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Effect of sintering temperatures and oxygen partial pressure on the magnetic properties of MnZn ferrite
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The relationships between m i c r o s t r u c t u r e a n d magnetic properties of sintered Fe-Nd-B m a g n e t s are discussed. The role of t h e non-ferromagnetic p h a s e s is reviewed. Heat t r e a t m e n t a t 600°C h a s been used to dissolve a magnetically soft p h a s e observed in grain boundaries. Grain size distribution a n d its d e v e l o p m e n t during sintering are given. BASIC TYPES OF FERRITE MICROSTRUCTURE
G.I. Z h u r a v l e v , e t al, P o r o s k o v a y a Metallurgiya, No 6, 1990, 68-73. In Russian. Three basic types of m i c r o s t r u c t u r e of ferrites are considered from t h e p o i n t of v i e w of m i c r o s t r u c t u r a l c o n t r o l . I t i s e s t a b l i s h e d t h a t high density, a uniform p a r t i c l e size, of 8 - 1 8 pm, a n d h i g h homogeneity are required to give o p t i m u m magnetic properties. It h a s been shown t h a t it is p o s s i b l e to c o n t r o l t h e m a g n e t i c permeability by control of t h e O p o t e n t i a l in t h e sintering a t m o s p h e r e a n d hence t h e 0 c o n c e n t r a t i o n in t h e material. STRUCTURAL CONTROL OF S I N T E R E D HARD F E R R I T E S
P.M. Nikolic, et al, (Belgrade University, Yugoslavia), Science of Sintering, Vol 22, No 2, 1990, 87-91. The effect of microstructural development during sintering on the m a g n e t i c p r o p e r t i e s of o r i e n t e d h a r d ferrites was investigated. The crystal s t r u c t u r e was d e t e r m i n e d by t h e size a n d s h a p e of the powder grains. The magnetic properties, permanent induction and coercive force, were m e a s u r e d by a novel m e t h o d of m a g n e t i z a t i o n with t r a n s i e n t periodical oscillations. E F F E C T OF SINTERING T E M P E R A T U R E S AND OXYGEN PARTIAL P R E S S U R E ON THE MAGNETIC P R O P E R T I E S OF MnZn FERRITE
Y-K. Park, et al, ( C h u n g n a m N a t i o n a l University, Taejon, Korea), J. Korean Inst. of Metals, Vol 26, No 8, 1990, 682-688. In Korean. The effects of sintering t e m p e r a t u r e s a n d O partial pressure in t h e sintering a t m o s p h e r e on t h e magnetic properties of MnZn ferrite h a s been studied. A sintering t e m p e r a t u r e of 1280°C a n d a n 0 partial pressure of 0.04 atmospheres gave materials with t h e lowest magnetic loss. I n c r e a s e d s i n t e r i n g t e m p e r a t u r e led to increased permeability. POWDER PREPARATION AND THE E F F E C T OF SINTERING CONDITIONS ON THE MAGNETIC PROPERTIES OF MnZn FERRITE B.W. Kang, et al, (Seoul National University, Seoul, Korea), J. Korean Inst. of Metals, Vol
58 MPR March 1991
m
m
26, No 9, 1990, 808-812. In Korean. MnZn ferrite powders were p r e p a r e d by a spray method. The effect of t h e process p a r a m e t e r s on particle size d i s t r i b u t i o n a n d magnetic properties of t h e powders were investigated a n d t h e results c o m p a r e d with t h o s e for powders p r o d u c e d by coprecipitation. O p t i m u m process conditions were determined. The powders were calcined, compacted and sintered. Sintering conditions were e x a m i n e d for t h e i r effects on t h e p r o p e r t i e s of t h e sintered compacts.
H a r d m a t e r i a l s a n d tool steels E F F E C T OF W PARTICLE SIZE AND FIRING TEMPERATURE ON BOND S T R E N G T H OF W-METALLIZED ALUMINA SUBSTRATES
T. Ueyama, T. Yamamoto, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No 6, 1990, 851-856. In Japanese. The p a p e r e x a m i n e s t h e influence of Wparticle size a n d firing t e m p e r a t u r e on the b o n d i n g s t r e n g t h of W-metallized a l u m i n a substrates. Firing was carried out in a wet reducing atmosphere. It was deduced t h a t t h e r e is a n o p t i m u m firing t e m p e r a t u r e where t h e bond s t r e n g t h is a m a x i m u m a n d t h a t this increases w i t h W-particle size. STRUCTURAL CHANGES ON ANNEALING OF WC CONTAINING TiCTiN-Ni-Co CERMETS
M. Ueki, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No 6, 1990, 869872. In Japanese. Two p h a s e TiC-34%TiN-7 to 14%WC7%Co-3.5%Ni alloys w e r e s i n t e r e d in vacuum at 1500°C for 1 hour and a n n e a l e d at 950-1250°C. It was found t h a t t h e two p h a s e region c o n t r a c t e d as a result of precipitation of ~/ or WC phases. The s t r e n g t h a n d cutting performance of t h e alloys were e x a m i n e d . Reasons for t h e instability of t h e alloys were discussed. PREPARATION OF TiC-Ni CERMETS FROM COMPOSITE POWDERS
I~ Tatsuzawa, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No. 7, 1990, 1009-1012. In Japanese. TiC powders were electroless Ni p l a t e d a n d t h e plating conditions investigated. The sintering b e h a v i o u r a n d t h e s t r u c t u r e of sintered compacts were studied. Annealing of the TiC powder p r i o r to plating improved the quality of t h e composite powder a n d densification of t h e compacts. Ni/B a n d Ni/N d e p o s i t s were also s t u d i e d u s i n g dimethylamine b o r a n e a n d hydrazine as reducing agents in t h e p l a t i n g process. C o m p a c t s were liquid p h a s e sintered at 1375°C.
REACTION HEAT SINTERING USING HIP AND DENSIFICATION OF TiC-Ni CERMETS
H. Nakanishi, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No. 7, 1990, 1013-1016. In Japanese. The d e v e l o p m e n t of a sintering process for TiC-Ni cermets is described. This uses HIP a n d t h e h e a t of reaction between Ti a n d C to form TiC. Rapid densification of t h e c e r m e t is a t t a i n e d . T h e effect of Ni c o n c e n t r a t i o n in t h e cermet was studied. The fracture t o u g h n e s s was m e a s u r e d a n d a value of 5 MPa.m ~/2 is reported. PREPARATION OF SOME NEW WC HARDMETALS
T. Farooq, TJ. Davies, (Materials Science Centre, M a n c h e s t e r University, UK), Pow-
der Metallurgy International, Vo122, No 4, 1990, 12-16. PM was used to p r o d u c e two new WC h a r d m e t a l s , WC + stainless steel a n d WC + Fe-Co-NiMoB by h o t p r e s s i n g a n d sintering. The microstructures and physical a n d mechanical p r o p e r t i e s were evaluated. The h a r d n e s s is similar to t h a t of WC + Co. The e x p e r i m e n t a l alloys are h e a t t r e a t a b l e a n d m a r t e n s i t e can be formed in the matrix resulting in improved m e c h a n i c a l properties. It is suggested t h a t t h e new compositions m a y find use in wear r e s i s t a n t applications. RELATIONSHIPS B E T W E E N S T R E N G T H AND RESIDUAL S T R E S S E S OF C E M E N T E D CARBIDES S U B J E C T E D TO P E E N I N G TREATMENT
I~ Kamachi, T. Yamamoto, (Kinki University, Higashi-Osaka, J a p a n ) , J. Japan Inst. of Metals, Vol 53, No 10, 1990, 1131-1135. In Japanese. A t t e n t i o n is d r a w n to t h e fact t h a t c e m e n t e d carbides have high s t r e n g t h b u t little or no plasticity a n d to t h e need to t r e a t t h e factors influencing m e c h a n i c a l p r o p e r t i e s , e.g. voids, in a s t a t i s t i c a l manner. The p a p e r describes e x p e r i m e n t s in which WC-5 to 15%Co alloys have b e e n s h o t b l a s t e d a n d t h e r e s i d u a l surface stresses measured. The effect of surface stresses on t h e m e c h a n i c a l properties are discussed. SINTERING AND HIGH TEMPERATURE EXTRUSION OF HARD ALLOYS WITH DAMPING B I N D E R S
S.N. Kulkov, et al, (Siberian B r a n c h of USSR Academy of Sciences, Tomsk, USSR), Sc/ence ofSintering, Vol 22, No 2, 1990, 65-72. The s i n t e r i n g a n d h i g h t e m p e r a t u r e e x t r u s i o n of TiC-NiTi c e m e n t e d carbide is considered. Three sintering m e c h a n i s m s are identified a n d are r e l a t e d to t h e alloy composition. High temperature
The relationships between m i c r o s t r u c t u r e a n d magnetic properties of sintered Fe-Nd-B m a g n e t s are discussed. The role of t h e non-ferromagnetic p h a s e s is reviewed. Heat t r e a t m e n t a t 600°C h a s been used to dissolve a magnetically soft p h a s e observed in grain boundaries. Grain size distribution a n d its d e v e l o p m e n t during sintering are given. BASIC TYPES OF FERRITE MICROSTRUCTURE
G.I. Z h u r a v l e v , e t al, P o r o s k o v a y a Metallurgiya, No 6, 1990, 68-73. In Russian. Three basic types of m i c r o s t r u c t u r e of ferrites are considered from t h e p o i n t of v i e w of m i c r o s t r u c t u r a l c o n t r o l . I t i s e s t a b l i s h e d t h a t high density, a uniform p a r t i c l e size, of 8 - 1 8 pm, a n d h i g h homogeneity are required to give o p t i m u m magnetic properties. It h a s been shown t h a t it is p o s s i b l e to c o n t r o l t h e m a g n e t i c permeability by control of t h e O p o t e n t i a l in t h e sintering a t m o s p h e r e a n d hence t h e 0 c o n c e n t r a t i o n in t h e material. STRUCTURAL CONTROL OF S I N T E R E D HARD F E R R I T E S
P.M. Nikolic, et al, (Belgrade University, Yugoslavia), Science of Sintering, Vol 22, No 2, 1990, 87-91. The effect of microstructural development during sintering on the m a g n e t i c p r o p e r t i e s of o r i e n t e d h a r d ferrites was investigated. The crystal s t r u c t u r e was d e t e r m i n e d by t h e size a n d s h a p e of the powder grains. The magnetic properties, permanent induction and coercive force, were m e a s u r e d by a novel m e t h o d of m a g n e t i z a t i o n with t r a n s i e n t periodical oscillations. E F F E C T OF SINTERING T E M P E R A T U R E S AND OXYGEN PARTIAL P R E S S U R E ON THE MAGNETIC P R O P E R T I E S OF MnZn FERRITE
Y-K. Park, et al, ( C h u n g n a m N a t i o n a l University, Taejon, Korea), J. Korean Inst. of Metals, Vol 26, No 8, 1990, 682-688. In Korean. The effects of sintering t e m p e r a t u r e s a n d O partial pressure in t h e sintering a t m o s p h e r e on t h e magnetic properties of MnZn ferrite h a s been studied. A sintering t e m p e r a t u r e of 1280°C a n d a n 0 partial pressure of 0.04 atmospheres gave materials with t h e lowest magnetic loss. I n c r e a s e d s i n t e r i n g t e m p e r a t u r e led to increased permeability. POWDER PREPARATION AND THE E F F E C T OF SINTERING CONDITIONS ON THE MAGNETIC PROPERTIES OF MnZn FERRITE B.W. Kang, et al, (Seoul National University, Seoul, Korea), J. Korean Inst. of Metals, Vol
58 MPR March 1991
m
m
26, No 9, 1990, 808-812. In Korean. MnZn ferrite powders were p r e p a r e d by a spray method. The effect of t h e process p a r a m e t e r s on particle size d i s t r i b u t i o n a n d magnetic properties of t h e powders were investigated a n d t h e results c o m p a r e d with t h o s e for powders p r o d u c e d by coprecipitation. O p t i m u m process conditions were determined. The powders were calcined, compacted and sintered. Sintering conditions were e x a m i n e d for t h e i r effects on t h e p r o p e r t i e s of t h e sintered compacts.
H a r d m a t e r i a l s a n d tool steels E F F E C T OF W PARTICLE SIZE AND FIRING TEMPERATURE ON BOND S T R E N G T H OF W-METALLIZED ALUMINA SUBSTRATES
T. Ueyama, T. Yamamoto, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No 6, 1990, 851-856. In Japanese. The p a p e r e x a m i n e s t h e influence of Wparticle size a n d firing t e m p e r a t u r e on the b o n d i n g s t r e n g t h of W-metallized a l u m i n a substrates. Firing was carried out in a wet reducing atmosphere. It was deduced t h a t t h e r e is a n o p t i m u m firing t e m p e r a t u r e where t h e bond s t r e n g t h is a m a x i m u m a n d t h a t this increases w i t h W-particle size. STRUCTURAL CHANGES ON ANNEALING OF WC CONTAINING TiCTiN-Ni-Co CERMETS
M. Ueki, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No 6, 1990, 869872. In Japanese. Two p h a s e TiC-34%TiN-7 to 14%WC7%Co-3.5%Ni alloys w e r e s i n t e r e d in vacuum at 1500°C for 1 hour and a n n e a l e d at 950-1250°C. It was found t h a t t h e two p h a s e region c o n t r a c t e d as a result of precipitation of ~/ or WC phases. The s t r e n g t h a n d cutting performance of t h e alloys were e x a m i n e d . Reasons for t h e instability of t h e alloys were discussed. PREPARATION OF TiC-Ni CERMETS FROM COMPOSITE POWDERS
I~ Tatsuzawa, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No. 7, 1990, 1009-1012. In Japanese. TiC powders were electroless Ni p l a t e d a n d t h e plating conditions investigated. The sintering b e h a v i o u r a n d t h e s t r u c t u r e of sintered compacts were studied. Annealing of the TiC powder p r i o r to plating improved the quality of t h e composite powder a n d densification of t h e compacts. Ni/B a n d Ni/N d e p o s i t s were also s t u d i e d u s i n g dimethylamine b o r a n e a n d hydrazine as reducing agents in t h e p l a t i n g process. C o m p a c t s were liquid p h a s e sintered at 1375°C.
REACTION HEAT SINTERING USING HIP AND DENSIFICATION OF TiC-Ni CERMETS
H. Nakanishi, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol 37, No. 7, 1990, 1013-1016. In Japanese. The d e v e l o p m e n t of a sintering process for TiC-Ni cermets is described. This uses HIP a n d t h e h e a t of reaction between Ti a n d C to form TiC. Rapid densification of t h e c e r m e t is a t t a i n e d . T h e effect of Ni c o n c e n t r a t i o n in t h e cermet was studied. The fracture t o u g h n e s s was m e a s u r e d a n d a value of 5 MPa.m ~/2 is reported. PREPARATION OF SOME NEW WC HARDMETALS
T. Farooq, TJ. Davies, (Materials Science Centre, M a n c h e s t e r University, UK), Pow-
der Metallurgy International, Vo122, No 4, 1990, 12-16. PM was used to p r o d u c e two new WC h a r d m e t a l s , WC + stainless steel a n d WC + Fe-Co-NiMoB by h o t p r e s s i n g a n d sintering. The microstructures and physical a n d mechanical p r o p e r t i e s were evaluated. The h a r d n e s s is similar to t h a t of WC + Co. The e x p e r i m e n t a l alloys are h e a t t r e a t a b l e a n d m a r t e n s i t e can be formed in the matrix resulting in improved m e c h a n i c a l properties. It is suggested t h a t t h e new compositions m a y find use in wear r e s i s t a n t applications. RELATIONSHIPS B E T W E E N S T R E N G T H AND RESIDUAL S T R E S S E S OF C E M E N T E D CARBIDES S U B J E C T E D TO P E E N I N G TREATMENT
I~ Kamachi, T. Yamamoto, (Kinki University, Higashi-Osaka, J a p a n ) , J. Japan Inst. of Metals, Vol 53, No 10, 1990, 1131-1135. In Japanese. A t t e n t i o n is d r a w n to t h e fact t h a t c e m e n t e d carbides have high s t r e n g t h b u t little or no plasticity a n d to t h e need to t r e a t t h e factors influencing m e c h a n i c a l p r o p e r t i e s , e.g. voids, in a s t a t i s t i c a l manner. The p a p e r describes e x p e r i m e n t s in which WC-5 to 15%Co alloys have b e e n s h o t b l a s t e d a n d t h e r e s i d u a l surface stresses measured. The effect of surface stresses on t h e m e c h a n i c a l properties are discussed. SINTERING AND HIGH TEMPERATURE EXTRUSION OF HARD ALLOYS WITH DAMPING B I N D E R S
S.N. Kulkov, et al, (Siberian B r a n c h of USSR Academy of Sciences, Tomsk, USSR), Sc/ence ofSintering, Vol 22, No 2, 1990, 65-72. The s i n t e r i n g a n d h i g h t e m p e r a t u r e e x t r u s i o n of TiC-NiTi c e m e n t e d carbide is considered. Three sintering m e c h a n i s m s are identified a n d are r e l a t e d to t h e alloy composition. High temperature