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Micro-infiltrated macro-laminated composites (MIMLC) — concepts for fabrication
PM
for direct Auger and secondary ion mass spectroscopy (SIMS), avoiding contact with air was described. Results for Ti-48at%A1 at various stages of p a r t production, using HIP, were presented. NON-DESTRUCTIVE WEAR T E S T FOR DIAMOND/CARBIDE CUTTING PLATE A.L. Maistranko et al (Inst for SuperHard Materials, Ukraine). A non-destructive wear test for cutting tool materials was described. The test was reported to be quick and efficient and to be based of acoustic emission (AE) for a s a m p l e u n d e r l o a d . T h e AE s i g n a l parameters were related to wear resistance and enabled quality control to be exercised.
Composite materials DEVELOPMENT OF NEAR N E T SHAPE STRUCTURAL PARTS IN METAL MATRIX COMPOSITE ( M M C ) H. Cohrt et al (Schunk Sintermetalltechnik, Oberhausen, Germany). Attention was drawn to the fact t h a t the high cost of MMC limits a p p l i c a t i o n s o u t s i d e t h e a e r o s p a c e i n d u s t r i e s . The p a p e r described an investigation of the PM processing of A1-4.5%Cu-0 5%Si-0.5%Mg powders with additions of ultrafine SiC particulates to produce p a r t s with high strength particularly at elevated temperatures. Tensile s t r e n g t h of 400 MPa and young's m o d u l u s of 105 GPa were reported. COMPACTION OF ALUMINIUM POWDERS REINFORCED WITH SILICON CARBIDE PARTICLES R. Sagar et al (Indian Inst of Technology, Delhi, India). I s o s t a t i c p r e s s i n g at 625 MPa a n d s i n t e r i n g were u s e d to c o n s o l i d a t e mixtures of A1 powder (75 to 150 ~m) with 10, 20, 30, or 40 wt% SiC powder (75 to 100 pm). The production of lightweight h i g h - s t r e n g t h c o m p o s i t e s was reported. Scanning electron microscopy was used to investigate grain s h a p e and distribution after sintering. MECHANICAL P R O P E R T I E S OF E X T R U D E D PM ALUMINIUM ALLOY REINFORCED WITH SILICON CARBIDE C-H. Lee et al (Inha University, Korea). The microstructure and properties of extruded 2024A1/SiC particulate composites were investigated as a function of extrusion ratio (ER). The distribution of SiC was reported to d e p e n d on the ratio, becoming more uniform with increase in ER which also reduced deviations in tensile strengths. Significant increase in tensile strength at 350°C was reported for alloy
LITERATURE
REVIEW
containing 20% SiC with a c o n s e q u e n t r e d u c t i o n in ductility. The c o m p o s i t e s were found to have reduced strain rate sensitivity. REINFORCED HIGH S P E E D S T E E L S ( H S S ) AS METAL MATRIX COMPOSITES ( M M C ) R.A. Queeney (Pennsylvania State University, USA). The properties of HSS, considered as MMC, were discussed. It was pointed out t h a t there is a limit to the p r o p o r t i o n of carbides which can be p r e s e n t w h e n the HSS is m a d e by ingot metallurgy but this does not apply w h e n PM processes are used. The addition of further carbides by comilling HSS powders, such as M4 or T15, with carbides of Ti, V, Mo and W and A1203 was considered and it was r e p o r t e d t h a t these h a d been successfully incorporated in the steel. The m o s t promising composites were reviewed and possible future t r e n d s were discussed. STRUCTURE AND P R O P E R T I E S OF METAL MATRIX COMPOSITES ( M M C ) BASED ON MIXTURES OF HIGH S P E E D STEEL ( H S S ) AND ADDITIONAL TITANIUM CARBIDE AND E F F E C T S OF COPPER P H O S P H I D E ON SINTERING
J.D. Bolton et al (Bradford University, Bradford, UK). Cu p h o s p h o r u s additions to PM HSS were r e p o r t e d to reduce the t e m p e r a t u r e r e q u i r e d to a t t a i n n e a r full d e n s i t y sufficiently to enable the use of c o n t i n u o u s belt s i n t e r i n g f u r n a c e s a n d thus facilitate m a s s production of wear resistant components. Addition of up to 15% TiC powder was reported to p r e s e n t little difficulty in attaining near full density on sintering at 1150 to 1200°C. Sintering was aided by use of Co coated TiC powder and graphite additions. The structures were r e p o r t e d to contain a fine dispersion of TiC with little evidence of dissolution of TiC. In presence of V there was an interfacial layer the presence of which was a t t r i b u t e d to a dissolution/precipitation mechanism. The p r o p e r t i e s of t h e HSS c o m p o s i t e were c o m p a r e d with conventional HSS and were said to be a d e q u a t e for t h e i n t e n d e d applications. MICRO-INFILTRATED MACROLAMINATED COMPOSITES (MIMLC) -- CONCEPTS FOR FABRICATION A. Bose (South West Research Inst, USA). The p a p e r described a novel composite architecture in which layers of a h a r d brittle ceramic alternate with ductile tough metallike layers. It was suggested t h a t this could incorporate a range of material p r o p e r t i e s by s e l e c t i o n o f l a y e r m a t e r i a l s a n d thicknesses and t h a t a graded structure
could also be made. Proposed application included wear resistant p a r t s where the h a r d p h a s e provides the wear resistance and the ductile p h a s e resistance to fracture. It was r e p o r t e d t h a t the ceramic layers were i n t e r p e n e t r a t e d with the ductile phase. APPLICATION OF G R A D E D STRUCTURES A S A MEANS OF IMPROVING PERFORMANCE OF ENGINEERING COMPONENTS G.P. Yiasemides, NJ.E. Adkins (BNF-Fulmer, Wantage, UK). Materials with compositionally graded structures were discussed with regard to the advantages offered in comparison with conventionally coated materials, p a r t i c u l a r l y t h e ability to avoid s h a r p c h a n g e s in p r o p e r t i e s , e.g. t h e r m a l e x p a n s i o n , at t h e interface. The p a p e r discussed the m e a n s for the production of such graded material. The application of g r a d e d m a t e r i a l s to m i n i n g tools w a s considered and applications in t r a n s p o r t were predicted. It was suggested t h a t the use of compositionally graded materials will o v e r c o m e c e r t a i n d i f f i c u l t i e s in t h e applications of engineering ceramics with metallic materials. FABRICATION OF FUNCTIONALLY GRADIENT MATERIALS ( F G M ) BY HOT P R E S S I N G AND THEIR THERMOMECHANICAL PERFORMANCE R. Watanabe et al (Tohoku University, Japan). The use of hot pressing to produce an FGM, a m a t e r i a l w i t h a c o m p o s i t i o n gradient, between a ceramic semis t a b i l i z e d ZrO2, a n d a s t a i n l e s s s t e e l s u b s t r a t e w a s d e s c r i b e d . The t h e r m a l behaviour of the materials was assessed u n d e r a steep t e m p e r a t u r e gradient as f u n c t i o n s of c o m p o s i t i o n p r o f i l e a n d t h i c k n e s s o f t h e g r a d e d layer. T h e m e c h a n i s m s of crack initiation and growth were discussed with regard to the thermal stress conditions. The i m p o r t a n c e of the composition profile design for o p t i m u m t h e r m o m e c h a n i c a l r e s p o n s e was discussed. CONTINUOUS CARBON FIBRE R E I N F O R C E D ALUMINIUM MATRIX COMPOSITES MADE BY PM P. R a m a k r i s h n a n et al (Indian Inst of Technology, Kanpur, India). The use of PM techniques to consolidate preforms m a d e from carbon fibre coated with A1 powder was described. Process conditions were optimized for the vacuum hot p r e s s i n g r o u t e used. The alloy containing 16 vol% C fibre e x h i b i t e d a tensile s t r e n g t h of 178 MPa c o m p a r e d with t h a t of the unreinforced alloy which was 73 MPa. Reaction between matrix and fibre were e x a m i n e d and the increased
M P R D e c e m b e r 1992 55
for direct Auger and secondary ion mass spectroscopy (SIMS), avoiding contact with air was described. Results for Ti-48at%A1 at various stages of p a r t production, using HIP, were presented. NON-DESTRUCTIVE WEAR T E S T FOR DIAMOND/CARBIDE CUTTING PLATE A.L. Maistranko et al (Inst for SuperHard Materials, Ukraine). A non-destructive wear test for cutting tool materials was described. The test was reported to be quick and efficient and to be based of acoustic emission (AE) for a s a m p l e u n d e r l o a d . T h e AE s i g n a l parameters were related to wear resistance and enabled quality control to be exercised.
Composite materials DEVELOPMENT OF NEAR N E T SHAPE STRUCTURAL PARTS IN METAL MATRIX COMPOSITE ( M M C ) H. Cohrt et al (Schunk Sintermetalltechnik, Oberhausen, Germany). Attention was drawn to the fact t h a t the high cost of MMC limits a p p l i c a t i o n s o u t s i d e t h e a e r o s p a c e i n d u s t r i e s . The p a p e r described an investigation of the PM processing of A1-4.5%Cu-0 5%Si-0.5%Mg powders with additions of ultrafine SiC particulates to produce p a r t s with high strength particularly at elevated temperatures. Tensile s t r e n g t h of 400 MPa and young's m o d u l u s of 105 GPa were reported. COMPACTION OF ALUMINIUM POWDERS REINFORCED WITH SILICON CARBIDE PARTICLES R. Sagar et al (Indian Inst of Technology, Delhi, India). I s o s t a t i c p r e s s i n g at 625 MPa a n d s i n t e r i n g were u s e d to c o n s o l i d a t e mixtures of A1 powder (75 to 150 ~m) with 10, 20, 30, or 40 wt% SiC powder (75 to 100 pm). The production of lightweight h i g h - s t r e n g t h c o m p o s i t e s was reported. Scanning electron microscopy was used to investigate grain s h a p e and distribution after sintering. MECHANICAL P R O P E R T I E S OF E X T R U D E D PM ALUMINIUM ALLOY REINFORCED WITH SILICON CARBIDE C-H. Lee et al (Inha University, Korea). The microstructure and properties of extruded 2024A1/SiC particulate composites were investigated as a function of extrusion ratio (ER). The distribution of SiC was reported to d e p e n d on the ratio, becoming more uniform with increase in ER which also reduced deviations in tensile strengths. Significant increase in tensile strength at 350°C was reported for alloy
LITERATURE
REVIEW
containing 20% SiC with a c o n s e q u e n t r e d u c t i o n in ductility. The c o m p o s i t e s were found to have reduced strain rate sensitivity. REINFORCED HIGH S P E E D S T E E L S ( H S S ) AS METAL MATRIX COMPOSITES ( M M C ) R.A. Queeney (Pennsylvania State University, USA). The properties of HSS, considered as MMC, were discussed. It was pointed out t h a t there is a limit to the p r o p o r t i o n of carbides which can be p r e s e n t w h e n the HSS is m a d e by ingot metallurgy but this does not apply w h e n PM processes are used. The addition of further carbides by comilling HSS powders, such as M4 or T15, with carbides of Ti, V, Mo and W and A1203 was considered and it was r e p o r t e d t h a t these h a d been successfully incorporated in the steel. The m o s t promising composites were reviewed and possible future t r e n d s were discussed. STRUCTURE AND P R O P E R T I E S OF METAL MATRIX COMPOSITES ( M M C ) BASED ON MIXTURES OF HIGH S P E E D STEEL ( H S S ) AND ADDITIONAL TITANIUM CARBIDE AND E F F E C T S OF COPPER P H O S P H I D E ON SINTERING
J.D. Bolton et al (Bradford University, Bradford, UK). Cu p h o s p h o r u s additions to PM HSS were r e p o r t e d to reduce the t e m p e r a t u r e r e q u i r e d to a t t a i n n e a r full d e n s i t y sufficiently to enable the use of c o n t i n u o u s belt s i n t e r i n g f u r n a c e s a n d thus facilitate m a s s production of wear resistant components. Addition of up to 15% TiC powder was reported to p r e s e n t little difficulty in attaining near full density on sintering at 1150 to 1200°C. Sintering was aided by use of Co coated TiC powder and graphite additions. The structures were r e p o r t e d to contain a fine dispersion of TiC with little evidence of dissolution of TiC. In presence of V there was an interfacial layer the presence of which was a t t r i b u t e d to a dissolution/precipitation mechanism. The p r o p e r t i e s of t h e HSS c o m p o s i t e were c o m p a r e d with conventional HSS and were said to be a d e q u a t e for t h e i n t e n d e d applications. MICRO-INFILTRATED MACROLAMINATED COMPOSITES (MIMLC) -- CONCEPTS FOR FABRICATION A. Bose (South West Research Inst, USA). The p a p e r described a novel composite architecture in which layers of a h a r d brittle ceramic alternate with ductile tough metallike layers. It was suggested t h a t this could incorporate a range of material p r o p e r t i e s by s e l e c t i o n o f l a y e r m a t e r i a l s a n d thicknesses and t h a t a graded structure
could also be made. Proposed application included wear resistant p a r t s where the h a r d p h a s e provides the wear resistance and the ductile p h a s e resistance to fracture. It was r e p o r t e d t h a t the ceramic layers were i n t e r p e n e t r a t e d with the ductile phase. APPLICATION OF G R A D E D STRUCTURES A S A MEANS OF IMPROVING PERFORMANCE OF ENGINEERING COMPONENTS G.P. Yiasemides, NJ.E. Adkins (BNF-Fulmer, Wantage, UK). Materials with compositionally graded structures were discussed with regard to the advantages offered in comparison with conventionally coated materials, p a r t i c u l a r l y t h e ability to avoid s h a r p c h a n g e s in p r o p e r t i e s , e.g. t h e r m a l e x p a n s i o n , at t h e interface. The p a p e r discussed the m e a n s for the production of such graded material. The application of g r a d e d m a t e r i a l s to m i n i n g tools w a s considered and applications in t r a n s p o r t were predicted. It was suggested t h a t the use of compositionally graded materials will o v e r c o m e c e r t a i n d i f f i c u l t i e s in t h e applications of engineering ceramics with metallic materials. FABRICATION OF FUNCTIONALLY GRADIENT MATERIALS ( F G M ) BY HOT P R E S S I N G AND THEIR THERMOMECHANICAL PERFORMANCE R. Watanabe et al (Tohoku University, Japan). The use of hot pressing to produce an FGM, a m a t e r i a l w i t h a c o m p o s i t i o n gradient, between a ceramic semis t a b i l i z e d ZrO2, a n d a s t a i n l e s s s t e e l s u b s t r a t e w a s d e s c r i b e d . The t h e r m a l behaviour of the materials was assessed u n d e r a steep t e m p e r a t u r e gradient as f u n c t i o n s of c o m p o s i t i o n p r o f i l e a n d t h i c k n e s s o f t h e g r a d e d layer. T h e m e c h a n i s m s of crack initiation and growth were discussed with regard to the thermal stress conditions. The i m p o r t a n c e of the composition profile design for o p t i m u m t h e r m o m e c h a n i c a l r e s p o n s e was discussed. CONTINUOUS CARBON FIBRE R E I N F O R C E D ALUMINIUM MATRIX COMPOSITES MADE BY PM P. R a m a k r i s h n a n et al (Indian Inst of Technology, Kanpur, India). The use of PM techniques to consolidate preforms m a d e from carbon fibre coated with A1 powder was described. Process conditions were optimized for the vacuum hot p r e s s i n g r o u t e used. The alloy containing 16 vol% C fibre e x h i b i t e d a tensile s t r e n g t h of 178 MPa c o m p a r e d with t h a t of the unreinforced alloy which was 73 MPa. Reaction between matrix and fibre were e x a m i n e d and the increased
M P R D e c e m b e r 1992 55