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Mechanical alloying of steels with dispersed oxide phase
intermetallic c o m p o u n d s are formed, l ~ n g t e r m i s o t h e r m a l sintering is a c c o m p a n i e d by a n i n c r e a s e in m i c r o h a r d n e s s a n d changes in t h e l a ~ i c e mpacing~s of t h e TiaN.
p r e s s u r e is a p p l i e d t h r o u g h a ram. A controlled a t m o s p h e r e or vacuum may be used. Near-net s h a p e Ti~M c o m p a c t s were prodcc~ff at. 870:C a n d 50 MPa pressure_
MOULDING AND SOLID PHASE S I N T E R I N G O F HIGH S P E E D S T E E L POWDERS
M E C H A N I C A L ALLOYING
L A Pozn:y~k, eL al, Pom.skovaya Metallurgia, No 4, 1990, 52-55. In Russian. I n e r t gas a n d w a t e r atomized powders were m o u l d e d into billets using static a n d c o m b i n e d compaction. Data is p r e s e n t e d on this a n d on solid p h a s e sintered specimens.
M E C H A N I S M O F OXIDATION O F TiCN i ( M o ) HARD ALLOYS E I Golovko, et al, Poroskovaya MetaUurg/a, No 4, 1990, 89-94. In Russian. Oxidation, in air, of TiC-18%Ni(Mo) was s t u d i e d in t h e t e m p e r a t u r e range 8001200°C u n d e r i s o t h e r m n a l conditions. A scale is tbrmed which c o n t a i n s TiO2 a n d o t h e r constituenLs.
INTERMETALLIC MATERIALS S I N T E R I N G OF TiNi POWDER V V Skorokhod, et al, Poroskovaya Metallurgia, No 4, 1990, 17-21. In Russian. Studies of the sintering of TiNi have s h o w n t h a t t h e process is a c c o m p a n i e d by a v o l u m e t r i c e x p a n s i o n of the c o m p a c t s , which is a t t r i b u t e d to a reverse m a r t e n s i t i c transformation. SYNTHESIS O F TiAI BY H I P AND REACTIVE S I N T E R I N G A Katitsuji, et al, J. Japan Soc Pawder and PawderMetallurgy, Vol 37 ,No 5, 1990, 665669. In J a p a n e s e . Ti-45 to 55% A1 alloys were synthesized from e l e m e n t a l powders ~ HIP a n d reactive sintering. Fully d e n s e 2LM, with excess Ti or AI in t h e form of o t h e r compounds, TiaAl , Z i a A l 2 o r TiAl a were produced. Laraellar structures were observed in the microstructures.
P S E U D O HIP P R O C E S S F O R P R O D U C T I O N O F NF~kR-NrET StLkPE A R T I C L E S IN INTERbLETALLIC COMPOUNDS P H Shingu, K N Ishihara, J. Japan Soc Powder and Pawder Meta2lurgy, Vol 37, No 5, 1990, 670-673. In Japanese. A pseudo HIP process, using silica s a n d as a p r e s s u r e t r a n s m i t t i n g m e d i u m , is described. Heating is by m e a n s of a helix of resistance wire inserted in t h e s a n d a n d
54 MPR January 1991
bIECH=~N~ICALLY LN'I)UCED PtL~SE TR.~NSFORSL~.TIONS IN Ni-Zr .M~LOYS N Merk et al, (University of Calitbrnia, USA), J. Less Common Meta£s, Vol 153, No 2, 1989, 299-310. Structures in mechanically alloyed Ni-Zr a l l o ~ were studied by differential s c a n n i n g calorimetry. Depending on time of milling, crystalline a n d a m o r p h o u s m a t e r i a l are shown to coexist. T h e r m o d y n a m i c ~alues are related to microstructures. The a m o r p h o u s material is more stable t h a n t h a t o b t a i n e d by melt-spinning. PREPARATION OF F ~ Z r ALLOYS BY MECHANICAL ALLOYING A N D MELTSPINNLNG G E n n a s et al, J. Mater Sci, Vol 24 , No 9, 1989, 3053-3058. A c o m p a r i s o n is made, using X-ray dillY'action analysis, between Fe-Zr alloys m a d e by m e c h a n i c a l a l l o y i n g , f r o m elemental powders and intermetallic c o m p o u n d s as s t a r t i n g materials. Some differences in reaction kinetics detected. Comparison with melt-spun material showed no s t r u c t u r a l differences. KINETICS OF LOW T E M P E R A T U R E HOMOGENIZATION ( L T H ) IN D I S P E R S E D POWDER SYSTEMS V V Bogdmmv, L N Paritskaya, Poroskovaya Metallurgia, 1990, No 1, 16-19. In Russian. U l t r a d i s p e r s e d m e c h a n i c a l alloyed powders were studied by X-ray analysis a n d microspectroscopy. Model for LTH is s u g g e s t e d in w h i c h h o m o g e n i z a t i o n is r e a l i z e d by m o v i n g b o u n d a r i e s . It is concluded t h a t c h a r a c t e r i z a t i o n of volume a n d b o u n d a r y diffusion is t h e same in u l t r a d i s p e r s e d MA p o w d e r s as in b u l k objects.
MECHANICAL ALLOYING O F S T E E L S WITH D I S P E R S E D OXIDE PHASE E Kohler, et al, (Technische Universit'at, Clausthal, Germany), Powder Metallurgy [nt.,Vol 22, No 3, 1990, 11-14. Microstructures consisting of a tough m a t r i x with h a r d fine-dispersed inclusions provide high resistance to sliding wear. Sintered steels with 10-25 vol% AlcOa h a r d p h a s e c a n be p r o d u c e d by m e c h a n i c a l alloying. Sintering behaviour, mechanical properties a n d w-ear characteristics of these new sintered steels are reported.
CORRELATION BETWEEN MECIL~NICAL ALLOttiNG ( M A ) ANq) MICROSTRUCTURE OF AI-Li-Mg _~LLOI~ A La.wous, et al, (Iscar Ltd, Tefen, Israel), Pc,_vder Metallurgy fnt., Vol 22, No 3, 21-24. P o w d e r s of A1-Mg a n d AI-Li w e r e produced by MA under different conditions. Cold welding d u r i n g MA w-as studied by electron microscopy a n d p h a s e s t r u c t u r e by X-ray diffraction. Effect of AI-Li (brittle) additions to A1-Mg (ductile) on particle morphology, size a n d d i s t r i b u t i o n studied. Particle agglomeration is minimized by AI-Li additions. Mechanical properties of hot pressed powders were measured. Specific elastic modulus increased by 37% on addition of I-3% Li to an A1-2 ~ % Mg alloy. bIECHANICAL ALLOYING OF A Ni BASE SUPERALLOY Y S Song, T H Kim (Dept of Metallurgical Engineering, N a t i o n a l University, Seoul, Korea), J. Korean Inst of Metals, Vol 28, No 2, 1990, 111-118. In Korean. T h e p r o c e s s of MA i n a N i - b a s e s u p e r a l l o y w a s s t u d i e d by e l e c t r o n microscopy, m i c r o h a r d n e s s testing, EPMA a n d X-ray diffractometry. Observations were made of t h e changes in powder morphology, microstructure, chemical homogeneity a n d d e g r e e of work h a r d e n i n g d u r i n g t h e a l l o ~ n g process. PHYSICS O F MECHANICAL ALLOYING D R Maurice, T H Courtney, (University of "virginia, Charlottesville, USA), Metallurgical Transactions A, Vol 21, No 2, 1990, 289303. An a t t e m p t is m a d e to define t h e basic geometry, mechanics a n d physics of biA. Modelling of the collisions is on the basis of Herzian c o n t a c t s between grinding bodies which e n t r a p materials between i m p a c t i n g surfaces, defining t h e volume of m a t e r i a l p e r collision. From t h i s a n d t h e mill a n d material characteristics, impact times, powder strains and strain rates, t e m p e r a t u r e increases a n d cooling a n d milling t i m e s can be a p p r o x i m a t e d . BEHAVIOUR OF A M O R P H O U S Pd4s Nia2P2o P R O D U C E D BY bIECHAN1CAL ALLOYING A Inoue, et al, (Tohoku University, Sendal, J a p a n ) , Materials Transactions J a p a n Inst. of Metals, Vol 31, No 2, 1990, 148-151. A glass transition, at 581K ~ s observed in t h e alloy which h a d been subject to MA for 300 hours. Specific h e a t s a n d h e a t s of crystallization for t h e alloy in a m o r p h o u s and supercooled liquid s t a t e s measured. Deduced t h a t t h e MA a m o r p h o u s material h a s a disordered s t r u c t u r e with a greater level of stored energy t h a n m e l t s p u n a m o r p h o u s alloy.
p r e s s u r e is a p p l i e d t h r o u g h a ram. A controlled a t m o s p h e r e or vacuum may be used. Near-net s h a p e Ti~M c o m p a c t s were prodcc~ff at. 870:C a n d 50 MPa pressure_
MOULDING AND SOLID PHASE S I N T E R I N G O F HIGH S P E E D S T E E L POWDERS
M E C H A N I C A L ALLOYING
L A Pozn:y~k, eL al, Pom.skovaya Metallurgia, No 4, 1990, 52-55. In Russian. I n e r t gas a n d w a t e r atomized powders were m o u l d e d into billets using static a n d c o m b i n e d compaction. Data is p r e s e n t e d on this a n d on solid p h a s e sintered specimens.
M E C H A N I S M O F OXIDATION O F TiCN i ( M o ) HARD ALLOYS E I Golovko, et al, Poroskovaya MetaUurg/a, No 4, 1990, 89-94. In Russian. Oxidation, in air, of TiC-18%Ni(Mo) was s t u d i e d in t h e t e m p e r a t u r e range 8001200°C u n d e r i s o t h e r m n a l conditions. A scale is tbrmed which c o n t a i n s TiO2 a n d o t h e r constituenLs.
INTERMETALLIC MATERIALS S I N T E R I N G OF TiNi POWDER V V Skorokhod, et al, Poroskovaya Metallurgia, No 4, 1990, 17-21. In Russian. Studies of the sintering of TiNi have s h o w n t h a t t h e process is a c c o m p a n i e d by a v o l u m e t r i c e x p a n s i o n of the c o m p a c t s , which is a t t r i b u t e d to a reverse m a r t e n s i t i c transformation. SYNTHESIS O F TiAI BY H I P AND REACTIVE S I N T E R I N G A Katitsuji, et al, J. Japan Soc Pawder and PawderMetallurgy, Vol 37 ,No 5, 1990, 665669. In J a p a n e s e . Ti-45 to 55% A1 alloys were synthesized from e l e m e n t a l powders ~ HIP a n d reactive sintering. Fully d e n s e 2LM, with excess Ti or AI in t h e form of o t h e r compounds, TiaAl , Z i a A l 2 o r TiAl a were produced. Laraellar structures were observed in the microstructures.
P S E U D O HIP P R O C E S S F O R P R O D U C T I O N O F NF~kR-NrET StLkPE A R T I C L E S IN INTERbLETALLIC COMPOUNDS P H Shingu, K N Ishihara, J. Japan Soc Powder and Pawder Meta2lurgy, Vol 37, No 5, 1990, 670-673. In Japanese. A pseudo HIP process, using silica s a n d as a p r e s s u r e t r a n s m i t t i n g m e d i u m , is described. Heating is by m e a n s of a helix of resistance wire inserted in t h e s a n d a n d
54 MPR January 1991
bIECH=~N~ICALLY LN'I)UCED PtL~SE TR.~NSFORSL~.TIONS IN Ni-Zr .M~LOYS N Merk et al, (University of Calitbrnia, USA), J. Less Common Meta£s, Vol 153, No 2, 1989, 299-310. Structures in mechanically alloyed Ni-Zr a l l o ~ were studied by differential s c a n n i n g calorimetry. Depending on time of milling, crystalline a n d a m o r p h o u s m a t e r i a l are shown to coexist. T h e r m o d y n a m i c ~alues are related to microstructures. The a m o r p h o u s material is more stable t h a n t h a t o b t a i n e d by melt-spinning. PREPARATION OF F ~ Z r ALLOYS BY MECHANICAL ALLOYING A N D MELTSPINNLNG G E n n a s et al, J. Mater Sci, Vol 24 , No 9, 1989, 3053-3058. A c o m p a r i s o n is made, using X-ray dillY'action analysis, between Fe-Zr alloys m a d e by m e c h a n i c a l a l l o y i n g , f r o m elemental powders and intermetallic c o m p o u n d s as s t a r t i n g materials. Some differences in reaction kinetics detected. Comparison with melt-spun material showed no s t r u c t u r a l differences. KINETICS OF LOW T E M P E R A T U R E HOMOGENIZATION ( L T H ) IN D I S P E R S E D POWDER SYSTEMS V V Bogdmmv, L N Paritskaya, Poroskovaya Metallurgia, 1990, No 1, 16-19. In Russian. U l t r a d i s p e r s e d m e c h a n i c a l alloyed powders were studied by X-ray analysis a n d microspectroscopy. Model for LTH is s u g g e s t e d in w h i c h h o m o g e n i z a t i o n is r e a l i z e d by m o v i n g b o u n d a r i e s . It is concluded t h a t c h a r a c t e r i z a t i o n of volume a n d b o u n d a r y diffusion is t h e same in u l t r a d i s p e r s e d MA p o w d e r s as in b u l k objects.
MECHANICAL ALLOYING O F S T E E L S WITH D I S P E R S E D OXIDE PHASE E Kohler, et al, (Technische Universit'at, Clausthal, Germany), Powder Metallurgy [nt.,Vol 22, No 3, 1990, 11-14. Microstructures consisting of a tough m a t r i x with h a r d fine-dispersed inclusions provide high resistance to sliding wear. Sintered steels with 10-25 vol% AlcOa h a r d p h a s e c a n be p r o d u c e d by m e c h a n i c a l alloying. Sintering behaviour, mechanical properties a n d w-ear characteristics of these new sintered steels are reported.
CORRELATION BETWEEN MECIL~NICAL ALLOttiNG ( M A ) ANq) MICROSTRUCTURE OF AI-Li-Mg _~LLOI~ A La.wous, et al, (Iscar Ltd, Tefen, Israel), Pc,_vder Metallurgy fnt., Vol 22, No 3, 21-24. P o w d e r s of A1-Mg a n d AI-Li w e r e produced by MA under different conditions. Cold welding d u r i n g MA w-as studied by electron microscopy a n d p h a s e s t r u c t u r e by X-ray diffraction. Effect of AI-Li (brittle) additions to A1-Mg (ductile) on particle morphology, size a n d d i s t r i b u t i o n studied. Particle agglomeration is minimized by AI-Li additions. Mechanical properties of hot pressed powders were measured. Specific elastic modulus increased by 37% on addition of I-3% Li to an A1-2 ~ % Mg alloy. bIECHANICAL ALLOYING OF A Ni BASE SUPERALLOY Y S Song, T H Kim (Dept of Metallurgical Engineering, N a t i o n a l University, Seoul, Korea), J. Korean Inst of Metals, Vol 28, No 2, 1990, 111-118. In Korean. T h e p r o c e s s of MA i n a N i - b a s e s u p e r a l l o y w a s s t u d i e d by e l e c t r o n microscopy, m i c r o h a r d n e s s testing, EPMA a n d X-ray diffractometry. Observations were made of t h e changes in powder morphology, microstructure, chemical homogeneity a n d d e g r e e of work h a r d e n i n g d u r i n g t h e a l l o ~ n g process. PHYSICS O F MECHANICAL ALLOYING D R Maurice, T H Courtney, (University of "virginia, Charlottesville, USA), Metallurgical Transactions A, Vol 21, No 2, 1990, 289303. An a t t e m p t is m a d e to define t h e basic geometry, mechanics a n d physics of biA. Modelling of the collisions is on the basis of Herzian c o n t a c t s between grinding bodies which e n t r a p materials between i m p a c t i n g surfaces, defining t h e volume of m a t e r i a l p e r collision. From t h i s a n d t h e mill a n d material characteristics, impact times, powder strains and strain rates, t e m p e r a t u r e increases a n d cooling a n d milling t i m e s can be a p p r o x i m a t e d . BEHAVIOUR OF A M O R P H O U S Pd4s Nia2P2o P R O D U C E D BY bIECHAN1CAL ALLOYING A Inoue, et al, (Tohoku University, Sendal, J a p a n ) , Materials Transactions J a p a n Inst. of Metals, Vol 31, No 2, 1990, 148-151. A glass transition, at 581K ~ s observed in t h e alloy which h a d been subject to MA for 300 hours. Specific h e a t s a n d h e a t s of crystallization for t h e alloy in a m o r p h o u s and supercooled liquid s t a t e s measured. Deduced t h a t t h e MA a m o r p h o u s material h a s a disordered s t r u c t u r e with a greater level of stored energy t h a n m e l t s p u n a m o r p h o u s alloy.