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Synthesis of Fe aluminides from elemental powders
MATERIAI~S BASED ON ULTRADISPERSED NITRIDE POWDERS
G.G. Gnesin et al, Poroshkovaya Metallurgiya, No 12, 1990, 78-82, (In Russian). The effects of additions of TiN on the cutting properties, hardness and fracture toughness of sintered tool materials based on Si and Al nitrides and A1 and Y oxides were investigated. Increased wear resistance resulted from TiN additions. Hardness and fracture toughness of Y oxide containing materials was increased by high temperature annealing and this was a t t r i b u t e d to crystallization of grain boundary phases. CORROSION OF TITANIUM NITRIDE BASED CERMETS
O.N. Kaidish et al, Poroshkovaya Metallurgiya, No 1, 1991, 77-81, (In Russian). The corrosion of TiN based cermets in dilute mineral acids has been measured. Materials with Ni, Cr and Mo, singly or in any combination were studied. An alloy with Ni, Cr and Mo had the highest corrosion resistance. The alloy TiN-30%Cr had high stability due to formation of a ternary nitride phase. INTERACTION OF HEXAGONAL BORON NITRIDE WITH MOLYBDENUM IN POWDER MIXTURES
V.V. Garbuz et al, Poroshkovaya Metallurgiya, No 1, 1991, 82-84, (In Russian). Interactions in hexagonal BN and Mo mixtures have been studied with the objective of improving the production process for PM BN-Mo articles. HARDENING MECHANISMS IN HEAT
TRRATMENT
OF HARD METALS
M_A. Kallya, M.G. Loshak, Poroshkovaya Metallurgiya, No 1, 1991, 94-96, (In Russian). Mechanisms of hardening during heat treatment of s i n t e r e d W alloys are discussed. It is r e p o r t e d t h a t h e a t treatment may be used to increase the durability of hardmetal components. HARDMETALS, C E M T S
AND
CERAMIC WEAR RESISTANT
MATERIALS H. Koilaska, I~ Dreyer, (RWTH, Aachen, Germany), Metall., Vol 45, No 3, 1991, 224235, (In German). Hard m a t e r i a l s , with or w i t h o u t coatings, which are used for wear resistant applications, are reviewed. An outline is given of their development and economic significance. Production m e t h o d s and properties are considered and possible future trends are discussed. HARDMETAL COATINGS FOR TOOLS O. Knotek, F. L5ffier, (Krupp Widia, Essen,
58 MPR July/August 1991
Germany), MetaU., Vol 45, No 3, 1991, 236240, (In German). Attention is drawn to the increasing importance of coatings on hard tool materials. Various functions are fulfilled by the coatings and they exert considerable influence on performance. The use of modern techniques to apply the coatings is discussed in relation to improved efficiency and wear resistance of tools.
monitor in situ HIP densification of TTi a l u m i n i d e is described. E x p e r i m e n t a l results were compared with the model proposed by Ashby and good agreement was obtained. It was found that significant densification occurs during the pressurization stage of the HIP process. A method is suggested for the estimation of sample density during HIP by use of a mathematical model.
A STUDY OF THE INTERFACE BETWEEN A Co BASED MATRIX AND
SYNTHESIS OF F e ALUMINIDES FROM ELEMENTAL POWDERS
DIAMOND PARTICLES
B.H. Rabin, P~N. Wright, (National Engineering Laboratory, Idaho, USA), MetaUurgical Transactions A, Vol 22A, No 2, 1991, 277-286. Experiments involving the pressureless sintering and hot pressing of elemental FeAI powder mixtures, corresponding to FeA1 and FesA1, are described. The exothermic reaction which results in the formation of the compound and the presence of a t r a n s i e n t liquid phase were observed. Thermodynamic properties were measured. The effects of process variables on sintered density were determined. Near full density compacts were obtained after hot pressing and a grain size less than 10 pan was found.
A. Molinari et al, (Univ of Trento, Italy), Materials Science and Engineering A, Vol 130A, No 2, 1990, 257-262. A study of the interface between diamond particles and a Co based mat~x is reported. Morphological structure and chemical analysis were obtained of the interface during consolidation. Graphite, Co carbide and a Co-C solid solution were detected and these were found to result in strong particle-matrix bonding but there was deterioration in the diamond C-C bond. The addition of Sn to the matrix is reported to c o u n t e r a c t g r a p h i t i z a t i o n of the diamond.
Intermetallic materials IIII
Mechanical alloying
I
DENSIFICATION OF RAPIDLY SOLIDIFIED ( R S ) Tl ALUMINIDE POWDERS - COMPARISON OF EXPERIMENTAL RESULTS WITH HIP MODELS
B.W. Choi et al, (Univ of California, Santa Barbara, California, USA), Acta Metall. et Mater., Vol 38, No 11, 1990, 2225-2234. RS Ti a l u m i n i d e p o w d e r s w e r e characterized and consolidated by HIP, Ti50at%Al-1.8%Nb and Ti-48%AI-2.4%Nb0.3%Ta alloys were compared. Alloys were found to solidify by formation of ~ close packed hexagonal, then interdendritic T with a small amount of [~ body centered c u b i c p h a s e . The e f f e c t s of t i m e , temperature and pressure on the progress of HIP were determined and compared with data predicted from HIP m a p s . Densification was found to be independent of particle size. Power law creep is suggested as the main mechanism of densification for which the best agreement between experiment and prediction was obtained. DENSIFICATION OF RAPIDLY SOLIDIFIED (RS) Ti ALUMINIDE POWDERS - USE OF AN EDDY CURRENT SENSOR TO VERIFY HIP MODELS
B.W. Choi et al, (Univ of California, Santa Barbara, California, USA), Acta Mftall. et MaWr., Vol 38, No 11, 1990, 2245-2252. The use of an eddy current sensor to
AMORPHIZATION OF Ni-ALUMINIDES
BY MECHANICAL ALLOYING (MA) S-CJ. Jang, (North Carolina State Univ, North Carolina, USA), Doctoral dissertation, North Carolina State Univ, 1990. M A has been applied to the disordering and amorphization of Ni aluminides. Structural evolution was studied by X-r~ diffraction, electron microscopy, differential scanning calorimetry and acoustic microscopy. The processing of Ni~Al was found to proceed as follows: ordered facecentered cubic (fcc) --, disordered fcc -* nanocrystalline fcc ~ amorphous material. Disordering of the fcc took 5 hours and 50 hours was required for the production of the a m o r p h o u s phase. A m e c h a n i s m through a dislocation cell structure, about 2 nm, is suggested. Interface energies were found to be consistent with the free energy difference between states. Deviations from stoichiometry were investigated and the effect was found to be small. NisAIs + Ni3Al mixtures were found to disorder more rapidly and the following sequence is suggested: ordered (Ni~AIs + NisAl) --* disordered (Ni2Al3 + Ni~Al) -~ disordered NiA1. USE OF ROD MILLING FOR AMORPHIZATION OF Ta-AI POWDERS
M.S. EI-Eskandarany et al, (Tohoku Univ, Japan), J. Less C o m m o n M~A~s, Vol 167, No 1, 1990, 113-118.
G.G. Gnesin et al, Poroshkovaya Metallurgiya, No 12, 1990, 78-82, (In Russian). The effects of additions of TiN on the cutting properties, hardness and fracture toughness of sintered tool materials based on Si and Al nitrides and A1 and Y oxides were investigated. Increased wear resistance resulted from TiN additions. Hardness and fracture toughness of Y oxide containing materials was increased by high temperature annealing and this was a t t r i b u t e d to crystallization of grain boundary phases. CORROSION OF TITANIUM NITRIDE BASED CERMETS
O.N. Kaidish et al, Poroshkovaya Metallurgiya, No 1, 1991, 77-81, (In Russian). The corrosion of TiN based cermets in dilute mineral acids has been measured. Materials with Ni, Cr and Mo, singly or in any combination were studied. An alloy with Ni, Cr and Mo had the highest corrosion resistance. The alloy TiN-30%Cr had high stability due to formation of a ternary nitride phase. INTERACTION OF HEXAGONAL BORON NITRIDE WITH MOLYBDENUM IN POWDER MIXTURES
V.V. Garbuz et al, Poroshkovaya Metallurgiya, No 1, 1991, 82-84, (In Russian). Interactions in hexagonal BN and Mo mixtures have been studied with the objective of improving the production process for PM BN-Mo articles. HARDENING MECHANISMS IN HEAT
TRRATMENT
OF HARD METALS
M_A. Kallya, M.G. Loshak, Poroshkovaya Metallurgiya, No 1, 1991, 94-96, (In Russian). Mechanisms of hardening during heat treatment of s i n t e r e d W alloys are discussed. It is r e p o r t e d t h a t h e a t treatment may be used to increase the durability of hardmetal components. HARDMETALS, C E M T S
AND
CERAMIC WEAR RESISTANT
MATERIALS H. Koilaska, I~ Dreyer, (RWTH, Aachen, Germany), Metall., Vol 45, No 3, 1991, 224235, (In German). Hard m a t e r i a l s , with or w i t h o u t coatings, which are used for wear resistant applications, are reviewed. An outline is given of their development and economic significance. Production m e t h o d s and properties are considered and possible future trends are discussed. HARDMETAL COATINGS FOR TOOLS O. Knotek, F. L5ffier, (Krupp Widia, Essen,
58 MPR July/August 1991
Germany), MetaU., Vol 45, No 3, 1991, 236240, (In German). Attention is drawn to the increasing importance of coatings on hard tool materials. Various functions are fulfilled by the coatings and they exert considerable influence on performance. The use of modern techniques to apply the coatings is discussed in relation to improved efficiency and wear resistance of tools.
monitor in situ HIP densification of TTi a l u m i n i d e is described. E x p e r i m e n t a l results were compared with the model proposed by Ashby and good agreement was obtained. It was found that significant densification occurs during the pressurization stage of the HIP process. A method is suggested for the estimation of sample density during HIP by use of a mathematical model.
A STUDY OF THE INTERFACE BETWEEN A Co BASED MATRIX AND
SYNTHESIS OF F e ALUMINIDES FROM ELEMENTAL POWDERS
DIAMOND PARTICLES
B.H. Rabin, P~N. Wright, (National Engineering Laboratory, Idaho, USA), MetaUurgical Transactions A, Vol 22A, No 2, 1991, 277-286. Experiments involving the pressureless sintering and hot pressing of elemental FeAI powder mixtures, corresponding to FeA1 and FesA1, are described. The exothermic reaction which results in the formation of the compound and the presence of a t r a n s i e n t liquid phase were observed. Thermodynamic properties were measured. The effects of process variables on sintered density were determined. Near full density compacts were obtained after hot pressing and a grain size less than 10 pan was found.
A. Molinari et al, (Univ of Trento, Italy), Materials Science and Engineering A, Vol 130A, No 2, 1990, 257-262. A study of the interface between diamond particles and a Co based mat~x is reported. Morphological structure and chemical analysis were obtained of the interface during consolidation. Graphite, Co carbide and a Co-C solid solution were detected and these were found to result in strong particle-matrix bonding but there was deterioration in the diamond C-C bond. The addition of Sn to the matrix is reported to c o u n t e r a c t g r a p h i t i z a t i o n of the diamond.
Intermetallic materials IIII
Mechanical alloying
I
DENSIFICATION OF RAPIDLY SOLIDIFIED ( R S ) Tl ALUMINIDE POWDERS - COMPARISON OF EXPERIMENTAL RESULTS WITH HIP MODELS
B.W. Choi et al, (Univ of California, Santa Barbara, California, USA), Acta Metall. et Mater., Vol 38, No 11, 1990, 2225-2234. RS Ti a l u m i n i d e p o w d e r s w e r e characterized and consolidated by HIP, Ti50at%Al-1.8%Nb and Ti-48%AI-2.4%Nb0.3%Ta alloys were compared. Alloys were found to solidify by formation of ~ close packed hexagonal, then interdendritic T with a small amount of [~ body centered c u b i c p h a s e . The e f f e c t s of t i m e , temperature and pressure on the progress of HIP were determined and compared with data predicted from HIP m a p s . Densification was found to be independent of particle size. Power law creep is suggested as the main mechanism of densification for which the best agreement between experiment and prediction was obtained. DENSIFICATION OF RAPIDLY SOLIDIFIED (RS) Ti ALUMINIDE POWDERS - USE OF AN EDDY CURRENT SENSOR TO VERIFY HIP MODELS
B.W. Choi et al, (Univ of California, Santa Barbara, California, USA), Acta Mftall. et MaWr., Vol 38, No 11, 1990, 2245-2252. The use of an eddy current sensor to
AMORPHIZATION OF Ni-ALUMINIDES
BY MECHANICAL ALLOYING (MA) S-CJ. Jang, (North Carolina State Univ, North Carolina, USA), Doctoral dissertation, North Carolina State Univ, 1990. M A has been applied to the disordering and amorphization of Ni aluminides. Structural evolution was studied by X-r~ diffraction, electron microscopy, differential scanning calorimetry and acoustic microscopy. The processing of Ni~Al was found to proceed as follows: ordered facecentered cubic (fcc) --, disordered fcc -* nanocrystalline fcc ~ amorphous material. Disordering of the fcc took 5 hours and 50 hours was required for the production of the a m o r p h o u s phase. A m e c h a n i s m through a dislocation cell structure, about 2 nm, is suggested. Interface energies were found to be consistent with the free energy difference between states. Deviations from stoichiometry were investigated and the effect was found to be small. NisAIs + Ni3Al mixtures were found to disorder more rapidly and the following sequence is suggested: ordered (Ni~AIs + NisAl) --* disordered (Ni2Al3 + Ni~Al) -~ disordered NiA1. USE OF ROD MILLING FOR AMORPHIZATION OF Ta-AI POWDERS
M.S. EI-Eskandarany et al, (Tohoku Univ, Japan), J. Less C o m m o n M~A~s, Vol 167, No 1, 1990, 113-118.