- Email: [email protected]
Shock densification and HIP of titanium aluminide
PM
be MC, MeC a n d M23C 6 in a ferritic matrix. Carbide particle size was found to increase with HIP t e m p e r a t u r e b u t t h e r e was no change in carbide volume fraction. For t h e larger particle sizes t h e carbide particle size distribution was found to be wider.
M I C R O S T U C T U R E AND P R O P E R T I E S O F H I P T15 TOOL S T E E L A F T E R HEAT T R E A T M E N T A. Lawley et al, (Drexel University, Philadelphia, Pennsylvania, USA), Metallurgical T r a n s A, Vol 22A, No 11, 1991, 2747-2759. The effects of initial particle size, in t h e range 44 to 1200 ~m, on t h e s t r u c t u r e of HIP consolidated, a t 1130 or 1195°C, a n d heat t r e a t e d T15 tool steel was investigated. Austenitization was at 1175 or 1225°C a n d t e m p e r i n g was a t 538, 552 or 565°C which enabled austenitic grain size, carbide type, volume fraction and particle size distribution to be controlled. Bend strength, n o t c h i m p a c t t o u g h n e s s a n d hot hardness were measured. The phase composition of the h e a t t r e a t e d specimens was d e t e r m i n e d as a function of t h e initial p o w d e r size. The h o t h a r d n e s s of t h e sample HIP at 1130°C is higher t h a n t h a t of a commercial s a m p l e HIP at 1195 due to a finer carbide p a r t i c l e size a n d it is established that the process cycle developed gives b e t t e r properties t h a n are found in commercial material.
Intermetallic materials MECHANICAL ALLOYING ( M A ) O F NICKEL A L U M I N I D E (NiaAl) AND CHARACTERIZATION O F HOT P R E S S E D COMPACTS S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 38, No 7, 1991, 963-966. (In J a p a n e s e ) . Elemental A1-75 at% Ni powder m i x t u r e s were MA in Ar in a horizontal ball mill for varying p e r i o d s w h i c h r e s u l t e d in t h e formation of a single p h a s e solid solution which t r a n s f o r m e d on heating at 425°C to Ni3A1. The h a r d n e s s of t h e h o t pressed p o w d e r was g r e a t e r t h a n t h a t of cast materials. Hot pressed c o m p a c t s formed from t h e powder showed inhomogeneities after s h o r t MA periods, less t h a n 10 hours, and voids after MA for over 100 hours. The o p t i m u m MA time is established to be 20 to 50 hours.
MECHANICAL ALLOYING ( M A ) O F NICKEL A L U M I N I D E (NiAI) AND CHARACTERIZATION O F HOT P R E S S E D COMPACTS S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J Japan Soc Powder
60 MPR July/August
LITERATURE
REVIEW
and PowderMetalluryy, Vol 38, No 7, 1991, 967-970. (In J a p a n e s e ) . T h e p a p e r d e s c r i b e s t h e MA o f equiatomic m i x t u r e s of elemental Ni a n d Al powder m i x t u r e s with respect to time. A1Ni w a s s y n t h e s i z e d a f t e r MA f o r 100 h o u r s a n d t h e p a r t i c l e size w a s reduced to 0.5 ~tm. Hot pressed c o m p a c t s showed segregation w h e n t h e MA time was below 20 hours. Powders MA for over 50 h o u r s failed to sinter completely a n d this t e n d e n c y increased for longer MA t i m e s a n d powder MA for 500 h o u r s did n o t sinter. A ~rlcker's h a r d n e s s of 500 is r e p o r t e d for h o t p r e s s e d p o w d e r MA for 5 h o u r s . The o p t i m u m MA time is suggested to be 28 hours.
MECHANICAL ALLOYING ( M A ) O F NICKEL ALUMINIDE (NiAls) AND C H A ~ C T E R I Z A T I O N OF HOT P R E S S E D COMPACTS S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 38, No 7, 1991, 971-975. (In J a p a n e s e ) . The m e c h a n i c a l alloying of AI-25 at% Ni elemental powder m i x t u r e s is described. After 500 h o u r s t h e powder consisted of a single disordered p h a s e which t r a n s f o r m e d into NiAl3 on heating at 325°C. Compositional segregation a n d voids were n o t e d in some hot pressed materials b u t well s i n t e r e d h o m o g e n e o u s c o m p a c t s r e s u l t e d f o r m p o w d e r MA for a b o v e 50 hours. Vicker's h a r d n e s s u p to 750 are reported.
MECHANICAL ALLOYING ( M A ) AND MECHANICAL G R I N D I N G ( M G ) O F NICKEL A L U M I N I D E (NiAIs) S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J. Japan Soc Powder and PowderMetalluryy, Vol 38, No 7, 1991, 976-980. (In J a p a n e s e ) . A comparison is m a d e between MA A125 at% Ni powders p r e p a r e d by MG of arc cast NiA12. In b o t h cases t h e powders consisted of a disordered solid solution which t r a n s f o r m e d to NiA13 on heating. The t r a n s f o r m a t i o n t e m p e r a t u r e of t h e MG material was reported to be higher t h a n f o r t h e MA a l l o y a n d t h e h e a t o f t r a n s f o r m a t i o n was smaller (MG powder 1.0 kJ/mol, MA powder 2.5 kJ/mol). This is a t t r i b u t e d to t h e presence of NiAI3 in t h e MG powder.
described. Ti a n d A1 powders were a d d e d to t h e aluminide powder p r i o r to compacting. HIP a t 1000°C initiated t h e exothermic formation of a l u m i n i d e s which e n h a n c e d b o n d i n g in t h e alloys. The compressive s t r e n g t h is reported to be 2G Pa w i t h a fracture s t r a i n of 20%. Due to t h e p r e s e n c e of flaws t h e tensile s t r e n g t h was 250 MPa.
CHEMICAL SYNTHESIS O F F I N E NICKEL A L U M I N I D E POWDERS J.C. Withers et al, J of Metals, Vol 43, No 8, 1991, 36-39. A description of t h e p r o d u c t i o n of NiaA1 powders form a chloride precursor is given. The powder sizes were in t h e micron range, h a d t h e L12 s t r u c t u r e a n d c o n t a i n e d 5 at% Al over t h e stoichiometric requirement. It is suggested that, because of t h e small grain size, t h e properties of t h e consolidated material may be improved and the a l u m i n i d e b r o u g h t into commercial use. THERMOCHEMICAL P R O C E S S I N G O F TITANIUM A L U M I N I D E POWDERS A N D COMPACTS L S Apgar a n d D. Eylon, (University of Dayton, Ohio, USA), J Int Iron and Steel Inst., Vol 31, No 8, 1991, 915-921 The p r o d u c t i o n of p a r t s from p l a s m a pre-alloyed powders m a d e by the r o t a t i n g electrode process and subsequent 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 is described. The p a r t s are reported to have a n ultrafine grain s t r u c t u r e of a b o u t 1 p m with a n c~2 structure. The mechanisms of microstructural refinement are discussed with a n e m p h a s i s on hydride formation. STRUCTURE AND PHASE C O M P O S I T I O N OF IRON A L U M I N I D E ( F e a A l ) POWDER P R E P A R E D BY MILLING T. Zak et al, (Technical University, Brno, C z e c h o s l o v a k i a ) , Material Science and Engineering A, Vol A141, No 1, 1991, 73-78. Milled FeaA1 p o w d e r w a s f o u n d to consist of t h e original a l u m i n i d e powder with t h e %Al reduced to 23 a t % with Fe a n d A1203. No interracial p h a s e was detected due to t h e creation of A1 rich slip planes during plastic deformation of the aluminide. The aluminide was found to decompose on heating. This is a t t r i b u t e d to t h e oxidation of t h e A1 which effectively reduces any Fe oxide formed.
Metal injection moulding SHOCK D E N S I F I C A T I O N AND HIP OF TITANIUM ALUMINIDE S-S. Shang a n d MA.Meyers, (University of California, San Diego, California, USA), Metallurgical Trans A Vol 22A, No 11, 1991, 2667-2676. The consolidation of TiaA1 powders by explosive compaction followed by HIP is
I
I
I II IIIIIII
I I[
METAL I N J E C T I O N MOULDING ( M I M ) O F COURSE IRON POWDERS S.K. Roy et al, ( B h a b h a Atomic Research Centre, Bombay, India), Powder MetaU. Int., Vol 24, No 2, 1992, 88-90.
be MC, MeC a n d M23C 6 in a ferritic matrix. Carbide particle size was found to increase with HIP t e m p e r a t u r e b u t t h e r e was no change in carbide volume fraction. For t h e larger particle sizes t h e carbide particle size distribution was found to be wider.
M I C R O S T U C T U R E AND P R O P E R T I E S O F H I P T15 TOOL S T E E L A F T E R HEAT T R E A T M E N T A. Lawley et al, (Drexel University, Philadelphia, Pennsylvania, USA), Metallurgical T r a n s A, Vol 22A, No 11, 1991, 2747-2759. The effects of initial particle size, in t h e range 44 to 1200 ~m, on t h e s t r u c t u r e of HIP consolidated, a t 1130 or 1195°C, a n d heat t r e a t e d T15 tool steel was investigated. Austenitization was at 1175 or 1225°C a n d t e m p e r i n g was a t 538, 552 or 565°C which enabled austenitic grain size, carbide type, volume fraction and particle size distribution to be controlled. Bend strength, n o t c h i m p a c t t o u g h n e s s a n d hot hardness were measured. The phase composition of the h e a t t r e a t e d specimens was d e t e r m i n e d as a function of t h e initial p o w d e r size. The h o t h a r d n e s s of t h e sample HIP at 1130°C is higher t h a n t h a t of a commercial s a m p l e HIP at 1195 due to a finer carbide p a r t i c l e size a n d it is established that the process cycle developed gives b e t t e r properties t h a n are found in commercial material.
Intermetallic materials MECHANICAL ALLOYING ( M A ) O F NICKEL A L U M I N I D E (NiaAl) AND CHARACTERIZATION O F HOT P R E S S E D COMPACTS S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 38, No 7, 1991, 963-966. (In J a p a n e s e ) . Elemental A1-75 at% Ni powder m i x t u r e s were MA in Ar in a horizontal ball mill for varying p e r i o d s w h i c h r e s u l t e d in t h e formation of a single p h a s e solid solution which t r a n s f o r m e d on heating at 425°C to Ni3A1. The h a r d n e s s of t h e h o t pressed p o w d e r was g r e a t e r t h a n t h a t of cast materials. Hot pressed c o m p a c t s formed from t h e powder showed inhomogeneities after s h o r t MA periods, less t h a n 10 hours, and voids after MA for over 100 hours. The o p t i m u m MA time is established to be 20 to 50 hours.
MECHANICAL ALLOYING ( M A ) O F NICKEL A L U M I N I D E (NiAI) AND CHARACTERIZATION O F HOT P R E S S E D COMPACTS S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J Japan Soc Powder
60 MPR July/August
LITERATURE
REVIEW
and PowderMetalluryy, Vol 38, No 7, 1991, 967-970. (In J a p a n e s e ) . T h e p a p e r d e s c r i b e s t h e MA o f equiatomic m i x t u r e s of elemental Ni a n d Al powder m i x t u r e s with respect to time. A1Ni w a s s y n t h e s i z e d a f t e r MA f o r 100 h o u r s a n d t h e p a r t i c l e size w a s reduced to 0.5 ~tm. Hot pressed c o m p a c t s showed segregation w h e n t h e MA time was below 20 hours. Powders MA for over 50 h o u r s failed to sinter completely a n d this t e n d e n c y increased for longer MA t i m e s a n d powder MA for 500 h o u r s did n o t sinter. A ~rlcker's h a r d n e s s of 500 is r e p o r t e d for h o t p r e s s e d p o w d e r MA for 5 h o u r s . The o p t i m u m MA time is suggested to be 28 hours.
MECHANICAL ALLOYING ( M A ) O F NICKEL ALUMINIDE (NiAls) AND C H A ~ C T E R I Z A T I O N OF HOT P R E S S E D COMPACTS S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 38, No 7, 1991, 971-975. (In J a p a n e s e ) . The m e c h a n i c a l alloying of AI-25 at% Ni elemental powder m i x t u r e s is described. After 500 h o u r s t h e powder consisted of a single disordered p h a s e which t r a n s f o r m e d into NiAl3 on heating at 325°C. Compositional segregation a n d voids were n o t e d in some hot pressed materials b u t well s i n t e r e d h o m o g e n e o u s c o m p a c t s r e s u l t e d f o r m p o w d e r MA for a b o v e 50 hours. Vicker's h a r d n e s s u p to 750 are reported.
MECHANICAL ALLOYING ( M A ) AND MECHANICAL G R I N D I N G ( M G ) O F NICKEL A L U M I N I D E (NiAIs) S. S h i g a et al, ( T o y o h a s h i University, Toyohashi, J a p a n ) , J. Japan Soc Powder and PowderMetalluryy, Vol 38, No 7, 1991, 976-980. (In J a p a n e s e ) . A comparison is m a d e between MA A125 at% Ni powders p r e p a r e d by MG of arc cast NiA12. In b o t h cases t h e powders consisted of a disordered solid solution which t r a n s f o r m e d to NiA13 on heating. The t r a n s f o r m a t i o n t e m p e r a t u r e of t h e MG material was reported to be higher t h a n f o r t h e MA a l l o y a n d t h e h e a t o f t r a n s f o r m a t i o n was smaller (MG powder 1.0 kJ/mol, MA powder 2.5 kJ/mol). This is a t t r i b u t e d to t h e presence of NiAI3 in t h e MG powder.
described. Ti a n d A1 powders were a d d e d to t h e aluminide powder p r i o r to compacting. HIP a t 1000°C initiated t h e exothermic formation of a l u m i n i d e s which e n h a n c e d b o n d i n g in t h e alloys. The compressive s t r e n g t h is reported to be 2G Pa w i t h a fracture s t r a i n of 20%. Due to t h e p r e s e n c e of flaws t h e tensile s t r e n g t h was 250 MPa.
CHEMICAL SYNTHESIS O F F I N E NICKEL A L U M I N I D E POWDERS J.C. Withers et al, J of Metals, Vol 43, No 8, 1991, 36-39. A description of t h e p r o d u c t i o n of NiaA1 powders form a chloride precursor is given. The powder sizes were in t h e micron range, h a d t h e L12 s t r u c t u r e a n d c o n t a i n e d 5 at% Al over t h e stoichiometric requirement. It is suggested that, because of t h e small grain size, t h e properties of t h e consolidated material may be improved and the a l u m i n i d e b r o u g h t into commercial use. THERMOCHEMICAL P R O C E S S I N G O F TITANIUM A L U M I N I D E POWDERS A N D COMPACTS L S Apgar a n d D. Eylon, (University of Dayton, Ohio, USA), J Int Iron and Steel Inst., Vol 31, No 8, 1991, 915-921 The p r o d u c t i o n of p a r t s from p l a s m a pre-alloyed powders m a d e by the r o t a t i n g electrode process and subsequent 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 is described. The p a r t s are reported to have a n ultrafine grain s t r u c t u r e of a b o u t 1 p m with a n c~2 structure. The mechanisms of microstructural refinement are discussed with a n e m p h a s i s on hydride formation. STRUCTURE AND PHASE C O M P O S I T I O N OF IRON A L U M I N I D E ( F e a A l ) POWDER P R E P A R E D BY MILLING T. Zak et al, (Technical University, Brno, C z e c h o s l o v a k i a ) , Material Science and Engineering A, Vol A141, No 1, 1991, 73-78. Milled FeaA1 p o w d e r w a s f o u n d to consist of t h e original a l u m i n i d e powder with t h e %Al reduced to 23 a t % with Fe a n d A1203. No interracial p h a s e was detected due to t h e creation of A1 rich slip planes during plastic deformation of the aluminide. The aluminide was found to decompose on heating. This is a t t r i b u t e d to t h e oxidation of t h e A1 which effectively reduces any Fe oxide formed.
Metal injection moulding SHOCK D E N S I F I C A T I O N AND HIP OF TITANIUM ALUMINIDE S-S. Shang a n d MA.Meyers, (University of California, San Diego, California, USA), Metallurgical Trans A Vol 22A, No 11, 1991, 2667-2676. The consolidation of TiaA1 powders by explosive compaction followed by HIP is
I
I
I II IIIIIII
I I[
METAL I N J E C T I O N MOULDING ( M I M ) O F COURSE IRON POWDERS S.K. Roy et al, ( B h a b h a Atomic Research Centre, Bombay, India), Powder MetaU. Int., Vol 24, No 2, 1992, 88-90.