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Particle fragmentation during supersolidus sintering
Fundamentals
COMPACTION OF SEMI-SOLID ALUMINIUM-SILICON POWDER MIXTURES T.Marooka et al. (Musashi Inst. of Technology, Tokyo, Japan.) JJapan Sot. Powder and Powder Metaflurm Yol 42, No 9, 1995, 1027-1031. (In Japanese.) It is reported that a process, similar to die casting, had been used to shape semisolid AI-S1 powders. The temperture used gave a volume fraction of solid of 0.7. The mixture was stirred and injected into the mould. Stirring fluidized the slurry, spheriodized the Al-rich phase and refined the eutectic. Structure and properties are described.
Sintering PARTICLE FRAGMENTATION SUPERSOLIDUS SINTERING
DURING
Effects of atomizing conditions on surface characteristics of a high Ni alloy and the properties of the consolidated materials were investigated. The surface condition of the particles was shown to depend on cooling rate after solidification
USE OF X-RAY CT SCANNER FOR DENSITY DISTRIBUTION MEASUREMENTS IN POWDER COMPACTS Y.Ohashi,
HArakawa.
(Sumit,omo
Met,al
Industries Ltd., Amagasaki, Japan.) J.Japan Sot. Powder and Powder Metaffurgr: Vol 42, No 9, 1995, 1032-1036. (In Japanese.) A study of the use of an X-ray CT scanner for investigation of density variations in powder compacts is described.
Absorption
of
X-rays
is
a
function of density and high intensity Xrays are used. It is reported that the method gave good correaltion between density and the X-ray image formed.
Copper
R.Tandon, R.M.German. (Pennsylvania State University, Pennsylvania, USA.) Int. J. Powder MetalfurVol 33, No 1, 1997, 54-59. Supersolidus sintering is discussed with regard to particle fragmentation. Experiments to simulate this using oil and polymer grains, for different solid:liquid ratios, are described. The polymer grains are reported to fracture due to a shear stress in the neck regions. Tests on a Ni base alloy and stainless steel confirmed the model experiments.
HIGH TEMPERATURE CREEP OF MICROCRYSTALLINE DISPERSION STRENGTHENED COPPER ALLOYS C.Sauer et al. (Max-Planck Inst., Stuttgart, Germany.) Int. J. Powder MetaIlur&r: Vol 33, No 1, 1997, 45-53. Creep strength of dispersion strengthened temperature reinforced investigated.
alloys
was
discussed.
High
creep of Cu and Cu-Ti alloys, with TiC dispersoids, was 3 to lOvol%TiC was formed
in situ giving a TIC particle size of 10 to 50 nm in a microcrystalline matrix of grain
GRAVITATIONAL EFFECTS ON MICROSTRUCTURAL DEVELOPMENT IN LIQUID PIIASE SINTERED ALLOYS
size 100 to 500 nm. Creep was discussed in terms of size, position and volume fraction
T.H.Courtney. (Michigan State University, Michigan, USA.) Scripta Mater., Vol 35, No 5, 1996, 567.571. Differing opinions concerning the effects of gravity during liquid phase sintering were discussed. Two gravity induced settling of isolated grains mechanisms, and settling of skeletal structures, were identified. It is noted that there is dissdgreement about the volume fraction of solid to form a skeleton structure.
of dispersoids.
Iron and steel COMPACTION MIXED WITH
OF IRON WAX
POWDER
S.Takahashi, T.Nakagawa. (University of Tokyo, Tokyo, Japan.) JJapan Sot. Powder and Powder MetaUurgv; Vol42, 1009-1014.
No 9, 1995,
(In Japanese.)
Mechanisms of skeletal settling are reviewed. It is suggested that floating of Fe particles in Fe-Cu is gravity induced.
It is reported that cups 20 mm in diameter, 3 mm wall thickness, by 24 mm high, bottom thickness 4mm had been fabricated from Fe powder, with controlled
EFFECTS PARTICLE
particle size distribution, with 1X microwax and 0.5’%Zn stearate. It is suggested that powder flows from the cup bottom into the wail. The green crushing strength of the cup
OF SOLUBILITY AND SIZE ON LIQUID PHASE
SINTERING R.N.Lumely, GHSchaffer. (University of Quennsland, Australia.) Scripta Mater., Vol 35, No 5, 1996, 589595. LPS is discussed with reference to mechanisms,
including
and controlling between additive was investigated sintering structures
transient
effects,
factors. The relationship particle size and solubility in terms of the effect on
and the development
of sintered
in AI-5’%Sn, AL-lO’%,Zn and
5.5%Cu alloys.
Al-
wall was 28 MPa.
Nickel SURFACE CHARACTERISTICS CONSOLIDATED PROPERTIES ATOMIZED
NICKEL
AND OF GAS
82, No
the material was vacuum degassed at 400°C. Mechanical properties were reported to be similar to those of wrought materials. BEHAVIOUR OF INERT GAS CONTAMINATION IN NICKEL POWDER AND CONSOLIDATED
ALLOY
COMPACTS TFukuda et al. (Sumitomo Metal Industries Ltd., Tokyo, Japan.) J. Iron and Steel Znst of Japan, Vol 82, No 7, 1996, 623-627. In Japanese. The effects of inert gas, entrapped in atomized metal powder and consolidated compacts, on structure and properties of Ni alloys was investigated. The Ar content is reported to depend on atomization conditions. The Ar content is increased by increased gas:met,al ratio and decreased by reduced particle size. Ar increases porosity in compacted alloys.
Tungsten PURE TUNGSTEN BAR SINTERED LOWER TEMPERATURES
AT
%.Deng. (Baoji Non-Ferrous Metal Works, China.) Kare Metals and Materials Engineering Vol 24, No 5, 1995, 62-64. (In Chinese.) It is reported that 50 mm diameter W bar has been prepared from fine W powder by isostatic pressing and sintering at 1700 to 1800°C.
Composite ANALYSIS POWDERS
materials
OF PACKED MIXTURES AND SHORT FIBRES
OF
Tltoh et al. (Nagoya University, Nagoya, Japan.) J.Japan Sot. Powder and Powder Metallurm, Vol 42, No 9, 1995, 992-997. (In English.) Quantitative characterization of powdershort fibre composites is described. A range of characterized Al, Cu and Fe powders and machined Al, Cu, brass and Fe fibres were used in various proportions were used. Packing characteristics were determined for the different mixtures and correlated with powder:fibre ratios.
ALLOYS
TFuknda et al. (Sumitomo Metal Industries Ltd., Tokyo, Japan.) J. Iron and Stcd Znst of Japan, Vol Japanese.)
even in inert gas. Water was found to be adsorbed on particle surfaces the amount depending on process conditions. Blowholes were not found provided that
7, 1996, 605-610.
(In
IT TAXES composite
TWO (to make metal-metal materials)
M.Judge. (Winnipeg, Canada.) New Scientist, Vol 153, No 2072, 1997, 36-40.
MPR July/August
1997
39
COMPACTION OF SEMI-SOLID ALUMINIUM-SILICON POWDER MIXTURES T.Marooka et al. (Musashi Inst. of Technology, Tokyo, Japan.) JJapan Sot. Powder and Powder Metaflurm Yol 42, No 9, 1995, 1027-1031. (In Japanese.) It is reported that a process, similar to die casting, had been used to shape semisolid AI-S1 powders. The temperture used gave a volume fraction of solid of 0.7. The mixture was stirred and injected into the mould. Stirring fluidized the slurry, spheriodized the Al-rich phase and refined the eutectic. Structure and properties are described.
Sintering PARTICLE FRAGMENTATION SUPERSOLIDUS SINTERING
DURING
Effects of atomizing conditions on surface characteristics of a high Ni alloy and the properties of the consolidated materials were investigated. The surface condition of the particles was shown to depend on cooling rate after solidification
USE OF X-RAY CT SCANNER FOR DENSITY DISTRIBUTION MEASUREMENTS IN POWDER COMPACTS Y.Ohashi,
HArakawa.
(Sumit,omo
Met,al
Industries Ltd., Amagasaki, Japan.) J.Japan Sot. Powder and Powder Metaffurgr: Vol 42, No 9, 1995, 1032-1036. (In Japanese.) A study of the use of an X-ray CT scanner for investigation of density variations in powder compacts is described.
Absorption
of
X-rays
is
a
function of density and high intensity Xrays are used. It is reported that the method gave good correaltion between density and the X-ray image formed.
Copper
R.Tandon, R.M.German. (Pennsylvania State University, Pennsylvania, USA.) Int. J. Powder MetalfurVol 33, No 1, 1997, 54-59. Supersolidus sintering is discussed with regard to particle fragmentation. Experiments to simulate this using oil and polymer grains, for different solid:liquid ratios, are described. The polymer grains are reported to fracture due to a shear stress in the neck regions. Tests on a Ni base alloy and stainless steel confirmed the model experiments.
HIGH TEMPERATURE CREEP OF MICROCRYSTALLINE DISPERSION STRENGTHENED COPPER ALLOYS C.Sauer et al. (Max-Planck Inst., Stuttgart, Germany.) Int. J. Powder MetaIlur&r: Vol 33, No 1, 1997, 45-53. Creep strength of dispersion strengthened temperature reinforced investigated.
alloys
was
discussed.
High
creep of Cu and Cu-Ti alloys, with TiC dispersoids, was 3 to lOvol%TiC was formed
in situ giving a TIC particle size of 10 to 50 nm in a microcrystalline matrix of grain
GRAVITATIONAL EFFECTS ON MICROSTRUCTURAL DEVELOPMENT IN LIQUID PIIASE SINTERED ALLOYS
size 100 to 500 nm. Creep was discussed in terms of size, position and volume fraction
T.H.Courtney. (Michigan State University, Michigan, USA.) Scripta Mater., Vol 35, No 5, 1996, 567.571. Differing opinions concerning the effects of gravity during liquid phase sintering were discussed. Two gravity induced settling of isolated grains mechanisms, and settling of skeletal structures, were identified. It is noted that there is dissdgreement about the volume fraction of solid to form a skeleton structure.
of dispersoids.
Iron and steel COMPACTION MIXED WITH
OF IRON WAX
POWDER
S.Takahashi, T.Nakagawa. (University of Tokyo, Tokyo, Japan.) JJapan Sot. Powder and Powder MetaUurgv; Vol42, 1009-1014.
No 9, 1995,
(In Japanese.)
Mechanisms of skeletal settling are reviewed. It is suggested that floating of Fe particles in Fe-Cu is gravity induced.
It is reported that cups 20 mm in diameter, 3 mm wall thickness, by 24 mm high, bottom thickness 4mm had been fabricated from Fe powder, with controlled
EFFECTS PARTICLE
particle size distribution, with 1X microwax and 0.5’%Zn stearate. It is suggested that powder flows from the cup bottom into the wail. The green crushing strength of the cup
OF SOLUBILITY AND SIZE ON LIQUID PHASE
SINTERING R.N.Lumely, GHSchaffer. (University of Quennsland, Australia.) Scripta Mater., Vol 35, No 5, 1996, 589595. LPS is discussed with reference to mechanisms,
including
and controlling between additive was investigated sintering structures
transient
effects,
factors. The relationship particle size and solubility in terms of the effect on
and the development
of sintered
in AI-5’%Sn, AL-lO’%,Zn and
5.5%Cu alloys.
Al-
wall was 28 MPa.
Nickel SURFACE CHARACTERISTICS CONSOLIDATED PROPERTIES ATOMIZED
NICKEL
AND OF GAS
82, No
the material was vacuum degassed at 400°C. Mechanical properties were reported to be similar to those of wrought materials. BEHAVIOUR OF INERT GAS CONTAMINATION IN NICKEL POWDER AND CONSOLIDATED
ALLOY
COMPACTS TFukuda et al. (Sumitomo Metal Industries Ltd., Tokyo, Japan.) J. Iron and Steel Znst of Japan, Vol 82, No 7, 1996, 623-627. In Japanese. The effects of inert gas, entrapped in atomized metal powder and consolidated compacts, on structure and properties of Ni alloys was investigated. The Ar content is reported to depend on atomization conditions. The Ar content is increased by increased gas:met,al ratio and decreased by reduced particle size. Ar increases porosity in compacted alloys.
Tungsten PURE TUNGSTEN BAR SINTERED LOWER TEMPERATURES
AT
%.Deng. (Baoji Non-Ferrous Metal Works, China.) Kare Metals and Materials Engineering Vol 24, No 5, 1995, 62-64. (In Chinese.) It is reported that 50 mm diameter W bar has been prepared from fine W powder by isostatic pressing and sintering at 1700 to 1800°C.
Composite ANALYSIS POWDERS
materials
OF PACKED MIXTURES AND SHORT FIBRES
OF
Tltoh et al. (Nagoya University, Nagoya, Japan.) J.Japan Sot. Powder and Powder Metallurm, Vol 42, No 9, 1995, 992-997. (In English.) Quantitative characterization of powdershort fibre composites is described. A range of characterized Al, Cu and Fe powders and machined Al, Cu, brass and Fe fibres were used in various proportions were used. Packing characteristics were determined for the different mixtures and correlated with powder:fibre ratios.
ALLOYS
TFuknda et al. (Sumitomo Metal Industries Ltd., Tokyo, Japan.) J. Iron and Stcd Znst of Japan, Vol Japanese.)
even in inert gas. Water was found to be adsorbed on particle surfaces the amount depending on process conditions. Blowholes were not found provided that
7, 1996, 605-610.
(In
IT TAXES composite
TWO (to make metal-metal materials)
M.Judge. (Winnipeg, Canada.) New Scientist, Vol 153, No 2072, 1997, 36-40.
MPR July/August
1997
39