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Mechanical alloying and consolidation of iron aluminide
E F F E C T OF A T M O S P H E R E ON E X T E N D E D M I L L I N G OF A M O R P H O U S NICKEL-TITANIUM POWDERS
K.Y. Wang et al (Academica Sinica, Beijing, China), J Materials Science Letters, Vol 11, No 17, 1992, 1170-1172. An investigation to determine the effects of a t m o s p h e r e on f u r t h e r m i l l i n g of a m o r p h o u s Ni-40 at% Ti p o w d e r s is d e s c r i b e d . The p o w d e r s w e r e initially milled for 20 hours in Ar and then for a further 8 hours in At, N or O. N and Ar had no effect a p a r t from an increase in the N c o n t e n t from 0.23 to 0.74 wt%. 0 is reported to be readily absorbed by the powder and reached 8 vet'.'/,, after 8 hours milling t h e p o w d e r t h e n being highly crystallized. It is suggested t h a t TiO,) and TieO:~ are formed in addition to absorption of O into the intermetallic. F A B R I C A T I O N OF T I T A N I U M A L U M I N I D E BY REACTIVE S I N T E R I N G
K. Sjibue, S u m i t o m o Light Metal Tech Rep, Vol 33, No 2, 1992, 32-38. (In J a p a n e s e ) . The development of reactive sintering for t h e p r o d u c t i o n of TiM b o d i e s is d e s c r i b e d . Ti-Al p o w d e r m i x t u r e s are compacted by extrusion and the e x t r u d e d material is reportedly sufficiently ductile to permit shaping. The s h a p e d material is reactively sintered or processed by HIP. After HIP, at 1300' C the structure is duplex containing a lamcllar constituent and 7 grains. The material is reported to have good oxidation resistance and mechanical properties. M E C H A N I C A L ALLOYING A N D C O N S O L I D A T I O N OF IRON A L U M I N I D E
Y. Tada and T. Sato, (University of Tokoshima, Tokoshima, J a p a n ) , J J a p a n Soc P o w d e r a n d P o w d e r Metallurgy, Vol 40, No 2, 1993, 236-240, (In J a p a n e s e ) . An investigation o f MA a n d consolidation of a Fe-25 at% A1 powder alloy is described. After 80 hours milling the powder is shown to consist of crystalline and non-c .rystalline aluminides which are converted t o Fe:~Al d u r i n g hot consolidation. A range of techniques was studied and HIP is reported to be the most effective in giving a fully dense material with good mechanical properties. Additions of 5 wt% Al.~O:~ conler increased h a r d n e s s and proof stress without loss of ductility. PORE F O R M A T I O N D U R I N G REACTIVE S I N T E R I N G OF E X T R U D E D TITANIUMA L U M I N I U M POWDER M I X T U R E S
M. Dahms et al (GKSS-Forschungzentru, Geesthacht, Germany), Z . f d r MetaUkunde, Vol 84, No 5, 1993, 351-357. A Ti-49 at% A1 powder mix was cold e x t r u d e d . Swelling during h e a t i n g was s t u d i e d by d i l a t o m e t r y and differential s c a n n i n g c a l o r i m e t r y . The s w e l l i n g is
46 MPR September 1993
attributed to Kirkendall pores, formation of macropores by reaction between liquid Ai and solid Ti and interdiffusion of TiAla and Ti forming 7TiAI and :~eTiaA1. Swelling is a n i s o t r o p i c c a u s e d by e l o n g a t e d Ti p a r t i c l e s . M i n i m i z a t i o n of p o r o s i t y is shown to be possible by optimization of process conditions. S Y N T H E S I S OF "/TITANIUM A L U M I N I D E ALLOYS BY REACTIVE POWDER P R O C E S S I N G
G. Wang and M. Dahms (GKSS-Forschungzenturm, Geesthacht, Germany), J o f Metals, Vol 45, No 5, 1993, 52-56. The microstructures and properties of "{TiA1 alloys, m a d e by reactive p o w d e r processing, are reported. It is noted t h a t powder processing circumvents the poor w o r k a b i l i t y o f 7TiAI a s s h a p i n g is completed before sintering. The reaction m e c h a n i s m s are discussed. M I C R O S T R U C T U R A L EVOLUTION A N D ITS E F F E C T ON T E N S I L E A N D F R A C T U R E OF :t2TITANIUM-NIOBIUMALUMINIUM INTERMETALLICS
C.H. Ward (Boiling Air Force Base, DC, USA), Int. M a t e r i a l s R e v i e w s , Vol 38, No 2, 1993, 79-101. Research on alloys based on TiaAl is critically reviewed. Phase transformation and stabilities are considered. Dislocation behaviour in ¢~esingle phase and :,2/[3(B2) d u a l p h a s e m a t e r i a l s is d e s c r i b e d . Microstructures and dislocation behaviour are correlated with tensile and fracture properties.
Mechanical alloying S T R U C T U R A L EVOLUTION D U R I N G M E C H A N I C A L ALLOYING OF N I O B I U M BERYLLIDES
T.C. Chou et al (Lockheed R a n d D), Scripta Metall Mater., Vol 27, No 7, 1992, 881-886. A description of structural evolution during MA of Nb-Be powder mixtures is given. With small Be additions the powders are reported to be well homogenised but inhomogeneities were ft)und at higher %Be. Particles sizes were reduced to sub-micron levels. Ainorphization required 24 hours. Vacuum annealing resulted in recrystallization to NbBele and NbaBe2 m i x t u r e s o r NbeBe17, a c c o r d i n g to composition, with traces of a minor phase. E F F E C T OF A M B I E N T T E M P E R A T U R E OF A M O R P H I Z A T I O N IN M E C H A N I C A L ALLOYING OF COPPER-TANTALUM
C.H. Lee et al (Nagoya University, Nagoya, J a p a n ) , J J a p a n Soc. P o w d e r a n d P o w d e r MetaUurgy, Vol 40, No 1, 1993, 87-91. (In Japanese). The p a p e r describes the effects of MA at
a m b i e n t t e m p e r a t u r e s ()n a Ta-30% Cu p o w d e r m i x t u r e for which the heat of mixing is 2 tal/mol. It is reported t h a t the rate of a m o r p h i z a t i o n is e n h a n c e d by increases in t e m p e r a t u r e and t h a t the t h e r m a l l y a s s i s t e d a m o r p h i z a t i o n is detectable after 60 hours. This was also d e t e c t e d d u r i n g a n n e a l i n g of partially amorphized powders below the recrystallization teml)erature. The results are discussed with reference to thermodynamics. A M O R P H I Z A T I O N OF I M M I S C I B L E COPPER-VANADIUM BY M E C H A N I C A L ALLOYING IN N I T R O G E N
N. Kuroda et a[ (Nagoya University, Nagoya, J a p a n ) , J J a p a n Soc P o w e r a n d P o w d e r Metallurgy, Vol 40, No 11, 1993, 92-95. (In J a p a n e s e ) . Mechanical alloying of V30 at% Cu in N is shown in gradual amorphization of the powder. After 200 hours the powder is s h o w n to c o n s i s t of a m i x t u r e of crystalline and a m o r p h o u s powder. It is suggested t h a t a body-centred cubic solid solutions is formed as a transient phase a n d t h a t N is i n c o r p o r a t e d into t h e a m o r p h o u s powder. MECHANICALLY ALLOYED TITANIUMNICKEL-COPPER POWDERS
T. Fukunaaga et al (Nagoya University, Nagoya, J a p a n ) J J a p a n Soc P o w d e r a n d P o w d e r Metallurgy, Vol 40, No 1, 1993, 9699. (In J a p a n e s e ) Amorphous (Ti-24 at% Ni)x-(Ti-30 at% Cu) l×. w h e r e x = 0 to l, alloys were synthesized by MA. Short range order was d e t e c t e d in t h e p o w d e r s by n e u t r o n diffraction and the Warren SRO parameter, ~, is reported to be negative and to decrease with increases in %Ni. The alloys are described as pseudo-binary. STRUCTURE AND MECHANICAL P R O P E R T I E S OF MECHANICALLY ALLOYED A N D S I N T E R E D COPPERT I T A N I U M - B O R O N ALLOY COMPACTS
T. Morooka et al (Musashi lnst of Technoloh,W, Tokyo, J a p a n ) , J Jctpan Soe. P o w d e r a n d P o w d e r Metallurgy, Vol 4(), No 1, 1993, 100-104. (In J a p a n e s e ) . Cu-ti-B compacts were p r e p a r e d for MA powder and sintered at 600 to 1000 C. Changes in structure and properties were determined. TiB:e is formed during sintering a n d t h i s is e n h a n c e d by i n c r e a s e d temperature. Two peaks in the hardening response curve are reported. It is shown, from the results of 3-point bend tests, t h a t the bonding strength increases with sintering time. X-RAY F I N E S T R U C T U R E S T U D I E S ON BALL M I L L E D COPPER-VANADIUM POWDERS
K. Sakurai et al (National Research Inst,
K.Y. Wang et al (Academica Sinica, Beijing, China), J Materials Science Letters, Vol 11, No 17, 1992, 1170-1172. An investigation to determine the effects of a t m o s p h e r e on f u r t h e r m i l l i n g of a m o r p h o u s Ni-40 at% Ti p o w d e r s is d e s c r i b e d . The p o w d e r s w e r e initially milled for 20 hours in Ar and then for a further 8 hours in At, N or O. N and Ar had no effect a p a r t from an increase in the N c o n t e n t from 0.23 to 0.74 wt%. 0 is reported to be readily absorbed by the powder and reached 8 vet'.'/,, after 8 hours milling t h e p o w d e r t h e n being highly crystallized. It is suggested t h a t TiO,) and TieO:~ are formed in addition to absorption of O into the intermetallic. F A B R I C A T I O N OF T I T A N I U M A L U M I N I D E BY REACTIVE S I N T E R I N G
K. Sjibue, S u m i t o m o Light Metal Tech Rep, Vol 33, No 2, 1992, 32-38. (In J a p a n e s e ) . The development of reactive sintering for t h e p r o d u c t i o n of TiM b o d i e s is d e s c r i b e d . Ti-Al p o w d e r m i x t u r e s are compacted by extrusion and the e x t r u d e d material is reportedly sufficiently ductile to permit shaping. The s h a p e d material is reactively sintered or processed by HIP. After HIP, at 1300' C the structure is duplex containing a lamcllar constituent and 7 grains. The material is reported to have good oxidation resistance and mechanical properties. M E C H A N I C A L ALLOYING A N D C O N S O L I D A T I O N OF IRON A L U M I N I D E
Y. Tada and T. Sato, (University of Tokoshima, Tokoshima, J a p a n ) , J J a p a n Soc P o w d e r a n d P o w d e r Metallurgy, Vol 40, No 2, 1993, 236-240, (In J a p a n e s e ) . An investigation o f MA a n d consolidation of a Fe-25 at% A1 powder alloy is described. After 80 hours milling the powder is shown to consist of crystalline and non-c .rystalline aluminides which are converted t o Fe:~Al d u r i n g hot consolidation. A range of techniques was studied and HIP is reported to be the most effective in giving a fully dense material with good mechanical properties. Additions of 5 wt% Al.~O:~ conler increased h a r d n e s s and proof stress without loss of ductility. PORE F O R M A T I O N D U R I N G REACTIVE S I N T E R I N G OF E X T R U D E D TITANIUMA L U M I N I U M POWDER M I X T U R E S
M. Dahms et al (GKSS-Forschungzentru, Geesthacht, Germany), Z . f d r MetaUkunde, Vol 84, No 5, 1993, 351-357. A Ti-49 at% A1 powder mix was cold e x t r u d e d . Swelling during h e a t i n g was s t u d i e d by d i l a t o m e t r y and differential s c a n n i n g c a l o r i m e t r y . The s w e l l i n g is
46 MPR September 1993
attributed to Kirkendall pores, formation of macropores by reaction between liquid Ai and solid Ti and interdiffusion of TiAla and Ti forming 7TiAI and :~eTiaA1. Swelling is a n i s o t r o p i c c a u s e d by e l o n g a t e d Ti p a r t i c l e s . M i n i m i z a t i o n of p o r o s i t y is shown to be possible by optimization of process conditions. S Y N T H E S I S OF "/TITANIUM A L U M I N I D E ALLOYS BY REACTIVE POWDER P R O C E S S I N G
G. Wang and M. Dahms (GKSS-Forschungzenturm, Geesthacht, Germany), J o f Metals, Vol 45, No 5, 1993, 52-56. The microstructures and properties of "{TiA1 alloys, m a d e by reactive p o w d e r processing, are reported. It is noted t h a t powder processing circumvents the poor w o r k a b i l i t y o f 7TiAI a s s h a p i n g is completed before sintering. The reaction m e c h a n i s m s are discussed. M I C R O S T R U C T U R A L EVOLUTION A N D ITS E F F E C T ON T E N S I L E A N D F R A C T U R E OF :t2TITANIUM-NIOBIUMALUMINIUM INTERMETALLICS
C.H. Ward (Boiling Air Force Base, DC, USA), Int. M a t e r i a l s R e v i e w s , Vol 38, No 2, 1993, 79-101. Research on alloys based on TiaAl is critically reviewed. Phase transformation and stabilities are considered. Dislocation behaviour in ¢~esingle phase and :,2/[3(B2) d u a l p h a s e m a t e r i a l s is d e s c r i b e d . Microstructures and dislocation behaviour are correlated with tensile and fracture properties.
Mechanical alloying S T R U C T U R A L EVOLUTION D U R I N G M E C H A N I C A L ALLOYING OF N I O B I U M BERYLLIDES
T.C. Chou et al (Lockheed R a n d D), Scripta Metall Mater., Vol 27, No 7, 1992, 881-886. A description of structural evolution during MA of Nb-Be powder mixtures is given. With small Be additions the powders are reported to be well homogenised but inhomogeneities were ft)und at higher %Be. Particles sizes were reduced to sub-micron levels. Ainorphization required 24 hours. Vacuum annealing resulted in recrystallization to NbBele and NbaBe2 m i x t u r e s o r NbeBe17, a c c o r d i n g to composition, with traces of a minor phase. E F F E C T OF A M B I E N T T E M P E R A T U R E OF A M O R P H I Z A T I O N IN M E C H A N I C A L ALLOYING OF COPPER-TANTALUM
C.H. Lee et al (Nagoya University, Nagoya, J a p a n ) , J J a p a n Soc. P o w d e r a n d P o w d e r MetaUurgy, Vol 40, No 1, 1993, 87-91. (In Japanese). The p a p e r describes the effects of MA at
a m b i e n t t e m p e r a t u r e s ()n a Ta-30% Cu p o w d e r m i x t u r e for which the heat of mixing is 2 tal/mol. It is reported t h a t the rate of a m o r p h i z a t i o n is e n h a n c e d by increases in t e m p e r a t u r e and t h a t the t h e r m a l l y a s s i s t e d a m o r p h i z a t i o n is detectable after 60 hours. This was also d e t e c t e d d u r i n g a n n e a l i n g of partially amorphized powders below the recrystallization teml)erature. The results are discussed with reference to thermodynamics. A M O R P H I Z A T I O N OF I M M I S C I B L E COPPER-VANADIUM BY M E C H A N I C A L ALLOYING IN N I T R O G E N
N. Kuroda et a[ (Nagoya University, Nagoya, J a p a n ) , J J a p a n Soc P o w e r a n d P o w d e r Metallurgy, Vol 40, No 11, 1993, 92-95. (In J a p a n e s e ) . Mechanical alloying of V30 at% Cu in N is shown in gradual amorphization of the powder. After 200 hours the powder is s h o w n to c o n s i s t of a m i x t u r e of crystalline and a m o r p h o u s powder. It is suggested t h a t a body-centred cubic solid solutions is formed as a transient phase a n d t h a t N is i n c o r p o r a t e d into t h e a m o r p h o u s powder. MECHANICALLY ALLOYED TITANIUMNICKEL-COPPER POWDERS
T. Fukunaaga et al (Nagoya University, Nagoya, J a p a n ) J J a p a n Soc P o w d e r a n d P o w d e r Metallurgy, Vol 40, No 1, 1993, 9699. (In J a p a n e s e ) Amorphous (Ti-24 at% Ni)x-(Ti-30 at% Cu) l×. w h e r e x = 0 to l, alloys were synthesized by MA. Short range order was d e t e c t e d in t h e p o w d e r s by n e u t r o n diffraction and the Warren SRO parameter, ~, is reported to be negative and to decrease with increases in %Ni. The alloys are described as pseudo-binary. STRUCTURE AND MECHANICAL P R O P E R T I E S OF MECHANICALLY ALLOYED A N D S I N T E R E D COPPERT I T A N I U M - B O R O N ALLOY COMPACTS
T. Morooka et al (Musashi lnst of Technoloh,W, Tokyo, J a p a n ) , J Jctpan Soe. P o w d e r a n d P o w d e r Metallurgy, Vol 4(), No 1, 1993, 100-104. (In J a p a n e s e ) . Cu-ti-B compacts were p r e p a r e d for MA powder and sintered at 600 to 1000 C. Changes in structure and properties were determined. TiB:e is formed during sintering a n d t h i s is e n h a n c e d by i n c r e a s e d temperature. Two peaks in the hardening response curve are reported. It is shown, from the results of 3-point bend tests, t h a t the bonding strength increases with sintering time. X-RAY F I N E S T R U C T U R E S T U D I E S ON BALL M I L L E D COPPER-VANADIUM POWDERS
K. Sakurai et al (National Research Inst,