- Email: [email protected]
Mechanical properties of extruded nickel aluminide produced by reaction synthesis
h o m o g e n e o u s m i x i n g was s h o w n to be s h e a r induced diffusion of particles in t h e binder. Small particles were shown to need more work d u r i n g mixing. MODELLING OF D E B I N D I N G OF STAINLESS STEEL WITH A THREECOMPONENT B I N D E R
C.W.P. Finn, U.N.S. Prasad (North E a s t e r n University, USA). A study of d e b i n d i n g of 316L stainless steel, w i t h a t h r e e c o m p o n e n t b i n d e r comprising paraffin wax, stearic acid a n d polypropylene, was described. Weight losses in m e d i u m to high v a c u u m was m e a s u r e d by t h e r m o g r a v i m e t r y a n d rates were shown to b e e x p o n e n t i a l a t t e m p e r a t u r e s of evaporation a n d decomposition of b i n d e r components. The correlations between t i m e a n d t e m p e r a t u r e were u s e d to m o d e l debinding. The results were discussed. METAL INJECTION MOULDING FOR MANUFACTURE OF PRECIOUS METAL COMPONENTS
J.T. Strauss (HJE Corp, USA). MIM for t h e p r o d u c t i o n of small m e t a l p a r t s was discussed with reference to t h e benefits gained including dimensional tolerances, material properties and p r o d u c t i o n rates. The p a p e r p r e s e n t e d t h e a d v a n t a g e s a n d d i s a d v a n t a g e s of using MIM in jewellery m a n u f a c t u r e a n d discussed t h e technological a n d o t h e r b a r r i e r s to its adoption. PROCESSING OF SUPERALLOYS BY POWDER INJECTION MOULDING
ICF. Hens, R.M. G e r m a n (Pennsylvania State University, Pennsylvania, USA). An i n v e s t i g a t i o n of MIM of Ni-base superalloys was described. It was r e p o r t e d t h a t Icone1625 can be injection m o u l d e d b u t t h a t Inconel718 a n d Rene88 required careful analysis a n d control. The s t u d y covered f e e d s t o c k rheology, d i l a t o m e t r y a n d d i f f e r e n t i a l t h e r m a l a n a l y s i s of debinding and sintering. Careful processing a n d m o n i t o r i n g were required to make complex s h a p e d components. ULTRASONIC S E N S O R S FOR POWDER INJECTION MOULDING
R.M. G e r m a n et al (Pennsylvania S t a t e University, Pennsylvania, USA). The use of ultrasonic sensors in t h e m o u l d cavity to m o n i t o r i n j e c t i o n was discussed with reference to detection of defects, s h o r t shots, flash, j e t t i n g sticking a n d variations in bulk a n d s h e a r moduli. Real time m o n i t o r i n g of a n o m a l i e s which d e t e r m i n e quality h a s been carried out. A novel ultrasonic guided wave t e c h n i q u e was reported.
42 MPR October 1994
SIMULATION OF POWDER INJECTION MOULDING
IN-SITU SYNTHE S I S / D E N S I F I C A T I O N OF CERMET MATERIALS
C. Wang et al ( C o n c u r r e n t Technologies Corp, USA) Recent developments in t h e evolution of a c o m p u t e r p r o g r a m m e for t h e simulation of i n j e c t i o n m o u l d i n g w e r e d e s c r i b e d including calculation of air p r e s s u r e in t h e m o u l d cavity, b i n d e r solidification a n d shrinkage during freezing. The system was r e p o r t e d to aid in t h e selection of design p a r a m e t e r s , optimization of moulding a n d process control. C o m p a r i s o n was m a d e with e x p e r i m e n t a l results a n d a n e x a m p l e of t h e calculation was given.
R.V. R a m a n et al (Ceracon Inc., Sacramento, California, USA). A new processing approach to production of dense materials was described. Results of a modelling procedure were incorporated in the process control system. Effects of process v a r i a b l e s o n p r o p e r t i e s were o u t l i n e d . Microstructure a n d p r o p e r t i e s of a cermet and an intermetallic material were described.
PRECISE MOULD TEMPERATURE CONTROL
D.I. Seres (Injection Moulding Industries, USA.) The i m p o r t a n c e of control of m o u l d a n d feedstock temperatures in MIM w a s discussed. It was suggested t h a t where only t h e m o u l d t e m p e r a t u r e is controlled t h e r e may be u n a c c e p t a b l e v a r i a t i o n s in temperature. The novel technology described was r e p o r t e d to allow t h e m o u l d to be p r e h e a t e d to t h e o p t i m u m process t e m p e r a t u r e a n d cooled with a high h e a t e x t r a c t i o n r a t e giving a m o r e u n i f o r m t e m p e r a t u r e profile t h r o u g h t h e mould.
Self-propagating high temperature synthesis JOINING BY SELF-PROPAGATING HIGH TEMPERATURE SYNTHESIS
R.W. Messler, T.T. Orling, (Rensselaer Polytechnic Inst., Troy, New York, USA.) The use of SHS for t h e p r o d u c t i o n of refractory metals, ceramics and intermetallic materials was discussed with reference to t h e p o t e n t i a l of t h e t e c h n i q u e to m a k e j o i n t s between similar or dissimilar materials. A model study of t h e use of Ni a n d Al powders to m a k e Ni a l u m i n i d e j o i n t s between Ni base alloy end e l e m e n t s a n d between Si a n d Ni base superalloys was reported. SELF-PROPAGATING HIGH TEMPERATURE SYNTHESIS OF SILICON NITRIDE AT LOWER NITROGEN P R E S S U R E
C.C. Ge et al (University of Science a n d Technology, Beijing, China). The synthesis of Si3N4 a n d Mg3N2 was described. It was concluded t h a t Si could be completely converted to SiaN4 in presence of Mg. The presence of Mg was found to influence to porosity of t h e m a t e r i a l during combustion. A mechanism for the f o r m a t i o n of Si3N4 u n d e r low p r e s s u r e s of N was proposed.
Fine-scale particulate materials CHEMICAL SYNTHESIS OF N A N O S T R U C T U R E S MATERIALS
ICE. Gonsalves et al (University of Connecticut, USA). The a p p l i c a t i o n s of chemical principles to the synthesis of nanostructured ceramics, i n t e r m e t a l l i c c o m p o u n d s a n d alloys w e r e d i s c u s s e d . T h e m a t e r i a l s considered included A1N/BN, Si3N4, Fe-Co, FeN/BN, B50 steel a n d Ni base alloys. C h a r a c t e r i s t i c s of p o w d e r s u s e d a n d consolidated m a t e r i a l s were described. A REVIEW OF SYNTHESIS A N D CONSOLIDATION OF NANOMATERIALS
J.J. Stiglich et al (Materials Modification Inc., USA). The history, synthesis a n d consolidation technology of n a n o s t r u c t u r e d materials was reviewed. It was e m p h a s i s e d t h a t f u r t h e r research a n d development, particularly in consolidation technology, is essential if t h e full p o t e n t i a l of t h e s e m a t e r i a l s is to be realized.
Intermetallic materials FABRICATION OF CARBIDES C E M E N T E D BY INTERMETALLIC C O M P O U N D S F O R M E D BY REACTION SYNTHESIS
K.P. McCoy, K. S h a w (Xform Inc., USA). The p r o d u c t i o n of c e m e n t e d carbides w i t h 5 to 10 wt% of a n i n t e r m e t a l l i c c o m p o u n d binder, i n s t e a d of t h e m o r e c o n v e n t i o n a l Co, w a s r e p o r t e d . T h e powder was fabricated by the s i m u l t a n e o u s r e a c t i o n s of c a r b i d e a n d intermetallic. M e c h a n i s m s were discussed with respect to p o w d e r characteristics a n d p h a s e formation. WC-NiA1 was c o m p a r e d with WC-Co. Applications of WC-NiA1 were discussed. MECHANICAL P R O P E R T I E S OF E X T R U D E D NICKEL ALUMINIDE P R O D U C E D BY REACTION SYNTHESIS
R.M. Cooper, V.K. Sikka (Oak Ridge National Laboratory, USA).
PM
lntermetallic materials, reinforced with alumina fibre, were discussed with regard to consolidation, properties and applications. Properties of NiAI-AI203 fibre, fabricated by extrusion, were evaluated. The alloy was further modified by additions of Fe, Mo and Zr. TITANIUM-MANGANESE-ALUMINIUM INTERMETALLIC MATERIALS REINFORCED WITH ZIRCONIA H. Lu et al (Central South University of Technology, Changsha, Hunan, China). It was reported t h a t Ti Mn aluminide, reinforced with ZrO:~ particles had been produced by high energy ball milling, CIP and HIP. The ZrOu was reported to be uniformly dispersed t h r o u g h o u t the matrix and to inhibit grain growth at the sintering t e m p e r a t u r e s of 140~T2:. The bend s t r e n g t h was e n h a n c e d u p t,) 660 MPa by t h e presence of ZrO~.
Machinability of ferrous materials PRODUCTION MODEL FOR DRILLING OF S I N T E R E D S T E E L S I. Shareef. K.tt. Boswell, (Bradley University, USA). The n e e d for s e c o n d a r y m a c h i n i n g operations on sintered ferrous p r o d u c t s was discussed. Drilling e x p e r i m e n t s on a Cu s t e e l w e r e d e s c r i b e d . P a r a m e t e r s studied included drilling forces, surface finish and drill wear. The incorporation of a resin in the steel was r e p o r t e d to give improved results. Models for the prediction of drilling forces were p r e s e n t e d and good agreement with e x p e r i m e n t was reported. Practical implications were outlined. MACHINING S I N T E R E D F E R R O U S MATERIALS WITH E F F I C I E N T MACHINE TOOLS E. Akpan et al (Reliance Electric Co., Weaterville, North Carolina, USA). Data from drilling t e s t s on a range of sintered steels were reported. Commonly used compositions, processed industrially, were drilled with high speed steel and cemented carbide drills. Effect of S on drilling was considered. Data on tool life and surface finish were p r e s e n t e d and the results evaluated with respect to process economies. IMPROVEMENT OF MACHINABILITY OF PM S T E E L S RA. Causton et al (ftoeganaes Corp, Riverton, New Jersey, USA). Machining of sintered steel p a r t s was discussed. It was suggested t h a t machining was a factor which limited production rates. The effects of a novel a d d i t i v e on machinability and sintered properties were evaluated by m e a n s of drilling tests.
LITERATURE
REVIEW
Aluminium alloys ANALYSIS OF GASES EVOLVED DURING D E G A S S I N G OF ALUMINIUM ALLOYS J. Duszczyk et al (Technical University, Delft, The Netherlands). Aspects of moisture and gas evolution during vacuum degassing of porous ternary A1-20%Si base billets were described. The gases were analysed. T e m p e r a t u r e w a s reported to be main factor controlling the rate of degassing. Diffusion of A1 t h r o u g h oxide surface layers was used to explain the k i n e t i c s of d e g a s s i n g of Al p o w d e r s . Thermodynamic data suggested that reaction between Mg and w a t e r vapour occurred in preference to t h a t between Al and H~O. ANALYSIS OF OXIDE FILM ON RAPIDLY SOLIDIFIED ALUMINIUM ALLOY POWDERS J.L.H. Estrada, J. Duszczyk (Technical University, Delft, The N e t h e r l a n d s ) . It was suggested t h a t t e r n a r y alloys based on A1-20%Si and m a d e from RS p o w d e r s have p o t e n t i a l for heavy duty applications. A study of the composition of the surface films on air and Ar atomized powders, using Auger electron spectroscopy, was described the objective being to optimize process conditions. The Ar a t o m i z e d were r e p o r t e d to have a smaller surface area, lower O c o n t e n t and t h i n n e r surface films. The composition of the surface film was influenced by t h e alloy compositions. STRUCTURAL FACTORS IN THE MECHANICAL BEHAVIOUR OF DISCONTINUOUSLY R E I N F O R C E D ALUMINIUM T.M. Osman et al (Case Western Reserve University, USA). The p r o p e r t i e s of d i s c o n t i n u o u s l y reinforced Al alloys were reviewed with r e g a r d to s t r u c t u r e s a n d a e r o s p a c e applications. The factors influencing the behaviour of sintered X2080 reinforced with SiC p a r t i c l e s w e r e d i s c u s s e d . B o t h conventional a n d l a m i n a t e d c o m p o s i t e s were considered.
High performance ferrous materials AUTOMOTIVE POWERTRAIN COMPONENTS BY PM W.F. J a n d e s k a (General Motors Powertrain, USA). The use of PM in the p r o d u c t i o n of automotive powertrain p a r t s was discussed with respect to properties, economics and e n v i r o n m e n t a l c o n s i d e r a t i o n s . It w a s e m p h a s i s e d t h a t higher load bearing capacities and closer dimensional
tolerances in the gear teeth were required if sintered gears were to be more widely used. Material and manufacturing needs w e r e d i s c u s s e d in t e r m s of p r o d u c t demands. DEVELOPMENT OF HIGH PERFORMANCE S l N T E R E D FERROUS MATERIALS W.B. J a m e s ( t t o e g a n a e s Corp, Riverton, New Jersey, USA). The mechanical p r o p e m e s of PM steels were discussed with reference to the effects of density, composition and microstructure. It was p o i n t e d out t h a t l h e r e may be a limiting value of density which can be attained. It was reported t h a t a double p r e s s / d o u b l e sinter approach, with a binder t r e a t e d powder, can attain densities of 7.3 t o 7.5 g i n / e r a 3 in s t e e l w h i c h g i v e s improvements in mechanical properties. HIGH DENSITY P R O C E S S I N G OF HIGH PERFORMANCE F E R R O U S MATERIALS H.G. Rutz, F.H. Hanejko (Los Alamos National Laboratory, USA). An i n v e s t i g a t i o n of ~he m e c h a n i c a l properties of W-8%Ni-2%Fe and W-9%Ni 1%Co was described the objective being to c o m p a r e the /Yacture behaviour of the two alloys a n d to i d e n t i f y t h e c o n n e c t i o n between fracture and ballistic performance. Differences were d e t e c t e d in crack initiation and propagation energies at higher loading rates, the Co alloy being tougher. Fracture by cleavage was found in the W grains and s h e a r in the matrix. CONTROL OF THERMAL CONDUCTIVITY OF TUNGSTENC O P P E R ALLOYS B. Yang, R.M. German (PennsTlvania State University, USA). The influence of process conditions (m the t h e r m a l conductivity of W-Ca alloys was i n v e s t i g a t e d w i t h r e s p e c t to p o w d e r c o a t i n g , ball m i l l i n g a n d i n f i l t r a t i o n sintering. The composition and purity of t h e alloy and process conditions had a significant effect. Conductivity was reported to increase with Cu content and the use of infiltration sintering. Powder coating gave a small increase over the mixed powders. Alloy purity, density and homogeneity all increased the t h e r m a l conductivity. MICROSTRUCTURAL ANALYSIS OF T U N G S T E N HEAVY ALLOYS R.M. G e r m a n et al (Pennsylvania Stale University, USA). It was r e p o r t e d t h a t samples of vacuum sintered W heavy alloys had been c h a r a c t e r i z e d for g r a v i t y s e g r e g a t i o n dimensional changes and microstructural evolution. Pore evolution and grain growth w e r e d i s c u s s e d . The o b j e c t i v e was to p r o v i d e s a m p l e s for c o m p a r i s o n with s p e c i m e n s s i n t e r e d u n d e r micro-gravity during a space shuttle flight.
M P R October 1994 43
C.W.P. Finn, U.N.S. Prasad (North E a s t e r n University, USA). A study of d e b i n d i n g of 316L stainless steel, w i t h a t h r e e c o m p o n e n t b i n d e r comprising paraffin wax, stearic acid a n d polypropylene, was described. Weight losses in m e d i u m to high v a c u u m was m e a s u r e d by t h e r m o g r a v i m e t r y a n d rates were shown to b e e x p o n e n t i a l a t t e m p e r a t u r e s of evaporation a n d decomposition of b i n d e r components. The correlations between t i m e a n d t e m p e r a t u r e were u s e d to m o d e l debinding. The results were discussed. METAL INJECTION MOULDING FOR MANUFACTURE OF PRECIOUS METAL COMPONENTS
J.T. Strauss (HJE Corp, USA). MIM for t h e p r o d u c t i o n of small m e t a l p a r t s was discussed with reference to t h e benefits gained including dimensional tolerances, material properties and p r o d u c t i o n rates. The p a p e r p r e s e n t e d t h e a d v a n t a g e s a n d d i s a d v a n t a g e s of using MIM in jewellery m a n u f a c t u r e a n d discussed t h e technological a n d o t h e r b a r r i e r s to its adoption. PROCESSING OF SUPERALLOYS BY POWDER INJECTION MOULDING
ICF. Hens, R.M. G e r m a n (Pennsylvania State University, Pennsylvania, USA). An i n v e s t i g a t i o n of MIM of Ni-base superalloys was described. It was r e p o r t e d t h a t Icone1625 can be injection m o u l d e d b u t t h a t Inconel718 a n d Rene88 required careful analysis a n d control. The s t u d y covered f e e d s t o c k rheology, d i l a t o m e t r y a n d d i f f e r e n t i a l t h e r m a l a n a l y s i s of debinding and sintering. Careful processing a n d m o n i t o r i n g were required to make complex s h a p e d components. ULTRASONIC S E N S O R S FOR POWDER INJECTION MOULDING
R.M. G e r m a n et al (Pennsylvania S t a t e University, Pennsylvania, USA). The use of ultrasonic sensors in t h e m o u l d cavity to m o n i t o r i n j e c t i o n was discussed with reference to detection of defects, s h o r t shots, flash, j e t t i n g sticking a n d variations in bulk a n d s h e a r moduli. Real time m o n i t o r i n g of a n o m a l i e s which d e t e r m i n e quality h a s been carried out. A novel ultrasonic guided wave t e c h n i q u e was reported.
42 MPR October 1994
SIMULATION OF POWDER INJECTION MOULDING
IN-SITU SYNTHE S I S / D E N S I F I C A T I O N OF CERMET MATERIALS
C. Wang et al ( C o n c u r r e n t Technologies Corp, USA) Recent developments in t h e evolution of a c o m p u t e r p r o g r a m m e for t h e simulation of i n j e c t i o n m o u l d i n g w e r e d e s c r i b e d including calculation of air p r e s s u r e in t h e m o u l d cavity, b i n d e r solidification a n d shrinkage during freezing. The system was r e p o r t e d to aid in t h e selection of design p a r a m e t e r s , optimization of moulding a n d process control. C o m p a r i s o n was m a d e with e x p e r i m e n t a l results a n d a n e x a m p l e of t h e calculation was given.
R.V. R a m a n et al (Ceracon Inc., Sacramento, California, USA). A new processing approach to production of dense materials was described. Results of a modelling procedure were incorporated in the process control system. Effects of process v a r i a b l e s o n p r o p e r t i e s were o u t l i n e d . Microstructure a n d p r o p e r t i e s of a cermet and an intermetallic material were described.
PRECISE MOULD TEMPERATURE CONTROL
D.I. Seres (Injection Moulding Industries, USA.) The i m p o r t a n c e of control of m o u l d a n d feedstock temperatures in MIM w a s discussed. It was suggested t h a t where only t h e m o u l d t e m p e r a t u r e is controlled t h e r e may be u n a c c e p t a b l e v a r i a t i o n s in temperature. The novel technology described was r e p o r t e d to allow t h e m o u l d to be p r e h e a t e d to t h e o p t i m u m process t e m p e r a t u r e a n d cooled with a high h e a t e x t r a c t i o n r a t e giving a m o r e u n i f o r m t e m p e r a t u r e profile t h r o u g h t h e mould.
Self-propagating high temperature synthesis JOINING BY SELF-PROPAGATING HIGH TEMPERATURE SYNTHESIS
R.W. Messler, T.T. Orling, (Rensselaer Polytechnic Inst., Troy, New York, USA.) The use of SHS for t h e p r o d u c t i o n of refractory metals, ceramics and intermetallic materials was discussed with reference to t h e p o t e n t i a l of t h e t e c h n i q u e to m a k e j o i n t s between similar or dissimilar materials. A model study of t h e use of Ni a n d Al powders to m a k e Ni a l u m i n i d e j o i n t s between Ni base alloy end e l e m e n t s a n d between Si a n d Ni base superalloys was reported. SELF-PROPAGATING HIGH TEMPERATURE SYNTHESIS OF SILICON NITRIDE AT LOWER NITROGEN P R E S S U R E
C.C. Ge et al (University of Science a n d Technology, Beijing, China). The synthesis of Si3N4 a n d Mg3N2 was described. It was concluded t h a t Si could be completely converted to SiaN4 in presence of Mg. The presence of Mg was found to influence to porosity of t h e m a t e r i a l during combustion. A mechanism for the f o r m a t i o n of Si3N4 u n d e r low p r e s s u r e s of N was proposed.
Fine-scale particulate materials CHEMICAL SYNTHESIS OF N A N O S T R U C T U R E S MATERIALS
ICE. Gonsalves et al (University of Connecticut, USA). The a p p l i c a t i o n s of chemical principles to the synthesis of nanostructured ceramics, i n t e r m e t a l l i c c o m p o u n d s a n d alloys w e r e d i s c u s s e d . T h e m a t e r i a l s considered included A1N/BN, Si3N4, Fe-Co, FeN/BN, B50 steel a n d Ni base alloys. C h a r a c t e r i s t i c s of p o w d e r s u s e d a n d consolidated m a t e r i a l s were described. A REVIEW OF SYNTHESIS A N D CONSOLIDATION OF NANOMATERIALS
J.J. Stiglich et al (Materials Modification Inc., USA). The history, synthesis a n d consolidation technology of n a n o s t r u c t u r e d materials was reviewed. It was e m p h a s i s e d t h a t f u r t h e r research a n d development, particularly in consolidation technology, is essential if t h e full p o t e n t i a l of t h e s e m a t e r i a l s is to be realized.
Intermetallic materials FABRICATION OF CARBIDES C E M E N T E D BY INTERMETALLIC C O M P O U N D S F O R M E D BY REACTION SYNTHESIS
K.P. McCoy, K. S h a w (Xform Inc., USA). The p r o d u c t i o n of c e m e n t e d carbides w i t h 5 to 10 wt% of a n i n t e r m e t a l l i c c o m p o u n d binder, i n s t e a d of t h e m o r e c o n v e n t i o n a l Co, w a s r e p o r t e d . T h e powder was fabricated by the s i m u l t a n e o u s r e a c t i o n s of c a r b i d e a n d intermetallic. M e c h a n i s m s were discussed with respect to p o w d e r characteristics a n d p h a s e formation. WC-NiA1 was c o m p a r e d with WC-Co. Applications of WC-NiA1 were discussed. MECHANICAL P R O P E R T I E S OF E X T R U D E D NICKEL ALUMINIDE P R O D U C E D BY REACTION SYNTHESIS
R.M. Cooper, V.K. Sikka (Oak Ridge National Laboratory, USA).
PM
lntermetallic materials, reinforced with alumina fibre, were discussed with regard to consolidation, properties and applications. Properties of NiAI-AI203 fibre, fabricated by extrusion, were evaluated. The alloy was further modified by additions of Fe, Mo and Zr. TITANIUM-MANGANESE-ALUMINIUM INTERMETALLIC MATERIALS REINFORCED WITH ZIRCONIA H. Lu et al (Central South University of Technology, Changsha, Hunan, China). It was reported t h a t Ti Mn aluminide, reinforced with ZrO:~ particles had been produced by high energy ball milling, CIP and HIP. The ZrOu was reported to be uniformly dispersed t h r o u g h o u t the matrix and to inhibit grain growth at the sintering t e m p e r a t u r e s of 140~T2:. The bend s t r e n g t h was e n h a n c e d u p t,) 660 MPa by t h e presence of ZrO~.
Machinability of ferrous materials PRODUCTION MODEL FOR DRILLING OF S I N T E R E D S T E E L S I. Shareef. K.tt. Boswell, (Bradley University, USA). The n e e d for s e c o n d a r y m a c h i n i n g operations on sintered ferrous p r o d u c t s was discussed. Drilling e x p e r i m e n t s on a Cu s t e e l w e r e d e s c r i b e d . P a r a m e t e r s studied included drilling forces, surface finish and drill wear. The incorporation of a resin in the steel was r e p o r t e d to give improved results. Models for the prediction of drilling forces were p r e s e n t e d and good agreement with e x p e r i m e n t was reported. Practical implications were outlined. MACHINING S I N T E R E D F E R R O U S MATERIALS WITH E F F I C I E N T MACHINE TOOLS E. Akpan et al (Reliance Electric Co., Weaterville, North Carolina, USA). Data from drilling t e s t s on a range of sintered steels were reported. Commonly used compositions, processed industrially, were drilled with high speed steel and cemented carbide drills. Effect of S on drilling was considered. Data on tool life and surface finish were p r e s e n t e d and the results evaluated with respect to process economies. IMPROVEMENT OF MACHINABILITY OF PM S T E E L S RA. Causton et al (ftoeganaes Corp, Riverton, New Jersey, USA). Machining of sintered steel p a r t s was discussed. It was suggested t h a t machining was a factor which limited production rates. The effects of a novel a d d i t i v e on machinability and sintered properties were evaluated by m e a n s of drilling tests.
LITERATURE
REVIEW
Aluminium alloys ANALYSIS OF GASES EVOLVED DURING D E G A S S I N G OF ALUMINIUM ALLOYS J. Duszczyk et al (Technical University, Delft, The Netherlands). Aspects of moisture and gas evolution during vacuum degassing of porous ternary A1-20%Si base billets were described. The gases were analysed. T e m p e r a t u r e w a s reported to be main factor controlling the rate of degassing. Diffusion of A1 t h r o u g h oxide surface layers was used to explain the k i n e t i c s of d e g a s s i n g of Al p o w d e r s . Thermodynamic data suggested that reaction between Mg and w a t e r vapour occurred in preference to t h a t between Al and H~O. ANALYSIS OF OXIDE FILM ON RAPIDLY SOLIDIFIED ALUMINIUM ALLOY POWDERS J.L.H. Estrada, J. Duszczyk (Technical University, Delft, The N e t h e r l a n d s ) . It was suggested t h a t t e r n a r y alloys based on A1-20%Si and m a d e from RS p o w d e r s have p o t e n t i a l for heavy duty applications. A study of the composition of the surface films on air and Ar atomized powders, using Auger electron spectroscopy, was described the objective being to optimize process conditions. The Ar a t o m i z e d were r e p o r t e d to have a smaller surface area, lower O c o n t e n t and t h i n n e r surface films. The composition of the surface film was influenced by t h e alloy compositions. STRUCTURAL FACTORS IN THE MECHANICAL BEHAVIOUR OF DISCONTINUOUSLY R E I N F O R C E D ALUMINIUM T.M. Osman et al (Case Western Reserve University, USA). The p r o p e r t i e s of d i s c o n t i n u o u s l y reinforced Al alloys were reviewed with r e g a r d to s t r u c t u r e s a n d a e r o s p a c e applications. The factors influencing the behaviour of sintered X2080 reinforced with SiC p a r t i c l e s w e r e d i s c u s s e d . B o t h conventional a n d l a m i n a t e d c o m p o s i t e s were considered.
High performance ferrous materials AUTOMOTIVE POWERTRAIN COMPONENTS BY PM W.F. J a n d e s k a (General Motors Powertrain, USA). The use of PM in the p r o d u c t i o n of automotive powertrain p a r t s was discussed with respect to properties, economics and e n v i r o n m e n t a l c o n s i d e r a t i o n s . It w a s e m p h a s i s e d t h a t higher load bearing capacities and closer dimensional
tolerances in the gear teeth were required if sintered gears were to be more widely used. Material and manufacturing needs w e r e d i s c u s s e d in t e r m s of p r o d u c t demands. DEVELOPMENT OF HIGH PERFORMANCE S l N T E R E D FERROUS MATERIALS W.B. J a m e s ( t t o e g a n a e s Corp, Riverton, New Jersey, USA). The mechanical p r o p e m e s of PM steels were discussed with reference to the effects of density, composition and microstructure. It was p o i n t e d out t h a t l h e r e may be a limiting value of density which can be attained. It was reported t h a t a double p r e s s / d o u b l e sinter approach, with a binder t r e a t e d powder, can attain densities of 7.3 t o 7.5 g i n / e r a 3 in s t e e l w h i c h g i v e s improvements in mechanical properties. HIGH DENSITY P R O C E S S I N G OF HIGH PERFORMANCE F E R R O U S MATERIALS H.G. Rutz, F.H. Hanejko (Los Alamos National Laboratory, USA). An i n v e s t i g a t i o n of ~he m e c h a n i c a l properties of W-8%Ni-2%Fe and W-9%Ni 1%Co was described the objective being to c o m p a r e the /Yacture behaviour of the two alloys a n d to i d e n t i f y t h e c o n n e c t i o n between fracture and ballistic performance. Differences were d e t e c t e d in crack initiation and propagation energies at higher loading rates, the Co alloy being tougher. Fracture by cleavage was found in the W grains and s h e a r in the matrix. CONTROL OF THERMAL CONDUCTIVITY OF TUNGSTENC O P P E R ALLOYS B. Yang, R.M. German (PennsTlvania State University, USA). The influence of process conditions (m the t h e r m a l conductivity of W-Ca alloys was i n v e s t i g a t e d w i t h r e s p e c t to p o w d e r c o a t i n g , ball m i l l i n g a n d i n f i l t r a t i o n sintering. The composition and purity of t h e alloy and process conditions had a significant effect. Conductivity was reported to increase with Cu content and the use of infiltration sintering. Powder coating gave a small increase over the mixed powders. Alloy purity, density and homogeneity all increased the t h e r m a l conductivity. MICROSTRUCTURAL ANALYSIS OF T U N G S T E N HEAVY ALLOYS R.M. G e r m a n et al (Pennsylvania Stale University, USA). It was r e p o r t e d t h a t samples of vacuum sintered W heavy alloys had been c h a r a c t e r i z e d for g r a v i t y s e g r e g a t i o n dimensional changes and microstructural evolution. Pore evolution and grain growth w e r e d i s c u s s e d . The o b j e c t i v e was to p r o v i d e s a m p l e s for c o m p a r i s o n with s p e c i m e n s s i n t e r e d u n d e r micro-gravity during a space shuttle flight.
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