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Effect of composition on ductile-brittle transition temperature
MEASUREMENT CHANGES
OF BONDING
IN NICKEL ALUMINIDE
D.A. Miiller (Cornell University, Ithaca, New York, USA). It was reported that electron enera loss spectroscopy (EELS) can be used to determine the electronic structure of thin films such as grain boundaries. The technique was applied to the study of polycrystalline Nit3A1, which exhibits brittle intergranular fracture whereas single crystal Ni:,Al is ductile. The role of B in improving the ductility of Nit3Al was investigated. Changes to the electronic structure brought about by B were used to develop a model for the changes in grain boundary cohesion and to explain the mechanical properties of Ni&l. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF METAL-CERAMIC INTERFACES M. Riihle (Max-Planck Inst, Stuttgart, Germany). The strength of the interfacial bond between metal and ceramic was discussed with reference to the effects of impurities. Studies of bonding in Nb/A120,, with and without impurities, Ag or Ti, were described. High resolution electron microscopy with analytical electron microscopy were used. The work of adhesion and the fracture energy in bending were determined. It was reported that Ag decreases adhesion and Ti enhances adhesion. EFFECT OF COMPOSITION ON DUCTILE-BRITTLE TRANSITION TEMPERATURE J.F. Knott (Ilniversity of Birmingham, Birmingham, IJK). Brittle fracture and the ductile/brittle transition in steels were discussed with reference to composition and the other factors involved. Temper embrittlement was considered in the light of the effects of process conditions on segregation of impurities and measures to alleviate the problem such as the addition of MO. Some results on a 2,251%,Cr-l’%Mo steel after prolonged service above 650 C were discussed.
PM’94: The abstracts which follow are from papers which were presented at the 1994 Powder Metallurgy World Congress which was held in Paris, France, from 6th
Powders A NEW PROCESS FOR PREPARATION OF MICROCRYSTALLITES G. Demazeau et al (Ilniversity Talence, France).
of Bordeaux,
Industrial use of finely divided metal powders, in a range of applications, was noted. A process, using the physicochemical properties of supercritical fluids for making such powders, and their applications were described. PRODUCTION OF FERROUS POWDERS BY REDUCTION OF METALLURGICAL SCALES A.A. Popov et al (Helsinki Iinivcrsity of Technology, Espoo, Finland). Thermodynamics and kinetics related to production of ferrous powders from scales were discussed with reference to the use of C or H as reducing agents and the effects of water vapour. Production of 18%Cr0.0 l’%,C and 18’?Cr-9’%,Ni steel powders was reported. PRODUCTION AND PROPERTIES OF TITANIUM POWDERS MADE BY HYDRIDE-DEHYDRIDE METHODS E.Bobrova (Slovak Academy of Sciences, Kosice, Slovakia). Processing of Ti and some alloys made from Ti sponge powders produced from scrap metals by hydrogenization/de-hydrogenization were discussed with reference to porosity. Mechanical properties were analysed in terms of sintering temperatures 01 900 to 138O’C. IMPROVED PROCESS TECHNOLOGY FOR PRODUCTION OF HIGH COMPRESSIBILITY IRON POWDERS K. Higuchi et al (Kawasaki Steel Corp, Chiba, Japan) It was reported that changes in process conditions had resulted in the production of Fe powders with improved compressibility. This was attained by purification of the molten metal, homogenization of the powders and standardization of process conditions. Green densities up to 7.18 gm/cm” were attained on compaction at 690 MPa with 11%,Znstearate. ATOMIZATION OF TITANIUM INTERMETALLICS WITH PLASMA MELTING INDUCTION GUIDING R. Gerling et al (GKSS-Forschungzcntrum GmbH, Geesthacht, Germany). Production of Ti intermetallic materials by a novel gas atomization process was described. Plasma torch melting in a water cooled Cu crucible and a novel design of transfer system to the gas jet, which guided the Ilow of metal, were used, Production of yTiA1 and Ti;Si:$, free from ceramic inclusions and with 0 and Cu contents below 250 and 35 ppm was reported.
ModeMing of compaction USE OF TRL4XL4L HIGH PRESSURE COMPACTION APPARATUS TO INVESTIGATE METAL POWDERS M. Dao et al (Pechiney ticsearch (‘(>ntIV, Voreppe, France). A numerically controlled triaxial prc~ss for experimental compaction of powders. which allowed a wide range of coditions to be used, was drscrihrd. F:xpt%mc>nls on F(l powder, which showed good Icprotiucit)ilily and small error, wcrc out lined. II was reportrd that t hc c,ffc,c1 of drviatoric strain, without dilatancy, could bc obsctvcd. A NEW EQUATION
FOR COMPACTION
I,. Parilak, E. Dudrova (Slovak Acadrmy 01 Sciences, Kosicc, Slovakia) A nrw compaction equal ion was presented and applicalion to cold prcxssing described. The rquat ion incorporates t tw physical and mt*tallurgical nal urc of t tw powder and compact. The rquation was reported to allow intc>gral c>valuat ion and prediction ofcompaction. EFFECTS OF FRICTION AT PUNCH FACES ON GREEN DENSITY OF COMPACTS G.F. Bocchini.
(Hi&an&
Italia Sri. liapallo.
Italy) The cffcxct of friction at thcb punch li~cc in causing non-uniform dc>nsilication during compaction was analyscd for a small clement of powder. Th(b highrst values 01’ pressure wCrr found al the ccntrc of 1hv element. I)istributil)n of forcc>s increase with cocfficicn( of friction when lhc compact thickness decreases. It was shown the standard compressibility curves do not apply to non-standard specimens. ANALYTICAL AND EXPERIMENTAL PREDICTION OF DENSIFICATION KINETICS FOR HIP A.f’ Matvcyonkov, Y.I. I’onomalyov (NI’O KOMPOZIT, Moscow, Russia). An experimental method of fIII’ tcmperaturc evaluation was prcbsc\nt cd. Mathematical models I’or densificalion kinetics wcrc analysetl. A graphical method of reprctsclntation of HII’ in t tw liwm
of nomograms
was dcscritwl.
POWDER PRESSING DESIGN ANALYSIS BY GRANULAR MODEL SIMULATION S.Tamurd (>t al (linivrrsity of Tokyo, Tokyo, .Japan). Analysis of the mechanical bc,haviour 01’ powder particles during compaction was discussed. Granular modt~lling to siniulal(* powder hchaviour under comprcbssion was used to fvaluatc powdrr forming design. The validity of the appr0ac.h was dcmonstratcd. Powder Ilow patl(brns and density distributions were prc~tlic~lc~d. MPR June 1995
37
OF BONDING
IN NICKEL ALUMINIDE
D.A. Miiller (Cornell University, Ithaca, New York, USA). It was reported that electron enera loss spectroscopy (EELS) can be used to determine the electronic structure of thin films such as grain boundaries. The technique was applied to the study of polycrystalline Nit3A1, which exhibits brittle intergranular fracture whereas single crystal Ni:,Al is ductile. The role of B in improving the ductility of Nit3Al was investigated. Changes to the electronic structure brought about by B were used to develop a model for the changes in grain boundary cohesion and to explain the mechanical properties of Ni&l. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF METAL-CERAMIC INTERFACES M. Riihle (Max-Planck Inst, Stuttgart, Germany). The strength of the interfacial bond between metal and ceramic was discussed with reference to the effects of impurities. Studies of bonding in Nb/A120,, with and without impurities, Ag or Ti, were described. High resolution electron microscopy with analytical electron microscopy were used. The work of adhesion and the fracture energy in bending were determined. It was reported that Ag decreases adhesion and Ti enhances adhesion. EFFECT OF COMPOSITION ON DUCTILE-BRITTLE TRANSITION TEMPERATURE J.F. Knott (Ilniversity of Birmingham, Birmingham, IJK). Brittle fracture and the ductile/brittle transition in steels were discussed with reference to composition and the other factors involved. Temper embrittlement was considered in the light of the effects of process conditions on segregation of impurities and measures to alleviate the problem such as the addition of MO. Some results on a 2,251%,Cr-l’%Mo steel after prolonged service above 650 C were discussed.
PM’94: The abstracts which follow are from papers which were presented at the 1994 Powder Metallurgy World Congress which was held in Paris, France, from 6th
Powders A NEW PROCESS FOR PREPARATION OF MICROCRYSTALLITES G. Demazeau et al (Ilniversity Talence, France).
of Bordeaux,
Industrial use of finely divided metal powders, in a range of applications, was noted. A process, using the physicochemical properties of supercritical fluids for making such powders, and their applications were described. PRODUCTION OF FERROUS POWDERS BY REDUCTION OF METALLURGICAL SCALES A.A. Popov et al (Helsinki Iinivcrsity of Technology, Espoo, Finland). Thermodynamics and kinetics related to production of ferrous powders from scales were discussed with reference to the use of C or H as reducing agents and the effects of water vapour. Production of 18%Cr0.0 l’%,C and 18’?Cr-9’%,Ni steel powders was reported. PRODUCTION AND PROPERTIES OF TITANIUM POWDERS MADE BY HYDRIDE-DEHYDRIDE METHODS E.Bobrova (Slovak Academy of Sciences, Kosice, Slovakia). Processing of Ti and some alloys made from Ti sponge powders produced from scrap metals by hydrogenization/de-hydrogenization were discussed with reference to porosity. Mechanical properties were analysed in terms of sintering temperatures 01 900 to 138O’C. IMPROVED PROCESS TECHNOLOGY FOR PRODUCTION OF HIGH COMPRESSIBILITY IRON POWDERS K. Higuchi et al (Kawasaki Steel Corp, Chiba, Japan) It was reported that changes in process conditions had resulted in the production of Fe powders with improved compressibility. This was attained by purification of the molten metal, homogenization of the powders and standardization of process conditions. Green densities up to 7.18 gm/cm” were attained on compaction at 690 MPa with 11%,Znstearate. ATOMIZATION OF TITANIUM INTERMETALLICS WITH PLASMA MELTING INDUCTION GUIDING R. Gerling et al (GKSS-Forschungzcntrum GmbH, Geesthacht, Germany). Production of Ti intermetallic materials by a novel gas atomization process was described. Plasma torch melting in a water cooled Cu crucible and a novel design of transfer system to the gas jet, which guided the Ilow of metal, were used, Production of yTiA1 and Ti;Si:$, free from ceramic inclusions and with 0 and Cu contents below 250 and 35 ppm was reported.
ModeMing of compaction USE OF TRL4XL4L HIGH PRESSURE COMPACTION APPARATUS TO INVESTIGATE METAL POWDERS M. Dao et al (Pechiney ticsearch (‘(>ntIV, Voreppe, France). A numerically controlled triaxial prc~ss for experimental compaction of powders. which allowed a wide range of coditions to be used, was drscrihrd. F:xpt%mc>nls on F(l powder, which showed good Icprotiucit)ilily and small error, wcrc out lined. II was reportrd that t hc c,ffc,c1 of drviatoric strain, without dilatancy, could bc obsctvcd. A NEW EQUATION
FOR COMPACTION
I,. Parilak, E. Dudrova (Slovak Acadrmy 01 Sciences, Kosicc, Slovakia) A nrw compaction equal ion was presented and applicalion to cold prcxssing described. The rquat ion incorporates t tw physical and mt*tallurgical nal urc of t tw powder and compact. The rquation was reported to allow intc>gral c>valuat ion and prediction ofcompaction. EFFECTS OF FRICTION AT PUNCH FACES ON GREEN DENSITY OF COMPACTS G.F. Bocchini.
(Hi&an&
Italia Sri. liapallo.
Italy) The cffcxct of friction at thcb punch li~cc in causing non-uniform dc>nsilication during compaction was analyscd for a small clement of powder. Th(b highrst values 01’ pressure wCrr found al the ccntrc of 1hv element. I)istributil)n of forcc>s increase with cocfficicn( of friction when lhc compact thickness decreases. It was shown the standard compressibility curves do not apply to non-standard specimens. ANALYTICAL AND EXPERIMENTAL PREDICTION OF DENSIFICATION KINETICS FOR HIP A.f’ Matvcyonkov, Y.I. I’onomalyov (NI’O KOMPOZIT, Moscow, Russia). An experimental method of fIII’ tcmperaturc evaluation was prcbsc\nt cd. Mathematical models I’or densificalion kinetics wcrc analysetl. A graphical method of reprctsclntation of HII’ in t tw liwm
of nomograms
was dcscritwl.
POWDER PRESSING DESIGN ANALYSIS BY GRANULAR MODEL SIMULATION S.Tamurd (>t al (linivrrsity of Tokyo, Tokyo, .Japan). Analysis of the mechanical bc,haviour 01’ powder particles during compaction was discussed. Granular modt~lling to siniulal(* powder hchaviour under comprcbssion was used to fvaluatc powdrr forming design. The validity of the appr0ac.h was dcmonstratcd. Powder Ilow patl(brns and density distributions were prc~tlic~lc~d. MPR June 1995
37