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Effects of extrusion conditions on mechanical properties of a sintered aluminium alloy
h e a t treated. The s t r u c t u r e a n d p r o p e r t i e s were investigated a n d it was found t h a t p a r t i c l e s of Fe b e a r i n g i n t e r m e t a l l i c c o m p o u n d s block t h e m o v e m e n t of grain b o u n d a r i e s a n d sub-grain boundaries. As a result of t h e Fe a d d i t i o n t h e h o t s t r e n g t h of the alloy up to 300°C was increased a n d this is considered to be of i m p o r t a n c e in IC engine use. STRUCTURAL INVESTIGATION OF T H E MECHANICALLY ALLOYED ( M A ) ALUMINIUM SYSTEM Y.D.Dong et al. (Academica Sinica, Beijing, China.) Materials Science and Engineering A Vol A134, 1991, 867-871. Elemental powder m i x t u r e s containing A1 a n d 10 to 60at%Fe were mechanical alloyed (MA) a n d the resulting powders w e r e e x a m i n e d by X - r a y d i f f r a c t i o n , electron microscopy and Mossbauer spectroscopy, Amorphous and nanocrystalline s t r u c t u r e s were observed. In t h e range 20 to 50%Fe the powders were found to be m a i n l y a m o r p h o u s a n d n a n o crystalline s t r u c t u r e s were found outside this range. Electron microscopy demonstrated t h e p r e s e n c e of s m a l l crystallites in A1-20%Fe. It is suggested t h e AI-Fe alloys cannot be completely a m o r p h i s e d by MA > MICROSTRUCTURAL CHARACTERISATION OF A T O M I S E D ALUMINIUM-SILICON-IRONMANGANESE ALLOY POWDERS L.A.Bendersky et al. (US National I n s t i t u t e of S t a n d a r d s a n d Technology, USA~) Mate-
rials Science and Engineering A, VolA134, 1991, 1098-1102. A1-5wt%Mn-5%Fe-2%Si rapidly solidified (RS) p o w d e r w a s c o n s o l i d a t e d and e x a m i n e d by e l e c t r o n m i c r o s c o p y in particle size sorted powders and consolidate forms. The relationships between s t r u c t u r e a n d particle size was, in increasing particle size order, microcellular/cellular AI with intercellular phases, euteetic and primary globular particles. The c o m p a c t e d alloy c o n t a i n e d fine, slow c o a r s e n i n g d i s p e r s o i d s . The s t r u c t u r e s were discussed with regard to t h e p h a s e s p r e s e n t a n d t h e degree of undercooling, HOT ROLLING O F RAPIDLY S O L I D I F I E D ( R S ) ALUMINIUMCHROMIUM-ZIRCONIUM-MANGANESE ALLOY POWDERS M.P.Silva et al, (University of Sheffield, England.) Materials SvienceandEngineeringA, VolA134, 1991, 1107-1110. The consolidation of A1-5wt%Cr-2%Zr1%Mn RS p o w d e r by h o t rolling a n d forging was studied w i t h respect to t h e effects of working on tensile properties. A useful c o m b i n a t i o n of s t r e n g t h a n d ductility was a t t a i n e d w h e n due regard was p a i d to process p a r a m e t e r s , degassing, c o m p a c t i o n
a n d rolling conditions. The occurrence of age h a r d e n i n g p h e n o m e n a was a t t r i b u t e d to t h e effectiveness of RS in r e t a i n i n g s u p e r s a t u r a t i o n of solute elements, SURFACE CHARACTERISATION O F ALUMINIUM ALLOY POWDER B E F O R E AND A F T E R HOT E X T R U S I O N A.Nylund, I.Olefjord. ( C h a l m e r s University of Technology, Sweden.) Materials Science and Engineemng A, Vol A134, 1991, 11391143. The surface reaction p r o d u c t s formed during atomisation, handling and consolidation on A1-5%Mn-2.5%Cr powders a n d consolidated m a t e r i a l were studied by electron spectroscopy (ESCA a n d Auger). The powders were found to be oxidised even at low 0 partial pressures equivalent to less t h a n 40ppm. At high t e m p e r a t u r e s oxide 'islands' are formed on particle surfaces a n d a t low t e m p e r a t u r e s a t h i n 20A oxide layer develops between t h e islands. Mean oxide thickness is a b o u t 50.~. On e x t r u s i o n at a ratio (ER) of 20 to 1 t h e surface oxide breaks u p a n d redistributes in t h e alloy. At a n ER of 10 to 1 t h e oxide r e m a i n s at t h e prior particle boundaries and reduces s t r e n g t h a n d ductility. M I C R O S T R U C T U R E AND P R O P E R T I E S O F H I G H P R E S S U R E GAS A T O M I S E D ALUMINIUM-LITHIUMFNIUM ALLOYS A~F.Norman, P.Tsakirpoulos. (University of Surrey, Guildford, E n g l a n d . ) Materials Science and Engineering A, Vol A134, 1991, 1144-1147. A1-2.2%Li-1.2%Hf powders were produced by high pressure gas a t o m i s a t i o n a n d t h e sub 45 ~ m fraction was separated and consolidated by e x t r u s i o n , p r e c i p i t a t i o n of a n A1-Li-Hf p h a s e was detected on solution t r e a t m e n t at 450°C a n d t h e 5' p h a s e during again at 190°C. Peak s t r e n g t h was developed after 1 h o u r at 190°C. The c o n t r i b u t i o n s of t h e various s t r e n g t h e n i n g m e c h a n i s m s were calculated. COLD D E F O R M A T I O N BEHAVIOUR O F SINTERED ALUMINIUM-COPPER ALLOYS POWDER P R E F O R M S I~S.Pandey. (Regional Engineering College, Tiruchirapalli, India.) Powder Metallurgy Science and Technology, Vol 2, No 4, 1991, 45-54. An i n v e s t i g a t i o n of t h e d e f o r m a t i o n behaviour of sinter~d A 1 - 4 % C u is described. The c o m p a c t s were p r o t e c t e d from o x i d a t i o n d u r i n g s i n t e r i n g by a ceramic coating. Cylindrical c o m p a c t s of different aspect ratios, in t h e r a n g e 1.5 to 3.0:1 were prepared, s i n t e r e d a n d subjected to d e f o r m a t i o n in c o m p r e s s i o n w i t h o u t l u b r i c a n t or with g r a p h i t e a t t h e c o m p a c t / die interface. D i m e n s i o n a l changes, t h e a p p e a r a n c e of cracks a n d t h e o n s e t of fracture were recorded. It was concluded
t h a t t h e densification curves were t h e same irrespective of aspect ratio a n d lubrication conditions, poisson's ratio was found to increase to a value a p p r o a c h i n g 0.5 as t h e density t e n d e d to 100%. STUDY OF DRY M I X I N G O F CERAMIC F I B R E S WITH A L U M I N I U M ALLOY POWDER J.H.ter Haar, J.Duszczyk. (Delft University of Technology, Delft, The N e t h e r l a n d s . ) J.
Materials Science, Vol 36, 1991, 36283638. The mixing of AI-20wt%Si-3%Cu-l%Mg alloy powder with A1203 a n d SiC fibres was studied with regard to de-agglomeration of t h e fibres a n d p r e p a r a t i o n of h o m o g e n e o u s m i x t u r e . Mixing was c a r r i e d o u t in a cylindrical tumbler with and without ceramic balls. After m i x i n g t h e powders were characterised as to particle size a n d shape, h a r d n e s s a n d specific surface. Only t h e A1203 f i b r e w a s s u c c e s s f u l l y deagglomerated. EFFECTS OF EXTRUSION CONDITIONS ON MECHANICAL PROPERTIES OF A SINTERED ALUMINIUM ALLOY J.Zhou, J.Duszczyk, (Delft University of T e c h n o l o g y , Delft, T h e N e t h e r l a n d s . ) J.Materials Science, Vol 26, 1991, 37393747. A s t u d y of t h e effects of e x t r u s i o n conditions on the properties,and m i c r o s t r u c t u r e of A1-20wt%Si-3%Cu-l%Mn, formed from rapidly solidified powder, is described. Optimum conditions were established. Comparison was made between t h e properties of a s - e x t r u d e d a n d h e a t t r e a t e d m a t e r i a l s a n d its suggested t h a t for applications above 200°C t h e h e a t t r e a t m e n t ( T 6 ) c a n be omitted. D E G A S S I N G O F ALUbIINIUM-SILICON BASED ALLOYS BY F L U S H I N G WITH A R G O N OR N I T R O G E N J.L.Estrada, J.Duszczyk. (Delft University of T e c h n o l o g y , Delft, T h e N e t h e r l a n d s . ) J.Materials Science, Vol 26, 1991, 39093913. The r e s e a r c h described in t h e p a p e r h a d t h e objective of improving t h e degassing of A1-20wt%Si-3%Cu-1%Mn alloys in p o w d e r a n d consolidated forms. The modification to t h e process involved flushing the system with Ar or N a n d it is concluded t h a t this i m p r o v e s t h e efficiency of H a n d H20 removal in comparison w i t h conventional degassing. H I G H T E M P E R A T U R E MECHANICAL PROPERTIES OF SUPERPLASTIC ALUMINIUM ALLOY MATRIX C O M P O S I T E R E I N F O R C E D WITH SILICON N I T R I D E P A R T I C L E S M.Mabuchi et al. ( G o v e r n m e n t Industrial Research Ins., Nagoya, J a p a n . ) J. Japan
MPR April 1992 47
rials Science and Engineering A, VolA134, 1991, 1098-1102. A1-5wt%Mn-5%Fe-2%Si rapidly solidified (RS) p o w d e r w a s c o n s o l i d a t e d and e x a m i n e d by e l e c t r o n m i c r o s c o p y in particle size sorted powders and consolidate forms. The relationships between s t r u c t u r e a n d particle size was, in increasing particle size order, microcellular/cellular AI with intercellular phases, euteetic and primary globular particles. The c o m p a c t e d alloy c o n t a i n e d fine, slow c o a r s e n i n g d i s p e r s o i d s . The s t r u c t u r e s were discussed with regard to t h e p h a s e s p r e s e n t a n d t h e degree of undercooling, HOT ROLLING O F RAPIDLY S O L I D I F I E D ( R S ) ALUMINIUMCHROMIUM-ZIRCONIUM-MANGANESE ALLOY POWDERS M.P.Silva et al, (University of Sheffield, England.) Materials SvienceandEngineeringA, VolA134, 1991, 1107-1110. The consolidation of A1-5wt%Cr-2%Zr1%Mn RS p o w d e r by h o t rolling a n d forging was studied w i t h respect to t h e effects of working on tensile properties. A useful c o m b i n a t i o n of s t r e n g t h a n d ductility was a t t a i n e d w h e n due regard was p a i d to process p a r a m e t e r s , degassing, c o m p a c t i o n
a n d rolling conditions. The occurrence of age h a r d e n i n g p h e n o m e n a was a t t r i b u t e d to t h e effectiveness of RS in r e t a i n i n g s u p e r s a t u r a t i o n of solute elements, SURFACE CHARACTERISATION O F ALUMINIUM ALLOY POWDER B E F O R E AND A F T E R HOT E X T R U S I O N A.Nylund, I.Olefjord. ( C h a l m e r s University of Technology, Sweden.) Materials Science and Engineemng A, Vol A134, 1991, 11391143. The surface reaction p r o d u c t s formed during atomisation, handling and consolidation on A1-5%Mn-2.5%Cr powders a n d consolidated m a t e r i a l were studied by electron spectroscopy (ESCA a n d Auger). The powders were found to be oxidised even at low 0 partial pressures equivalent to less t h a n 40ppm. At high t e m p e r a t u r e s oxide 'islands' are formed on particle surfaces a n d a t low t e m p e r a t u r e s a t h i n 20A oxide layer develops between t h e islands. Mean oxide thickness is a b o u t 50.~. On e x t r u s i o n at a ratio (ER) of 20 to 1 t h e surface oxide breaks u p a n d redistributes in t h e alloy. At a n ER of 10 to 1 t h e oxide r e m a i n s at t h e prior particle boundaries and reduces s t r e n g t h a n d ductility. M I C R O S T R U C T U R E AND P R O P E R T I E S O F H I G H P R E S S U R E GAS A T O M I S E D ALUMINIUM-LITHIUMFNIUM ALLOYS A~F.Norman, P.Tsakirpoulos. (University of Surrey, Guildford, E n g l a n d . ) Materials Science and Engineering A, Vol A134, 1991, 1144-1147. A1-2.2%Li-1.2%Hf powders were produced by high pressure gas a t o m i s a t i o n a n d t h e sub 45 ~ m fraction was separated and consolidated by e x t r u s i o n , p r e c i p i t a t i o n of a n A1-Li-Hf p h a s e was detected on solution t r e a t m e n t at 450°C a n d t h e 5' p h a s e during again at 190°C. Peak s t r e n g t h was developed after 1 h o u r at 190°C. The c o n t r i b u t i o n s of t h e various s t r e n g t h e n i n g m e c h a n i s m s were calculated. COLD D E F O R M A T I O N BEHAVIOUR O F SINTERED ALUMINIUM-COPPER ALLOYS POWDER P R E F O R M S I~S.Pandey. (Regional Engineering College, Tiruchirapalli, India.) Powder Metallurgy Science and Technology, Vol 2, No 4, 1991, 45-54. An i n v e s t i g a t i o n of t h e d e f o r m a t i o n behaviour of sinter~d A 1 - 4 % C u is described. The c o m p a c t s were p r o t e c t e d from o x i d a t i o n d u r i n g s i n t e r i n g by a ceramic coating. Cylindrical c o m p a c t s of different aspect ratios, in t h e r a n g e 1.5 to 3.0:1 were prepared, s i n t e r e d a n d subjected to d e f o r m a t i o n in c o m p r e s s i o n w i t h o u t l u b r i c a n t or with g r a p h i t e a t t h e c o m p a c t / die interface. D i m e n s i o n a l changes, t h e a p p e a r a n c e of cracks a n d t h e o n s e t of fracture were recorded. It was concluded
t h a t t h e densification curves were t h e same irrespective of aspect ratio a n d lubrication conditions, poisson's ratio was found to increase to a value a p p r o a c h i n g 0.5 as t h e density t e n d e d to 100%. STUDY OF DRY M I X I N G O F CERAMIC F I B R E S WITH A L U M I N I U M ALLOY POWDER J.H.ter Haar, J.Duszczyk. (Delft University of Technology, Delft, The N e t h e r l a n d s . ) J.
Materials Science, Vol 36, 1991, 36283638. The mixing of AI-20wt%Si-3%Cu-l%Mg alloy powder with A1203 a n d SiC fibres was studied with regard to de-agglomeration of t h e fibres a n d p r e p a r a t i o n of h o m o g e n e o u s m i x t u r e . Mixing was c a r r i e d o u t in a cylindrical tumbler with and without ceramic balls. After m i x i n g t h e powders were characterised as to particle size a n d shape, h a r d n e s s a n d specific surface. Only t h e A1203 f i b r e w a s s u c c e s s f u l l y deagglomerated. EFFECTS OF EXTRUSION CONDITIONS ON MECHANICAL PROPERTIES OF A SINTERED ALUMINIUM ALLOY J.Zhou, J.Duszczyk, (Delft University of T e c h n o l o g y , Delft, T h e N e t h e r l a n d s . ) J.Materials Science, Vol 26, 1991, 37393747. A s t u d y of t h e effects of e x t r u s i o n conditions on the properties,and m i c r o s t r u c t u r e of A1-20wt%Si-3%Cu-l%Mn, formed from rapidly solidified powder, is described. Optimum conditions were established. Comparison was made between t h e properties of a s - e x t r u d e d a n d h e a t t r e a t e d m a t e r i a l s a n d its suggested t h a t for applications above 200°C t h e h e a t t r e a t m e n t ( T 6 ) c a n be omitted. D E G A S S I N G O F ALUbIINIUM-SILICON BASED ALLOYS BY F L U S H I N G WITH A R G O N OR N I T R O G E N J.L.Estrada, J.Duszczyk. (Delft University of T e c h n o l o g y , Delft, T h e N e t h e r l a n d s . ) J.Materials Science, Vol 26, 1991, 39093913. The r e s e a r c h described in t h e p a p e r h a d t h e objective of improving t h e degassing of A1-20wt%Si-3%Cu-1%Mn alloys in p o w d e r a n d consolidated forms. The modification to t h e process involved flushing the system with Ar or N a n d it is concluded t h a t this i m p r o v e s t h e efficiency of H a n d H20 removal in comparison w i t h conventional degassing. H I G H T E M P E R A T U R E MECHANICAL PROPERTIES OF SUPERPLASTIC ALUMINIUM ALLOY MATRIX C O M P O S I T E R E I N F O R C E D WITH SILICON N I T R I D E P A R T I C L E S M.Mabuchi et al. ( G o v e r n m e n t Industrial Research Ins., Nagoya, J a p a n . ) J. Japan
MPR April 1992 47