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Effects of inclusions and pore content on fracture toughness of elemental titanium alloys
PM A m e t h o d for t h e i m p r o v e m e n t in c o r r o s i o n r e s i s t a n c e of p o r o u s Fe is proposed. Carburizing, Cr plating, polymer sealing and dichromat passivation are used in the process.
Molybdenum C O R R U G A T I O N OF G R A I N S IN L I Q U I D P H A S E S I N T E R E D MOLYBDENUMN I C K E L - T U N G S T E N ALLOY
Y-H. Park and D-Y. Yoon (Inst of Science and Technology, Taejon, Korea), Z Met.,,llkunde, Vol 83, No 12. 1992, 881-886. It is reported t h a t when Mo-15 wt% Ni is liquid p h a s e sintered in contact with MoNi-W the surfaces of the near spherical MoNi grains become corrugated by a solution/ precipitation mechanism. The driving force for the process is considered to arise from coherence strains at the dissolving surfaces. The p h e n o m e n o n only occurs intermittently at 10% W in the Mo-NLW alloy but at 20% W the corrugation is extensive and results in a skeletal structure of Mo-Ni-W solid solution. It is suggested t h a t the properties of the skeletal structure will be very different from those of thc spherical grain structured material.
Nickel P R O C E S S I N G MAP FOR C O N T R O L OF M I C R O S T R U C T U R E D U R I N G HOT WORKING OF H I P NIMONIC-AP-1
M.C. Somani et al (Defence Metallurgical Laboratory, Hyderabad, India), Metallurgical Trans A, Vol 23A, No 10, 1992, 28492857. Processing maps are used to characterize the deformation behaviour of a HIP superalloy in the range 950 to 1200°C and strain rates of 0.001 to 100 SEC ]. Dynamic r e c r y s t a l l i z a t i o n w i t h a p e a k efficiency of 40% is reported for 1 1 2 5 C and 0.3 see 1 which are considered to be the o p t i m u m hot working conditions. The microstructures produced under these conditions are found to be free of prior particle boundary defects. Intercrystalline cracking was found at 1200°C a n d 100 sec ~ and wedge cracking at 1200~C and 0.0(}l sec ~. Prior particle boundary cracking is noted at 1000'C. Adiabatic s h e a r o c c u r r e d a~ s t a i n r a t e s a b o v e 10 sec 1 E F F E C T S OF HIP A N D H E A T T R E A T M E N T ON C H A R A C T E R I S T I C S OF P R I O R B O U N D A R I E S OF R E N E 9 5 SUPERALLOY
B.H. Choe and N.K. Park (Inst of Machinery and Metals, Changwon, Korea), J Korean Inst of Metals, Vol 30, No 9, 1992, 10471055, (In Korean). The occurrence o f P P B in H I P c o n s o l i d a t e d Rene95 is d i s c u s s e d with respect to the effects of PPB and grain
64
MPR June 1993
LITERATURE
REVIEW
boundaries on mechanical properties. An a t t e m p t is made to improve PPB and 7' morphology by changes in HIP and h e a t t r e a t m e n t conditions. Thickness of PPB decreases with increase in HIP t e m p e r a t u r e and the PPB are shown to consist of AI and Zr rich oxides and Nb and Ti carbides and 7'. Grain boundaries are shown to be serrated and PPB to occur within grains after post-HIP heat treatment. Long h e a t t r e a t m e n t t i m e s at high t e m p e r a t u r e s results in y' depleted zones at grain boundaries. RAPID S O L I D I F I C A T I O N OF T I T A N I U M ALLOYS
T.A. B h a s k a r a n (National A e r o n a u t i c a l Laboratory, Bangalore, India), Int J Rapid Solidification, Vol 7, No 2, 1992, 127-149. The RS of Ti alloys is reviewed. Means of achieving high cooling rates are described. The e f f e c t s of RS on s t r u c t u r e s a n d properties of Ti alloys are discussed. It is shown that powders with amorphous, quasi-crystalline and crystalline structures may be o b t a i n e d a n d t h e p h a s e s are illustrated. I m p r o v e m e n t s in mechanical properties are indicated. PRESSING SINTERING AND P R O P E R T I E S OF T I T A N I U M MATERIALS
E. Dudrova et al (Ustav Materialoveho Vyskumu SAV, Kosice, Slovakia), Pokroky Psaskove Metalurgie, No 3-4, 1992, 31-50. (In Czech). The p a p e r p r e s e n t s an analysis of the compressibility and sinterability of Ti alloys p r e p a r e d from Ti sponge and cuttings of solid metal. Relationships between porosity, plasticity and c o m p a c t i n g p r e s s u r e are t a k e n i n t o a c c o u n t . S i n t e r a b i l i t y is assessed as a function of volume change and porosity on sintering at 900 to 1380°C. The mechanical p r o p e r t i e s of the sintered materials are analysed with reference to area and volume porosises. It is shown t h a t the properties are controlled by matrix structure at low porosities. E F F E C T S OF I N C L U S I O N S A N D P O R E C O N T E N T ON F R A C T U R E T O U G H N E S S OF E L E M E N T A L T I T A N I U M ALLOYS
N.R. Moody et al (Sandia National Laboratory, Livermore, California, USA), Metalluw gical TransA, Vol 24, No 1, 1993, 161-174. The effects of m i c r o s t r u c t u r a l f a w s , inclusion and pores, in a range of Ti alloys, m a d e f r o m b l e n d e d e l e m e n t a l p o w d e r s , on f r a c t u r e t o u g h n e s s w e r e i n v e s t i g a t e d . It is r e p o r t e d t h a t t h e fracture toughness was inversely d e p e n d e n t on t h e v o l u m e f r a c t i o n of d e f e c t s a n d on t h e p r o p e r t i e s of t h e d i f f e r e n t d e f e c t t y p e s . T o u g h n e s s is r e p o r t e d to be h i g h e r for p o r e only s p e c i m e n s . F r a c t u r e is s h o w n to take p l a c e by m i c r o v o i d c o a l e s c e n c e . A relationship between defects and fracture
mode is defined. The smallest defects are r e p o r t e d not to pal%ieipitate in the fracture process. I N I T I A L S T A G E OF HOT P R E S S I N G OF MONOSIZED TITANIUM AND TITANIUM-TITANIUM-TITANIUM CARBIDE POWDERS
N. Taylor et al (Massachusettes Inst of Technology, Cambridge, USA), Acta Metall Mater, Vol 41, No 3, 1993, 955-965. Densification, by vacuum hot pressing, of monosized spherical pure Ti and Ti10 vol% TiC powders was investigated. It is r e p o r t e d t h a t the kinetics of densification can be described lay power law creep. The TiC reduces the rate of densification by a factor of 5 to 20 and this is attributed to a lower initial density and reduced densifieation at inLerparticle contacts.
Tungsten E F F E C T S OF D I S P E R S I O N ON C O M P A C T I O N OF T U N G S T E N POWDERS UNDER HYDROSTATIC PRESSURE
V.P. Filonenko et al, Poroshkovaya Metal lurgiya, No 4, 19q2, 16-20. (In Russian). W powders in the size ranges 0.02 to 0.1, 0.1 to 0.5 and 3 to 8 pm were c o m p a c t e d u n d e r hydrostatic pressures of up to 5 GPa. Analysis of relative and defect densities shows t h a t deformation fi'ee mutual sliding of particles is the d o m i n a n t densification mechanism for the finest powder. Densification of the coarse powders takes place by plastic deformation. Both these m e c h a n i s m s occur in compaction of the intermediate size range. E F F E C T OF B I N D E R C O M P O S I T I O N O N S T R U C T U R E A N D P R O P E R T I E S OF T U N G S T E N HEAVY ALLOYS
E-P. Kim et al ( A g e n c y for D e f e n c e M a t e r i a l s Research, Daejon, K o r e a ) , J Korean Inst of Metals, Vol 30, No 8, 1992, 963-971. (In Korean). The effects of sintering t e m p e r a t u r e and Ni:Fe ratio on the structure and properties of W - 7 % ( N e + F e ) heavy alloys were investigated for Ni:Fe ratios of 7:3, 4:1 and 9:1. The volume fraction of matrix present in the alloy increased as the Ni content increased because of increased solubility of W in the matrix. The increased proportion of matrix reduced the contiguity of the V¢ grains increasing ductility and t o u g h n e s s The o p t i m u m Ni:Fe ratio is r e p o r t e d to be 4:1.
Composites MICROSTRUCTURE AND MECHANICAl, P R O P E R T I E S OF ALUMINAMOLYBDENUM NANOCOMPOSITES M. Nawa et al (Matsushita Electrical Co Ltd, Kadoma, J a p a n ) , J Japan Soc Powder
Molybdenum C O R R U G A T I O N OF G R A I N S IN L I Q U I D P H A S E S I N T E R E D MOLYBDENUMN I C K E L - T U N G S T E N ALLOY
Y-H. Park and D-Y. Yoon (Inst of Science and Technology, Taejon, Korea), Z Met.,,llkunde, Vol 83, No 12. 1992, 881-886. It is reported t h a t when Mo-15 wt% Ni is liquid p h a s e sintered in contact with MoNi-W the surfaces of the near spherical MoNi grains become corrugated by a solution/ precipitation mechanism. The driving force for the process is considered to arise from coherence strains at the dissolving surfaces. The p h e n o m e n o n only occurs intermittently at 10% W in the Mo-NLW alloy but at 20% W the corrugation is extensive and results in a skeletal structure of Mo-Ni-W solid solution. It is suggested t h a t the properties of the skeletal structure will be very different from those of thc spherical grain structured material.
Nickel P R O C E S S I N G MAP FOR C O N T R O L OF M I C R O S T R U C T U R E D U R I N G HOT WORKING OF H I P NIMONIC-AP-1
M.C. Somani et al (Defence Metallurgical Laboratory, Hyderabad, India), Metallurgical Trans A, Vol 23A, No 10, 1992, 28492857. Processing maps are used to characterize the deformation behaviour of a HIP superalloy in the range 950 to 1200°C and strain rates of 0.001 to 100 SEC ]. Dynamic r e c r y s t a l l i z a t i o n w i t h a p e a k efficiency of 40% is reported for 1 1 2 5 C and 0.3 see 1 which are considered to be the o p t i m u m hot working conditions. The microstructures produced under these conditions are found to be free of prior particle boundary defects. Intercrystalline cracking was found at 1200°C a n d 100 sec ~ and wedge cracking at 1200~C and 0.0(}l sec ~. Prior particle boundary cracking is noted at 1000'C. Adiabatic s h e a r o c c u r r e d a~ s t a i n r a t e s a b o v e 10 sec 1 E F F E C T S OF HIP A N D H E A T T R E A T M E N T ON C H A R A C T E R I S T I C S OF P R I O R B O U N D A R I E S OF R E N E 9 5 SUPERALLOY
B.H. Choe and N.K. Park (Inst of Machinery and Metals, Changwon, Korea), J Korean Inst of Metals, Vol 30, No 9, 1992, 10471055, (In Korean). The occurrence o f P P B in H I P c o n s o l i d a t e d Rene95 is d i s c u s s e d with respect to the effects of PPB and grain
64
MPR June 1993
LITERATURE
REVIEW
boundaries on mechanical properties. An a t t e m p t is made to improve PPB and 7' morphology by changes in HIP and h e a t t r e a t m e n t conditions. Thickness of PPB decreases with increase in HIP t e m p e r a t u r e and the PPB are shown to consist of AI and Zr rich oxides and Nb and Ti carbides and 7'. Grain boundaries are shown to be serrated and PPB to occur within grains after post-HIP heat treatment. Long h e a t t r e a t m e n t t i m e s at high t e m p e r a t u r e s results in y' depleted zones at grain boundaries. RAPID S O L I D I F I C A T I O N OF T I T A N I U M ALLOYS
T.A. B h a s k a r a n (National A e r o n a u t i c a l Laboratory, Bangalore, India), Int J Rapid Solidification, Vol 7, No 2, 1992, 127-149. The RS of Ti alloys is reviewed. Means of achieving high cooling rates are described. The e f f e c t s of RS on s t r u c t u r e s a n d properties of Ti alloys are discussed. It is shown that powders with amorphous, quasi-crystalline and crystalline structures may be o b t a i n e d a n d t h e p h a s e s are illustrated. I m p r o v e m e n t s in mechanical properties are indicated. PRESSING SINTERING AND P R O P E R T I E S OF T I T A N I U M MATERIALS
E. Dudrova et al (Ustav Materialoveho Vyskumu SAV, Kosice, Slovakia), Pokroky Psaskove Metalurgie, No 3-4, 1992, 31-50. (In Czech). The p a p e r p r e s e n t s an analysis of the compressibility and sinterability of Ti alloys p r e p a r e d from Ti sponge and cuttings of solid metal. Relationships between porosity, plasticity and c o m p a c t i n g p r e s s u r e are t a k e n i n t o a c c o u n t . S i n t e r a b i l i t y is assessed as a function of volume change and porosity on sintering at 900 to 1380°C. The mechanical p r o p e r t i e s of the sintered materials are analysed with reference to area and volume porosises. It is shown t h a t the properties are controlled by matrix structure at low porosities. E F F E C T S OF I N C L U S I O N S A N D P O R E C O N T E N T ON F R A C T U R E T O U G H N E S S OF E L E M E N T A L T I T A N I U M ALLOYS
N.R. Moody et al (Sandia National Laboratory, Livermore, California, USA), Metalluw gical TransA, Vol 24, No 1, 1993, 161-174. The effects of m i c r o s t r u c t u r a l f a w s , inclusion and pores, in a range of Ti alloys, m a d e f r o m b l e n d e d e l e m e n t a l p o w d e r s , on f r a c t u r e t o u g h n e s s w e r e i n v e s t i g a t e d . It is r e p o r t e d t h a t t h e fracture toughness was inversely d e p e n d e n t on t h e v o l u m e f r a c t i o n of d e f e c t s a n d on t h e p r o p e r t i e s of t h e d i f f e r e n t d e f e c t t y p e s . T o u g h n e s s is r e p o r t e d to be h i g h e r for p o r e only s p e c i m e n s . F r a c t u r e is s h o w n to take p l a c e by m i c r o v o i d c o a l e s c e n c e . A relationship between defects and fracture
mode is defined. The smallest defects are r e p o r t e d not to pal%ieipitate in the fracture process. I N I T I A L S T A G E OF HOT P R E S S I N G OF MONOSIZED TITANIUM AND TITANIUM-TITANIUM-TITANIUM CARBIDE POWDERS
N. Taylor et al (Massachusettes Inst of Technology, Cambridge, USA), Acta Metall Mater, Vol 41, No 3, 1993, 955-965. Densification, by vacuum hot pressing, of monosized spherical pure Ti and Ti10 vol% TiC powders was investigated. It is r e p o r t e d t h a t the kinetics of densification can be described lay power law creep. The TiC reduces the rate of densification by a factor of 5 to 20 and this is attributed to a lower initial density and reduced densifieation at inLerparticle contacts.
Tungsten E F F E C T S OF D I S P E R S I O N ON C O M P A C T I O N OF T U N G S T E N POWDERS UNDER HYDROSTATIC PRESSURE
V.P. Filonenko et al, Poroshkovaya Metal lurgiya, No 4, 19q2, 16-20. (In Russian). W powders in the size ranges 0.02 to 0.1, 0.1 to 0.5 and 3 to 8 pm were c o m p a c t e d u n d e r hydrostatic pressures of up to 5 GPa. Analysis of relative and defect densities shows t h a t deformation fi'ee mutual sliding of particles is the d o m i n a n t densification mechanism for the finest powder. Densification of the coarse powders takes place by plastic deformation. Both these m e c h a n i s m s occur in compaction of the intermediate size range. E F F E C T OF B I N D E R C O M P O S I T I O N O N S T R U C T U R E A N D P R O P E R T I E S OF T U N G S T E N HEAVY ALLOYS
E-P. Kim et al ( A g e n c y for D e f e n c e M a t e r i a l s Research, Daejon, K o r e a ) , J Korean Inst of Metals, Vol 30, No 8, 1992, 963-971. (In Korean). The effects of sintering t e m p e r a t u r e and Ni:Fe ratio on the structure and properties of W - 7 % ( N e + F e ) heavy alloys were investigated for Ni:Fe ratios of 7:3, 4:1 and 9:1. The volume fraction of matrix present in the alloy increased as the Ni content increased because of increased solubility of W in the matrix. The increased proportion of matrix reduced the contiguity of the V¢ grains increasing ductility and t o u g h n e s s The o p t i m u m Ni:Fe ratio is r e p o r t e d to be 4:1.
Composites MICROSTRUCTURE AND MECHANICAl, P R O P E R T I E S OF ALUMINAMOLYBDENUM NANOCOMPOSITES M. Nawa et al (Matsushita Electrical Co Ltd, Kadoma, J a p a n ) , J Japan Soc Powder