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Structure and properties of tri-titanium aluminide-niobium alloys
TIO,, Al and C is described. The exothermic reaction starts at 1000 “C. Poor wetting results in an inhomogeneous structure during direct hot pressing. Processing was split into two stages, partial amorphization at room temperature by mechanical alloying and hot pressing at 10 “C min.’ and 25 MPa up to 1000 “C, followed by heating up to 1600 to 1650 “C. There was no liquidation and an homogeneous, fine grained Tic-A&O, composite was obtained.
Mould casting of high speed steel with therm@setting binder J.M.To&.ba et al. (Carlos III Uniueniry, Madrid, Spain.) Mater. Chem./Physics, Vol 67, No l/3, 2001, 43-48. It is reported that T15 high speed steel powder had been mixed with a thermo-setting resin, moulded and heated to 90 “C to poly merize the resin. The part is thermally debound and sintered. Feedstock and process conditions were optimized for best structure and properties. which were similar to those of conventionally made MIM parts. MC and M,C carbides were detected in the microstructure and were homogeneously distributed in the matrix.
Formation of oxides of carbon during carbo-thermal reduction of refractoty metal oxides W.Gruner et al. (Inst. of Solid State and Materials Research, Dresden, Germany.) Int. J. Refract. Metals/Hard Mater., Vol 18, No 2/3, 2000, 137-145.
Oxides of C formed during carbo-thermal rediction of oxides of W, MO, Zr, Cr, X and Si were investigated. The presence of CO, was detected in the case of W and MO. Analysis of the gases allowed the reduction processes to be monitored. New aspects of the role of CO and CO, were discussed.
Intermetallic materials Characteristics of vacuum hot pressed titanium silicide at room and elevated temperatures K.Isonishi, M.Hamada. (Shiga University, Otsu, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 12, 1999, 1226-1331. (InJapanese.)
The effects of a second, ductile, phase, cx or PX, on mechanical properties of Ti,Si, were investigated. A further element is required to stabilize PTi and V or MO were used. Samples were made by mechanical alloying and vacuum hot pressing. Properties up to 1100 “C were measured. lO%V increased fracture toughness from 2.60 to 4.43 MPa m I’*. 5%Mo increased properties at elevated tempera&es by more than 5%V.
MPR
July/August
K.Kudaka et al. (Tokyo Inst. of Polytechnics, At.+, Japan.) J. Jpn Sot. Powde#owder Metall., Vol47, No I, 2000, 3-8. (In Japanese.) It is reported that CrBz could only be sintered from elemental powders by application of pressure, hot pressing at 1200 “C. Cr-66.7at%B powders were mechano-chemically processed and sintered with and without applied pressure. Synthesis of CrB2 is exothermic and this aids sintering. The mechano-chemical processing reduced the heat of reaction. Optimum conditions were given.
Refractory metal substitution in molybdenum-silicon-boron alloys J.H.Perepe&o et al. (1509, University Aue, Madison, WI, USA.) Int. J. Refractory Metals Hard Materials, Vol 18, No 4-5, 2000, 193-204.
A study of phase stability of Mo-Si-B alloys, in which some MO is replaced by Cr and Nb, is described. Phases present included intermetallit compounds of MO, Nb or Cr and Si, borides and solid solutions based on MO. Phase stability is shown to be related to atomic size factor.
Structure and properties of tri-titanium aluminide-niobium alloy’s
Refractory metals
24
Mechanochemical processing and reactive sintering of chromium-boron powders
2001
T.Abe et al. (Tohoku National Industrial Research Inst, Sendai, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 47, No 3, 2000, 315-321. (In English.)
T&Al-(0, 3, 7, 11 and 13)at%Nb alloys were prepared from elemental powders by pulse discharge sintering. Structures, oxidation resistance and mechanical properties were investigated. Low sintering temperatures left unreacted elements. Higher temperatures resulted in more homogeneous structures. Hardness and oxidation resistance increased with %Nb and sintering temperature. In alloys with Nb the oxide scale was TiO, with fine dispersed Nb particles.
Mechanical alloying Mechanically simulated reaction of metal-polymer powder mixtures Y.Takemoto et al. (Okayama University, Okuyama, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol46, No 12, 1999, 1309-1314. (ln Japanese.)
Metal - Mg, l? or Mg,Ni - and polymer PTFE, PVC or PE - were mechanically alloyed and the powders characterized. Metal halides were detected in the powders. Reactions proceeded rapidly. Single C-C bonds changed to double C=C bonds. H released by decomposition of polymers was adsorbed by Mg. The investigation demonstrated a means of making engineering plastics.
Analysis of mechanical alloying and design of milling system by simulation of ball milling
H.Hashimoto. (Tohoku National Industrial Research Inst., Se&i, Japan.)J. Jpn Sot. Powder/Powder Metall., Vol47, No 1, 2000, 47-51. (In Japanese.)
The need for theoretical analysis of mechanical alloying by ball milling is noted. A computer-based simulation of the motion of a single ball is presented. The result was helpful in understanding metal powder coating during milling in a tumbling ball mill.
Powder injection moulding Net shape processing using an aqueous based injection moulding binder J.C.L.aSalle, M.Zedalis. (Allied Signal PowderFlo Technologies, USA.) J.Metals (JOM) VoI 51, No 7, 1999, 38-39.
It is reported that injection moulding, with an aqueous-based binder in the feedstock, had been used to make large thick parts. Comparison is made with parts made by investment casting. Cost reductions resulting from elimination of machining and other process steps and lower development costs are reported.
PM components Ceramic brake discs for high performance vehicles Anon. (Daimler-Chrysler AG Communications, Srurrgart, Germany.) DaimlerChrysler High Tech Report, 2000,96.
Development of a fibre reinforced, lightweight, ceramic brake disc for high performance vehicles, including Fl racing cars, is reported. C powder, C fibre and resin are pressed and ‘sintered’ at 1000 “C to create a stable C structure which can easily be cut to size and shape. This is infiltrated with molten Si and Sic forms. The disc is finished on the working surfaces. The material is reported to have a service life of 300 000 km, to withstand high temperatures and to allow high speed braking.
Miscellaneous Selective laser sintering of electrodes for electrodispersive machining H.Diirr et al. (University of Chemnitz, Chemnitz, Germany.) Computers in Industry, Vol39, No 1, 1999, 35-45.
Application of computer controlled selective laser sintering for production of N&bronze electrodes for electrodispersive machining is reported. It is shown that this has improved the quality of the electrodes evaluated by machining tests with parameters electrode wear and material removal rate in which porosity played a role. Reduced porosity improved quality. Porosity could be reduced by infiltration with an Ag solder alloy, which gave better results than Sn solder.
www.metal-powder.net
Mould casting of high speed steel with therm@setting binder J.M.To&.ba et al. (Carlos III Uniueniry, Madrid, Spain.) Mater. Chem./Physics, Vol 67, No l/3, 2001, 43-48. It is reported that T15 high speed steel powder had been mixed with a thermo-setting resin, moulded and heated to 90 “C to poly merize the resin. The part is thermally debound and sintered. Feedstock and process conditions were optimized for best structure and properties. which were similar to those of conventionally made MIM parts. MC and M,C carbides were detected in the microstructure and were homogeneously distributed in the matrix.
Formation of oxides of carbon during carbo-thermal reduction of refractoty metal oxides W.Gruner et al. (Inst. of Solid State and Materials Research, Dresden, Germany.) Int. J. Refract. Metals/Hard Mater., Vol 18, No 2/3, 2000, 137-145.
Oxides of C formed during carbo-thermal rediction of oxides of W, MO, Zr, Cr, X and Si were investigated. The presence of CO, was detected in the case of W and MO. Analysis of the gases allowed the reduction processes to be monitored. New aspects of the role of CO and CO, were discussed.
Intermetallic materials Characteristics of vacuum hot pressed titanium silicide at room and elevated temperatures K.Isonishi, M.Hamada. (Shiga University, Otsu, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 12, 1999, 1226-1331. (InJapanese.)
The effects of a second, ductile, phase, cx or PX, on mechanical properties of Ti,Si, were investigated. A further element is required to stabilize PTi and V or MO were used. Samples were made by mechanical alloying and vacuum hot pressing. Properties up to 1100 “C were measured. lO%V increased fracture toughness from 2.60 to 4.43 MPa m I’*. 5%Mo increased properties at elevated tempera&es by more than 5%V.
MPR
July/August
K.Kudaka et al. (Tokyo Inst. of Polytechnics, At.+, Japan.) J. Jpn Sot. Powde#owder Metall., Vol47, No I, 2000, 3-8. (In Japanese.) It is reported that CrBz could only be sintered from elemental powders by application of pressure, hot pressing at 1200 “C. Cr-66.7at%B powders were mechano-chemically processed and sintered with and without applied pressure. Synthesis of CrB2 is exothermic and this aids sintering. The mechano-chemical processing reduced the heat of reaction. Optimum conditions were given.
Refractory metal substitution in molybdenum-silicon-boron alloys J.H.Perepe&o et al. (1509, University Aue, Madison, WI, USA.) Int. J. Refractory Metals Hard Materials, Vol 18, No 4-5, 2000, 193-204.
A study of phase stability of Mo-Si-B alloys, in which some MO is replaced by Cr and Nb, is described. Phases present included intermetallit compounds of MO, Nb or Cr and Si, borides and solid solutions based on MO. Phase stability is shown to be related to atomic size factor.
Structure and properties of tri-titanium aluminide-niobium alloy’s
Refractory metals
24
Mechanochemical processing and reactive sintering of chromium-boron powders
2001
T.Abe et al. (Tohoku National Industrial Research Inst, Sendai, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 47, No 3, 2000, 315-321. (In English.)
T&Al-(0, 3, 7, 11 and 13)at%Nb alloys were prepared from elemental powders by pulse discharge sintering. Structures, oxidation resistance and mechanical properties were investigated. Low sintering temperatures left unreacted elements. Higher temperatures resulted in more homogeneous structures. Hardness and oxidation resistance increased with %Nb and sintering temperature. In alloys with Nb the oxide scale was TiO, with fine dispersed Nb particles.
Mechanical alloying Mechanically simulated reaction of metal-polymer powder mixtures Y.Takemoto et al. (Okayama University, Okuyama, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol46, No 12, 1999, 1309-1314. (ln Japanese.)
Metal - Mg, l? or Mg,Ni - and polymer PTFE, PVC or PE - were mechanically alloyed and the powders characterized. Metal halides were detected in the powders. Reactions proceeded rapidly. Single C-C bonds changed to double C=C bonds. H released by decomposition of polymers was adsorbed by Mg. The investigation demonstrated a means of making engineering plastics.
Analysis of mechanical alloying and design of milling system by simulation of ball milling
H.Hashimoto. (Tohoku National Industrial Research Inst., Se&i, Japan.)J. Jpn Sot. Powder/Powder Metall., Vol47, No 1, 2000, 47-51. (In Japanese.)
The need for theoretical analysis of mechanical alloying by ball milling is noted. A computer-based simulation of the motion of a single ball is presented. The result was helpful in understanding metal powder coating during milling in a tumbling ball mill.
Powder injection moulding Net shape processing using an aqueous based injection moulding binder J.C.L.aSalle, M.Zedalis. (Allied Signal PowderFlo Technologies, USA.) J.Metals (JOM) VoI 51, No 7, 1999, 38-39.
It is reported that injection moulding, with an aqueous-based binder in the feedstock, had been used to make large thick parts. Comparison is made with parts made by investment casting. Cost reductions resulting from elimination of machining and other process steps and lower development costs are reported.
PM components Ceramic brake discs for high performance vehicles Anon. (Daimler-Chrysler AG Communications, Srurrgart, Germany.) DaimlerChrysler High Tech Report, 2000,96.
Development of a fibre reinforced, lightweight, ceramic brake disc for high performance vehicles, including Fl racing cars, is reported. C powder, C fibre and resin are pressed and ‘sintered’ at 1000 “C to create a stable C structure which can easily be cut to size and shape. This is infiltrated with molten Si and Sic forms. The disc is finished on the working surfaces. The material is reported to have a service life of 300 000 km, to withstand high temperatures and to allow high speed braking.
Miscellaneous Selective laser sintering of electrodes for electrodispersive machining H.Diirr et al. (University of Chemnitz, Chemnitz, Germany.) Computers in Industry, Vol39, No 1, 1999, 35-45.
Application of computer controlled selective laser sintering for production of N&bronze electrodes for electrodispersive machining is reported. It is shown that this has improved the quality of the electrodes evaluated by machining tests with parameters electrode wear and material removal rate in which porosity played a role. Reduced porosity improved quality. Porosity could be reduced by infiltration with an Ag solder alloy, which gave better results than Sn solder.
www.metal-powder.net