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Surface temperature and deformation of polycrystalline tungsten during grinding
t)rcscntcd. It. is shown that the diffusion alloyed powders have no advantage and are more costly to prtxtuce. Jt is r e c o m m e n d e d t h a t homogeneously alloyed powders are uscd for the m a n u f a c t u r e of structural parts in low alloy steel.
Molybdenum E F F E C T S OF A D D I T I O N S OF RHENIUM AND CARBON ON LOW TEMPERATURE FRACTURE OF MOLYBDENUM Y. Jliraoka (Okayama University of Science, Okayama, .lapan), J Japan Inst qf MetaLs, Vol 56, N() 2, 1992, 161-167 (in J a p a n e s e ) . Thc effects of additions of C and Re on lhc fracture characteriztics of sintered Mo were invcstigate(l. It is reported t h a t the fracture strength and ductility are i n c r e a s e d by up to l()%Re anti small a d d i t i o n s o f ('. T h e i n c r e a s e s a r e a t t r i b u t e d to increases in intergranular fracture st rengths.
Nickel CHARACTERIZATION OF NICKELBASED SUPERALLOYS M.C. Jim6nez-Rivero c! al (University Ciudad, Madrid, Spain), Re*., de Metall, Vol 28, No 3, 1992, 156-164 (in Spanish). The properties of Ni base superalh)ys are discussed with reference to chemical and microstructural c h a r a c t e r i z t i c s . The mcthotls for characterization are described and discussed with respect to the accuratT attained.
Titanium III
NANOSTRUCTURE PROCESSING FOR TITANIUM BASED MATERIALS F.tt. Frocs
e l al (University of Idaho, Moscow, Idaho, USA), J of MetaL~, Vol 44, No 5, 1992, 26-29. The properties of nano-structure materials are discussed with reference to grain size, about 100 nm. It is shown thal. Ti base alloys and intermetallic p h a s e s with ttlcse grain sizes show properties superior to materials with grain sizes above l pro.
Tungsten 1
COLLAPSE OF INTERCONNECTING PORES IN SOLID STATE SINTERING OF TUNGSTEN-NICKEL ALLOYS J-W. Noh ct al (Agen(T for Dcfcnce J)evclo p m c n t , "Faejon, Korea), Metallurgical 7~'ans A, Vol 23A, No 8, 2141-2145.
Sintcring of W c o m p a c t s with 0.03 to 0.1%Ni w a s s t u d i e d . M i c r o s t r u e t u r a l analysis showed that pore collapse occurred at three-grain j u n c t i o n p o i n t s and closed p o r e s formed at four-grain junctions. The critical density, below which all pores art, in isolated form, is reported to be d o u b l e t h e v a l u e p r e d i c t e d by morphological perturbation theory. It is concluded that grain boundary diffusion and capilliary force play i m p o r t a n t roles in pore ch)sure. DEVELOPMENT AND P R O P E R T I E S OF NEW T U N G S T E N BASE COMPOSITE FOR PENETRATORS A. Bose et al (S(mthwestern Research Inst., San Antonio, Texas, lISA), lnt J Powder Metallu~.y, Vol 28, No 4, 1992, 383-394. The use of high d e n s i t y m a t e r i a l s , depleted t; (I)U) and W heavy alloys, as kinetic enerKw p e n e t r a t o r s , is discussed with regard to environmental factors and it is shown t h a t the W alloy is preferred. For the application a self s h a r p e n i n g ability is required and it is suggested t h a t this is related to the ability of J)U to undergo adiabatic shear. An investigation of W-NiMn and W-Jif alloys is described and it is s h o w n t h a t W-Ni-Mn alloys e x h i b i t e d localiscd s h e a r instability. IMPROVEMENT IN P R O P E R T I E S OF LIQUID PHASE S I N T E R E D T U N G S T E N ALLOYS T. Kaneko (.Japan Dcfcnce Agency, Tokyo, .lapan), J ,lapa~ Soc Powder and Powder Metallurgy, Vol 39, No 8, 1992, 670-674 (in .Japanese). The production of W-Ni-Fe alloys with i m p r o v e d p r o p e r t i e s is d e s c r i b e d . To optimize the composition the p r o p o r t i o n s of Ni ~-Fc anti the ratios of Ni:Fi were varied, and the effects of s i n t c r i n g temperaturc, 1480"C, 1500°C and 1510°C, and a d d i t i o n of Co, were investigated. Strength and dut'tility showed m a x i m a at an Ni:Fe ratio of 4, and 0.5% Co. SURFACE TEMPERATURE AND DEFORMATION OF POLYCRYSTALLINE T U N G S T E N DURING GRINDING A.A. A d a m o v s k y c t al, Poroshkovaya Metallurgiya, No 1, 1992, 72-77 (in Russian). It is shown t h a t the t e m p e r a t u r e at the surface of polycrystalline W during grinding may reach 100 to 95(FC according to type of grinding wheel, speed and applied load. Xray line broadening was used to e x a m i n e the deformed layer on the metal and this increa~ses in thickness to a m a x i m u m at 550~C and then stabilizes. The results are used to make r e c o m m e n d a t i o n s about grinding conditions for W.
CHARACTERISTICS OF POWDER P R O D U C E D BY CO-REDUCTION OF C O P P E R AND T U N G S T E N OXIDES T-ll. Kim et al (Hanyang University, Ansan, Korea), J. Korean Inst oj" MetaLs, Vol 30, No 2, 1992, 203-209 (in Korean). The production of a W-Cu powder by coreduction, in H, of a mixture of Cu and W oxides is described. It is shown t h a t a two stage process, at 200-'100:'C followed by 800"C gives the best. combination of grain size and compositional homogeneity in the powder. This is a t t r i b u t e d to the low lempcrature re(luction minimizing segregation of Cu and the formation of WCu agglomerates because of sintcring of Cu powder. E F F E C T S OF A T M O S P H E R E AND TRACE ELEMENT A D D I T I O N S ON WETTABILITY OF SILVER TO TUNGSTEN S. Wu and D. Zhang (Southeast University, Nanjing, China), Acta Metallurgical Sinica B, Vol 28, No l, 1992, B12-16 (in Chinese). "l~le wetting of W by molten Ag was m e a s u r e d by m e a n s of a sessile d r o p mcth(xi in vacuum, II or cracked NH3. It is shown that wetting is increased by addition of traccs of Ni, Cu or Ce which reduce the contact angle from 19 to 10-20':.
Ceramics C R E E P BEHAVIOUR OF SILICON CARBIDE WHISKER REINFORCED ALUMINA/ZIRCONIA COMPOSITES P. Wang et al (1)aimler-Bcnz Ag, ['lmB6fingen, Germany) Powd~,r Metall Int, Vol 24, No 6, 1992, 365-372. A description of the crt~,p anti oxidation bchaviour of SiC whisker rciniorced AlzO:;,." ZrO 2 is presented. The addition of SiC is shown to reduce the creep rate by a factor of 100. Activation energies are reported to be lower and the stress e x p o n c n t of the creep rate equation is higher than for the unreinforccd matrix. The creep m e c h a n i s m s and kinetics are discussed in t e r m s of two creep models. D E P E N D E N C E OF FRACTURE T O U G H N E S S OF CERAMICS ON TEMPERATURE O. Kamigaito (Toyota ('enlral Rcsear('h, Aichi, J a p a n ) , J. Japan Soc. Powder and Powder Metalluryy. Vol 23, No 8, 1992, 624-629 (in ,lapanese). A review of published values of fracture toughness of ceramics is i)rcsented. It is noted t h a t therc is considerable variation in Kit and its t e m p e r a t u r e coefficients in the reported values and this is attributed to the
MPR April 1993 49
Molybdenum E F F E C T S OF A D D I T I O N S OF RHENIUM AND CARBON ON LOW TEMPERATURE FRACTURE OF MOLYBDENUM Y. Jliraoka (Okayama University of Science, Okayama, .lapan), J Japan Inst qf MetaLs, Vol 56, N() 2, 1992, 161-167 (in J a p a n e s e ) . Thc effects of additions of C and Re on lhc fracture characteriztics of sintered Mo were invcstigate(l. It is reported t h a t the fracture strength and ductility are i n c r e a s e d by up to l()%Re anti small a d d i t i o n s o f ('. T h e i n c r e a s e s a r e a t t r i b u t e d to increases in intergranular fracture st rengths.
Nickel CHARACTERIZATION OF NICKELBASED SUPERALLOYS M.C. Jim6nez-Rivero c! al (University Ciudad, Madrid, Spain), Re*., de Metall, Vol 28, No 3, 1992, 156-164 (in Spanish). The properties of Ni base superalh)ys are discussed with reference to chemical and microstructural c h a r a c t e r i z t i c s . The mcthotls for characterization are described and discussed with respect to the accuratT attained.
Titanium III
NANOSTRUCTURE PROCESSING FOR TITANIUM BASED MATERIALS F.tt. Frocs
e l al (University of Idaho, Moscow, Idaho, USA), J of MetaL~, Vol 44, No 5, 1992, 26-29. The properties of nano-structure materials are discussed with reference to grain size, about 100 nm. It is shown thal. Ti base alloys and intermetallic p h a s e s with ttlcse grain sizes show properties superior to materials with grain sizes above l pro.
Tungsten 1
COLLAPSE OF INTERCONNECTING PORES IN SOLID STATE SINTERING OF TUNGSTEN-NICKEL ALLOYS J-W. Noh ct al (Agen(T for Dcfcnce J)evclo p m c n t , "Faejon, Korea), Metallurgical 7~'ans A, Vol 23A, No 8, 2141-2145.
Sintcring of W c o m p a c t s with 0.03 to 0.1%Ni w a s s t u d i e d . M i c r o s t r u e t u r a l analysis showed that pore collapse occurred at three-grain j u n c t i o n p o i n t s and closed p o r e s formed at four-grain junctions. The critical density, below which all pores art, in isolated form, is reported to be d o u b l e t h e v a l u e p r e d i c t e d by morphological perturbation theory. It is concluded that grain boundary diffusion and capilliary force play i m p o r t a n t roles in pore ch)sure. DEVELOPMENT AND P R O P E R T I E S OF NEW T U N G S T E N BASE COMPOSITE FOR PENETRATORS A. Bose et al (S(mthwestern Research Inst., San Antonio, Texas, lISA), lnt J Powder Metallu~.y, Vol 28, No 4, 1992, 383-394. The use of high d e n s i t y m a t e r i a l s , depleted t; (I)U) and W heavy alloys, as kinetic enerKw p e n e t r a t o r s , is discussed with regard to environmental factors and it is shown t h a t the W alloy is preferred. For the application a self s h a r p e n i n g ability is required and it is suggested t h a t this is related to the ability of J)U to undergo adiabatic shear. An investigation of W-NiMn and W-Jif alloys is described and it is s h o w n t h a t W-Ni-Mn alloys e x h i b i t e d localiscd s h e a r instability. IMPROVEMENT IN P R O P E R T I E S OF LIQUID PHASE S I N T E R E D T U N G S T E N ALLOYS T. Kaneko (.Japan Dcfcnce Agency, Tokyo, .lapan), J ,lapa~ Soc Powder and Powder Metallurgy, Vol 39, No 8, 1992, 670-674 (in .Japanese). The production of W-Ni-Fe alloys with i m p r o v e d p r o p e r t i e s is d e s c r i b e d . To optimize the composition the p r o p o r t i o n s of Ni ~-Fc anti the ratios of Ni:Fi were varied, and the effects of s i n t c r i n g temperaturc, 1480"C, 1500°C and 1510°C, and a d d i t i o n of Co, were investigated. Strength and dut'tility showed m a x i m a at an Ni:Fe ratio of 4, and 0.5% Co. SURFACE TEMPERATURE AND DEFORMATION OF POLYCRYSTALLINE T U N G S T E N DURING GRINDING A.A. A d a m o v s k y c t al, Poroshkovaya Metallurgiya, No 1, 1992, 72-77 (in Russian). It is shown t h a t the t e m p e r a t u r e at the surface of polycrystalline W during grinding may reach 100 to 95(FC according to type of grinding wheel, speed and applied load. Xray line broadening was used to e x a m i n e the deformed layer on the metal and this increa~ses in thickness to a m a x i m u m at 550~C and then stabilizes. The results are used to make r e c o m m e n d a t i o n s about grinding conditions for W.
CHARACTERISTICS OF POWDER P R O D U C E D BY CO-REDUCTION OF C O P P E R AND T U N G S T E N OXIDES T-ll. Kim et al (Hanyang University, Ansan, Korea), J. Korean Inst oj" MetaLs, Vol 30, No 2, 1992, 203-209 (in Korean). The production of a W-Cu powder by coreduction, in H, of a mixture of Cu and W oxides is described. It is shown t h a t a two stage process, at 200-'100:'C followed by 800"C gives the best. combination of grain size and compositional homogeneity in the powder. This is a t t r i b u t e d to the low lempcrature re(luction minimizing segregation of Cu and the formation of WCu agglomerates because of sintcring of Cu powder. E F F E C T S OF A T M O S P H E R E AND TRACE ELEMENT A D D I T I O N S ON WETTABILITY OF SILVER TO TUNGSTEN S. Wu and D. Zhang (Southeast University, Nanjing, China), Acta Metallurgical Sinica B, Vol 28, No l, 1992, B12-16 (in Chinese). "l~le wetting of W by molten Ag was m e a s u r e d by m e a n s of a sessile d r o p mcth(xi in vacuum, II or cracked NH3. It is shown that wetting is increased by addition of traccs of Ni, Cu or Ce which reduce the contact angle from 19 to 10-20':.
Ceramics C R E E P BEHAVIOUR OF SILICON CARBIDE WHISKER REINFORCED ALUMINA/ZIRCONIA COMPOSITES P. Wang et al (1)aimler-Bcnz Ag, ['lmB6fingen, Germany) Powd~,r Metall Int, Vol 24, No 6, 1992, 365-372. A description of the crt~,p anti oxidation bchaviour of SiC whisker rciniorced AlzO:;,." ZrO 2 is presented. The addition of SiC is shown to reduce the creep rate by a factor of 100. Activation energies are reported to be lower and the stress e x p o n c n t of the creep rate equation is higher than for the unreinforccd matrix. The creep m e c h a n i s m s and kinetics are discussed in t e r m s of two creep models. D E P E N D E N C E OF FRACTURE T O U G H N E S S OF CERAMICS ON TEMPERATURE O. Kamigaito (Toyota ('enlral Rcsear('h, Aichi, J a p a n ) , J. Japan Soc. Powder and Powder Metalluryy. Vol 23, No 8, 1992, 624-629 (in ,lapanese). A review of published values of fracture toughness of ceramics is i)rcsented. It is noted t h a t therc is considerable variation in Kit and its t e m p e r a t u r e coefficients in the reported values and this is attributed to the
MPR April 1993 49