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Manufacture of tool steels for plastics injection moulding machine dies
PM
properties are explained in terms of the impurities and non-uniform distribution within the particles. CHARACTERISTICS OF A Ni BASE HEAT RESISTANT ALLOY AFTER LIQUID PHASE SINTERING
A.P. Gulyaev, et al, Metalloved, Term Obrab, Met, No 8, 1990, 51-56. In Russian. The effects of liquid phase sintering and HIP on the structure and properties of a PM Ni alloy, Ni-10%Co-16%Cr-12%A1-2%Ti2%Mo-2%W-l%Nb, were investigated. The powder structure was 100% 7 phase. After processing Ni3A1, 7' phase, carbides and nitrides were detected in t h e microstructure and the mechanical properties were reduced. Heat treatment restored the mechanical properties. APPLICATION OF COMBUSTION SYNTHESIS TO PRODUCTION OF INTERMETALLIC SHAPE MEMORY ALLOYS (SMA) IN Ni-Ti
JZ. Moore, H.C. Yi, (University of Auckland, New Zealand), Materials Science Forum, 1990, 56-58 and 637-642. Combustion synthesis makes use of the exothermie heat of reaction to make certain intermetaUic compounds and has been applied to produce NiTi shape memory alloys from equiatomic mixtures of Ni and Ti powders. The alloys were completely fused during combustion and could be r e a d i l y f a b r i c a t e d by r o l l i n g . T h e advantage of the technique lies in the ability to co n t ro l c o m p o s i t i o n more accurately than is possible with ingot technology. The effect of Ni particle size on SMA temperatures which were in the range 20 to 100°C, was studied. It was also found possible to control SMA temperature by additions of a third element to the alloy.
Tungsten llllll
III
EFFECTS OF DOPING ON HIGH TEMPERATURE STRENGTH OF PM TUNGSTEN WIRES
K. Tanoue, et al, (Kyushi Institute of Technology, Kitaktushu, Japan), J. Japan Inst. of Metals, Vol 54, No 9, 1990, 991-998. In Japanese. The c h a r a c t e r i s t i c s of s e c o n d a r y recrystallized grains grown in W wire with and without doping agents have been studied at different heating rates. The creep strength has been measured with respect to the secondary recwstailization. Doped wire with large grain size shows transgranular fracture but in the nondoped wire the fracture is intergranular. Creep stress exponents were calculated. It is suggested that bubbles may be present in the doped wire and that the configuration of the grains affects the creep stress exponent. It was shown that the presence
74 MPR May 1991
LITERATURE
REVIEW
of elongated grains in wire suppresses creep strain at high temperatures. PRODUCTION OF FINE W AND WC POWDERS BY VAPOUR PHASE REACTION
G.Y. Zhao, et al, (State University of New York, USA), J. Less Common Metals, Vol. 163, No 2, 1990, 269-280. Vapour phase reactions to produce ultrafine powders of refractory metals and compounds are described. W and WC have been produced on a laboratory scale. The powders were found to be spherical in shape, free from pores and with a narrow size distribution range. The characteristics of the powders have been correlated with process parameters.
Electrical and Magnetic Materials PM MATERIALS WITH PRESCRIBED ELECTRICAL AND MAGNETIC PROPERTIES FOR APPLICATION IN ELECTRIC INDUCTION MOTOR COMPONENTS
E.A. Anisimova, et al, Poroshkavaya Metallurgiya, No 9, 1990, 87-91. In Russian. The production of PM metal/ceramic components, for electrical machines, with specified electrical and magnetic properties, is described with respect to production parameters. Parts have been tested in experimental machines. MEASUREMENT OF ELECTRICAL CONDUCTIVITY OF SiC POWDERS BY ELECTRON PARAMAGNETIC RESONANCE
A.S. Kheifets, et al, P o r o s h k a v a y a Metailurgiya, No 9, 1990, 95-99. In Russian. Electrical properties of SiC powders were measured by electron paramagnetic resonance with regard to additives used in manufacture. The electrical conductivity was found to be closely related to the concentration of additives used. The effect of N2 on conductivity of SiC was measured. EFFECT OF SUBSTITUTION OF OTHER ELEMENTS FOR Nd ON MAGNETIC PROPERTIES OF NdFeB SINTERED MAGNETS
M. Leonowicz, (Polytechnic of Warsaw, Poland), Archives of Metallurgy, Vol 35, No 3, 1990, 475-480. The effects of elements added in partial substitution for Nd on the magnetic properties of 16%(Nd +X)77%(85%Fe+15%Co)-7%B sintered magnets have been studied. (X = Ga, Nb, Zr, Ti, Cr, Mo or Dy). Remenance and coercive force were reduced and the d e c l i n e in m a g n e t i c p r o p e r t i e s is a t t r i b u t e d to decrease in anisotropy,
saturation magnetization and the presence of magnetically soft precipitates in the structure.
Hard Materials and Tool Steels EFFECT OF EXTENDED HEATING ON OXIDATION OF TITANIUM CARBIDE ALLOYS
V.B. Voitovich, et al, Poroshkavaya MetaUurgiya, No 9, 1990, 41-46. In Russian. The oxidation of TiC has been studied during long exposure to air at 1000°C. A two layer scale was formed and was examined by scanning electron microscopy with microanalysis facilities used to determine impurity (Fe, Co, Cr and Si) distribution. The outer layer of the scale was found to be enriched in impurities. The impurities were also found to be effective in the promotion of sintering. STRENGTH OF A DIAMOND BEARING COMPOSITE LAYER ON A TUNGSTEN CARBIDE SUBSTRATE
D.K. Bronshtein, et al, Poroshkavaya Metallurgiya, No 9, 1990, 64-68. In Russian. A diamond bearing hard material has been applied to a high temperature WC substrate by hot compaction, and physical and mechanical properties measured. Improvements in crack resistance and bend strength, in comparison with low t e m p e r a t u r e WC, w i t h a s u p e r h a r d coating, are reported. Reduced thermal expansion is also reported. ELECTRON STRUCTURE OF NONSTOICHIOMETRIC TUNGSTEN CARBIDES W2Cx
O.Y. Khizhun, et al, P o r o s h k a v a y a MetaUurgiya, No 9, 1990, 77-83. In Russian. Th e e l e c t r o n s t r u c t u r e of n o n stoichiometric tungsten carbide has been determined by photoelectron spectroscopy and X-ray e m i s s i o n and a b s o r p t i o n spectroscopy. Hybridization of electron states was observed. Reduction of %C r e s u l t s in l i n e b r o a d e n i n g in t h e photoelectron spectra. Charge transfer from W atoms to C atoms was detected. MANUFACTURE OF TOOL STEELS FOR PLASTICS INJECTION MOULDING MACHINE DIES
H. Esaka, et al, (Kobe Steel, Japan), Kobelco Technology Review, No 9, 1990, 19-23. The production of injection moulding machine dies in two tool steels, Fe-2%C18%Cr-2%Mo-l%V and Fe-l%C-18%Crl%Mo-l%V, is described. Gas atomized powders and HIP processing were used. The alloys were reported to have good mechanical properties, high wear and
corrosion resistance and could be polished to high reflectivity and flatness.
CHARACTERISTICS A N D APPLICATIONS OF A N E W Fe-BASE HARD ALLOY
M. Hirano, H. Kawatani, (Kobe Steel, Japan), Kobelco Technology Review, No 9, 1990, 29-32. The production of a new hard alloy made from high speed steel powder (HSS) and 17% TiN and VC by high energy ball milling, CIP, sintering and HIP. The structure is reported to be a fine dispersion of the hard particles in a HSS matrix. The Rockwell hardness exceeds 72 Rc and bend strength is above 200 Kgf/mm 2. The life of punches made from the new alloy is claimed to be three times that of HSS.
S T R E N G T H A N D RESIDUAL S T R E S S E S IN C E M E N T E D C A R B I D E S S U B J E C T E D TO ABRASIVE PARTICLE T R E A T M E N T
K. Kamachi, T. Yamamoto, (Kinki University, Osaka, Japan), J. Japan Inst. of Metals, Vol 54, No 10, 1990, 1131-1135. In Japanese. The paper draws attention to the need to treat defects, such as voids which may cause fracture in cemented carbides, in a statistical manner. In this study, changes in fracture properties of cemented WC-(5 to 15%)Co, which had been subjected to bombardment by hard abrasive particles, were investigated. In particular, the effects of residual stresses, p r o d u c e d by t h e blasting media of differing hardness, on the fracture properties were considered. THERMAL E X P A N S I O N A N D S T R E N G T H O F INVAR43ORDIERITE S I N T E R E D C E R M E T COMPACTS
N. Ikeda, et al, (University of Tokyo, Japan),
J. Japan Inst. of Metals, Vol 54, No 10, 1990, 1136-1141. In Japanese. Sinterability, t h e r m a l expansion and t r a n s v e r s e r u p t u r e s t r e n g t h (TRS) of invar-cordierite compacts made from fine Ni, Fe a n d c o r d i e r i t e p o w d e r s w e r e measured in relationship to the amount of B added as a sintering aid. It was shown that at least 0.2wt%B is required to give an i m p r o v e m e n t in sinterability. T h e r m a l expansion was reduced by an increase in the proportion of cordierite but at the expense of a reduction in strength. CLASSIFICATION O F WC POWDERS FOR P R O D U C T I O N O F HARD ALLOYS
T.B. Gorbacheva, et al, Tsvetn. MetaU, No 3, 1990, 70-74. In Russian. A study was made of the effects of reduction temperatures of WO, and of the carburization temperature to WC, on the morphology, granularity, lattice perfection
and c o m p o s i t i o n of t h e WC p o w d e r s produced. Measurements were m a d e of p a r t i c l e size d i s t r i b u t i o n and specific surface for all stages in the production of WC from WO. The WC lattice was found to have a high degree of perfection. The impurity content of the WC declined with increase in carburization temperature. S I N T E R I N G O F HIGH S P E E D STEEL ( H S S ) POWDER COMPACTS
A.N. Shumilin, et al, (Moscow Inst. of Steel and Alloys, USSR), Izvestia E U.Z Chernaya Metall, No 3, 1990, 102-103. In Russian. A comparison is made of water and gas atomized HSS powders with respect to the production of sintered materials. Differences in compacting pressures were noted. Water atomized powders were said to have an advantage although coated with an oxide layer which must be reduced during sintering. The kinetics of the reduction were also studied. CUTTING P E R F O R M A N C E O F PM HIGH S P E E D STEELS ( H S S )
L. Zima, Strojfr. Vyroba, Vol 37, No 12, 1989, 45-48. In Czech. A study of the cutting performance of HSS is described. The effects of variables in p r e s s i n g a n d s i n t e r i n g on s t r u c t u r e , properties and cutting were investigated. PM high speed steels (HSS) were found to be comparable in efficiency with HSS made by melting and casting. In the case of face milling, PM HSS c o m p a r e d well w i t h cemented carbides. A S P E C T OF T H E P R O D U C T I O N OF F I N I S H E D P R O D U C T S MADE FROM HIGH S P E E D STEEL ( H S S ) POWDER
K-D. Lietzmann, et al, (Bergakademie, Frieberg, Germany), Neue HO:tte, Vol 35, No 7, 255-262. In German. A study was made of gas and water atomized high speed steel (HSS) powders and it is reported that the water atomized powders are rougher than the gas atomized. On pressing of the gas atomized powders there was greater movement of the powder in the die and this led to a greater incidence of cracking. D e n s i f i c a t i o n of t h e two powders was compared and it is suggested that in the case of the water atomized powders optimum densification is obtained by a combination of forging and rolling.
Intermetallic Materials rrH,III
H
II
MODELLING O F HIP CONSOLIDATION O F Ni A L U M I N I D E POWDERS
P~N. Wright, et al, (E.G. & G, Idaho Inc. Idaho Falls, USA), Powder Metallurgy, Vol 33, No 3, 1990, 253-259.
A model has been constructed for the HIP consolidation of Ni3A1 powders. The additive effects of plastic flow, power law creep, boundary diffusion and NabarroHerring and Goble creep are taken into account. HIP maps have been derived which d e s c r i b e t h e HIP c o n s o l i d a t i o n w i t h reasonable accuracy compared with experimental results. Finite element analysis was used as an extension to the HIP map approach.
P R O D U C T I O N OF N | T i SHAPE MEMORY ALLOYS ( S M A ) BY C O M B U S T I O N SYNTHESIS
M. Otaguchi, et al, (National Research Inst. for Metals, Tokyo, Japan), J. Japan Inst. of Metals, Vol 54, No 2, 1990, 214-223. In Japanese. The use of PM to produce NiTi shape memory alloys (SMA) with the objective of attaining closer control of composition is described. Small changes in composition result in large changes in SMA temperature. Combustion synthesis was used. The alloy was found to consist of 100% NiTi which could be HIPed to full density. Wire made from the alloy showed a SMA temperature of about IO0°C.
APPLICATION O F C O M B U S T I O N SYNTHESIS TO P R O D U C T I O N OF ZrNi INTERMETALLIC COMPOUND
C. Nashimura, et al, (National Research Inst. for Metals, Tokyo, Japan), J. Japan Inst. of Metals, Vol 54, No 5, 1990, 603-610. In English. ZrNi i n t e r m e t a l l i c c o m p o u n d s were produced by combustion synthesis and the effects of preheat temperature, in the range 25 to 400°C were studied. The product was porous when the preheat temperature was 100°C and was completely fused at 400°C. The products were found to contain ZrNi, ZrgNi11 and Zr2Ni according to composition of the powder mixture and the process conditions.
STRUCTURE AND P R O P E R T I E S OF Ti ALUMINIDE COMPACTS P R O D U C E D BY HOT P R E S S I N G MECHANICALLY ALLOYED POWDER
& Miyazaki, et al, (Sony Ltd, Tokyo, Japan), J. Japan Inst. of Metals, Vol 54, No 11, 1990, 1279-1283. In Japanese. A m i x t u r e c o n t a i n i n g 70at%Ti and 30%A1 were mechanically alloyed (MA) and hot pressed for 1 hour at 900°C. Near full density was attained. It was shown that the compact consisted of TiaAl with a mean grain size of 1.5~m. The alloy had high compressive strength and low ductility. Recrystallization and grain r e f i n e m e n t occurred during hot working at 900°C.
MPR May 1991 75
properties are explained in terms of the impurities and non-uniform distribution within the particles. CHARACTERISTICS OF A Ni BASE HEAT RESISTANT ALLOY AFTER LIQUID PHASE SINTERING
A.P. Gulyaev, et al, Metalloved, Term Obrab, Met, No 8, 1990, 51-56. In Russian. The effects of liquid phase sintering and HIP on the structure and properties of a PM Ni alloy, Ni-10%Co-16%Cr-12%A1-2%Ti2%Mo-2%W-l%Nb, were investigated. The powder structure was 100% 7 phase. After processing Ni3A1, 7' phase, carbides and nitrides were detected in t h e microstructure and the mechanical properties were reduced. Heat treatment restored the mechanical properties. APPLICATION OF COMBUSTION SYNTHESIS TO PRODUCTION OF INTERMETALLIC SHAPE MEMORY ALLOYS (SMA) IN Ni-Ti
JZ. Moore, H.C. Yi, (University of Auckland, New Zealand), Materials Science Forum, 1990, 56-58 and 637-642. Combustion synthesis makes use of the exothermie heat of reaction to make certain intermetaUic compounds and has been applied to produce NiTi shape memory alloys from equiatomic mixtures of Ni and Ti powders. The alloys were completely fused during combustion and could be r e a d i l y f a b r i c a t e d by r o l l i n g . T h e advantage of the technique lies in the ability to co n t ro l c o m p o s i t i o n more accurately than is possible with ingot technology. The effect of Ni particle size on SMA temperatures which were in the range 20 to 100°C, was studied. It was also found possible to control SMA temperature by additions of a third element to the alloy.
Tungsten llllll
III
EFFECTS OF DOPING ON HIGH TEMPERATURE STRENGTH OF PM TUNGSTEN WIRES
K. Tanoue, et al, (Kyushi Institute of Technology, Kitaktushu, Japan), J. Japan Inst. of Metals, Vol 54, No 9, 1990, 991-998. In Japanese. The c h a r a c t e r i s t i c s of s e c o n d a r y recrystallized grains grown in W wire with and without doping agents have been studied at different heating rates. The creep strength has been measured with respect to the secondary recwstailization. Doped wire with large grain size shows transgranular fracture but in the nondoped wire the fracture is intergranular. Creep stress exponents were calculated. It is suggested that bubbles may be present in the doped wire and that the configuration of the grains affects the creep stress exponent. It was shown that the presence
74 MPR May 1991
LITERATURE
REVIEW
of elongated grains in wire suppresses creep strain at high temperatures. PRODUCTION OF FINE W AND WC POWDERS BY VAPOUR PHASE REACTION
G.Y. Zhao, et al, (State University of New York, USA), J. Less Common Metals, Vol. 163, No 2, 1990, 269-280. Vapour phase reactions to produce ultrafine powders of refractory metals and compounds are described. W and WC have been produced on a laboratory scale. The powders were found to be spherical in shape, free from pores and with a narrow size distribution range. The characteristics of the powders have been correlated with process parameters.
Electrical and Magnetic Materials PM MATERIALS WITH PRESCRIBED ELECTRICAL AND MAGNETIC PROPERTIES FOR APPLICATION IN ELECTRIC INDUCTION MOTOR COMPONENTS
E.A. Anisimova, et al, Poroshkavaya Metallurgiya, No 9, 1990, 87-91. In Russian. The production of PM metal/ceramic components, for electrical machines, with specified electrical and magnetic properties, is described with respect to production parameters. Parts have been tested in experimental machines. MEASUREMENT OF ELECTRICAL CONDUCTIVITY OF SiC POWDERS BY ELECTRON PARAMAGNETIC RESONANCE
A.S. Kheifets, et al, P o r o s h k a v a y a Metailurgiya, No 9, 1990, 95-99. In Russian. Electrical properties of SiC powders were measured by electron paramagnetic resonance with regard to additives used in manufacture. The electrical conductivity was found to be closely related to the concentration of additives used. The effect of N2 on conductivity of SiC was measured. EFFECT OF SUBSTITUTION OF OTHER ELEMENTS FOR Nd ON MAGNETIC PROPERTIES OF NdFeB SINTERED MAGNETS
M. Leonowicz, (Polytechnic of Warsaw, Poland), Archives of Metallurgy, Vol 35, No 3, 1990, 475-480. The effects of elements added in partial substitution for Nd on the magnetic properties of 16%(Nd +X)77%(85%Fe+15%Co)-7%B sintered magnets have been studied. (X = Ga, Nb, Zr, Ti, Cr, Mo or Dy). Remenance and coercive force were reduced and the d e c l i n e in m a g n e t i c p r o p e r t i e s is a t t r i b u t e d to decrease in anisotropy,
saturation magnetization and the presence of magnetically soft precipitates in the structure.
Hard Materials and Tool Steels EFFECT OF EXTENDED HEATING ON OXIDATION OF TITANIUM CARBIDE ALLOYS
V.B. Voitovich, et al, Poroshkavaya MetaUurgiya, No 9, 1990, 41-46. In Russian. The oxidation of TiC has been studied during long exposure to air at 1000°C. A two layer scale was formed and was examined by scanning electron microscopy with microanalysis facilities used to determine impurity (Fe, Co, Cr and Si) distribution. The outer layer of the scale was found to be enriched in impurities. The impurities were also found to be effective in the promotion of sintering. STRENGTH OF A DIAMOND BEARING COMPOSITE LAYER ON A TUNGSTEN CARBIDE SUBSTRATE
D.K. Bronshtein, et al, Poroshkavaya Metallurgiya, No 9, 1990, 64-68. In Russian. A diamond bearing hard material has been applied to a high temperature WC substrate by hot compaction, and physical and mechanical properties measured. Improvements in crack resistance and bend strength, in comparison with low t e m p e r a t u r e WC, w i t h a s u p e r h a r d coating, are reported. Reduced thermal expansion is also reported. ELECTRON STRUCTURE OF NONSTOICHIOMETRIC TUNGSTEN CARBIDES W2Cx
O.Y. Khizhun, et al, P o r o s h k a v a y a MetaUurgiya, No 9, 1990, 77-83. In Russian. Th e e l e c t r o n s t r u c t u r e of n o n stoichiometric tungsten carbide has been determined by photoelectron spectroscopy and X-ray e m i s s i o n and a b s o r p t i o n spectroscopy. Hybridization of electron states was observed. Reduction of %C r e s u l t s in l i n e b r o a d e n i n g in t h e photoelectron spectra. Charge transfer from W atoms to C atoms was detected. MANUFACTURE OF TOOL STEELS FOR PLASTICS INJECTION MOULDING MACHINE DIES
H. Esaka, et al, (Kobe Steel, Japan), Kobelco Technology Review, No 9, 1990, 19-23. The production of injection moulding machine dies in two tool steels, Fe-2%C18%Cr-2%Mo-l%V and Fe-l%C-18%Crl%Mo-l%V, is described. Gas atomized powders and HIP processing were used. The alloys were reported to have good mechanical properties, high wear and
corrosion resistance and could be polished to high reflectivity and flatness.
CHARACTERISTICS A N D APPLICATIONS OF A N E W Fe-BASE HARD ALLOY
M. Hirano, H. Kawatani, (Kobe Steel, Japan), Kobelco Technology Review, No 9, 1990, 29-32. The production of a new hard alloy made from high speed steel powder (HSS) and 17% TiN and VC by high energy ball milling, CIP, sintering and HIP. The structure is reported to be a fine dispersion of the hard particles in a HSS matrix. The Rockwell hardness exceeds 72 Rc and bend strength is above 200 Kgf/mm 2. The life of punches made from the new alloy is claimed to be three times that of HSS.
S T R E N G T H A N D RESIDUAL S T R E S S E S IN C E M E N T E D C A R B I D E S S U B J E C T E D TO ABRASIVE PARTICLE T R E A T M E N T
K. Kamachi, T. Yamamoto, (Kinki University, Osaka, Japan), J. Japan Inst. of Metals, Vol 54, No 10, 1990, 1131-1135. In Japanese. The paper draws attention to the need to treat defects, such as voids which may cause fracture in cemented carbides, in a statistical manner. In this study, changes in fracture properties of cemented WC-(5 to 15%)Co, which had been subjected to bombardment by hard abrasive particles, were investigated. In particular, the effects of residual stresses, p r o d u c e d by t h e blasting media of differing hardness, on the fracture properties were considered. THERMAL E X P A N S I O N A N D S T R E N G T H O F INVAR43ORDIERITE S I N T E R E D C E R M E T COMPACTS
N. Ikeda, et al, (University of Tokyo, Japan),
J. Japan Inst. of Metals, Vol 54, No 10, 1990, 1136-1141. In Japanese. Sinterability, t h e r m a l expansion and t r a n s v e r s e r u p t u r e s t r e n g t h (TRS) of invar-cordierite compacts made from fine Ni, Fe a n d c o r d i e r i t e p o w d e r s w e r e measured in relationship to the amount of B added as a sintering aid. It was shown that at least 0.2wt%B is required to give an i m p r o v e m e n t in sinterability. T h e r m a l expansion was reduced by an increase in the proportion of cordierite but at the expense of a reduction in strength. CLASSIFICATION O F WC POWDERS FOR P R O D U C T I O N O F HARD ALLOYS
T.B. Gorbacheva, et al, Tsvetn. MetaU, No 3, 1990, 70-74. In Russian. A study was made of the effects of reduction temperatures of WO, and of the carburization temperature to WC, on the morphology, granularity, lattice perfection
and c o m p o s i t i o n of t h e WC p o w d e r s produced. Measurements were m a d e of p a r t i c l e size d i s t r i b u t i o n and specific surface for all stages in the production of WC from WO. The WC lattice was found to have a high degree of perfection. The impurity content of the WC declined with increase in carburization temperature. S I N T E R I N G O F HIGH S P E E D STEEL ( H S S ) POWDER COMPACTS
A.N. Shumilin, et al, (Moscow Inst. of Steel and Alloys, USSR), Izvestia E U.Z Chernaya Metall, No 3, 1990, 102-103. In Russian. A comparison is made of water and gas atomized HSS powders with respect to the production of sintered materials. Differences in compacting pressures were noted. Water atomized powders were said to have an advantage although coated with an oxide layer which must be reduced during sintering. The kinetics of the reduction were also studied. CUTTING P E R F O R M A N C E O F PM HIGH S P E E D STEELS ( H S S )
L. Zima, Strojfr. Vyroba, Vol 37, No 12, 1989, 45-48. In Czech. A study of the cutting performance of HSS is described. The effects of variables in p r e s s i n g a n d s i n t e r i n g on s t r u c t u r e , properties and cutting were investigated. PM high speed steels (HSS) were found to be comparable in efficiency with HSS made by melting and casting. In the case of face milling, PM HSS c o m p a r e d well w i t h cemented carbides. A S P E C T OF T H E P R O D U C T I O N OF F I N I S H E D P R O D U C T S MADE FROM HIGH S P E E D STEEL ( H S S ) POWDER
K-D. Lietzmann, et al, (Bergakademie, Frieberg, Germany), Neue HO:tte, Vol 35, No 7, 255-262. In German. A study was made of gas and water atomized high speed steel (HSS) powders and it is reported that the water atomized powders are rougher than the gas atomized. On pressing of the gas atomized powders there was greater movement of the powder in the die and this led to a greater incidence of cracking. D e n s i f i c a t i o n of t h e two powders was compared and it is suggested that in the case of the water atomized powders optimum densification is obtained by a combination of forging and rolling.
Intermetallic Materials rrH,III
H
II
MODELLING O F HIP CONSOLIDATION O F Ni A L U M I N I D E POWDERS
P~N. Wright, et al, (E.G. & G, Idaho Inc. Idaho Falls, USA), Powder Metallurgy, Vol 33, No 3, 1990, 253-259.
A model has been constructed for the HIP consolidation of Ni3A1 powders. The additive effects of plastic flow, power law creep, boundary diffusion and NabarroHerring and Goble creep are taken into account. HIP maps have been derived which d e s c r i b e t h e HIP c o n s o l i d a t i o n w i t h reasonable accuracy compared with experimental results. Finite element analysis was used as an extension to the HIP map approach.
P R O D U C T I O N OF N | T i SHAPE MEMORY ALLOYS ( S M A ) BY C O M B U S T I O N SYNTHESIS
M. Otaguchi, et al, (National Research Inst. for Metals, Tokyo, Japan), J. Japan Inst. of Metals, Vol 54, No 2, 1990, 214-223. In Japanese. The use of PM to produce NiTi shape memory alloys (SMA) with the objective of attaining closer control of composition is described. Small changes in composition result in large changes in SMA temperature. Combustion synthesis was used. The alloy was found to consist of 100% NiTi which could be HIPed to full density. Wire made from the alloy showed a SMA temperature of about IO0°C.
APPLICATION O F C O M B U S T I O N SYNTHESIS TO P R O D U C T I O N OF ZrNi INTERMETALLIC COMPOUND
C. Nashimura, et al, (National Research Inst. for Metals, Tokyo, Japan), J. Japan Inst. of Metals, Vol 54, No 5, 1990, 603-610. In English. ZrNi i n t e r m e t a l l i c c o m p o u n d s were produced by combustion synthesis and the effects of preheat temperature, in the range 25 to 400°C were studied. The product was porous when the preheat temperature was 100°C and was completely fused at 400°C. The products were found to contain ZrNi, ZrgNi11 and Zr2Ni according to composition of the powder mixture and the process conditions.
STRUCTURE AND P R O P E R T I E S OF Ti ALUMINIDE COMPACTS P R O D U C E D BY HOT P R E S S I N G MECHANICALLY ALLOYED POWDER
& Miyazaki, et al, (Sony Ltd, Tokyo, Japan), J. Japan Inst. of Metals, Vol 54, No 11, 1990, 1279-1283. In Japanese. A m i x t u r e c o n t a i n i n g 70at%Ti and 30%A1 were mechanically alloyed (MA) and hot pressed for 1 hour at 900°C. Near full density was attained. It was shown that the compact consisted of TiaAl with a mean grain size of 1.5~m. The alloy had high compressive strength and low ductility. Recrystallization and grain r e f i n e m e n t occurred during hot working at 900°C.
MPR May 1991 75