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Interface bonding in sintered copper-titanium-boron alloys made by mechanical alloying
PM
Powder production GAS VELOCITIES FROM F R E E FALL GAS ATOMIZER
S~.Moir et al. (British Steel Teeside Technology Centre, Middlesborough, UK.) PowderMetal]., Vol 39, No 4, 1996, 271-274. The flow field of a free fall gas a t o m i z e r was m e a s u r e d in t h r e e d i m e n s i o n s . The gas flow w a s m o d e l l e d by finite difference fluid d y n a m i c s m e t h o d s . A close fit was o b t a i n e d for velocities p a r a l l e l to a n d along t h e axis of t h e atomizer. A1 was used in e x p e r i m e n t a l s t u d i e s a n d it is r e p o r t e d t h a t t h e gas flow was modified in c o m p a r i s o n with single p h a s e gas flow a n d c o r r e s p o n d e d to t h a t e x p e c t e d from t h e law of c o n s e r v a t i o n of m o m e n t u m . A NEW ATOMIZING NOZZLE WITH RING HOLES
Z.Malqun, W.Digong. (Xi'an University of Technology, Shanxi, China.) P M TechnoI., Vol 14, No 4, 1996, 272-275. (In Chinese.) It is r e p o r t e d t h a t a t o m i z e r nozzles with ring holes for focusing h a d been m a d e a n d e v a l u a t e d w i t h r e s p e c t to p a r t i c l e size a n d atomizer pressure. As far as p o w d e r collection is concerned t h e o p t i m u m system was t h e one with q u a t e r n a r y focusing. At e q u a l p r e s s u r e s single focusing gave a particle size of 360 lam a n d q u a t e r n a r y 150 pm.
LITERATURE
REVIEW
A m e t h o d for simulation of ball motion, in p r e s e n c e of a powder, in a t u m b l i n g mill is proposed. The basis of t h e model is t h e p a r t i c l e e l e m e n t m e t h o d a n d uses t h e friction between colliding balls. Ball movement was observed, with and without powders, using video techniques and observations compared with t h e simulations. It is r e p o r t e d t h a t ball m o t i o n is influenced by p o w d e r type. Non-metallic materials were used experimentally.
Aluminium MANUFACTURE OF BULK COMPOSITIONALLY GRADED MATERIALS BY EXTRUSION
R.D.Rawlings e t al. (Imperial College, London, UK.) P o w d e r Metal[, Vol 39, No 3, 1996, 219-222. Investigations of extrusion of compositionally graded composite m a t e r i a l s are described. The m a t e r i a l was b a s e d o n 2124A1 alloy w i t h u p to 30 vol% SiC particles. Preforms were b u i l t u p in concentric cylinders with p u r e AI on t h e outside to minimize friction in the extrusion press. E x t r u s i o n ratios of 10:1 to 20:1 were used. MICROSTRUCTURAL C H A N G E S IN MECHANICALLY ALLOYED ALUMINIUM ALLOYS A N D COMPOSITES
Pressing ON-LINE ULTRASONIC MONITORING OF IRON POWDER DURING COMPACTION
A_Hamel et al. (National Research Council of Canada, Quebec, Canada.) P o w d e r MetalI., Vol 39, No 4, 1996, 275-280. An ultrasonic m e t h o d for m o n i t o r i n g c o m p a c t i o n of Fe p o w d e r is d e s c r i b e d a n d discussed with respect to precision. Sensitivity to changes in p o w d e r p r o p e r t i e s was investigated. The m e t h o d was applied to a multi-level p a r t a n d it is s h o w n t h a t d e n s i t y a t e a c h level c o u l d b e determined.
Fundamentals SIMULATION OF THREEDIMENSIONAL MOTION OF BALLS IN A MILL IN P R E S E N C E OF A POWDER
J.Kano e t al. (Tohoku University, Sendai, J a p a n . ) Adv. P o w d e r TechnoI., Vol 8, No 1, 1997, 39-51.
36 MPR October 1997
A_P.Miodownik e t al. (University of Surrey, Guildford, UI~) Metall. Mater. :l~ans. ,4, Vol 27A, No 11, 1996, 3718-3726. I t is r e p o r t e d t h a t A l - Z n - M g - C u powders, c o x r e s p o n d i n g to 7010A1 alloy, h a d b e e n n~echanically alloyed w i t h a n d w i t h o u t SiC particles. SiC i n h i b i t e d t h e alloying process. Results front X-ray a n d e l e c t r o n optics t e c h n i q u e s are c o m p a r e d . X-ray diffraction d i d n o t d e t e c t solute-rich zones. Zn alloys w i t h g r e a t e r difficulty t h a t Cu or Mg. QUASI-CRYSTALLIZATION IN ALUMINIUM-COPPER-IRON POWDERS BY MECHANICAL ALLOYING
N.Asahi, T.Maki. (Science U n i v e r s i t y of Tokyo, Tokyo, J a p a n . ) J. Jpn. Soc. P o w d e r P o w d e r Metall., Vol 42, No 12, 1995, 14371440. (In Japanese.) Mechanical alloying of A1-20at%Cu- 15%Fe p o w d e r s in Ar was i n v e s t i g a t e d by Xray diffraction, differential scanning calorimetry a n d electron microscopy. The p h a s e s synthesized were identified.
DISPERSION STRENGTHENED ALUMINIUM PRODUCED BY MECHANICAL ALLOYING
M.Besterci. (Ustav Materialoveho ~yskumu, Kosoce, Slovak Republic.) Pokrol~yPraskove Metal., No 2, 1996, 5-74. (In Czech.) Results of lengthy s t u d y of m e c h a n i c a l a l l o y i n g (MA) of AI-C p o w d e r s a r e reviewed. It is shown t h a t t h e final carbide is A14Cs. Kinetics a n d m e c h a n i s m s of MA, m e t h o d s of compaction a n d h e a t t r e a t m e n t of pressed p a r t s are discussed. Models of spatial a r r a n g e m e n t , ~md t h e i r evaluation, of t h e dispersoids are outlined. E m p h a s i s is placed on i n t e r p r c t a t i o n of m e c h a n i cal p r o p e r t i e s a t a m b i e n t a n d elevated temperatures. OXIDE D I S P E R S E D ALUMINIUM BASE MATERIALS MADE BY REACTION MILLING
J.Kanako e t al. (Nihon University, Chiba, J a p a n . ) J. Jpn. Inst. Metals, Vol 60, No 12, 1996, 1207-1214. (In Japanese.) It is r e p o r t e d t h a t A1-Li a n d AI-Li-Mg powders h a d b e e n mec:hanically alloyed a n d pressed with t h e object of investigating selective o x i d a t i o n of s o l u t e e l e m e n t s . Phases p r e s e n t t~ powders, pressed a n d h e a t t r e a t e d m a t e r i a l s were determined. It is shown t h a t Li is oxidized to IAAIO2 in A1Li a n d t h a t Mg is oxidized in preference to Li in A1-Li-Mg. Growth of LiAIO2 occurred o n h e a t i n g a t 500°C. F r o m h a r d n e s s m e a s u r e m e n t s it is deduced t h a t LiA102 is responsible for t h e hm~iening. D E G A S S I N G OF GAS ATOMIZED ALUMINIUM-LITHIUM ALLOY POWDERS
S d . D a v i s e t al. ( U n i v e r s i t y of Surrey, Gufldford, UK.) Int. J. R a p l d Solidification, Vol 9, No 3, 1996, 187-209. Degassing of Al-Li powders was investigated using quadrupole mass spectroscopy to m o n i t o r t h e evolved gases. H was evolved a t 20()°C a n d 500°C. The 200°C evolution was lower for powders with less e x p o s u r e to a m b i e n t a t m o s p h e r e . H20 was evolved at 100°C a n d 200°C a n d N a t 460°C.
Copper INTERFACE B O N D I N G IN S I N T E R E D COPPER-TITANIUM-BORON ALLOYS MADE BY MECHANICAL ALLOYING
T.Morooka e t al. (Musashi Inst. of Technology, Tokyo, J a p a n ) . J. Jpn. Soc. P o w d e r
P o w d e r MetMl., Vol 42, No 12, 1995, 13791383. (In Japanese.) Cu-5at%Ti-10%B and Cu-9%Ti-18%B powders were mechanically alloyed. Powders of each composition were separately compacted and bonded to each o t h e r by s i n t e r i n g at 600-900°C. The thickness of the diffusion zone increased with duration of MA- The strength of the bond was measured and shown to decrease with increase in milling time.
E F F E C T OF STRUCTURE A N D LOAD CYCLE ON FATIGUE OF LAMINATED C O P P E R ALLOYS V.A.Kuzmenko e t al. Porosbkovaya Metall., No 3/4, 1996, 97-103. (In Russian.) The fatigue properties of laminated CuFe, C u - C r a n d Cu-Mo s a m p l e s w e r e investigated as functions of layer thickness and period of cyclic loading. Photographs were used to analyse fast crack propagation.
Iron a n d steel CRYSTALLINE TO A M O R P H O U S T R A N S F O R M A T I O N S IN MECHANICALLY ALLOYED IRONT U N G S T E N POWDERS
I~Suzuki e t M. (Tohoku University, Sendai, Japan.) A c t a Mater., Vol 45, No 3, 1997, 1175-1187. It is reported t h a t Fe-50at%W powders had been mechanically alloyed. In t h e early stages W atoms migrate into the Fe to form a nanocrystalline body-centred cubic Fe-W solid solution. After 720 hours this phase amorphizes and there is residual W which is u l t i m a t e l y a b s o r b e d into t h e Fe-W solid solution. The powder crystallized at 565°C. SPRAY F O R M I N G OF LARGE D I A M E T E R SPECIAL S T E E L BILLETS
L.Shaw, C.Spiegelhauer. (Special Melted Products Ltd, Sheffield, UK). Int. J. P o w d e r Metal]., Vol 33, No 3, 1997, 31-36. An extended inter-company study of spray forming of large steel billets is outlined. The objective was to develop an understanding of the technology of spray forming large billets in the horizontal mode with particular respect to process control. Project work including equipment, continuing process development, evaluation and extension of the process fTom the i n i t i a l t r i a l s to o t h e r m a t e r i a l s was described. C O N S O L I D A T I O N OF NANOS T R U C T U R E D POWDERS BY RAPID FORGING
G.R.Shaik, W.W.Milligan. (Michigan Technological University, Houghton, USA.) Metall. Mater. Trans. ~ Vol 28A, No 3, 1997, 895-901.
It is r e p o r t e d t h a t a rapid forging technique had been developed to process 20 nm Fe-10%Cu powders into fidly dense compacts whilst retaining the nano-scale grain size. Grain growth was minimized by reducing t i m e at process t e m p e r a t u r e . Green compacts were induction heated, rapidly forged and cooled. Ar was used to restrict contamination. Resulting grain size was 45 nm after forging at 530°C to full density. The material was characterized and t h e p r o c e s s m o d e l l e d . The d o m i n a n t densification mechanism is shown to be creep. Industrial application is discussed. S T A I N L E S S S T E E L S I N T E R E D WITH COPPER
A.Radon, J.Frydrych. (Akademia GorniczoHutnicza, Krakow, Poland.) Metal. Proszkow, Vol 29, No 2, 1996, 34-38. (In Polish.) Measurements of density and hardness of a PM stainless steel, with up to 6%Cu, sintered at 1000, 1100 or 1200°C, and microstructures are presented. M E C H A N I S M OF D E F L U I D I Z A T I O N O F IRON PARTICLES IN A FLUIDIZED B E D
M.Horio et a]. (Tokyo University of Technology and Agriculture, Tokyo, Japan.) P o w d e r Tecbnol., Vol 89, No 3, 1996, 231-238. The behaviour of cohesive Fe powder in a fluidized bed was investigated in order to develop a model. Attention is given to d e f l u i d i z a t i o n a n d i n t e r - p a r t i c l e neck growth. The tensile strength of the neck was 20 MPa. Criteria for defluidization were discussed.
strengths. The PM steels had the higher impact strength. Impact fracture modes were described and discussed.
Nickel IMPURITY S E G R E G A T I O N IN GRAIN B O U N D A R I E S OF NICKEL BASE ALLOYS
V.M.Danilenko e t M. Po~shkovay-a Metal1., No 3/4, 1996, 71-76. (In :Russian.) Segregation of Ti, Mo and C at grain boundaries in Ni alloys was simulated with regard to effects of temperature. The effects of Ti and Mo on C segregation is analysed.
Tungsten U N D U I ~ T I O N OF T U N G S T E N / M A T R I X INTERFACE D U R I N G R E S I N T E R I N G O F T U N G S T E N HEAVY ALLOYS B.S.Chun et M. (Chungnam National University, Taejon, Korea.) MetMl. Mater. Trans. .,4, Vol 28A~ No 2, 1997, 485-489. It is reported that the W/matrix interface in W heavy alloys becomes irregular during thermal cycling to 1100°C, the undulations becoming more pronounced with increased number of cycles. This is discussed in terms of anisotropic residual stresses. Finite element methods were used in calculation of stresses. The irregularities are attributed to non-uniform dissolution of W in zones of higher strain energy and precipitation in zones of low. The undulations were removed by prolonged re-sintering at 1485°C.
Zirconium
E F F E C T S O F SULPHUR ON DIMENSIONAL CHANGES DURING S I N T E R I N G O F IRON B A S E D POWDER COMPACTS
FABRICATION OF BULK A M O R P H O U S ALLOYS BY POWDER CONSOLIDATION
J.Takata, N.Kawai. (Kobe Steel Co Ltd, Kobe, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 42, No 12, 1995, 1430-1436. (In Japanese.) E f f e c t s of 0.01 a n d 0.3 wt%S on dimensional change during sintering of Fe2%Cu-0.8%C, in endogas, H' or At, was investigated. High S alloy showed increased expansion in endogas.. S was shown to reduce C solubility in austenite. Mechanisms were discussed with regard to thermodynamics.
A.Inoue e t M. (Tohoku University, Sendai, Japan.) Int. J. PowderMet~ll., Vol 33, No 2, 1997, 50-61. It is r e p o r t e d t h a t b u l k a m o r p h o u s Zr-10at%Al-10%Ni-15%Cu had been produced f r o m a m o r p h o u s p o w d e r by p o w d e r processing and warm extrusion to give tensile strength up to 1520 MPa. The high strength is attributed to full densification a n d g o o d i n t e r p a r t i c l e b o n d i n g . The implications of the study are discussed.
EFFECT OF QUENCH TEMPERATURE ON MECHANICAL BEHAVIOUR OF HOT WORK TOOL S T E E L S
CRITICAL COOLING RATES FOR AMORPHIZATION IN ZIRCONIUMALUMINIUM-COPPER-NI CKEL ALLOYS
N.Tsujii e t M. (Sanyo Special Steel Co, Himeji, Japan.) J. Jpn. Soc. P o w d e r P o w d e r MetMl., Vol 42, No 12, 1995, 1446-1451. (In English.) The effects of hardening temperature on mechanical properties of PM hot work tool steels were investigated and results c o m p a r e d with c a s t / w r o u g h t materials. I n c r e a s e in h a r d e n i n g t e m p e r a t u r e i n c r e a s e d tensile but r e d u c e d i m p a c t
C.K.Ong e t al. (National University of Singapore, Singapore.) Int: J. R a p i d Solidification, Vol 9, No 2, 1996, 91-102. It is reported that the critical cooling rate for a m o r p h i z a t i o n of Zr-16at%Cu9%A1-9%Ni h a d b e e n m e a s u r e d at (4.1 ± 1.0)xl03 deg.s -1. This is within the limits p r e d i c t e d by U h i m a n n ' s kinetic m o d e l for glass f o r m a t i o n . Effects of viscosity were discussed.
MPR October 1997 37
Powder production GAS VELOCITIES FROM F R E E FALL GAS ATOMIZER
S~.Moir et al. (British Steel Teeside Technology Centre, Middlesborough, UK.) PowderMetal]., Vol 39, No 4, 1996, 271-274. The flow field of a free fall gas a t o m i z e r was m e a s u r e d in t h r e e d i m e n s i o n s . The gas flow w a s m o d e l l e d by finite difference fluid d y n a m i c s m e t h o d s . A close fit was o b t a i n e d for velocities p a r a l l e l to a n d along t h e axis of t h e atomizer. A1 was used in e x p e r i m e n t a l s t u d i e s a n d it is r e p o r t e d t h a t t h e gas flow was modified in c o m p a r i s o n with single p h a s e gas flow a n d c o r r e s p o n d e d to t h a t e x p e c t e d from t h e law of c o n s e r v a t i o n of m o m e n t u m . A NEW ATOMIZING NOZZLE WITH RING HOLES
Z.Malqun, W.Digong. (Xi'an University of Technology, Shanxi, China.) P M TechnoI., Vol 14, No 4, 1996, 272-275. (In Chinese.) It is r e p o r t e d t h a t a t o m i z e r nozzles with ring holes for focusing h a d been m a d e a n d e v a l u a t e d w i t h r e s p e c t to p a r t i c l e size a n d atomizer pressure. As far as p o w d e r collection is concerned t h e o p t i m u m system was t h e one with q u a t e r n a r y focusing. At e q u a l p r e s s u r e s single focusing gave a particle size of 360 lam a n d q u a t e r n a r y 150 pm.
LITERATURE
REVIEW
A m e t h o d for simulation of ball motion, in p r e s e n c e of a powder, in a t u m b l i n g mill is proposed. The basis of t h e model is t h e p a r t i c l e e l e m e n t m e t h o d a n d uses t h e friction between colliding balls. Ball movement was observed, with and without powders, using video techniques and observations compared with t h e simulations. It is r e p o r t e d t h a t ball m o t i o n is influenced by p o w d e r type. Non-metallic materials were used experimentally.
Aluminium MANUFACTURE OF BULK COMPOSITIONALLY GRADED MATERIALS BY EXTRUSION
R.D.Rawlings e t al. (Imperial College, London, UK.) P o w d e r Metal[, Vol 39, No 3, 1996, 219-222. Investigations of extrusion of compositionally graded composite m a t e r i a l s are described. The m a t e r i a l was b a s e d o n 2124A1 alloy w i t h u p to 30 vol% SiC particles. Preforms were b u i l t u p in concentric cylinders with p u r e AI on t h e outside to minimize friction in the extrusion press. E x t r u s i o n ratios of 10:1 to 20:1 were used. MICROSTRUCTURAL C H A N G E S IN MECHANICALLY ALLOYED ALUMINIUM ALLOYS A N D COMPOSITES
Pressing ON-LINE ULTRASONIC MONITORING OF IRON POWDER DURING COMPACTION
A_Hamel et al. (National Research Council of Canada, Quebec, Canada.) P o w d e r MetalI., Vol 39, No 4, 1996, 275-280. An ultrasonic m e t h o d for m o n i t o r i n g c o m p a c t i o n of Fe p o w d e r is d e s c r i b e d a n d discussed with respect to precision. Sensitivity to changes in p o w d e r p r o p e r t i e s was investigated. The m e t h o d was applied to a multi-level p a r t a n d it is s h o w n t h a t d e n s i t y a t e a c h level c o u l d b e determined.
Fundamentals SIMULATION OF THREEDIMENSIONAL MOTION OF BALLS IN A MILL IN P R E S E N C E OF A POWDER
J.Kano e t al. (Tohoku University, Sendai, J a p a n . ) Adv. P o w d e r TechnoI., Vol 8, No 1, 1997, 39-51.
36 MPR October 1997
A_P.Miodownik e t al. (University of Surrey, Guildford, UI~) Metall. Mater. :l~ans. ,4, Vol 27A, No 11, 1996, 3718-3726. I t is r e p o r t e d t h a t A l - Z n - M g - C u powders, c o x r e s p o n d i n g to 7010A1 alloy, h a d b e e n n~echanically alloyed w i t h a n d w i t h o u t SiC particles. SiC i n h i b i t e d t h e alloying process. Results front X-ray a n d e l e c t r o n optics t e c h n i q u e s are c o m p a r e d . X-ray diffraction d i d n o t d e t e c t solute-rich zones. Zn alloys w i t h g r e a t e r difficulty t h a t Cu or Mg. QUASI-CRYSTALLIZATION IN ALUMINIUM-COPPER-IRON POWDERS BY MECHANICAL ALLOYING
N.Asahi, T.Maki. (Science U n i v e r s i t y of Tokyo, Tokyo, J a p a n . ) J. Jpn. Soc. P o w d e r P o w d e r Metall., Vol 42, No 12, 1995, 14371440. (In Japanese.) Mechanical alloying of A1-20at%Cu- 15%Fe p o w d e r s in Ar was i n v e s t i g a t e d by Xray diffraction, differential scanning calorimetry a n d electron microscopy. The p h a s e s synthesized were identified.
DISPERSION STRENGTHENED ALUMINIUM PRODUCED BY MECHANICAL ALLOYING
M.Besterci. (Ustav Materialoveho ~yskumu, Kosoce, Slovak Republic.) Pokrol~yPraskove Metal., No 2, 1996, 5-74. (In Czech.) Results of lengthy s t u d y of m e c h a n i c a l a l l o y i n g (MA) of AI-C p o w d e r s a r e reviewed. It is shown t h a t t h e final carbide is A14Cs. Kinetics a n d m e c h a n i s m s of MA, m e t h o d s of compaction a n d h e a t t r e a t m e n t of pressed p a r t s are discussed. Models of spatial a r r a n g e m e n t , ~md t h e i r evaluation, of t h e dispersoids are outlined. E m p h a s i s is placed on i n t e r p r c t a t i o n of m e c h a n i cal p r o p e r t i e s a t a m b i e n t a n d elevated temperatures. OXIDE D I S P E R S E D ALUMINIUM BASE MATERIALS MADE BY REACTION MILLING
J.Kanako e t al. (Nihon University, Chiba, J a p a n . ) J. Jpn. Inst. Metals, Vol 60, No 12, 1996, 1207-1214. (In Japanese.) It is r e p o r t e d t h a t A1-Li a n d AI-Li-Mg powders h a d b e e n mec:hanically alloyed a n d pressed with t h e object of investigating selective o x i d a t i o n of s o l u t e e l e m e n t s . Phases p r e s e n t t~ powders, pressed a n d h e a t t r e a t e d m a t e r i a l s were determined. It is shown t h a t Li is oxidized to IAAIO2 in A1Li a n d t h a t Mg is oxidized in preference to Li in A1-Li-Mg. Growth of LiAIO2 occurred o n h e a t i n g a t 500°C. F r o m h a r d n e s s m e a s u r e m e n t s it is deduced t h a t LiA102 is responsible for t h e hm~iening. D E G A S S I N G OF GAS ATOMIZED ALUMINIUM-LITHIUM ALLOY POWDERS
S d . D a v i s e t al. ( U n i v e r s i t y of Surrey, Gufldford, UK.) Int. J. R a p l d Solidification, Vol 9, No 3, 1996, 187-209. Degassing of Al-Li powders was investigated using quadrupole mass spectroscopy to m o n i t o r t h e evolved gases. H was evolved a t 20()°C a n d 500°C. The 200°C evolution was lower for powders with less e x p o s u r e to a m b i e n t a t m o s p h e r e . H20 was evolved at 100°C a n d 200°C a n d N a t 460°C.
Copper INTERFACE B O N D I N G IN S I N T E R E D COPPER-TITANIUM-BORON ALLOYS MADE BY MECHANICAL ALLOYING
T.Morooka e t al. (Musashi Inst. of Technology, Tokyo, J a p a n ) . J. Jpn. Soc. P o w d e r
P o w d e r MetMl., Vol 42, No 12, 1995, 13791383. (In Japanese.) Cu-5at%Ti-10%B and Cu-9%Ti-18%B powders were mechanically alloyed. Powders of each composition were separately compacted and bonded to each o t h e r by s i n t e r i n g at 600-900°C. The thickness of the diffusion zone increased with duration of MA- The strength of the bond was measured and shown to decrease with increase in milling time.
E F F E C T OF STRUCTURE A N D LOAD CYCLE ON FATIGUE OF LAMINATED C O P P E R ALLOYS V.A.Kuzmenko e t al. Porosbkovaya Metall., No 3/4, 1996, 97-103. (In Russian.) The fatigue properties of laminated CuFe, C u - C r a n d Cu-Mo s a m p l e s w e r e investigated as functions of layer thickness and period of cyclic loading. Photographs were used to analyse fast crack propagation.
Iron a n d steel CRYSTALLINE TO A M O R P H O U S T R A N S F O R M A T I O N S IN MECHANICALLY ALLOYED IRONT U N G S T E N POWDERS
I~Suzuki e t M. (Tohoku University, Sendai, Japan.) A c t a Mater., Vol 45, No 3, 1997, 1175-1187. It is reported t h a t Fe-50at%W powders had been mechanically alloyed. In t h e early stages W atoms migrate into the Fe to form a nanocrystalline body-centred cubic Fe-W solid solution. After 720 hours this phase amorphizes and there is residual W which is u l t i m a t e l y a b s o r b e d into t h e Fe-W solid solution. The powder crystallized at 565°C. SPRAY F O R M I N G OF LARGE D I A M E T E R SPECIAL S T E E L BILLETS
L.Shaw, C.Spiegelhauer. (Special Melted Products Ltd, Sheffield, UK). Int. J. P o w d e r Metal]., Vol 33, No 3, 1997, 31-36. An extended inter-company study of spray forming of large steel billets is outlined. The objective was to develop an understanding of the technology of spray forming large billets in the horizontal mode with particular respect to process control. Project work including equipment, continuing process development, evaluation and extension of the process fTom the i n i t i a l t r i a l s to o t h e r m a t e r i a l s was described. C O N S O L I D A T I O N OF NANOS T R U C T U R E D POWDERS BY RAPID FORGING
G.R.Shaik, W.W.Milligan. (Michigan Technological University, Houghton, USA.) Metall. Mater. Trans. ~ Vol 28A, No 3, 1997, 895-901.
It is r e p o r t e d t h a t a rapid forging technique had been developed to process 20 nm Fe-10%Cu powders into fidly dense compacts whilst retaining the nano-scale grain size. Grain growth was minimized by reducing t i m e at process t e m p e r a t u r e . Green compacts were induction heated, rapidly forged and cooled. Ar was used to restrict contamination. Resulting grain size was 45 nm after forging at 530°C to full density. The material was characterized and t h e p r o c e s s m o d e l l e d . The d o m i n a n t densification mechanism is shown to be creep. Industrial application is discussed. S T A I N L E S S S T E E L S I N T E R E D WITH COPPER
A.Radon, J.Frydrych. (Akademia GorniczoHutnicza, Krakow, Poland.) Metal. Proszkow, Vol 29, No 2, 1996, 34-38. (In Polish.) Measurements of density and hardness of a PM stainless steel, with up to 6%Cu, sintered at 1000, 1100 or 1200°C, and microstructures are presented. M E C H A N I S M OF D E F L U I D I Z A T I O N O F IRON PARTICLES IN A FLUIDIZED B E D
M.Horio et a]. (Tokyo University of Technology and Agriculture, Tokyo, Japan.) P o w d e r Tecbnol., Vol 89, No 3, 1996, 231-238. The behaviour of cohesive Fe powder in a fluidized bed was investigated in order to develop a model. Attention is given to d e f l u i d i z a t i o n a n d i n t e r - p a r t i c l e neck growth. The tensile strength of the neck was 20 MPa. Criteria for defluidization were discussed.
strengths. The PM steels had the higher impact strength. Impact fracture modes were described and discussed.
Nickel IMPURITY S E G R E G A T I O N IN GRAIN B O U N D A R I E S OF NICKEL BASE ALLOYS
V.M.Danilenko e t M. Po~shkovay-a Metal1., No 3/4, 1996, 71-76. (In :Russian.) Segregation of Ti, Mo and C at grain boundaries in Ni alloys was simulated with regard to effects of temperature. The effects of Ti and Mo on C segregation is analysed.
Tungsten U N D U I ~ T I O N OF T U N G S T E N / M A T R I X INTERFACE D U R I N G R E S I N T E R I N G O F T U N G S T E N HEAVY ALLOYS B.S.Chun et M. (Chungnam National University, Taejon, Korea.) MetMl. Mater. Trans. .,4, Vol 28A~ No 2, 1997, 485-489. It is reported that the W/matrix interface in W heavy alloys becomes irregular during thermal cycling to 1100°C, the undulations becoming more pronounced with increased number of cycles. This is discussed in terms of anisotropic residual stresses. Finite element methods were used in calculation of stresses. The irregularities are attributed to non-uniform dissolution of W in zones of higher strain energy and precipitation in zones of low. The undulations were removed by prolonged re-sintering at 1485°C.
Zirconium
E F F E C T S O F SULPHUR ON DIMENSIONAL CHANGES DURING S I N T E R I N G O F IRON B A S E D POWDER COMPACTS
FABRICATION OF BULK A M O R P H O U S ALLOYS BY POWDER CONSOLIDATION
J.Takata, N.Kawai. (Kobe Steel Co Ltd, Kobe, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 42, No 12, 1995, 1430-1436. (In Japanese.) E f f e c t s of 0.01 a n d 0.3 wt%S on dimensional change during sintering of Fe2%Cu-0.8%C, in endogas, H' or At, was investigated. High S alloy showed increased expansion in endogas.. S was shown to reduce C solubility in austenite. Mechanisms were discussed with regard to thermodynamics.
A.Inoue e t M. (Tohoku University, Sendai, Japan.) Int. J. PowderMet~ll., Vol 33, No 2, 1997, 50-61. It is r e p o r t e d t h a t b u l k a m o r p h o u s Zr-10at%Al-10%Ni-15%Cu had been produced f r o m a m o r p h o u s p o w d e r by p o w d e r processing and warm extrusion to give tensile strength up to 1520 MPa. The high strength is attributed to full densification a n d g o o d i n t e r p a r t i c l e b o n d i n g . The implications of the study are discussed.
EFFECT OF QUENCH TEMPERATURE ON MECHANICAL BEHAVIOUR OF HOT WORK TOOL S T E E L S
CRITICAL COOLING RATES FOR AMORPHIZATION IN ZIRCONIUMALUMINIUM-COPPER-NI CKEL ALLOYS
N.Tsujii e t M. (Sanyo Special Steel Co, Himeji, Japan.) J. Jpn. Soc. P o w d e r P o w d e r MetMl., Vol 42, No 12, 1995, 1446-1451. (In English.) The effects of hardening temperature on mechanical properties of PM hot work tool steels were investigated and results c o m p a r e d with c a s t / w r o u g h t materials. I n c r e a s e in h a r d e n i n g t e m p e r a t u r e i n c r e a s e d tensile but r e d u c e d i m p a c t
C.K.Ong e t al. (National University of Singapore, Singapore.) Int: J. R a p i d Solidification, Vol 9, No 2, 1996, 91-102. It is reported that the critical cooling rate for a m o r p h i z a t i o n of Zr-16at%Cu9%A1-9%Ni h a d b e e n m e a s u r e d at (4.1 ± 1.0)xl03 deg.s -1. This is within the limits p r e d i c t e d by U h i m a n n ' s kinetic m o d e l for glass f o r m a t i o n . Effects of viscosity were discussed.
MPR October 1997 37