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Segregation phenomena in a shaker
A.T.Potapov, C.S.Campbell. (University of S.California, Los Angeles, USA.) Powder Technol., Vol 93, No 1, 1997, 1321. A two-dimensional simulation of impact breakage of brittle particles is described. Two cracking mechanisms are identified. Mechanism I is the formation of cracks, due to tensile stresses, radiating from the point of impact. Mechanism II is the formation of cracks perpendicular to those formed by mechanism I and is due to buckling of fragments created by mechanism I. Impact velocity determines the contribution of each mechanism. SHAPE FACTOR TO ASSESS PARTICLE SHAPE USING IMAGE ANALYSIS
F.Podczeck. (School of Pharmacy, University of London, London, UK.) Powder Technol., Vol 93, No 1, 1997, 4753. Particle shape analysis is discussed and note is taken of difficulties. A shape factor is developed for two-dimensional images which depends on deviations from standard shapes - circle, square and triangle. The proposed shape factor is evaluated for mathematically defined shapes and takes the number of corners and aspect ratio into account. It is shown that the proposed shape factor can differentiate between the model shapes. Tests were carried out on fine non-metallic powders. It is reported that the technique improves shape characterization of powders. SEGREGATION SHAKER
PHENOMENA
IN A
S.S.Hsiau, H.Y.Yu. (National Central University, Chung-li, Taiwan.) Powder Technol., Vo193, No 1, 1997, 83-88. Segregation of particles of differing sizes in a vertical shaker was investigated. The segregation was more pronounced with larger size differences. A coefficient of segregation was calculated and was found to increase with vertical acceleration to a maximum and then to decline. The greatest segregation occurred when the bed of powder changed from a dense to a loose state. MODELLING PROCESSES ELEMENT
OF DEFORMATION BY PERMEABLE METHODS
L.Delaey et al. (Katholieke University, Louvain, Heverlee, Belgium.) Powder Technol., Vol 93, No 2, 1997, 127-141. The permeable element method, developed from finite element approximation and intended for description of densification of porous bodies, is
described. Pressing of hollow cylinders in a rigid die is considered. Computed and measured data are compared using quantitative metallography. A solution is given for pressing a stepped shape. Material flow and density distribution are considered. COINCIDENCE COULTER
CORRECTION PARTICLE SIZE
FOR ANALYSER
E.J.W.Wynn, M.J.Hounslow. (University of Cambridge, Cambridge, UK.) Powder Technol., Vol 93, No 2, 1997, 163-175. A source of error in particle size analysis, due to more than one particle passing through an orifice simultaneously, is identified. This reduces the number of particles counted and increases the observed mean particle size. A model to enable correction of this is proposed. Experimental results are presented and the correction applied. The method is validated and shown to improve the measurements.
Aluminium CONSOLIDATION OF ALUMINIUM
AND ALLOY
PROPERTIES
M.Otsuki et al. (Mitsubishi Materials Corporation, Omiya, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 43, No 10, 1996, 1183-1187. (In Japanese.) A study of an Al-transition metallanthanide alloy, made by forging from rapidly solidified powder, is described for Al-4.3%Ni-1.5%Ti-l.O%Cu-0.8%Zr0.2%Ce. Test pieces preheated at 450°C for 1 hour showed a tensile strength of 670 MPa with 2% elongation which is comparable with extruded materials. SPARK PLASMA ALUMINIUM-SILICON
SINTERING ALLOY
OF
T.Nagae et al. (Toyama Industrial Technology Centre, Takaoka, Japan.) J. Jpn Sot. Powder Powder Metall., Vo143, No 10, 1996, 1193-1197. (In Japanese.) A study of structure and properties of spark plasma sintered Ar atomized Al-25wt%Si-3.5%Ni-3.5%Fe-l%Mg powder is described. Structures comprised various intermetallic compounds in an Al-S1 matrix. Rockwell hardness was higher than for a powder forged alloy owing to finer structure arising from short process times. EFFECT OF MILLING CHARACTERISTICS FLAKE
ON OF ALUMINIUM
G.G.Lee et al. (Inst. of Machinery and Materials, Changwon, Korea.) J. Jpn
Sot. Powder Powder Metall., Vol 43, No 10, 1996, 1253-1258. (In Japanese.) Tumbler ball milling for preparation of Al flake from powders was investigated as functions of initial powder size, milling speed and duration and ball size. The flake was characterized for specific surface. ‘The best conditions for a fingerprint detection application were: powder size 25 pm; ball size 9.5 mm; and 40 hours milling at 80 rpm.
Iron and steel SIMULATION SHRINKAGE
OF SINTERING FOR STAINLESS
STEEL
R.Watanabe et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 43, No 10, 1996, 1171-1176. (In Japanese.) Simulation of sintering shrinkage of injection moulded stainless steel compacts is described. The low initial packing density, around 55%, should cause a large, possibly nonuniform, sintering shrinkage. The simulation uses finite difference analysis to determine temperature distrilbution in the compact in a vacuum furnace, densification analysis using a sintering rate equation and finite element analysis to convert shrinkage into shape change. It is shown that temperature differences contribute to nonuniform shrinkage. INJECTION RESISTANT
MOULDED FER:ROUS
WEARMATERIALS
H.Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 43, No 11 1996, 1333-1338. (ln Japanese.) A study, aimed at the production of wear resistant parts by MIM is described. 3wt% TiN was added to a prealloyed SCM440 steel powder. It is reported that the addition of TIN improved the abrasive wear resistance compared with PM and wrought alloys without TIN. Use of MIM was considered a viable method.
Titanium BORON IN MECHANICALLY TITANIUM-BORON NITRIDE
ALLOYED
M.Motoyama et al. (Hyogo Inst. of Industrial R.esearch, Kobe, Japan.) J. Jpn Sot. Powder Powder Metall., Vol43, No 11, 1996, 1300-1304. (In Japanese.) The progress of mechanical alloying of Ti-hexagonal EIN powder was monitored by X-ray spectroscopy. The results were compared with results from mechanically ground materials.
MPR June 1998 35
F.Podczeck. (School of Pharmacy, University of London, London, UK.) Powder Technol., Vol 93, No 1, 1997, 4753. Particle shape analysis is discussed and note is taken of difficulties. A shape factor is developed for two-dimensional images which depends on deviations from standard shapes - circle, square and triangle. The proposed shape factor is evaluated for mathematically defined shapes and takes the number of corners and aspect ratio into account. It is shown that the proposed shape factor can differentiate between the model shapes. Tests were carried out on fine non-metallic powders. It is reported that the technique improves shape characterization of powders. SEGREGATION SHAKER
PHENOMENA
IN A
S.S.Hsiau, H.Y.Yu. (National Central University, Chung-li, Taiwan.) Powder Technol., Vo193, No 1, 1997, 83-88. Segregation of particles of differing sizes in a vertical shaker was investigated. The segregation was more pronounced with larger size differences. A coefficient of segregation was calculated and was found to increase with vertical acceleration to a maximum and then to decline. The greatest segregation occurred when the bed of powder changed from a dense to a loose state. MODELLING PROCESSES ELEMENT
OF DEFORMATION BY PERMEABLE METHODS
L.Delaey et al. (Katholieke University, Louvain, Heverlee, Belgium.) Powder Technol., Vol 93, No 2, 1997, 127-141. The permeable element method, developed from finite element approximation and intended for description of densification of porous bodies, is
described. Pressing of hollow cylinders in a rigid die is considered. Computed and measured data are compared using quantitative metallography. A solution is given for pressing a stepped shape. Material flow and density distribution are considered. COINCIDENCE COULTER
CORRECTION PARTICLE SIZE
FOR ANALYSER
E.J.W.Wynn, M.J.Hounslow. (University of Cambridge, Cambridge, UK.) Powder Technol., Vol 93, No 2, 1997, 163-175. A source of error in particle size analysis, due to more than one particle passing through an orifice simultaneously, is identified. This reduces the number of particles counted and increases the observed mean particle size. A model to enable correction of this is proposed. Experimental results are presented and the correction applied. The method is validated and shown to improve the measurements.
Aluminium CONSOLIDATION OF ALUMINIUM
AND ALLOY
PROPERTIES
M.Otsuki et al. (Mitsubishi Materials Corporation, Omiya, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 43, No 10, 1996, 1183-1187. (In Japanese.) A study of an Al-transition metallanthanide alloy, made by forging from rapidly solidified powder, is described for Al-4.3%Ni-1.5%Ti-l.O%Cu-0.8%Zr0.2%Ce. Test pieces preheated at 450°C for 1 hour showed a tensile strength of 670 MPa with 2% elongation which is comparable with extruded materials. SPARK PLASMA ALUMINIUM-SILICON
SINTERING ALLOY
OF
T.Nagae et al. (Toyama Industrial Technology Centre, Takaoka, Japan.) J. Jpn Sot. Powder Powder Metall., Vo143, No 10, 1996, 1193-1197. (In Japanese.) A study of structure and properties of spark plasma sintered Ar atomized Al-25wt%Si-3.5%Ni-3.5%Fe-l%Mg powder is described. Structures comprised various intermetallic compounds in an Al-S1 matrix. Rockwell hardness was higher than for a powder forged alloy owing to finer structure arising from short process times. EFFECT OF MILLING CHARACTERISTICS FLAKE
ON OF ALUMINIUM
G.G.Lee et al. (Inst. of Machinery and Materials, Changwon, Korea.) J. Jpn
Sot. Powder Powder Metall., Vol 43, No 10, 1996, 1253-1258. (In Japanese.) Tumbler ball milling for preparation of Al flake from powders was investigated as functions of initial powder size, milling speed and duration and ball size. The flake was characterized for specific surface. ‘The best conditions for a fingerprint detection application were: powder size 25 pm; ball size 9.5 mm; and 40 hours milling at 80 rpm.
Iron and steel SIMULATION SHRINKAGE
OF SINTERING FOR STAINLESS
STEEL
R.Watanabe et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 43, No 10, 1996, 1171-1176. (In Japanese.) Simulation of sintering shrinkage of injection moulded stainless steel compacts is described. The low initial packing density, around 55%, should cause a large, possibly nonuniform, sintering shrinkage. The simulation uses finite difference analysis to determine temperature distrilbution in the compact in a vacuum furnace, densification analysis using a sintering rate equation and finite element analysis to convert shrinkage into shape change. It is shown that temperature differences contribute to nonuniform shrinkage. INJECTION RESISTANT
MOULDED FER:ROUS
WEARMATERIALS
H.Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 43, No 11 1996, 1333-1338. (ln Japanese.) A study, aimed at the production of wear resistant parts by MIM is described. 3wt% TiN was added to a prealloyed SCM440 steel powder. It is reported that the addition of TIN improved the abrasive wear resistance compared with PM and wrought alloys without TIN. Use of MIM was considered a viable method.
Titanium BORON IN MECHANICALLY TITANIUM-BORON NITRIDE
ALLOYED
M.Motoyama et al. (Hyogo Inst. of Industrial R.esearch, Kobe, Japan.) J. Jpn Sot. Powder Powder Metall., Vol43, No 11, 1996, 1300-1304. (In Japanese.) The progress of mechanical alloying of Ti-hexagonal EIN powder was monitored by X-ray spectroscopy. The results were compared with results from mechanically ground materials.
MPR June 1998 35