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Aluminium foam produced by PM
Pressing DEVELOPMENT OF ELASTIC DIE FOR PRESSING ALUMINIUM POWDER METAL MATRIX COMPOSITES
T.Canta, D.Frunza. (Technical University of Cluj-Napoca, Cluj-Napoca, Romania.) Powder Metall., Vol 40, No 3, 1997, 189-192. It is reported that Al-Sic composites had been compacted from powders in an elastic die. Effects of process variables on density and springback of the composite and unreinforced Al compacts were compared. It is shown that high-density compacts, free ejection and reduced die wear are attained. High compact quality is reported. SIMULATION OF COLD DIE COMPACTION DENSIFICATION OF IRON AND COPPER BY CAM-CLAY MODEL
X.K.Sun, K.T.Kim. (Pohang University of Science and Technology, Pohang, Korea.) Powder Metall., Vol 40, No 3, 1997, 193-195. Densification of Fe and Cu powders during die compaction was simulated with models and results compared with experiment. Experimental data were used to determine empirical constants for the Cam-Clay model, which simulated compaction better than the Shima and Fleck models. FREEFORM POWDER MOULDING FROM CAD MODEL TO PART WITHOUT TOOLING
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W.Z.Misolek et al. (Lehigh University, Bethlehem, PA, USA.) Int. J. Powder Metall., Vol 33, No 6, 1997, 37-44. Freeform powder moulding is reported to make it possible to produce small batches of PM parts without costly tooling. The method is one of a group of processes known as rapid prototyping which facilitate conversion of a computer model into parts. The method allows parts with spatially varied composition to be made. The process is described and results of process development are presented. Applications are suggested.
Fundamentals ELECTROPLATING COMPACTS
POROUS
PM
P.Leisner et al. (Technical University of Denmark, Lyngby, Denmark.) Powder Metall., Vol 40, No 3, 1997, 207-210.
Electroplating of porous PM parts was discussed with regard to the need for modifications to the process to take the porous nature of the substrate into account. Protective plating against corrosion was investigated. Levelling effects and coating thickness were found to be important factors, particularly when Fe compacts were sealed with Cu and where coating porosity is a problem. It is shown that Zn and Zn alloy coatings gave cathodic protection to Fe even with porous coatings. MIXEDNESS ENGINEERING FOR ADVANCED MULTICOMPONENT MATERIALS
R.E.Riman et al. (Rutgers University, Piscataway, NJ, USA.) Int. J. Powder Metall., Vol 33, No 6, 1997, 29-36. The concept of mixedness is introduced with application to metal powder materials. It is reported that mixedness can be predicted and determined using new methodology. Prediction is through a concentric shell model of mixedness. Measurement is through use of scanning field emission microscopy coupled with positron tagged spectroscopy. Prediction and measurement are shown to facilitate design, optimization and monitoring of multicomponent mixtures. MODELLING RELATIONSHIPS BETWEEN PARTICLE AND PORE SIZE DISTRIBUTIONS
Y.Rouault, S.Assouline. (Max-Planck Inst. for Polymer Research, Mainz, Germany.) Powder Technol., Vol 96, No 1, 199833-41. A model for the distribution of voids, in packed spheres of given size distribution, is proposed. Tetrahedral dense random packing, radii, size distribution, probability of pair formation and void volume are considered. The void distribution is shown to be bell shaped. Fractallike particle characteristics do not necessarily induce fractal-like behaviour of the voids. Increases in void size distribution are similar to particle size distributions in some cases. In others void size distribution is related to the standard deviation of particle size distribution. Increase in this standard deviation leads to a broader void size distribution and increases mean void size.
Powder Metall., Vol 44, No 4, 1997, 313. 316. (In English.) The importance of dimensional tolerance in PM parts and the need to minimize scatter are discussed with regard to sizing operations to correct dimensional error. Difficulty in sizing high strength materials is noted. A model to calculate scatter is proposed. Factors considered include powder mix composition, press variables and the effect of these on dimensional change. Material and process parameters can be compared to reach best dimensional precision in PM parts. The need for lowest costs and demands for strength are considered to make sizing of sintered parts essential.
Aluminium ALUMINIUM
FOAM PRODUCED
BY PM
M.Sakamaki. (Tokushima Y.Tada, University, Tokushima, Japan.) J. Jpn Sot. Powder Powder Metall., Vol44, No 4, 1997, 323-328. (In Japanese.) Production of foamed cellular metallic materials is discussed. Production of Al foam is described. Al powder is mixed with a foaming agent and extruded to form a dense, gas-tight, compact material. Further heating decomposes the foaming agent to gas and the foam is formed. A steel sleeve prevents surface cracking and allows attainment of higher porosity.
Copper EFFECT OF COPPER COATING ON CONSOLIDATION AND SINTERING OF COPPER-GRAPHITE COMPOSITES
A.M.Sanad et al. (Al-Azhar University, Cairo, Egypt.) Powder Metall., Vol40, No 3, 1997,201-206. Cu-8wt% graphite compacts were made from elemental powders. Comparison was made between graphite powders with and without a Cu coating and pure Cu. Cylindrical compacts, 8 mm diameter by 12 mm long were pressed at 400 to 1200 MPa. When sintered at lOOO”C, compacts with coated graphite sintered more rapidly, had higher density, tensile properties and electrical conductivity than those made from uncoated graphite powders.
NET SHAPE AFTER SINTERING OF CONSISTENT POWDER MIXTURES
METHOD OF MANUFACTURE OF BRONZE FILTERS
J.Tengzelius, M.Larsson. (Hoganas AB, Hoganas, Sweden.) J. Jpn Sot. Powder
A.Formoso et al. (Centro National de Investigaciones Metalurgicas, Madrid,
MPR October 1998 33
T.Canta, D.Frunza. (Technical University of Cluj-Napoca, Cluj-Napoca, Romania.) Powder Metall., Vol 40, No 3, 1997, 189-192. It is reported that Al-Sic composites had been compacted from powders in an elastic die. Effects of process variables on density and springback of the composite and unreinforced Al compacts were compared. It is shown that high-density compacts, free ejection and reduced die wear are attained. High compact quality is reported. SIMULATION OF COLD DIE COMPACTION DENSIFICATION OF IRON AND COPPER BY CAM-CLAY MODEL
X.K.Sun, K.T.Kim. (Pohang University of Science and Technology, Pohang, Korea.) Powder Metall., Vol 40, No 3, 1997, 193-195. Densification of Fe and Cu powders during die compaction was simulated with models and results compared with experiment. Experimental data were used to determine empirical constants for the Cam-Clay model, which simulated compaction better than the Shima and Fleck models. FREEFORM POWDER MOULDING FROM CAD MODEL TO PART WITHOUT TOOLING
-
W.Z.Misolek et al. (Lehigh University, Bethlehem, PA, USA.) Int. J. Powder Metall., Vol 33, No 6, 1997, 37-44. Freeform powder moulding is reported to make it possible to produce small batches of PM parts without costly tooling. The method is one of a group of processes known as rapid prototyping which facilitate conversion of a computer model into parts. The method allows parts with spatially varied composition to be made. The process is described and results of process development are presented. Applications are suggested.
Fundamentals ELECTROPLATING COMPACTS
POROUS
PM
P.Leisner et al. (Technical University of Denmark, Lyngby, Denmark.) Powder Metall., Vol 40, No 3, 1997, 207-210.
Electroplating of porous PM parts was discussed with regard to the need for modifications to the process to take the porous nature of the substrate into account. Protective plating against corrosion was investigated. Levelling effects and coating thickness were found to be important factors, particularly when Fe compacts were sealed with Cu and where coating porosity is a problem. It is shown that Zn and Zn alloy coatings gave cathodic protection to Fe even with porous coatings. MIXEDNESS ENGINEERING FOR ADVANCED MULTICOMPONENT MATERIALS
R.E.Riman et al. (Rutgers University, Piscataway, NJ, USA.) Int. J. Powder Metall., Vol 33, No 6, 1997, 29-36. The concept of mixedness is introduced with application to metal powder materials. It is reported that mixedness can be predicted and determined using new methodology. Prediction is through a concentric shell model of mixedness. Measurement is through use of scanning field emission microscopy coupled with positron tagged spectroscopy. Prediction and measurement are shown to facilitate design, optimization and monitoring of multicomponent mixtures. MODELLING RELATIONSHIPS BETWEEN PARTICLE AND PORE SIZE DISTRIBUTIONS
Y.Rouault, S.Assouline. (Max-Planck Inst. for Polymer Research, Mainz, Germany.) Powder Technol., Vol 96, No 1, 199833-41. A model for the distribution of voids, in packed spheres of given size distribution, is proposed. Tetrahedral dense random packing, radii, size distribution, probability of pair formation and void volume are considered. The void distribution is shown to be bell shaped. Fractallike particle characteristics do not necessarily induce fractal-like behaviour of the voids. Increases in void size distribution are similar to particle size distributions in some cases. In others void size distribution is related to the standard deviation of particle size distribution. Increase in this standard deviation leads to a broader void size distribution and increases mean void size.
Powder Metall., Vol 44, No 4, 1997, 313. 316. (In English.) The importance of dimensional tolerance in PM parts and the need to minimize scatter are discussed with regard to sizing operations to correct dimensional error. Difficulty in sizing high strength materials is noted. A model to calculate scatter is proposed. Factors considered include powder mix composition, press variables and the effect of these on dimensional change. Material and process parameters can be compared to reach best dimensional precision in PM parts. The need for lowest costs and demands for strength are considered to make sizing of sintered parts essential.
Aluminium ALUMINIUM
FOAM PRODUCED
BY PM
M.Sakamaki. (Tokushima Y.Tada, University, Tokushima, Japan.) J. Jpn Sot. Powder Powder Metall., Vol44, No 4, 1997, 323-328. (In Japanese.) Production of foamed cellular metallic materials is discussed. Production of Al foam is described. Al powder is mixed with a foaming agent and extruded to form a dense, gas-tight, compact material. Further heating decomposes the foaming agent to gas and the foam is formed. A steel sleeve prevents surface cracking and allows attainment of higher porosity.
Copper EFFECT OF COPPER COATING ON CONSOLIDATION AND SINTERING OF COPPER-GRAPHITE COMPOSITES
A.M.Sanad et al. (Al-Azhar University, Cairo, Egypt.) Powder Metall., Vol40, No 3, 1997,201-206. Cu-8wt% graphite compacts were made from elemental powders. Comparison was made between graphite powders with and without a Cu coating and pure Cu. Cylindrical compacts, 8 mm diameter by 12 mm long were pressed at 400 to 1200 MPa. When sintered at lOOO”C, compacts with coated graphite sintered more rapidly, had higher density, tensile properties and electrical conductivity than those made from uncoated graphite powders.
NET SHAPE AFTER SINTERING OF CONSISTENT POWDER MIXTURES
METHOD OF MANUFACTURE OF BRONZE FILTERS
J.Tengzelius, M.Larsson. (Hoganas AB, Hoganas, Sweden.) J. Jpn Sot. Powder
A.Formoso et al. (Centro National de Investigaciones Metalurgicas, Madrid,
MPR October 1998 33