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Formation of metastable phases in aluminium-zirconium base alloys
for t h e Heckel p l o t d e p e n d i n g of t h e position at which measurements are made. Brittle m a t e r i a l s are shown n o t to differ w h e n t h e m e t h o d of m e a s u r e m e n t is changed. S P E C I M E N PREPARATION FOR T E M EXAMINATION OF RS POWDERS N~l.E.Adkins et al, (Univ of Surrey, Guildford, UK). Int, J, Rapid Solidification, Vol 6, 1991, 77-86. Preparation o f p o w d e r s f o r TEM examination is discussed. Three techniques, microtomy, Ni-plating powder sedimentation and Cu-plating powder adhesion are described. These allow preparation of electron transparent specimens, of non-ferrous materials, w i t h negligible effect on t h e RS structure. Typical results are p r e s e n t e d a n d t h e a d v a n t a g e s a n d d r a w b a c k s to t h e t e c h n i q u e s are discussed. C O N T I N U U M THEORY FOR MECHANICAL R E S P O N S E OF MATERIALS TO THERMODYNAMIC S T R E S S ON S I N T E R I N G C.R.Reid a n d R.G. Oakberg, (Univ of Wyoming, Wyoming, USA). Mechanics of Materials, Vol 19, No 3, 1990, 203-213, Continuum mechanics have been applied to t h e s t u d y of stresses w h i c h provide t h e driving force for sintering of metals and alloys. An expression quantifying sintering stresses is developed a n d is a s s u m e d to be d e p e n d e n t on specific surface and curvature at void/solid interfaces. The model developed is applied to t h e s t u d y of t h e sintering of Cu powders.
PRODUCTS: Aluminium E X T R U S I O N A N D P R O P E R T I E S OF 7075 A L U M I N I U M ALLOY INGOT AND PARTICULATE MATERIAL M.H.Carvahlo et al. (LNETI, Lisbon, Portugal). PowderMetaUurgy, Vol 33, No 4, 1990, 339-348. 7075 A1 alloy p r e p a r e d from ingot a n d p o w d e r were c a n n e d in 6061 A1 a n d t h e n extruded. The flow stress of t h e p o w d e r m a t e r i a l was found to be 87% of t h a t for t h e ingot alloy. The s t a r t i n g m a t e r i a l a n d t h e e x t r u s i o n variables were f o u n d to have little effect on t h e room t e m p e r a t u r e properties of t h e e x t r u d e d alloys. Porosity developed during e x t r u s i o n of t h e p o w d e r materials a n d t h i s was a t t r i b u t e d to i n a d e q u a t e degassing of t h e initial powders. P R E H E A T I N G O F ALUMINIUM ALLOY COMPACTS B E F O R E E X T R U S I O N T.H.Lee a n d S.S.Cho, ( C h u n g n a m National Univ, Taejon, Korea), J, Korean Inst, of Metals, Vol 28, No 3, 1991, 263-269, (In Korean). The effect of p r e h e a t i n g conditions o n
48 MPR December 1991
t h e e x t r u s i o n of A1-8%Zn-2.5%Mg-1.5%Col%Ni rapidly solidified powder c o m p a c t s was investigated. Structural studies showed t h a t t h e cellular d e n d r i t e s in t h e p o w d e r are d e c o m p o s e d above 490°C. C o m p a c t s p r e h e a t e d to 490°C a n d e x t r u d e d were found to have a pore density less t h a n 0.1% a n d a m a x i m u m pore size of less t h a n 1 ~m, Grain size is less t h a n 1 p m a n d oxide inclusions were found a t grain b o u n d a r i e s a n d w i t h i n t h e grain. Mechanical properties were measured. C R E E P FAILURE O F CARBIDE D I S P E R S I O N A L U M I N I U M ALLOYS M.Besterci et al, (Ostav Metallurgical SAV, Kosice Czechoslovakia). Pokroky Praskove Metalurgie, No 4, 1990, 44-61, (In Czech). Deformation a n d fracture m e c h a n i s m s in A1-5 vol% AI4C3, a n d creep b e h a v i o u r a t 3 5 0 ° C a n d 450°C, w e r e i n v e s t i g a t e d , Polygonization of t h e m a t r i x was shown to be the dominant mechanism of deformation. STRUCTURE A N D MECHANICAL P R O P E R T I E S OF MICROCRYSTALLINE ALUMINIUM-IRON POWDER ALLOYS T.I.Lebedeva et al, Poroshkovaya Metallurgiya, No 4, 1991, 93-98, (In Russian). Structure and properties, including creep, for A1-8wt%Fe alloys p r o d u c e d by PM from r a p i d l y - s o l i d i f i e d strip, were investigated. The alloys were found to be structurally stable a t t e m p e r a t u r e s up to 350°C a n d to r e t a i n s t r e n g t h a t elevated t e m p e r a t u r e s . The alloy was found to have high s t r e n g t h a n d d u c t i l i t y a t 25°C. MICROSTRUCTURE OF RAPIDLY S O L I D I F I E D ALUMINIUM ALLOY POWDER A~Liu et al, (General I n s t for t h e NonFerrous Metals, China). J, Materials Svience, Letters, Vol 10, No 1, 1991, 42-44. The s t r u c t u r e a n d p r o p e r t i e s of a n A18 . 5 w t % P b - 5 . 0 % S i - 1.5%Cu- 1.0%Sn a l l o y powder, i n t e n d e d for t h e p r o d u c t i o n of bearings, were investigated. The f o r m a t i o n of m a t r i x a n d precipitates d u r i n g r a p i d s o l i d i f i c a t i o n w a s s t u d i e d a n d it w a s d e d u c e d t h a t Si a n d S n c r y s t a l l i z e t o g e t h e r with residual Pb a n d t h a t Cu c o m p o u n d s p r e c i p i t a t e uniformly d u r i n g solidification. The a d d e d alloy e l e m e n t s were dispersed w i t h i n t h e p o w d e r particles. S I N T E R I N G OF P O W D E R E D METAL BY F O C U S E D HIGH INTENSITY ION BEAM Y.Matsukawa a n d I~Vegami, (Osaka City Univ, J a p a n ) . Japan J. Applied Physics
Letters, Vol 28, No 5, 1989, L8880L890. A small a m o u n t of A1 a n d Sn powders were s i n t e r e d by i r r a d i a t i o n with a high energy focused ion b e a m with a n energy density of 1.1xl0 l° W / c m 2" The m e t a l did not melt b u t t h e powder grains merged into a t h i n alloy layer 0.8 p m t h i c k on t h e grain
surface which boundaries.
also
penetrated
grain
SOLIDIFICATION OF H I G H P R E S S U R E GAS ATOMIZED ALUMINIUMCHROMIUM ALLOY POWDERS N~l.E_~dkins a n d P.Tsakiropoulos, (Univ of Surrey, Guildford, UK). Int, J, Rapid Solidification, Vol 6, 10991, 87-100. A s t u d y of All3Cr 2 i n t e r m e t a l l i c in rapidly solidified A1-Cr alloys, w i t h u p to 5wt%Cr, is d e s c r i b e d . T h e f r a c t i o n of powder particles free from the intermetallic was d e t e r m i n e d as a function of particle size a n d alloy composition. The d a t a w a s f o u n d to b e c o n s i s t e n t w i t h h e t e r o g e n e o u s nucleation. The d e p e n d e n c e of n u c l e a t i o n t e m p e r a t u r e o n n u c l e a n t p o t e n c y was d e d u c e d as a f u n c t i o n of c o n t a c t angle, 8. Values of 0 for a c h a n g e from heterogeneous to homogeneous nucleation have b e e n calculated for e a c h alloy composition. F O R M A T I O N OF METASTABLE P H A S E S IN ALUMIN1UM-ZIRCONIUM BASE ALLOYS P.B.Desch et ah (Los Alamos N a t i o n a l Lab, USA). J.Less Common Metals, Vol 168, no 1, 1991, 69-80. The s t r u c t u r e s of A1-25at%Zr a n d AI25%Zr-12. 5%X ( X = L i , Fe, Ni, Cr or Cu) powder were investigated after rapid solidification a n d m e c h a n i c a l alloying. The s t r u c t u r e a n d s t a b i l i t y of t h e A l a Z r intermetallic are influenced by t h e t e r n a r y additions. Li or C increase t h e stability b u t Fe or Ni lead to a m o r p h i z a t i o n , The alloy A1-25%Zr-12.5%Cu consists of t h e single p h a s e intermetallic a n d is stable to 1300°C.
Copper M I C R O S T R U C T U R E A N D MECHANICAL P R O P E R T I E S OF OSPREY NICKEL-BRONZE R.H.Cookey a n d J.V.Wood, (Univ of Nottingham, Nottingham, UK) Powder Metallurgy, Vol 33, No 4, 1990, 335-338. The use of r a p i d solidification by t h e Osprey process was s h o w n to improve t h e m e c h a n i c a l p r o p e r t i e s of Cu-15%Ni-8%Sn by confering on t h e alloy a more refined a n d h o m o g e n e o u s m i c r o s t r u c t u r e after t h e r m o m e c h a n i c a l processing a n d aging a t 400°C. It was suggested t h a t t h e presence of N in t h e alloy h a s a d e t r i m e n t a l effect on t h e p e r f o r m a n c e of t h e alloy.
Iron and steel nnrnnrrnl
FORMATION OF N I T R I D E P H A S E S IN N I T R I D I N G O F POROUS IRON V.G.Gorbach et al, Poroshkovaya Metallurgiya, No 4, 1991, 24-28. (In Russian).
PRODUCTS: Aluminium E X T R U S I O N A N D P R O P E R T I E S OF 7075 A L U M I N I U M ALLOY INGOT AND PARTICULATE MATERIAL M.H.Carvahlo et al. (LNETI, Lisbon, Portugal). PowderMetaUurgy, Vol 33, No 4, 1990, 339-348. 7075 A1 alloy p r e p a r e d from ingot a n d p o w d e r were c a n n e d in 6061 A1 a n d t h e n extruded. The flow stress of t h e p o w d e r m a t e r i a l was found to be 87% of t h a t for t h e ingot alloy. The s t a r t i n g m a t e r i a l a n d t h e e x t r u s i o n variables were f o u n d to have little effect on t h e room t e m p e r a t u r e properties of t h e e x t r u d e d alloys. Porosity developed during e x t r u s i o n of t h e p o w d e r materials a n d t h i s was a t t r i b u t e d to i n a d e q u a t e degassing of t h e initial powders. P R E H E A T I N G O F ALUMINIUM ALLOY COMPACTS B E F O R E E X T R U S I O N T.H.Lee a n d S.S.Cho, ( C h u n g n a m National Univ, Taejon, Korea), J, Korean Inst, of Metals, Vol 28, No 3, 1991, 263-269, (In Korean). The effect of p r e h e a t i n g conditions o n
48 MPR December 1991
t h e e x t r u s i o n of A1-8%Zn-2.5%Mg-1.5%Col%Ni rapidly solidified powder c o m p a c t s was investigated. Structural studies showed t h a t t h e cellular d e n d r i t e s in t h e p o w d e r are d e c o m p o s e d above 490°C. C o m p a c t s p r e h e a t e d to 490°C a n d e x t r u d e d were found to have a pore density less t h a n 0.1% a n d a m a x i m u m pore size of less t h a n 1 ~m, Grain size is less t h a n 1 p m a n d oxide inclusions were found a t grain b o u n d a r i e s a n d w i t h i n t h e grain. Mechanical properties were measured. C R E E P FAILURE O F CARBIDE D I S P E R S I O N A L U M I N I U M ALLOYS M.Besterci et al, (Ostav Metallurgical SAV, Kosice Czechoslovakia). Pokroky Praskove Metalurgie, No 4, 1990, 44-61, (In Czech). Deformation a n d fracture m e c h a n i s m s in A1-5 vol% AI4C3, a n d creep b e h a v i o u r a t 3 5 0 ° C a n d 450°C, w e r e i n v e s t i g a t e d , Polygonization of t h e m a t r i x was shown to be the dominant mechanism of deformation. STRUCTURE A N D MECHANICAL P R O P E R T I E S OF MICROCRYSTALLINE ALUMINIUM-IRON POWDER ALLOYS T.I.Lebedeva et al, Poroshkovaya Metallurgiya, No 4, 1991, 93-98, (In Russian). Structure and properties, including creep, for A1-8wt%Fe alloys p r o d u c e d by PM from r a p i d l y - s o l i d i f i e d strip, were investigated. The alloys were found to be structurally stable a t t e m p e r a t u r e s up to 350°C a n d to r e t a i n s t r e n g t h a t elevated t e m p e r a t u r e s . The alloy was found to have high s t r e n g t h a n d d u c t i l i t y a t 25°C. MICROSTRUCTURE OF RAPIDLY S O L I D I F I E D ALUMINIUM ALLOY POWDER A~Liu et al, (General I n s t for t h e NonFerrous Metals, China). J, Materials Svience, Letters, Vol 10, No 1, 1991, 42-44. The s t r u c t u r e a n d p r o p e r t i e s of a n A18 . 5 w t % P b - 5 . 0 % S i - 1.5%Cu- 1.0%Sn a l l o y powder, i n t e n d e d for t h e p r o d u c t i o n of bearings, were investigated. The f o r m a t i o n of m a t r i x a n d precipitates d u r i n g r a p i d s o l i d i f i c a t i o n w a s s t u d i e d a n d it w a s d e d u c e d t h a t Si a n d S n c r y s t a l l i z e t o g e t h e r with residual Pb a n d t h a t Cu c o m p o u n d s p r e c i p i t a t e uniformly d u r i n g solidification. The a d d e d alloy e l e m e n t s were dispersed w i t h i n t h e p o w d e r particles. S I N T E R I N G OF P O W D E R E D METAL BY F O C U S E D HIGH INTENSITY ION BEAM Y.Matsukawa a n d I~Vegami, (Osaka City Univ, J a p a n ) . Japan J. Applied Physics
Letters, Vol 28, No 5, 1989, L8880L890. A small a m o u n t of A1 a n d Sn powders were s i n t e r e d by i r r a d i a t i o n with a high energy focused ion b e a m with a n energy density of 1.1xl0 l° W / c m 2" The m e t a l did not melt b u t t h e powder grains merged into a t h i n alloy layer 0.8 p m t h i c k on t h e grain
surface which boundaries.
also
penetrated
grain
SOLIDIFICATION OF H I G H P R E S S U R E GAS ATOMIZED ALUMINIUMCHROMIUM ALLOY POWDERS N~l.E_~dkins a n d P.Tsakiropoulos, (Univ of Surrey, Guildford, UK). Int, J, Rapid Solidification, Vol 6, 10991, 87-100. A s t u d y of All3Cr 2 i n t e r m e t a l l i c in rapidly solidified A1-Cr alloys, w i t h u p to 5wt%Cr, is d e s c r i b e d . T h e f r a c t i o n of powder particles free from the intermetallic was d e t e r m i n e d as a function of particle size a n d alloy composition. The d a t a w a s f o u n d to b e c o n s i s t e n t w i t h h e t e r o g e n e o u s nucleation. The d e p e n d e n c e of n u c l e a t i o n t e m p e r a t u r e o n n u c l e a n t p o t e n c y was d e d u c e d as a f u n c t i o n of c o n t a c t angle, 8. Values of 0 for a c h a n g e from heterogeneous to homogeneous nucleation have b e e n calculated for e a c h alloy composition. F O R M A T I O N OF METASTABLE P H A S E S IN ALUMIN1UM-ZIRCONIUM BASE ALLOYS P.B.Desch et ah (Los Alamos N a t i o n a l Lab, USA). J.Less Common Metals, Vol 168, no 1, 1991, 69-80. The s t r u c t u r e s of A1-25at%Zr a n d AI25%Zr-12. 5%X ( X = L i , Fe, Ni, Cr or Cu) powder were investigated after rapid solidification a n d m e c h a n i c a l alloying. The s t r u c t u r e a n d s t a b i l i t y of t h e A l a Z r intermetallic are influenced by t h e t e r n a r y additions. Li or C increase t h e stability b u t Fe or Ni lead to a m o r p h i z a t i o n , The alloy A1-25%Zr-12.5%Cu consists of t h e single p h a s e intermetallic a n d is stable to 1300°C.
Copper M I C R O S T R U C T U R E A N D MECHANICAL P R O P E R T I E S OF OSPREY NICKEL-BRONZE R.H.Cookey a n d J.V.Wood, (Univ of Nottingham, Nottingham, UK) Powder Metallurgy, Vol 33, No 4, 1990, 335-338. The use of r a p i d solidification by t h e Osprey process was s h o w n to improve t h e m e c h a n i c a l p r o p e r t i e s of Cu-15%Ni-8%Sn by confering on t h e alloy a more refined a n d h o m o g e n e o u s m i c r o s t r u c t u r e after t h e r m o m e c h a n i c a l processing a n d aging a t 400°C. It was suggested t h a t t h e presence of N in t h e alloy h a s a d e t r i m e n t a l effect on t h e p e r f o r m a n c e of t h e alloy.
Iron and steel nnrnnrrnl
FORMATION OF N I T R I D E P H A S E S IN N I T R I D I N G O F POROUS IRON V.G.Gorbach et al, Poroshkovaya Metallurgiya, No 4, 1991, 24-28. (In Russian).