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Jetting phenomenon in powder injection moulding (PIM)
powder mixtures in a vibratory mill. the progress of MA was monitored by electrical resistivity measurements. It is reported t h a t d o m a i n s of TiAl were found in the powder and t h a t lor complete amorphization the ball size should be below 4.76 ram. MORPHOLOGICAL AND STRUCTURAL EVALUATION OF S O L I D S T A T E AMORPHIZED ALUMINIUM-TANTALUM POWDERS
M.S.el Eskandarany et al. (Tohoku University, Sendal, Japan.) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 7, 1991, 934-939. The s t r u c t u r e a n d m o r p h o l o g y of mechanically alloyed (MA), in a rod mill, elemental Ta 50at%Al powder mixtures is described. The powders were characterized as a function of milling time. The initial powders had a flaky shape. Three stages in the MA process were identified. These are agglomeration, amorphiszation and h o m o g e n i s z a t i o n . The a g g l o m e r a t e d powders had a layered structure with a grain size 20 to 100 ktm. The layered structure progressively degenerates as the agglomerates are broken. At the end of milling a fine h o m o g e n e o u s p o w d e r is formed.
Mechanical alloying S T A G E S IN T H E M E C H A N I C A L ALLOYING ( M A ) OF PALLADIUMS I L I C O N ALLOY P O W D E R S
M.Magini et al, J. Materiaks Science, Vol 26, No 14, 1991, The characterization of MA Pd-Si alloys is described. The initial stage of MA consists of p a r t i c l e f r a g m e n t a t i o n followed by formation of Pd3Si d e p e n d i n g onf alloy composition and milling conditions. Further milling is reported to result in a m o r p h i z a t i o n . Very p r o l o n g e d milling leads to de-mixing into elemental species and this is confirmed by thermal treatment.
I N V E S T I G A T I O N OF BALL M I L L E D A M O R P H O U S I R O N - A L U M I N I U M ALLOY POWDERS
G.Wang et al. (University of Science and Technology of China.) J. Magnetisms and Magnetic MateriaLs, Vol 97, nos 1-3, 1991, 7-10. An investigation into the effects of MA on Al (10 to 7 0 ) a t % F e p o w d e r s is described. A range of t e c h n i q u e s were used to characterize the powder and make magnetic measurements. It is reported t h a t short range order in a m o r p h o u s powder changes with Fe content. The p h a s e s in A15Oat%Fe powders are similar to those in a m o r p h o u s r i b b o n s p r e p a r e d by r a p i d solidification.
P R E P A R A T I O N OF M E T A S T A B L E RARE E A R T H S U L P H I D E BY M E C H A N I C A L ALLOYING A N D M E C H A N I C A L M I L L I N G
S.H.Han et al. (Iowa State University, USA_)
Scripta Metal. Mater., Vol 25, No 2, 1991, 295-298. The application of MA to p r e p a r a t i o n of rare earth-Cu mixed sulphide powders is described. It is concluded t h a t MA is t h a t the best m e t h o d of making (RE2 x,CUx) $3 m a t e r i a l s for p o s s i b l e use in t h e r m o electric devices. The elements studied were Dy and Y. SOLID STATE AMORPHIZATON AND C O N T A M I N A T I O N OF NICKELTANTALUM ALLOY P O W D E R S D U R I N G BALL M I L L I N G
N.Merk, L.E.Tanner. Scripta Metal, Mater., Vol 25, No 2, 1991, 309-313. The solid state amorphization of NiTa and Ni3Ta alloys is described. The process was studied with reference to c o n t a m i n a t i o n during milling using Co c e m e n t e d WC for mill liner and balls. It was found the powders contained a fine dispersion of WC and t h a t the Co entered the a m o r p h o u s phase. MECHANICALLY ALLOYED AMORPHOUS COPPER-TITANIUM AND N I C K E L - T I T A N I U M ALLOY P O W D E R S
G.Qiu et al. (Central South University of Technology, China.) J. Central South Inst Mining and Metallurgy (China), Vol 22, No 1, 74-79. (In Chinese.) The production and characterization of MA Cu-Ti and Ni-Ti alloy p o w d e r s is described. The t h e r m a l stability of t h e powders up to 800°C was investigated. It is r e p o r t e d t h a t the ball to powder weight ratio should be limited to 10:1. The free energy curves for t h e m e t a s t a b l e a n d equilibrium p h a s e s were calculated. The results are discussed in t e r m s of diffusion. SOLID S T A T E A M O R P H I S A T I O N
1(F.Kobayashi, (Osaka University, Osaka, Japan.) J. Japan Soc, Heat Treatment, Vol 31, No 2, 1991, 66-72, (In Japanese.) The various m e t h o d s of m e c h a n i c a l alloying (MA), rotary milling, vibratory milling and forge milling are described and discussed with reference to a m o r p h i z a t i o n a n d f o r m a t i o n of solid solutions. Structural evolution and t h e r m a l s t a b i l i t y of MA p o w d e r s are discussed. A comparison is m a d e between A1-Cr powders made by MA and rapid solidification.
F O R M A T I O N OF QUASI-CRYSTALLINE ALLOY P O W D E R S BY M E C H A N I C A L ALLOYING ( M A )
E . I v a n o v et al. ( I n s t . of Solid S t a t e Chemistry, Novosibirsk, Russia.) J.Japan
Soc, Powder and
Powder Metallurgy,
Vol 38, No 7, 1991, 903-905. (In English.) The use of MA to obtain quasi-crystalline powders of Mg-Zn-Al and Mg-Cu-Al alloys, s t a r t i n g w i t h e l e m e n t a l p o w d e r s is described. X-ray analysis was used for structure d e t e r m i n a t i o n . Phases p r e s e n t are r e p o r t e d to be the s a m e as t h o s e found in rapidly solidified powders. BEHAVIOUR OF SILVER-DYSPROSIUM POWDER MIXTURES DURING M E C H A N I C A L ALLOYING
N.Asahi, M.Oyama. (Science University of Tokyo, Yamazaki Noda, Japan.) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 7, 1991, 906-909. (In Japanese.) The mechanical alloying of Ag and Dy powder m i x t u r e s is described. The milled powders were examined by X - r a y diffraction, m i c r o s c o p y a n d differential scanning calorimetry. In the initial stages o f MA t h e d e v e l o p m e n t o f l a y e r e d structures was found and the particle size was progressively redueed with increased milling time. The presence of AgDy and o t h e r intermetallic p h a s e s is discussed as a function of milling time. STRUCTURAL OBSERVATIONS DURING A M O R P H I Z A T I O N OF CHROMIUMI R O N N I T R I D E P O W D E R S BY M E C H A N I C A L ALLOYING
T . F u k u n a g a et al. (Nagoya University, Nagoya, Japan.) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 7, 1991, 940 943. (In Japanese.) Elemental powder mixtures of Cr with 30at%Fe were milled in a vibratory mill u n d e r an N atmosphere. The uptake of N by t h e p o w d e r s i n c r e a s e d with t i m e a n d reached 15at% N after 320 hours. X-ray analysis and differential scanning calorimetry were used for characterization of t h e materialise. It is r e p o r t e d t h a t octahedral unit of the body centred cubic structure is replaced by a t e t r a h e d r a l unit during the amorphizatiou process.
Metal injection moulding J E T T I N G P H E N O M E N O N IN P O W D E R INJECTION MOULDING (PIM)
N.Piccirillo, D. Lee. (Rensselaer Polytechnic Institute, Troy, New York, USA-) Int. J. Powder Metallurgy, Vol 28, No 1, 1992, 1325. The term .jetting is used to denote non uniform filling of an die by the p o w d e r / binder mixture during PIM. A continuous p h o t o g r a p h y technique, used to study the p h e n o m e n o n , is described. Two forms of jetting are identified and are described. Liquid p h a s e jetting is a t t r i b u t e d to the lack of wetting of the die wall as the melt enters the die cavity and is more likely to occur when the thickness of the die is
MPR June 1992 53
P~ ~I~ER~URS greater t h a n the dimensions of the gate. Solid p h a s e jetting is said to be related to t h e t h r e s h o l d melt t e m p e r a t u r e (TMT) i n d e p e n d e n t of the s h e a r rate and die parameters. TMT has been associated with the liquid to solid transition of the p o w d e r / b i n d e r m i x t u r e . The TMT, m e a s u r e d experimentally, is c o m p a r e d with rheological d a t a related to the onset of solid type flow behaviour. The experimental results and the predications from rheological d a t a are said to be consistent. SHAPING OF PM PARTS BY METAL INJECTION MOULDING ( M I M ) W.Michaeli, R. Bielzer, Advanced Materials (Germany,) Vol 3, No 5, 1991, 260-262. A description of the MIM process, as used for the production of close tolerance m e t a l p a r t s is given. The i n j e c t i o n moulding, debinding and sintering stages are discussed. B I N D E R EXTRACTION IN INJECTION MOULDING N.Kasahara et al. (Mitsui Kinzoku, Yamanashi, J a p a n . ) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 6, 1991, 774-776. (In Japanese.) The debinding of MIM p a r t s is discussed and a comparison is m a d e between t h e times for solvent and t h e r m a l debinding. An investigation of debinding of Cu powder compacts is described for which solvent extraction required 8 hours and thermal d e b i n d i n g over 40 hours. S i n t e r i n g at 1020°C gave a density of 95% with mainly closed pores. The binder was a m i x t u r e polyethylene glycol, polyolefines and oil.
REV|EW
INJECTION OF CERAMIC POWDER WITH POLYETHYLENE GLYCOL BINDER Y.Kankawe et al. (Kyoto Inst, of Industrial r e s e a r c h , Kyoto, J a p a n . ) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 6, 1991, 777-781. (In Japanese.) The d e b i n d i n g of injection m o u l d e d alumina and zirconia p a r t s first by solvent extraction and t h e n by thermal m e a n s was investigated. It is r e p o r t e d t h a t solvent extraction is ten times faster t h a n t h e r m a l debinding. The density of the sintered p a r t s is said to be above 99%. It is suggested t h a t injection moulding may be used to produce p a r t s from ultrafine powders with specific surface of more t h a n 15 m2/gm. SHAPE RETENTION DURING D E B I N D I N G OF INJECTION MOULDED PARTS T.Kouno et al. (Industrial Research Inst. of Iwate, Japan.) J.Japan Soc. Powder and Powder Metallurgy., Vol 38, No 6, 1991, 7910795. (In Japanese.) The p a p e r d e s c r i b e s a v a r i a t i o n in thermal debinding in which MIM p a r t s are buried in zirconia s a n d and h e a t e d to 450°C for 9 to 22 hours. The burying of the p a r t s results in better s h a p e retention. E F F E C T S OF B I N D E R COMPOSITION ON THE D E B I N D I N G OF INJECTION MOULDED IRON-NICKEL ALLOYS J.Takekawa. (Ishinomaki Senshu University, Ishenomaki Miyagi, Japan.) J.Japan
PM parts FINITE E L E M E N T ANALYSIS OF COMPOSITE X-RAY ROTARY A N O D E U N D E R CYCLIC THERMAL LOADING J . E b e r h a r d s t e i n e r et al. (Technical University of Vienna, Vienna, Austria.) Int, J.
Refractory Metals & Hard Materials, Vol 10, No 3, 1991, 147-154. The b e h a v i o u r o f c o m p o s i t e X - r a y anodes u n d e r t h e r m a l cyclic loading has been modelled by finite element analysis (FEA). The anodes consist of a g r a p h i t e base on to which a Mo alloy is brazed a n d a thin layer on W-Re alloy is deposited on the Mo a l l o y s u b s t r a t e . The a n o d e s a r e c o m p o n e n t s of m e d i c a l X-ray u n i t s in which the t h e r m a l conditions of service are severe. It is shown t h a t the distribution odd stress can be evaluated by a time d e p e n d e n t analysis and t h a t it is essential to consider creep effects.
Soc. Powder and Powder Metallurgy, Vol 38, No 6, 1991, 800-803. (In Japanese.)
FABRICATION OF TITANIUM ALLOY MATRIX SILICON CARBIDE FIBRE REINFORCED COMPOSITE
FABRICATION AND STRENGTH OF NICKEL ALUMINIDE REINFORCED WITH ALUMINA F I B R E S
P.D Nicolaou et al. (Carnegie-Mellon University, Pittsburg, Philadelphia, USA.) A study of the consolidation, by hot pressing, of composites m a d e from Ti-6%Al4%V foils and SiC fibres, was described. The objective of the study was to d e t e r m i n e the o p t i m u m p r o c e s s i n g c o n d i t i o n s and to minimise fibre damage during processing. The critical step was said to be the closure of pores at each side of the mid-plane of the fibre. Tests were carried out to determine the size and shape of pores from which the m e c h a n i s m of mass t r a n s p o r t was inferred. The e x t e n t of fibre/matrix interaction was d e t e r m i n e d with regard to temperature, time and applied stress.
E.P. George, C.G. McKamey, (Oak Ridge National Laboratory, U S A ) An investigation of c o n t i n u o u s fibre single crystal a l u m i n a reinforced Ni3A1 was reported. The materials were fabricated by hot pressing a fibre/metal foil mixture. The effects of interfaces, fibre volume fraction and the t h e r m a l m i s - m a t c h between fibre and m a t r i x were described. F o r a vol, f r a c t i o n o f 105 f i b r e t h e m e c h a n i c a l p r o p e r t i e s o f Ni-16at%A18%Cr-0,5%Zr-0,02%B were increased and it was suggested t h a t this was due to t h e p r e s e n c e of Cr whereas the p r o p e r t i e s of Ni22%A1-0.5%Zr-0.1%B were only marginally increased by fibre.
54 MPR June 1992
The effects of binder compositions on the debinding and sintering of Fe-8%Ni was investigated. Polymer/wax binder m i x t u r e s were used. It is r e p o r t e d t h a t distortion during debinding was least when the polymer c o n t e n t of the b i n d e r was 35%. The rate of binder removal was reduced with a polymer c o n t e n t above 28% and shrinkage increased. The sintered densities also increased with increased debinding temperature.
FABRICATION AND MICROSTRUCTURE OF NIOBIUM ALUMINIDES L. Murugesh et al. (University of California, Berkeley, California, USA_) A description of the fabrication, by hot p r e s s i n g a n d r e a c t i v e s i n t e r i n g o f Nb a l u m i n i d e m a t e r i a l s w a s g i v e n . The structures produces were a composite containing ductile Nb solid solution in a brittle Nb3A1 matrix. T h e r m o m e c h a n i c a l t r e a t m e n t p r o d u c e d a lamellar Nb3A1/Nb structure after aging. Electron microscopy of aged specimens also showed the precipitation o f Nb b y a m a s s i v e t r a n s f o r m a t i o n resulting in a uniform and fine distribution of filamentary Nb in t h e Nb3Al matrix. It was suggested t h a t this structure can enhance crack growth resistance by crack bridging and
M.S.el Eskandarany et al. (Tohoku University, Sendal, Japan.) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 7, 1991, 934-939. The s t r u c t u r e a n d m o r p h o l o g y of mechanically alloyed (MA), in a rod mill, elemental Ta 50at%Al powder mixtures is described. The powders were characterized as a function of milling time. The initial powders had a flaky shape. Three stages in the MA process were identified. These are agglomeration, amorphiszation and h o m o g e n i s z a t i o n . The a g g l o m e r a t e d powders had a layered structure with a grain size 20 to 100 ktm. The layered structure progressively degenerates as the agglomerates are broken. At the end of milling a fine h o m o g e n e o u s p o w d e r is formed.
Mechanical alloying S T A G E S IN T H E M E C H A N I C A L ALLOYING ( M A ) OF PALLADIUMS I L I C O N ALLOY P O W D E R S
M.Magini et al, J. Materiaks Science, Vol 26, No 14, 1991, The characterization of MA Pd-Si alloys is described. The initial stage of MA consists of p a r t i c l e f r a g m e n t a t i o n followed by formation of Pd3Si d e p e n d i n g onf alloy composition and milling conditions. Further milling is reported to result in a m o r p h i z a t i o n . Very p r o l o n g e d milling leads to de-mixing into elemental species and this is confirmed by thermal treatment.
I N V E S T I G A T I O N OF BALL M I L L E D A M O R P H O U S I R O N - A L U M I N I U M ALLOY POWDERS
G.Wang et al. (University of Science and Technology of China.) J. Magnetisms and Magnetic MateriaLs, Vol 97, nos 1-3, 1991, 7-10. An investigation into the effects of MA on Al (10 to 7 0 ) a t % F e p o w d e r s is described. A range of t e c h n i q u e s were used to characterize the powder and make magnetic measurements. It is reported t h a t short range order in a m o r p h o u s powder changes with Fe content. The p h a s e s in A15Oat%Fe powders are similar to those in a m o r p h o u s r i b b o n s p r e p a r e d by r a p i d solidification.
P R E P A R A T I O N OF M E T A S T A B L E RARE E A R T H S U L P H I D E BY M E C H A N I C A L ALLOYING A N D M E C H A N I C A L M I L L I N G
S.H.Han et al. (Iowa State University, USA_)
Scripta Metal. Mater., Vol 25, No 2, 1991, 295-298. The application of MA to p r e p a r a t i o n of rare earth-Cu mixed sulphide powders is described. It is concluded t h a t MA is t h a t the best m e t h o d of making (RE2 x,CUx) $3 m a t e r i a l s for p o s s i b l e use in t h e r m o electric devices. The elements studied were Dy and Y. SOLID STATE AMORPHIZATON AND C O N T A M I N A T I O N OF NICKELTANTALUM ALLOY P O W D E R S D U R I N G BALL M I L L I N G
N.Merk, L.E.Tanner. Scripta Metal, Mater., Vol 25, No 2, 1991, 309-313. The solid state amorphization of NiTa and Ni3Ta alloys is described. The process was studied with reference to c o n t a m i n a t i o n during milling using Co c e m e n t e d WC for mill liner and balls. It was found the powders contained a fine dispersion of WC and t h a t the Co entered the a m o r p h o u s phase. MECHANICALLY ALLOYED AMORPHOUS COPPER-TITANIUM AND N I C K E L - T I T A N I U M ALLOY P O W D E R S
G.Qiu et al. (Central South University of Technology, China.) J. Central South Inst Mining and Metallurgy (China), Vol 22, No 1, 74-79. (In Chinese.) The production and characterization of MA Cu-Ti and Ni-Ti alloy p o w d e r s is described. The t h e r m a l stability of t h e powders up to 800°C was investigated. It is r e p o r t e d t h a t the ball to powder weight ratio should be limited to 10:1. The free energy curves for t h e m e t a s t a b l e a n d equilibrium p h a s e s were calculated. The results are discussed in t e r m s of diffusion. SOLID S T A T E A M O R P H I S A T I O N
1(F.Kobayashi, (Osaka University, Osaka, Japan.) J. Japan Soc, Heat Treatment, Vol 31, No 2, 1991, 66-72, (In Japanese.) The various m e t h o d s of m e c h a n i c a l alloying (MA), rotary milling, vibratory milling and forge milling are described and discussed with reference to a m o r p h i z a t i o n a n d f o r m a t i o n of solid solutions. Structural evolution and t h e r m a l s t a b i l i t y of MA p o w d e r s are discussed. A comparison is m a d e between A1-Cr powders made by MA and rapid solidification.
F O R M A T I O N OF QUASI-CRYSTALLINE ALLOY P O W D E R S BY M E C H A N I C A L ALLOYING ( M A )
E . I v a n o v et al. ( I n s t . of Solid S t a t e Chemistry, Novosibirsk, Russia.) J.Japan
Soc, Powder and
Powder Metallurgy,
Vol 38, No 7, 1991, 903-905. (In English.) The use of MA to obtain quasi-crystalline powders of Mg-Zn-Al and Mg-Cu-Al alloys, s t a r t i n g w i t h e l e m e n t a l p o w d e r s is described. X-ray analysis was used for structure d e t e r m i n a t i o n . Phases p r e s e n t are r e p o r t e d to be the s a m e as t h o s e found in rapidly solidified powders. BEHAVIOUR OF SILVER-DYSPROSIUM POWDER MIXTURES DURING M E C H A N I C A L ALLOYING
N.Asahi, M.Oyama. (Science University of Tokyo, Yamazaki Noda, Japan.) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 7, 1991, 906-909. (In Japanese.) The mechanical alloying of Ag and Dy powder m i x t u r e s is described. The milled powders were examined by X - r a y diffraction, m i c r o s c o p y a n d differential scanning calorimetry. In the initial stages o f MA t h e d e v e l o p m e n t o f l a y e r e d structures was found and the particle size was progressively redueed with increased milling time. The presence of AgDy and o t h e r intermetallic p h a s e s is discussed as a function of milling time. STRUCTURAL OBSERVATIONS DURING A M O R P H I Z A T I O N OF CHROMIUMI R O N N I T R I D E P O W D E R S BY M E C H A N I C A L ALLOYING
T . F u k u n a g a et al. (Nagoya University, Nagoya, Japan.) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 7, 1991, 940 943. (In Japanese.) Elemental powder mixtures of Cr with 30at%Fe were milled in a vibratory mill u n d e r an N atmosphere. The uptake of N by t h e p o w d e r s i n c r e a s e d with t i m e a n d reached 15at% N after 320 hours. X-ray analysis and differential scanning calorimetry were used for characterization of t h e materialise. It is r e p o r t e d t h a t octahedral unit of the body centred cubic structure is replaced by a t e t r a h e d r a l unit during the amorphizatiou process.
Metal injection moulding J E T T I N G P H E N O M E N O N IN P O W D E R INJECTION MOULDING (PIM)
N.Piccirillo, D. Lee. (Rensselaer Polytechnic Institute, Troy, New York, USA-) Int. J. Powder Metallurgy, Vol 28, No 1, 1992, 1325. The term .jetting is used to denote non uniform filling of an die by the p o w d e r / binder mixture during PIM. A continuous p h o t o g r a p h y technique, used to study the p h e n o m e n o n , is described. Two forms of jetting are identified and are described. Liquid p h a s e jetting is a t t r i b u t e d to the lack of wetting of the die wall as the melt enters the die cavity and is more likely to occur when the thickness of the die is
MPR June 1992 53
P~ ~I~ER~URS greater t h a n the dimensions of the gate. Solid p h a s e jetting is said to be related to t h e t h r e s h o l d melt t e m p e r a t u r e (TMT) i n d e p e n d e n t of the s h e a r rate and die parameters. TMT has been associated with the liquid to solid transition of the p o w d e r / b i n d e r m i x t u r e . The TMT, m e a s u r e d experimentally, is c o m p a r e d with rheological d a t a related to the onset of solid type flow behaviour. The experimental results and the predications from rheological d a t a are said to be consistent. SHAPING OF PM PARTS BY METAL INJECTION MOULDING ( M I M ) W.Michaeli, R. Bielzer, Advanced Materials (Germany,) Vol 3, No 5, 1991, 260-262. A description of the MIM process, as used for the production of close tolerance m e t a l p a r t s is given. The i n j e c t i o n moulding, debinding and sintering stages are discussed. B I N D E R EXTRACTION IN INJECTION MOULDING N.Kasahara et al. (Mitsui Kinzoku, Yamanashi, J a p a n . ) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 6, 1991, 774-776. (In Japanese.) The debinding of MIM p a r t s is discussed and a comparison is m a d e between t h e times for solvent and t h e r m a l debinding. An investigation of debinding of Cu powder compacts is described for which solvent extraction required 8 hours and thermal d e b i n d i n g over 40 hours. S i n t e r i n g at 1020°C gave a density of 95% with mainly closed pores. The binder was a m i x t u r e polyethylene glycol, polyolefines and oil.
REV|EW
INJECTION OF CERAMIC POWDER WITH POLYETHYLENE GLYCOL BINDER Y.Kankawe et al. (Kyoto Inst, of Industrial r e s e a r c h , Kyoto, J a p a n . ) J.Japan Soc. Powder and Powder Metallurgy, Vol 38, No 6, 1991, 777-781. (In Japanese.) The d e b i n d i n g of injection m o u l d e d alumina and zirconia p a r t s first by solvent extraction and t h e n by thermal m e a n s was investigated. It is r e p o r t e d t h a t solvent extraction is ten times faster t h a n t h e r m a l debinding. The density of the sintered p a r t s is said to be above 99%. It is suggested t h a t injection moulding may be used to produce p a r t s from ultrafine powders with specific surface of more t h a n 15 m2/gm. SHAPE RETENTION DURING D E B I N D I N G OF INJECTION MOULDED PARTS T.Kouno et al. (Industrial Research Inst. of Iwate, Japan.) J.Japan Soc. Powder and Powder Metallurgy., Vol 38, No 6, 1991, 7910795. (In Japanese.) The p a p e r d e s c r i b e s a v a r i a t i o n in thermal debinding in which MIM p a r t s are buried in zirconia s a n d and h e a t e d to 450°C for 9 to 22 hours. The burying of the p a r t s results in better s h a p e retention. E F F E C T S OF B I N D E R COMPOSITION ON THE D E B I N D I N G OF INJECTION MOULDED IRON-NICKEL ALLOYS J.Takekawa. (Ishinomaki Senshu University, Ishenomaki Miyagi, Japan.) J.Japan
PM parts FINITE E L E M E N T ANALYSIS OF COMPOSITE X-RAY ROTARY A N O D E U N D E R CYCLIC THERMAL LOADING J . E b e r h a r d s t e i n e r et al. (Technical University of Vienna, Vienna, Austria.) Int, J.
Refractory Metals & Hard Materials, Vol 10, No 3, 1991, 147-154. The b e h a v i o u r o f c o m p o s i t e X - r a y anodes u n d e r t h e r m a l cyclic loading has been modelled by finite element analysis (FEA). The anodes consist of a g r a p h i t e base on to which a Mo alloy is brazed a n d a thin layer on W-Re alloy is deposited on the Mo a l l o y s u b s t r a t e . The a n o d e s a r e c o m p o n e n t s of m e d i c a l X-ray u n i t s in which the t h e r m a l conditions of service are severe. It is shown t h a t the distribution odd stress can be evaluated by a time d e p e n d e n t analysis and t h a t it is essential to consider creep effects.
Soc. Powder and Powder Metallurgy, Vol 38, No 6, 1991, 800-803. (In Japanese.)
FABRICATION OF TITANIUM ALLOY MATRIX SILICON CARBIDE FIBRE REINFORCED COMPOSITE
FABRICATION AND STRENGTH OF NICKEL ALUMINIDE REINFORCED WITH ALUMINA F I B R E S
P.D Nicolaou et al. (Carnegie-Mellon University, Pittsburg, Philadelphia, USA.) A study of the consolidation, by hot pressing, of composites m a d e from Ti-6%Al4%V foils and SiC fibres, was described. The objective of the study was to d e t e r m i n e the o p t i m u m p r o c e s s i n g c o n d i t i o n s and to minimise fibre damage during processing. The critical step was said to be the closure of pores at each side of the mid-plane of the fibre. Tests were carried out to determine the size and shape of pores from which the m e c h a n i s m of mass t r a n s p o r t was inferred. The e x t e n t of fibre/matrix interaction was d e t e r m i n e d with regard to temperature, time and applied stress.
E.P. George, C.G. McKamey, (Oak Ridge National Laboratory, U S A ) An investigation of c o n t i n u o u s fibre single crystal a l u m i n a reinforced Ni3A1 was reported. The materials were fabricated by hot pressing a fibre/metal foil mixture. The effects of interfaces, fibre volume fraction and the t h e r m a l m i s - m a t c h between fibre and m a t r i x were described. F o r a vol, f r a c t i o n o f 105 f i b r e t h e m e c h a n i c a l p r o p e r t i e s o f Ni-16at%A18%Cr-0,5%Zr-0,02%B were increased and it was suggested t h a t this was due to t h e p r e s e n c e of Cr whereas the p r o p e r t i e s of Ni22%A1-0.5%Zr-0.1%B were only marginally increased by fibre.
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The effects of binder compositions on the debinding and sintering of Fe-8%Ni was investigated. Polymer/wax binder m i x t u r e s were used. It is r e p o r t e d t h a t distortion during debinding was least when the polymer c o n t e n t of the b i n d e r was 35%. The rate of binder removal was reduced with a polymer c o n t e n t above 28% and shrinkage increased. The sintered densities also increased with increased debinding temperature.
FABRICATION AND MICROSTRUCTURE OF NIOBIUM ALUMINIDES L. Murugesh et al. (University of California, Berkeley, California, USA_) A description of the fabrication, by hot p r e s s i n g a n d r e a c t i v e s i n t e r i n g o f Nb a l u m i n i d e m a t e r i a l s w a s g i v e n . The structures produces were a composite containing ductile Nb solid solution in a brittle Nb3A1 matrix. T h e r m o m e c h a n i c a l t r e a t m e n t p r o d u c e d a lamellar Nb3A1/Nb structure after aging. Electron microscopy of aged specimens also showed the precipitation o f Nb b y a m a s s i v e t r a n s f o r m a t i o n resulting in a uniform and fine distribution of filamentary Nb in t h e Nb3Al matrix. It was suggested t h a t this structure can enhance crack growth resistance by crack bridging and