYSTALLINE COPPER POWDERS
M. Seidel a n d R. Natzke, (Technical Univ of Zwickau, Zwickau, Germany), Powder Me-
G.E. Folmanis a n d V ~ Uglov, Poroshkovaya Metallurgiya, No 2, 1991, 5-7, (In Russian). An improved m e t h o d for t h e p r o d u c t i o n of nanocrystalline electrolytic Cu powders is described. The p o w d e r was shown to consist of d e n d r i t e s composed of sub-micron Cu particles. M e a s u r e m e n t of p a r t i c l e size d i s t r i b u t i o n s h o w e d t h a t 70% of t h e p o w d e r s w e r e b e l o w 80 nm. P r o c e s s parameters studied were electrolyte c o m p o s i t i o n , cell v o l t a g e a n d c a t h o d e c u r r e n t density.
E F F E C T S OF A D D I T I O N S O F ALUMINIUM, CHROMIUM AND SILICON ON D E N S I F I C A T I O N CHARACTERISTICS OF S I N T E R E D FINE COPPER POWDER T-W. Lim a n d K. Hayashi, J. Japan Soc. Powder and Powder Metallurgy, Vol 38, No 2, 1991, 114-120, (In J a p a n e s e ) . The effects of a d d i t i o n s of Si, Cr or Cr (4%) on thedensification during sintering of 5 ~ m Cu powder was investigated at green densities of 52 a n d 92%. Sintering was e i t h e r in H or vacuum. It was found t h a t in general the alloy additions had a d e t r i m e n t a l effect on a t t a i n m e n t of full density for green densities of 52%. For green densities of 92% t h e alloy compacts r e a c h e d full density e x c e p t for t h e Cu-Si alloy a n d this was a t t r i b u t e d to gas p r e s s u r e within t h e compacts.
Iron and steel PORE FORMATION IN PM IRON-BASED FERRITIC OXIDE D I S P E R S I O N STRENGTHENED (ODS) SUPERALLOYS D U R I N G HIGH T E M P E R A T U R E HEAT T R E A T M E N T D. Sporer et al, (Metallwerk Plansee, Reutte, Austria), Powder Metall. Int., Vol 23, No 2, 1991, 162-165. Mechanisms of pore formation in Febase ferritic superalloys have been studied. From thermodynamic and other considerations it was deduced t h a t gases, H, 0 a n d N, were n o t responsible for pore formation. A model for pore initiation a n d g r o w t h is p r o p o s e d . T h e m e c h a n i s m s
tall. Int., Vol 23, No3, 1991, 166-168. Non-destructive quality control testing of ferrous PM p a r t s by m a g n e t i c induction techniques is discussed. The e x t e n s i o n of t h e m e t h o d to s t r u c t u r e d e t e r m i n a t i o n h a s been investigated. The m e t h o d h a s been applied to powder forged steel, h a r d m e t a l s a n d bronze parts. RECRYSTALLIZATION O F ELECTROLYTIC IRON POWDERS Petrov et al, Poroshkovaya Metallurgiya, No 2, 1991, 4-5, (In Russian)
A.S.
Diffusion of Cr a n d Cu in Fe-base alloys has been studied by radiochemical m e t h o d s . It was e s t a b l i s h e d t h a t m a s s t r a n s f e r of a t o m s is by v o l u m e a n d b o u n d a r y diffusion. The i n t r o d u c t i o n of volatile a n d fusible c o n s t i t u e n t s intensifies diffusion by enhancing the diffusion coefficients and results in a more homogenous s t r u c t u r e . V a r i a t i o n of diffusion coefficients with t e m p e r a t u r e h a s been d e t e r m i n e d for powder steels alloyed with Cu a n d brass. E F F E C T S OF PULSE LASER RADIATION ON THE P R O P E R T I E S OF ELECTROSPARK HARD METAL COATINGS ON PM STEEL A.V. Paustovsky a n d V.P. Botvinko, Poroshkovaya Metallurgiya, No 2, 1991, 55-57, (In Russian). Hard metal coatings have been applied to PM steel by m e a n s of a l a s e r / e l e c t r o s p a r k t e c h n i q u e . Use of t h e l a s e r r e s u l t s in melting of t h e coating a n d t h e s u b s t r a t e a n d new p h a s e s were d e t e c t e d in t h e c o m p o s i t e c o a t i n g . T h e u s e of l a s e r / e l e c t r o s p a r k m e t h o d s results in closure of pores a n d microcracks a n d increases wear life by a factor of t h r e e to four. TRIBOLOGICAL P R O P E R T I E S OF C E R M E T S BASED ON N I T R I D E / S T E E L MIXTURES A.D. Panasyuk et al, Poroshkovaya Metallurgiya, No 2, 1991, 65-68, (In Russian). The effect of oxide films on t h e friction a n d wear of powder steels with additions of e i t h e r Al nitride or A1 a n d Si nitrides h a s been investigated. Where t h e oxide films were found to be strongly a d h e r e n t to the s u b s t r a t e t h e r e was a reduction in friction a n d a n increase in wear resistance. Weakly a d h e r e n t films did not favour i m p r o v e m e n t in friction a n d wear properties.