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Microalloying of powder steels with boron
a n d P o w d e r Metallurgy, Vol 40, No 5, 1993, 484-487. (In J a p a n e s e ) . It is reported t h a t injection moulded 316L s t a i n l e s s c o m p a c t s , f o r m e d from l0 Bm p o w d e r , d i s t o r t e d s i g n i f i c a n t l y during sintering when less t h a n 95% of the binder was removed. It is r e c o m m e n d e d t h a t d e b i n d i n g is carried on p o l i s h e d porous Al203 plates heated at a rate to ensure uniform shrinkage with temperature. DENSIFICATION AND STRUCTURE EVOLUTION OF S T A I N L E S S S T E E L DURING PSEUDO-HIP
M. Miyajima et a] (Tohoku University, Sendal, J a p a n ) J. Japa'r~ Soc. Powder a n d t'owder Metallurgy, Vol. 40, No 5, 1993, 506-510. (In J a p a n e s e ) . A study of densification and structural evolution (luring p s e u d o }tiP of atomized u l t r a f i n e s t a i n l e s s s t e e l p o w d e r is d e s c r i b e d , effects of t e m p e r a t u r e a n d pressure being investigated. It is reported t h a t lower sintering t e m p e r a t u r e s t h a n for normal sintering (:an be employed. MAGNETIC AND MECHANICAL P R O P E R T I E S OF VACUUM S I N T E R E D IRON-SILICON MATERIALS
A. Salek, E. Dudrova (lnsl. of Materials Research, Kosice, Slovakia) P M Science a n d Technoh,gy, Yk)l 4, No :3, 1993, 27-37. An investigation of m e c h a n i c a l and physical properties of vacuum sintered Fe(2 to 6)%Si alloys is described, effects of compaction pressure and sintering conditions being determined. The alloys are used for m a g n e t s in e l e c t r o m o t o r braking swstems for which the properties found are reported to be satisfactm7. High d e n s i f i c a t i o n r e s u l t i n g from a c t i v a t e d sintering is reported. ACTIVATING E F F E C T S OF B O R O N ON S I N T E R I N G A N D P R O P E R T I E S OF IRON A N D PREALLOYED C O M P A C T S
A. Salek, E, Dudrova (Inst. of Materials Research, Kosice, Slovakia). PM Science a n d Technology, Vol 4, No 3, 1993, 46-56. The effects of up to 0.6% B, a d d e d as Ibrro-boron, and sintering conditions on the hardness and strength of Fe and Fe-2% Ni0.5% Mo alloys were investigated. For Fe the addition of 0.6% gave an increase in density of 6% and a Vicker's h a r d n e s s of 95. For the Fe-Ni-Mo alloy the increase in density was 26% and h a r d n e s s 240. The effects are attributed to the activating effect of B in producing a liquid phase during sintering. MICROALLOYING OF P O W D E R S T E E L S WITH B O R O N
B.B. Korol'kov (Tula Poiytechnieal Inst., Tula, Russia) lzv. V.U.Z. C h e r n a y a Metall., No 6, 1992, 47-48. (In Russian).
The effect of adding 0.025wt% B and 0.2% Hf oxychloride to a 0,4% C steel is shown to be beneficial in retarding loss of s t r e n g t h at elevated temperatures. The Hf o x y c h l o r i d e is c o n s i d e r e d to aid t h e uniform distribution of B t h r o u g h o u t the steel and gives i m p r o v e m e n t s in impact toughness.
Molybdenum PHYSICO-MECHANICAL P R O P E R T I E S A N D S T R U C T U R E OF MOLYBDENUMIRON-TUNGSTEN POWDER MASTER ALLOY
P.N. Ostrik et al (Dnepropetrovsk Metallurgical Inst., Dnepropetrovsk, Ukraine) Izv. V.U.Z. C h e r n a y a Metall., No 6, 1992, 7-10. (in Russian). The characteristics of Mo-35% Fe-5% W powder were investigated with regard to particle size distribution and average grain parameters. The powder is applied as a master alloy in the production of steel p a r t s and ensures better incorporation of Mo in the steel.
Niobium N A N O P H A S E S T R U C T U R E S IN MECHANICALLY ALLOYED N I O B I U M RICH N I O B I U M A L U M I N I D E
M2. TracT, J.R. Groza (University of California, Davis, California, USA), Nanostructured Materials Vol 1, No 5, 1992, 369-378. It is r e p o r t e d t h a t MA has been used to p r e p a r e Nb- 15.4at%A1 alloys from elemental powders. A nanosized solid solution was produced. Nb3AI formed during heating to 875°C. Densities 7.6 to 7.8 g m / c m :3 were attained in 4 m i n u t e s by p l a s m a activated vacuum sintering at 1200°C and an applied load of 30 MPA.
Tantalum E F F E C T S OF I N T E R M E T A L L I C C O M P O U N D S ON P R O P E R T I E S OF TANTALUM
P. Kumar, C.E. Mosheim (Cabot Corp, Boyertown, Pennsylvania, USA), Int. J. Refractory Metals & Hard Materials, Vol 12, No 1, 1993-1334, 35-40. It is noted t h a t whilst pure Ta has good corrosion resistance and formability at high temperature the high temperature properties are marginal for some applications. I m p r o v e m e n t s t h r o u g h solid solution and dispersion s t r e n g t h e n i n g are discussed and precipitation of intermetallic c o m p o u n d s is suggested as an alternative. An investigation of a PM Ta, reinforced with Y silicides particles, in which structure and p r o p e r t i e s were d e t e r m i n e d is described. It is r e p o r t e d t h a t there were i m p r o v e m e n t s in the mechanical properties.
Titanium S T R U C T U R A L E V O L U T I O N IN MECHANICALLY ALLOYED T I T A N I U M A L U M I N I U M ALLOYS
F.H. Froes et al (University of Idaho, Moscow, Idaho, USA), Materials Science a n d E n g i n e e r i n g A, Vol A158, No 1, 1992, 93-101. An investigation of structural evolution in Ti (25 or 50) at%Al is described. The sequence is r e p o r t e d to be solid solution formation, synthesis o f Ti:3A1, a m o r p h i z a t i o n a n d crystallization in a face-centred-cubic structure. The results are discussed in t e r m s of t h e r m o d y n a m i c s and it is suggested t h a t the FCC p h a s e may be TiN due to contamination.
Tungsten S E P A R A T I O N OF D O P E C O M P O U N D S FROM NON-SAG T U N G S T E N M E T A L POWDER
J. Neugebauer et al (Hungarian Academy of Sciences, B u d a p e s t , Hungary), Inst. J. Refractory. M e t a l s & H a r d M a t e r i a l s , Vol 12, No 12, 1993-1994, 3-7. It is reported t h a t the dope c o n s t i t u e n t s in NS WO 2 and W can be s e p a r a t e d by t r e a t m e n t in H peroxide. The intermediate 'brown' oxide from reduction of K-AL-Si d o p e r W 'blue' oxides contains differenl types of inclusions which are removed by H202 a n d HF t r e a t m e n t leaving only s p h e r i c a l m e t a l particles. The d o p e inclusions are shown to consist mainly of K and Si or K, Si and A1. DOPANT INCORPORATION DURING R E D U C T I O N OF D O P E D T U N G S T E N BLUE OXIDE
W.D. Schubert et al (Technical University of Vienna, Vienna, Austria), Int. J. R e f r a c t o ~ Metals & H a r d Materials, Vol 12, No 1, 1993-1994, 9-16. The p a p e r d e s c r i b e s h o w p r o c e s s p a r a m e t e r s in the reduction of W blue oxide, d o p e d with K, Si and Ai, influence powder properties, grain size and c o n c e n t r a t i o n , c o m p o s i t i o n a n d size of d o p a n t inclusions. A model for d o p a n t incorporation is p r e s e n t e d and is shown to agree with e x p e r i m e n t a l observations and to explain the action of the d o p a n t elements. WHAT IS B E H I N D ' T U N G S T E N B L U E OXIDES'
H-J. Lunk et al (Humboldt University of Berlin, Berlin, Germany), Int. J. Refractov~ Metals & H a r d Materials, Vol 12, No l, 1993-1994, 17-26. It. is r e p o r t e d t h a t the composition of W blue oxides (TBO) varies widely according to production conditions or t h o s e of the
MPR July/August 1994 51
M. Miyajima et a] (Tohoku University, Sendal, J a p a n ) J. Japa'r~ Soc. Powder a n d t'owder Metallurgy, Vol. 40, No 5, 1993, 506-510. (In J a p a n e s e ) . A study of densification and structural evolution (luring p s e u d o }tiP of atomized u l t r a f i n e s t a i n l e s s s t e e l p o w d e r is d e s c r i b e d , effects of t e m p e r a t u r e a n d pressure being investigated. It is reported t h a t lower sintering t e m p e r a t u r e s t h a n for normal sintering (:an be employed. MAGNETIC AND MECHANICAL P R O P E R T I E S OF VACUUM S I N T E R E D IRON-SILICON MATERIALS
A. Salek, E. Dudrova (lnsl. of Materials Research, Kosice, Slovakia) P M Science a n d Technoh,gy, Yk)l 4, No :3, 1993, 27-37. An investigation of m e c h a n i c a l and physical properties of vacuum sintered Fe(2 to 6)%Si alloys is described, effects of compaction pressure and sintering conditions being determined. The alloys are used for m a g n e t s in e l e c t r o m o t o r braking swstems for which the properties found are reported to be satisfactm7. High d e n s i f i c a t i o n r e s u l t i n g from a c t i v a t e d sintering is reported. ACTIVATING E F F E C T S OF B O R O N ON S I N T E R I N G A N D P R O P E R T I E S OF IRON A N D PREALLOYED C O M P A C T S
A. Salek, E, Dudrova (Inst. of Materials Research, Kosice, Slovakia). PM Science a n d Technology, Vol 4, No 3, 1993, 46-56. The effects of up to 0.6% B, a d d e d as Ibrro-boron, and sintering conditions on the hardness and strength of Fe and Fe-2% Ni0.5% Mo alloys were investigated. For Fe the addition of 0.6% gave an increase in density of 6% and a Vicker's h a r d n e s s of 95. For the Fe-Ni-Mo alloy the increase in density was 26% and h a r d n e s s 240. The effects are attributed to the activating effect of B in producing a liquid phase during sintering. MICROALLOYING OF P O W D E R S T E E L S WITH B O R O N
B.B. Korol'kov (Tula Poiytechnieal Inst., Tula, Russia) lzv. V.U.Z. C h e r n a y a Metall., No 6, 1992, 47-48. (In Russian).
The effect of adding 0.025wt% B and 0.2% Hf oxychloride to a 0,4% C steel is shown to be beneficial in retarding loss of s t r e n g t h at elevated temperatures. The Hf o x y c h l o r i d e is c o n s i d e r e d to aid t h e uniform distribution of B t h r o u g h o u t the steel and gives i m p r o v e m e n t s in impact toughness.
Molybdenum PHYSICO-MECHANICAL P R O P E R T I E S A N D S T R U C T U R E OF MOLYBDENUMIRON-TUNGSTEN POWDER MASTER ALLOY
P.N. Ostrik et al (Dnepropetrovsk Metallurgical Inst., Dnepropetrovsk, Ukraine) Izv. V.U.Z. C h e r n a y a Metall., No 6, 1992, 7-10. (in Russian). The characteristics of Mo-35% Fe-5% W powder were investigated with regard to particle size distribution and average grain parameters. The powder is applied as a master alloy in the production of steel p a r t s and ensures better incorporation of Mo in the steel.
Niobium N A N O P H A S E S T R U C T U R E S IN MECHANICALLY ALLOYED N I O B I U M RICH N I O B I U M A L U M I N I D E
M2. TracT, J.R. Groza (University of California, Davis, California, USA), Nanostructured Materials Vol 1, No 5, 1992, 369-378. It is r e p o r t e d t h a t MA has been used to p r e p a r e Nb- 15.4at%A1 alloys from elemental powders. A nanosized solid solution was produced. Nb3AI formed during heating to 875°C. Densities 7.6 to 7.8 g m / c m :3 were attained in 4 m i n u t e s by p l a s m a activated vacuum sintering at 1200°C and an applied load of 30 MPA.
Tantalum E F F E C T S OF I N T E R M E T A L L I C C O M P O U N D S ON P R O P E R T I E S OF TANTALUM
P. Kumar, C.E. Mosheim (Cabot Corp, Boyertown, Pennsylvania, USA), Int. J. Refractory Metals & Hard Materials, Vol 12, No 1, 1993-1334, 35-40. It is noted t h a t whilst pure Ta has good corrosion resistance and formability at high temperature the high temperature properties are marginal for some applications. I m p r o v e m e n t s t h r o u g h solid solution and dispersion s t r e n g t h e n i n g are discussed and precipitation of intermetallic c o m p o u n d s is suggested as an alternative. An investigation of a PM Ta, reinforced with Y silicides particles, in which structure and p r o p e r t i e s were d e t e r m i n e d is described. It is r e p o r t e d t h a t there were i m p r o v e m e n t s in the mechanical properties.
Titanium S T R U C T U R A L E V O L U T I O N IN MECHANICALLY ALLOYED T I T A N I U M A L U M I N I U M ALLOYS
F.H. Froes et al (University of Idaho, Moscow, Idaho, USA), Materials Science a n d E n g i n e e r i n g A, Vol A158, No 1, 1992, 93-101. An investigation of structural evolution in Ti (25 or 50) at%Al is described. The sequence is r e p o r t e d to be solid solution formation, synthesis o f Ti:3A1, a m o r p h i z a t i o n a n d crystallization in a face-centred-cubic structure. The results are discussed in t e r m s of t h e r m o d y n a m i c s and it is suggested t h a t the FCC p h a s e may be TiN due to contamination.
Tungsten S E P A R A T I O N OF D O P E C O M P O U N D S FROM NON-SAG T U N G S T E N M E T A L POWDER
J. Neugebauer et al (Hungarian Academy of Sciences, B u d a p e s t , Hungary), Inst. J. Refractory. M e t a l s & H a r d M a t e r i a l s , Vol 12, No 12, 1993-1994, 3-7. It is reported t h a t the dope c o n s t i t u e n t s in NS WO 2 and W can be s e p a r a t e d by t r e a t m e n t in H peroxide. The intermediate 'brown' oxide from reduction of K-AL-Si d o p e r W 'blue' oxides contains differenl types of inclusions which are removed by H202 a n d HF t r e a t m e n t leaving only s p h e r i c a l m e t a l particles. The d o p e inclusions are shown to consist mainly of K and Si or K, Si and A1. DOPANT INCORPORATION DURING R E D U C T I O N OF D O P E D T U N G S T E N BLUE OXIDE
W.D. Schubert et al (Technical University of Vienna, Vienna, Austria), Int. J. R e f r a c t o ~ Metals & H a r d Materials, Vol 12, No 1, 1993-1994, 9-16. The p a p e r d e s c r i b e s h o w p r o c e s s p a r a m e t e r s in the reduction of W blue oxide, d o p e d with K, Si and Ai, influence powder properties, grain size and c o n c e n t r a t i o n , c o m p o s i t i o n a n d size of d o p a n t inclusions. A model for d o p a n t incorporation is p r e s e n t e d and is shown to agree with e x p e r i m e n t a l observations and to explain the action of the d o p a n t elements. WHAT IS B E H I N D ' T U N G S T E N B L U E OXIDES'
H-J. Lunk et al (Humboldt University of Berlin, Berlin, Germany), Int. J. Refractov~ Metals & H a r d Materials, Vol 12, No l, 1993-1994, 17-26. It. is r e p o r t e d t h a t the composition of W blue oxides (TBO) varies widely according to production conditions or t h o s e of the
MPR July/August 1994 51