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Secondary pressing of injection moulded part for improvement in sinterability
PM described. The parameters studied included process variables, alloy composition, chip formation, and power consumption during machining. The additives used were S, Cu, Mn02 and MoS2. It was noted that additives w e r e m o r e e f f e c t i v e w h e n a d d e d in combination than when used singly.
Mechanical alloying EFFECTS OF MILLING CONDITIONS ON SYNTHESIS OF HIGH TEMPERATURE INTERMETALLIC MATERIALS
A. Calka (Australian National University, Canberra, Australia). A study of the formation of metal carbides or nitrides b y MA i n hydrocarbons, N or ammonia was described. Effects of process conditions on nanostructural mixtures containing C, N and H were investigated. Effects of heat treatment of milled powders were determined. Effects of H in the milled p o w d e r s on s i n t e r i n g and m e c h a n i c a l properties were discussed. MECHANISMS OF DENSIFICATION OF MECHANICALLY ALLOYED NICKEL ALUMINIDE BASED MATERIALS
H. Ardy, P. Nash (Illinois Inst of Technology, Chicago, USA). A study in which Ni and Al powders were MA and consolidated by hot pressing was described. The MA powders contained A1203 which gave dispersion strengthening of the NiAl. Compressibility and sintering behaviour were studied by cold compaction, cold isostatic pressing followed sintering. The data were used to c o n s t r u c t d e n s i f i c a t i o n maps. Effects of process conditions were discussed. CONSOLIDATION OF MECHANICALLY ALLOYED TITANIUM ALUMINIDES
H. Kim, P. Nash (Illinois Inst of Technology, Chicago, USA). MA was used to produce Ti aluminide p o w d e r s c o n t a i n i n g d i s p e r s o i d s . The powders were consolidated by CIP and s i n t e r i n g o r by h o t p r e s s i n g . T h e structures were shown to be very fine, c o n s i s t i n g of TiA12, Ti3A1 a n d o x i d e dispersoids. Heat treatment was shown to alter the structures. Consolidation was a n a l y s e d u s i n g A s h b y ' s HIP m o d e l . Compaction, sintering and HIP maps were compiled from the experimental data. COMPACTION OF MECHANICALLY MILLED PURE NANOCRYSTALLINE TUNGSTEN POWDER
E. Ivanov, C.E. Wickersham (Tosoh SMD Inc, Grove City, Ohio, USA). The use of MA in an inert gas to
44 MPR March 1994
LITERATURE
REVIEW
synthesize the disilicides of W and Mo was reported. W or Mo mills and balls were used to avoid contamination. Metastable phases were detected in the milled powders. HIP was u s e d for c o n s o l i d a t i o n a n d t h e properties of the compacted powders were described. MECHANICAL ALLOYING OF INTERMETALLIC MATERIALS
J.V. Wood et al (University of Nottingham, UK). An investigation of mechanical alloying of Ti, Ni and Fe base intermetallic alloys was described. A model for d e v e l o p m e n t of t h e p h a s e s found was presented. The powders were compacted by HIP or by reactive sintering. A s u r v e y of t h e s t r u c t u r e s d e t e c t e d was given. EFFECTS OF THE ADDITIONS OF DISPERSOIDS IN THE PROPERTIES OF PM COPPER-TITANIUM ALLOYS
C. Sauer et al (Dresden University of Technology, Dresden, Germany). It w a s r e p o r t e d t h a t d i s p e r s i o n s t r e n g t h e n e d and age h a r d e n a b l e CuTi alloy p o w d e r s h a d b e e n p r e p a r e d by attritor milling followed by cold compaction and reactive sintering. High v a l u e s of m e c h a n i c a l p r o p e r t i e s were reported and these were attributed to t h e dual effects of age h a r d e n i n g and dispersion strengthening. The dispersoids were shown to be TiC and TiN about 100 nm in size. GRAIN REFINING OF TWO-PHASE STAINLESS STEELS BY MECHANICAL MILLING
S. Takaki, Y. Kimura (Kyushi University, Japan). It was shown that mechanical grinding of 8/7 24%Cr-8%Ni stainless steel p o w d e r r e s u l t s in g r a i n r e f i n e m e n t . The raw powder was said to be ferritic and became duplex after heat treatment. The large strains induced by the milling was found to promote y phase nucleation. PROPERTIES OF MECHANICALLY ALLOYED HIGH SPEED STEELS WITH DISPERSOIDS
YJ. Kim et al (Korea Inst of Machinery and Metals, Chungwon Kyungnam, Korea). A study of the effects of dispersoids on the mechanical properties of MA and consolidated high speed steels was d e s c r i b e d . The d i s p e r s o i d s w e r e r e p o r t e d to s t a b i l i z e fine s t r u c t u r e s but also to inhibit sintering. Full density could not be attained by sintering alone in presence of the dispersoids. Mechanical
p r o p e r t i e s were c o m p a r e d in r e l a t i o n to t h e c o n c e n t r a t i o n a n d t y p e s of dispersoids.
Injection moulding ORIENTATION FORMING OF FERRITE POWDERS USING A BINDER
I~ Okimoto et al (Industrial Research Inst, Kyushi, Japan). The moulding, in a magnetic field, of ferromagnetic Sr ferrite, m i x e d with a polymer binder was reported. The oriented material was debound and sintered. An i n c r e a s e in f l u x d e n s i t y to 4 4 0 0 G, compared with 3800 G for the material not moulded in the magnetic field, was reported SECONDARY PRESSING OF INJECTION MOULDED PART FOR IMPROVEMENT IN SINTERABILITY
I-H, Moon et al (Hanyang University, Seoul, Korea). The production of MIM parts from sieve sized powders was described. The brown parts were isostatically pressed to improve densification during sintering. This resulted in increased sintered density. The effects on mechanical properties were discussed. EVOLUTION OF GASES AND SINTERING BEHAVIOUR IN ATOMIZED IRON POWDER FOR INJECTION MOULDING
S. Igarashi et al (Sumitomo Metal Mining Co Ltd, Tokyo, Japan). Studies of the evolution of gas from atomized powder were described. It .was considered that evolution of gases during sintering of MIM parts influenced the final density. Correlations between gas evolution and sintering density were presented. METHODS FOR ENHANCEMENT OF SINTERING OF INJECTION MOULDED PURE IRON COMPACTS
K.S. Hwand, R.F. Lau (National Taiwan University, Taipei, Taiwan). It was p o i n t e d o u t t h a t i n j e c t i o n moulded pure Fe parts may only attain densities of about 90% after debinding and sintering. Methods to improve this were investigated including alloying with Ni or Cu, addition of oxides and use of high density polyethylene as a b i n d e r c o m p o n e n t . D i l a t o m e t r y was used to show t h a t Ni and Cu inhibit low t e m p e r a t u r e sintering but enhance sintering at higher temperatures. Oxide additions and binder residues i n h i b i t e d g r a i n growth. I n c r e a s e s in density, using these methods, of about 5% were reported.
Mechanical alloying EFFECTS OF MILLING CONDITIONS ON SYNTHESIS OF HIGH TEMPERATURE INTERMETALLIC MATERIALS
A. Calka (Australian National University, Canberra, Australia). A study of the formation of metal carbides or nitrides b y MA i n hydrocarbons, N or ammonia was described. Effects of process conditions on nanostructural mixtures containing C, N and H were investigated. Effects of heat treatment of milled powders were determined. Effects of H in the milled p o w d e r s on s i n t e r i n g and m e c h a n i c a l properties were discussed. MECHANISMS OF DENSIFICATION OF MECHANICALLY ALLOYED NICKEL ALUMINIDE BASED MATERIALS
H. Ardy, P. Nash (Illinois Inst of Technology, Chicago, USA). A study in which Ni and Al powders were MA and consolidated by hot pressing was described. The MA powders contained A1203 which gave dispersion strengthening of the NiAl. Compressibility and sintering behaviour were studied by cold compaction, cold isostatic pressing followed sintering. The data were used to c o n s t r u c t d e n s i f i c a t i o n maps. Effects of process conditions were discussed. CONSOLIDATION OF MECHANICALLY ALLOYED TITANIUM ALUMINIDES
H. Kim, P. Nash (Illinois Inst of Technology, Chicago, USA). MA was used to produce Ti aluminide p o w d e r s c o n t a i n i n g d i s p e r s o i d s . The powders were consolidated by CIP and s i n t e r i n g o r by h o t p r e s s i n g . T h e structures were shown to be very fine, c o n s i s t i n g of TiA12, Ti3A1 a n d o x i d e dispersoids. Heat treatment was shown to alter the structures. Consolidation was a n a l y s e d u s i n g A s h b y ' s HIP m o d e l . Compaction, sintering and HIP maps were compiled from the experimental data. COMPACTION OF MECHANICALLY MILLED PURE NANOCRYSTALLINE TUNGSTEN POWDER
E. Ivanov, C.E. Wickersham (Tosoh SMD Inc, Grove City, Ohio, USA). The use of MA in an inert gas to
44 MPR March 1994
LITERATURE
REVIEW
synthesize the disilicides of W and Mo was reported. W or Mo mills and balls were used to avoid contamination. Metastable phases were detected in the milled powders. HIP was u s e d for c o n s o l i d a t i o n a n d t h e properties of the compacted powders were described. MECHANICAL ALLOYING OF INTERMETALLIC MATERIALS
J.V. Wood et al (University of Nottingham, UK). An investigation of mechanical alloying of Ti, Ni and Fe base intermetallic alloys was described. A model for d e v e l o p m e n t of t h e p h a s e s found was presented. The powders were compacted by HIP or by reactive sintering. A s u r v e y of t h e s t r u c t u r e s d e t e c t e d was given. EFFECTS OF THE ADDITIONS OF DISPERSOIDS IN THE PROPERTIES OF PM COPPER-TITANIUM ALLOYS
C. Sauer et al (Dresden University of Technology, Dresden, Germany). It w a s r e p o r t e d t h a t d i s p e r s i o n s t r e n g t h e n e d and age h a r d e n a b l e CuTi alloy p o w d e r s h a d b e e n p r e p a r e d by attritor milling followed by cold compaction and reactive sintering. High v a l u e s of m e c h a n i c a l p r o p e r t i e s were reported and these were attributed to t h e dual effects of age h a r d e n i n g and dispersion strengthening. The dispersoids were shown to be TiC and TiN about 100 nm in size. GRAIN REFINING OF TWO-PHASE STAINLESS STEELS BY MECHANICAL MILLING
S. Takaki, Y. Kimura (Kyushi University, Japan). It was shown that mechanical grinding of 8/7 24%Cr-8%Ni stainless steel p o w d e r r e s u l t s in g r a i n r e f i n e m e n t . The raw powder was said to be ferritic and became duplex after heat treatment. The large strains induced by the milling was found to promote y phase nucleation. PROPERTIES OF MECHANICALLY ALLOYED HIGH SPEED STEELS WITH DISPERSOIDS
YJ. Kim et al (Korea Inst of Machinery and Metals, Chungwon Kyungnam, Korea). A study of the effects of dispersoids on the mechanical properties of MA and consolidated high speed steels was d e s c r i b e d . The d i s p e r s o i d s w e r e r e p o r t e d to s t a b i l i z e fine s t r u c t u r e s but also to inhibit sintering. Full density could not be attained by sintering alone in presence of the dispersoids. Mechanical
p r o p e r t i e s were c o m p a r e d in r e l a t i o n to t h e c o n c e n t r a t i o n a n d t y p e s of dispersoids.
Injection moulding ORIENTATION FORMING OF FERRITE POWDERS USING A BINDER
I~ Okimoto et al (Industrial Research Inst, Kyushi, Japan). The moulding, in a magnetic field, of ferromagnetic Sr ferrite, m i x e d with a polymer binder was reported. The oriented material was debound and sintered. An i n c r e a s e in f l u x d e n s i t y to 4 4 0 0 G, compared with 3800 G for the material not moulded in the magnetic field, was reported SECONDARY PRESSING OF INJECTION MOULDED PART FOR IMPROVEMENT IN SINTERABILITY
I-H, Moon et al (Hanyang University, Seoul, Korea). The production of MIM parts from sieve sized powders was described. The brown parts were isostatically pressed to improve densification during sintering. This resulted in increased sintered density. The effects on mechanical properties were discussed. EVOLUTION OF GASES AND SINTERING BEHAVIOUR IN ATOMIZED IRON POWDER FOR INJECTION MOULDING
S. Igarashi et al (Sumitomo Metal Mining Co Ltd, Tokyo, Japan). Studies of the evolution of gas from atomized powder were described. It .was considered that evolution of gases during sintering of MIM parts influenced the final density. Correlations between gas evolution and sintering density were presented. METHODS FOR ENHANCEMENT OF SINTERING OF INJECTION MOULDED PURE IRON COMPACTS
K.S. Hwand, R.F. Lau (National Taiwan University, Taipei, Taiwan). It was p o i n t e d o u t t h a t i n j e c t i o n moulded pure Fe parts may only attain densities of about 90% after debinding and sintering. Methods to improve this were investigated including alloying with Ni or Cu, addition of oxides and use of high density polyethylene as a b i n d e r c o m p o n e n t . D i l a t o m e t r y was used to show t h a t Ni and Cu inhibit low t e m p e r a t u r e sintering but enhance sintering at higher temperatures. Oxide additions and binder residues i n h i b i t e d g r a i n growth. I n c r e a s e s in density, using these methods, of about 5% were reported.