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Strengthening mechanisms in sintered and heat treated steel compacts made from partially prealloyed powders
PM the discussion is e x t e n d e d to multicomponent mixtures. The method of optimizing particle size distribution for maximum packing density is illustrated by a typical example. CONTACT GROWTH CONSOLIDATION IN RANDOMLY D E N S E PACKED POWDER A G G L O M E R A T E S
S. Bhargava (Indian Inst of Technology, Kanpur, India), Z f i i r MetaUkunde, Vol 84, No 9, 1993, 645-651. D e fo r m at i o n and c o n s o l i d a t i o n of powder compacts are discussed with respect of growth of interparticle contact areas and plastic flow. Analysis is in t e r m s of D i r i c h l e t t e s s a l a t i o n . It is suggested that pore volume and shrinkage are appropriate parameters for monitoring d e n s i f i c a t i o n . It is s h o w n t h a t to maintain geometric compatibility between plastically deforming particles the free surface: co n t act area and shrinkage: pore volume ratios must be constant. A relationship between total contact area and relative density is established. Good a g r e e m e n t b e t w e e n e x p e r i m e n t and analysis is reported. STRESS-STRAINED STATE O F POWDER U N D E R CENTRIFUGAL ROLLING
O-~. Labzin et al, Poroshkovaya Metallurgiya, No 8, 1992, 35-38. (In Russian). Deformation of powder during rolling is determined by means of slip line fields. Stresses, r e l a t e d to d e f o r m a t i o n are determined and relationships with density are established. A MODEL FOR QUASI-STATIC COMPACTION OF POROUS B O D I E S A C C O U N T I N G FOR F U S I O N O F P O R E S
A. Yu et al, Poroshkovaya MetaUurgiya, No 8, 1992, 39-43. (In Russian). Equations describing quasi-static d e f o r m a t i o n of p o r o u s m a t e r i a l s , with regard to pore coalescence within the compact, are presented. Surface pores are considered for the effect of the magnitude of stresses on the punch and on the process of densification. REAL TIME VIDEO IMAGING OF HIGHLUMINOSITY P R O C E S S E S
LITERATURE
REVIEW
PRODUCTS" Aluminium P R O C E S S I N G STRUCTURE A N D P R O P E R T I E S O F 2 1 2 4 ALUMINIUM ALLOY SILICON CARBIDE COMPOSITES
M.I~ Jain et al (Defence Metallurgical Laboratory, Hyerabad, India), Int J Powder Metallurgy, Vol 29, No 3, 1993, 267-275. The a t t a i n m e n t of u n i f o r m a n d reproducible properties in SiC particle r e i n f o r c e d 2 1 2 4 A1 a l l o y m a t r i x composites is discussed with regard to the selection of process conditions. Effects of p r o c e s s v a r i a b l e s on s t r u c t u r e an d properties are considered and it is shown t h a t s e c o n d a r y p r o c e s s i n g , such as extrusion or rolling, and an homogenization treatment are required to attain optimum properties. E F F E C T S O F COMPACTION C O N D I T I O N S ON STRUCTURE AND P R O P E R T I E S O F ALUMINIUM ALLOYS WITH C O P P E R A N D MAGNESIUM
K.A. Yu, Poroshkovaya Metalluryiya, No 8, 1992, 44-49. (In Russian). The effects of c o m p a c t i o n mode, admixed lubricant and/or die wall lubrication, on the structure and properties of A1 alloys with Cu and Mg were investigated. It is reported that the addition of lubricant reduces the strength and ductility of the compacts. This is attributed to contamination of interfaces between particles and to gas desorption. I N F L U E N C E OF FORMING P R O C E S S ON STRUCTURE A N D P R O P E R T I E S OF RAPIDLY S O L I D I F I E D ALUMINIUMCOPPER-MAGNESIUM ALLOYS
C. Yang et al (Tianjin University, Tianjin, China), PM Technology, Vol 10, No 4, 1992, 260-265. (In Chinese). It is r e p o r t e d t h a t an AI-Cu-Mg a l l o y p o w d e r h a d b e e n m a d e by centrifugal atomization and consolidated by vacuum hot-pressing, and extrusion. T h e p o w d e r s a r e r e p o r t e d to be tear shaped, to have dendritic or cellular structures and to have been compacted to high density and strength of 430 MPa.
Iron and steel T.T. Hoffman (Control Vision Inc, Idaho Falls, Idaho, USA), Powder MetaU Int, Vol 25, No 2, 1993, 86-90. A new s t r o b s c o p i c v id e o c a m e r a system, for use in s t u d i e s of h i g h luminosity processes involving combustion, plasmas or laser sources, is described. The system is reported to have value in the study of powder processes. The potential for real time monitoring of p r o c e s s e s an d f e e d b a c k c o n t r o l is o u t l i n e d . E x a m p l e s of a p p l i c a t i o n s are given.
40 MPR March 1994
LASER T R E A T M E N T OF IRONGRAPHITE POWDER MATERIALS
E F F E C T S OF ALLOYING E L E M E N T S ON WEAR RESISTANCE O F S I N T E R E D IRON BASE MATERIALS
Z. Xisheng (No 1 Automobile Factory, Changchun, Ch i n a) , PM Technology, Vol 10, No 4, 1992, 292-294. (In Chinese). Comparisons of the wear resistance of a range of sintered steels are made. Data of value in materials selection is presented. S T R E N G T H E N I N G M E C H A N I S M S IN S I N T E R E D A N D HEAT TREATED S T E E L COMPACTS MADE FROM PARTIALLY PREALLOYED POWDERS
Y. Saito et al (Kawasaki Steel Corporation, Kawasaki, Japan), J. Iron and Steel Inst of Japan, Vol 79, No 8, 1993, 1003-1010. (In Japanese). A study of the chemistry of partially prealloyed steel powders with Ni and Mo is d e s c r i b e d . It is r e p o r t e d t h a t high strength alloys are produced by double pressing and double sintering f o l l o w e d by h e a t t r e a t m e n t . T h e presence of retained austenite in Ni rich domains is noted in steels with 0.6% g r a p h i t e . The f o r m of t h e s t r e s s / s t r a i n c u r v e is a n a l y s e d a nd it is shown that deformation is localized in the r e t a i n e d 7 and t h a t s t r a i n i nduc e d martensite is formed. The tensile strength is shown to increase with decrease in %Ni. Sintered and heat treated 2%Ni-l%Mo steel is reported to have a tensile strength of 1920 MPa and an un-notched Charpey impact strength of 53J.
Molybdenum BRAZING OF MOLYBDENUM USING A PALLADIUM-SILVER ALLOY
Y. Hiraoka (Okayama University of Science, Okayama, Japan), Int J Refractory Metals & Hard Materials, Vol 11, No 5, 1992, 303307. It is reported that Mo had been brazed by u se of a Pd-20%Ag alloy. The microstructure, hardness and composition of the joint were examined and the ambient temperature bend strength determined. The brazed layer is reported to contain three phases, Mo and Ag rich, which when deformed showed some ductility prior to fracture. Brazed joints made at higher temperatures contained only two phases, one of which, Mo rich, was where fracture occurred and is shown to be the most brittle.
P_A. Vityaz et al, Poroshkovaya Metallurgiya, No 8, 1992, 54-56. (In Russian).
Titanium
Laser t r e a t m e n t of F e - g r a p h i t e alloys was investigated. It is shown t h a t the laser t r e a t m e n t significantly changes the structure and positively influences the tribological properties of the materials.
D E N S I F I C A T I O N OF TITANIUMALUMINIUM-VANDIUM POWDER COMPACTS
H. Sujata et al (Indian Inst of Technology, Kanpur, India), Powder Metall Int, Vol 25, No 2, 1993, 70-72.
S. Bhargava (Indian Inst of Technology, Kanpur, India), Z f i i r MetaUkunde, Vol 84, No 9, 1993, 645-651. D e fo r m at i o n and c o n s o l i d a t i o n of powder compacts are discussed with respect of growth of interparticle contact areas and plastic flow. Analysis is in t e r m s of D i r i c h l e t t e s s a l a t i o n . It is suggested that pore volume and shrinkage are appropriate parameters for monitoring d e n s i f i c a t i o n . It is s h o w n t h a t to maintain geometric compatibility between plastically deforming particles the free surface: co n t act area and shrinkage: pore volume ratios must be constant. A relationship between total contact area and relative density is established. Good a g r e e m e n t b e t w e e n e x p e r i m e n t and analysis is reported. STRESS-STRAINED STATE O F POWDER U N D E R CENTRIFUGAL ROLLING
O-~. Labzin et al, Poroshkovaya Metallurgiya, No 8, 1992, 35-38. (In Russian). Deformation of powder during rolling is determined by means of slip line fields. Stresses, r e l a t e d to d e f o r m a t i o n are determined and relationships with density are established. A MODEL FOR QUASI-STATIC COMPACTION OF POROUS B O D I E S A C C O U N T I N G FOR F U S I O N O F P O R E S
A. Yu et al, Poroshkovaya MetaUurgiya, No 8, 1992, 39-43. (In Russian). Equations describing quasi-static d e f o r m a t i o n of p o r o u s m a t e r i a l s , with regard to pore coalescence within the compact, are presented. Surface pores are considered for the effect of the magnitude of stresses on the punch and on the process of densification. REAL TIME VIDEO IMAGING OF HIGHLUMINOSITY P R O C E S S E S
LITERATURE
REVIEW
PRODUCTS" Aluminium P R O C E S S I N G STRUCTURE A N D P R O P E R T I E S O F 2 1 2 4 ALUMINIUM ALLOY SILICON CARBIDE COMPOSITES
M.I~ Jain et al (Defence Metallurgical Laboratory, Hyerabad, India), Int J Powder Metallurgy, Vol 29, No 3, 1993, 267-275. The a t t a i n m e n t of u n i f o r m a n d reproducible properties in SiC particle r e i n f o r c e d 2 1 2 4 A1 a l l o y m a t r i x composites is discussed with regard to the selection of process conditions. Effects of p r o c e s s v a r i a b l e s on s t r u c t u r e an d properties are considered and it is shown t h a t s e c o n d a r y p r o c e s s i n g , such as extrusion or rolling, and an homogenization treatment are required to attain optimum properties. E F F E C T S O F COMPACTION C O N D I T I O N S ON STRUCTURE AND P R O P E R T I E S O F ALUMINIUM ALLOYS WITH C O P P E R A N D MAGNESIUM
K.A. Yu, Poroshkovaya Metalluryiya, No 8, 1992, 44-49. (In Russian). The effects of c o m p a c t i o n mode, admixed lubricant and/or die wall lubrication, on the structure and properties of A1 alloys with Cu and Mg were investigated. It is reported that the addition of lubricant reduces the strength and ductility of the compacts. This is attributed to contamination of interfaces between particles and to gas desorption. I N F L U E N C E OF FORMING P R O C E S S ON STRUCTURE A N D P R O P E R T I E S OF RAPIDLY S O L I D I F I E D ALUMINIUMCOPPER-MAGNESIUM ALLOYS
C. Yang et al (Tianjin University, Tianjin, China), PM Technology, Vol 10, No 4, 1992, 260-265. (In Chinese). It is r e p o r t e d t h a t an AI-Cu-Mg a l l o y p o w d e r h a d b e e n m a d e by centrifugal atomization and consolidated by vacuum hot-pressing, and extrusion. T h e p o w d e r s a r e r e p o r t e d to be tear shaped, to have dendritic or cellular structures and to have been compacted to high density and strength of 430 MPa.
Iron and steel T.T. Hoffman (Control Vision Inc, Idaho Falls, Idaho, USA), Powder MetaU Int, Vol 25, No 2, 1993, 86-90. A new s t r o b s c o p i c v id e o c a m e r a system, for use in s t u d i e s of h i g h luminosity processes involving combustion, plasmas or laser sources, is described. The system is reported to have value in the study of powder processes. The potential for real time monitoring of p r o c e s s e s an d f e e d b a c k c o n t r o l is o u t l i n e d . E x a m p l e s of a p p l i c a t i o n s are given.
40 MPR March 1994
LASER T R E A T M E N T OF IRONGRAPHITE POWDER MATERIALS
E F F E C T S OF ALLOYING E L E M E N T S ON WEAR RESISTANCE O F S I N T E R E D IRON BASE MATERIALS
Z. Xisheng (No 1 Automobile Factory, Changchun, Ch i n a) , PM Technology, Vol 10, No 4, 1992, 292-294. (In Chinese). Comparisons of the wear resistance of a range of sintered steels are made. Data of value in materials selection is presented. S T R E N G T H E N I N G M E C H A N I S M S IN S I N T E R E D A N D HEAT TREATED S T E E L COMPACTS MADE FROM PARTIALLY PREALLOYED POWDERS
Y. Saito et al (Kawasaki Steel Corporation, Kawasaki, Japan), J. Iron and Steel Inst of Japan, Vol 79, No 8, 1993, 1003-1010. (In Japanese). A study of the chemistry of partially prealloyed steel powders with Ni and Mo is d e s c r i b e d . It is r e p o r t e d t h a t high strength alloys are produced by double pressing and double sintering f o l l o w e d by h e a t t r e a t m e n t . T h e presence of retained austenite in Ni rich domains is noted in steels with 0.6% g r a p h i t e . The f o r m of t h e s t r e s s / s t r a i n c u r v e is a n a l y s e d a nd it is shown that deformation is localized in the r e t a i n e d 7 and t h a t s t r a i n i nduc e d martensite is formed. The tensile strength is shown to increase with decrease in %Ni. Sintered and heat treated 2%Ni-l%Mo steel is reported to have a tensile strength of 1920 MPa and an un-notched Charpey impact strength of 53J.
Molybdenum BRAZING OF MOLYBDENUM USING A PALLADIUM-SILVER ALLOY
Y. Hiraoka (Okayama University of Science, Okayama, Japan), Int J Refractory Metals & Hard Materials, Vol 11, No 5, 1992, 303307. It is reported that Mo had been brazed by u se of a Pd-20%Ag alloy. The microstructure, hardness and composition of the joint were examined and the ambient temperature bend strength determined. The brazed layer is reported to contain three phases, Mo and Ag rich, which when deformed showed some ductility prior to fracture. Brazed joints made at higher temperatures contained only two phases, one of which, Mo rich, was where fracture occurred and is shown to be the most brittle.
P_A. Vityaz et al, Poroshkovaya Metallurgiya, No 8, 1992, 54-56. (In Russian).
Titanium
Laser t r e a t m e n t of F e - g r a p h i t e alloys was investigated. It is shown t h a t the laser t r e a t m e n t significantly changes the structure and positively influences the tribological properties of the materials.
D E N S I F I C A T I O N OF TITANIUMALUMINIUM-VANDIUM POWDER COMPACTS
H. Sujata et al (Indian Inst of Technology, Kanpur, India), Powder Metall Int, Vol 25, No 2, 1993, 70-72.