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Relationship between compaction and morphology of metal powders
Pressing WARM COMPACTION POWDERS
fraction of the mill and is asymptotic to a set value, which is the traditional CRS. OF METAL
G.F.Bocchini. (Via A.Vespucci 48/18, Papallo, Italy.) Powder Metall., Vol 42, No 2,1999,171-180. Warm compaction of metal powders is critically reviewed with reference to effects of temperature on powder properties, lubrication, attainment of porosity less than 2%, porosity distribution, ejection and springback. Sintering is shown to require regimes that allow through penetration of reducing gases to reduce included oxides; failure to do so may lead to unsintered cores. The concept of reduction depth is introduced and methods for measurement are suggested. The need for low porosity, oxide and inclusion contents is emphasized. Operating conditions and differences with ambient temperature compaction are discussed. The need for good design calculation and use of electrodischarge machining for die making is emphasized. RELATIONSHIP BETWEEN COMPACTION AND MORPHOLOGY OF METAL POWDERS
T.Itoh, Y.Wanibe. (Nagoya University, Nagoya, Japan.) J. Jpn Sot. Powder Powder Metal., Vo146, No 1,1999,16-21. (In English.) The influence of powder morphology on compaction is discussed and an analysis is described. Compaction is considered in terms of mechanisms of particle rearrangement and particle deformation. Particle shape is quantified by particle size/shape dispersion diagrams. Particle rearrangement is correlated with four morphological factors by two linear equations. Deformation is characterized by packing density and powder hardness.
Fundamentals CRITICAL ROTATION BALL MILLING
USE OF PHOSPHIDE ADDITIONS TO PROMOTE LIQUID PHASE SINTERING OF STAINLESS STEEL
H.Preusse, J.D.Bolton. (University of Bradford, Bradford, UK.) Powder Metall., Vol42, No 1,1999,51-62. Addition of 8 to 10% Cu,P or Fe,P, as sintering aids, to 316L stainless steel powder was investigated for the effects on vacuum sintering at 1200 and 1250°C. Densities above 96% and interconnected porosity less than 0.2% were attained. Without phosphide addition only 80% density and 17% interconnected porosity were reached. Cu,P reacted with the matrix to form a mixture of Cu and a Fe-Cr phase which aided liquid phase sintering. This did not occcur with Fe,P. Microstructures were correlated with measured and calculated reaction temperatures. Useful levels of tensile strength were attained but there was low ductility.
Magnesium FRICTION AND WEAR OF MAGNESIUM-BORON ALLOYS
J.Saito et al. (Science University of Tokyo, Tokyo, Japan.) J. Jpn Sot. Powder Powder Metal., Vol 46, No 1, 1999, 3-8. (In Japanese.) Wear of a new Mg based alloy containing Mg borides and C steel was investigated using ring-on-block tests at a sliding speed of 3.55 m.s-l under a load of 20.6 N for 66.6 to 600 m. The new alloys had better wear resistance than conventional Mg alloys. This is attributed to higher hardness and formation of MgO and B,O,, which may act as lubricants.
Molybdenum SPEED FOR
H.Watanabe. (Kagawa Industrial Technology Centre, Kagawa, Japan.) Powder TechnoZ., Vol 104, No 1,1999,95-99. The critical rotation speed, CRS, of ball mills was studied experimentally and by numerical simulation. It is noted that CRS is related to ball and mill diameters. The present study showed that CRS is also linked to the filled
46 MPR May 2000
Iron and steel
ENHANCED SINTERING OF MOLYBDENUM BY SMALL ADDITIONS OF NICKEL AND/OR ZIRCONIUM
University, (Senshu J.Takekawa. Ishinomaki, Japan.) J. Jpn Sot. Powder Powder Metal., Vol46, No 1,1999,22-27. (In Japanese.) Sintering of MO with small additions of Ni and/or Zr was investigated. It is shown that additions of Ni and Zr, in a ratio 4 parts to 1, or Ni enhanced sinter-
ing. No enhancement was observed with Zr alone; Zr inhibited MO grain growth. Mo-0.8wt%Ni-0.2%Zr sintered to near full density at 1300°C in 6.75 hours.
Titanium EARLY STAGE CONSOLIDATION DURING HOT ISOSTATIC PRESSING OF TITANIUM ALLOY
D.P.Delo, H.R.Piehler. (Carnegie-Mellon University, Pittsburgh, USA.) Acta Mater., Vol47, No 9,1999,2841-2852. Ti-G%Al-4%V compacts were HIPed to a range of density to identify mechanisms in the initial stages of compaction. The HIPed compacts were examined by optical and stereo-pair scanning electron microscopy. Particle movement is shown to contribute to densification. Preferential deformation of smaller particles is shown to lead to increased density. Tensile fractures provided evidence of cooperative movement in clusters of particles. There was agreement between experiment and mechanistic models for powder compaction. STRUCTURE AND PROPERTIES OF TITANIUM-SILICON COMPACTS MADE BY HIGH PRESSURE CONSOLIDATION
A.Matsumoto et al. (National Industrial Research Inst. of Nagoya, Nagoya, Japan.) J. Jpn Sot. Powder Powder Metal., Vol 45, No 12, 1998, 1211-1215. (In Japanese.) Ti-37.5at%Si powder was mechanically alloyed in Ar. The powder was amorphous and had nano-sized particles. The powders were consolidated at high pressure (5.4 GPa) and at 400°C to give a fully dense compact with retention of non-equilibrium structures. Compressive strength at ambient temperature was 2.5 GPa. NITRIDING OF TITANIUM UNDER MICROGBAVITY - MICROSTRUCTURE
Y.Kaieda. (National Research Inst. for Metals, Tsukuba, Japan.) J. Jpn Sot. Powder Powder Metal., Vol 46, No 1, 1999,9-15. (In Japanese.) Ti wire was nitrided under normal and microgravity, in a drop shaft that gives 10 seconds of microgravity, in order to simulate the effects of microgravity on powder/gas reactions. Effects on microstructure were studied. The nitriding reaction is shown to be enhanced by microgravity due to
fraction of the mill and is asymptotic to a set value, which is the traditional CRS. OF METAL
G.F.Bocchini. (Via A.Vespucci 48/18, Papallo, Italy.) Powder Metall., Vol 42, No 2,1999,171-180. Warm compaction of metal powders is critically reviewed with reference to effects of temperature on powder properties, lubrication, attainment of porosity less than 2%, porosity distribution, ejection and springback. Sintering is shown to require regimes that allow through penetration of reducing gases to reduce included oxides; failure to do so may lead to unsintered cores. The concept of reduction depth is introduced and methods for measurement are suggested. The need for low porosity, oxide and inclusion contents is emphasized. Operating conditions and differences with ambient temperature compaction are discussed. The need for good design calculation and use of electrodischarge machining for die making is emphasized. RELATIONSHIP BETWEEN COMPACTION AND MORPHOLOGY OF METAL POWDERS
T.Itoh, Y.Wanibe. (Nagoya University, Nagoya, Japan.) J. Jpn Sot. Powder Powder Metal., Vo146, No 1,1999,16-21. (In English.) The influence of powder morphology on compaction is discussed and an analysis is described. Compaction is considered in terms of mechanisms of particle rearrangement and particle deformation. Particle shape is quantified by particle size/shape dispersion diagrams. Particle rearrangement is correlated with four morphological factors by two linear equations. Deformation is characterized by packing density and powder hardness.
Fundamentals CRITICAL ROTATION BALL MILLING
USE OF PHOSPHIDE ADDITIONS TO PROMOTE LIQUID PHASE SINTERING OF STAINLESS STEEL
H.Preusse, J.D.Bolton. (University of Bradford, Bradford, UK.) Powder Metall., Vol42, No 1,1999,51-62. Addition of 8 to 10% Cu,P or Fe,P, as sintering aids, to 316L stainless steel powder was investigated for the effects on vacuum sintering at 1200 and 1250°C. Densities above 96% and interconnected porosity less than 0.2% were attained. Without phosphide addition only 80% density and 17% interconnected porosity were reached. Cu,P reacted with the matrix to form a mixture of Cu and a Fe-Cr phase which aided liquid phase sintering. This did not occcur with Fe,P. Microstructures were correlated with measured and calculated reaction temperatures. Useful levels of tensile strength were attained but there was low ductility.
Magnesium FRICTION AND WEAR OF MAGNESIUM-BORON ALLOYS
J.Saito et al. (Science University of Tokyo, Tokyo, Japan.) J. Jpn Sot. Powder Powder Metal., Vol 46, No 1, 1999, 3-8. (In Japanese.) Wear of a new Mg based alloy containing Mg borides and C steel was investigated using ring-on-block tests at a sliding speed of 3.55 m.s-l under a load of 20.6 N for 66.6 to 600 m. The new alloys had better wear resistance than conventional Mg alloys. This is attributed to higher hardness and formation of MgO and B,O,, which may act as lubricants.
Molybdenum SPEED FOR
H.Watanabe. (Kagawa Industrial Technology Centre, Kagawa, Japan.) Powder TechnoZ., Vol 104, No 1,1999,95-99. The critical rotation speed, CRS, of ball mills was studied experimentally and by numerical simulation. It is noted that CRS is related to ball and mill diameters. The present study showed that CRS is also linked to the filled
46 MPR May 2000
Iron and steel
ENHANCED SINTERING OF MOLYBDENUM BY SMALL ADDITIONS OF NICKEL AND/OR ZIRCONIUM
University, (Senshu J.Takekawa. Ishinomaki, Japan.) J. Jpn Sot. Powder Powder Metal., Vol46, No 1,1999,22-27. (In Japanese.) Sintering of MO with small additions of Ni and/or Zr was investigated. It is shown that additions of Ni and Zr, in a ratio 4 parts to 1, or Ni enhanced sinter-
ing. No enhancement was observed with Zr alone; Zr inhibited MO grain growth. Mo-0.8wt%Ni-0.2%Zr sintered to near full density at 1300°C in 6.75 hours.
Titanium EARLY STAGE CONSOLIDATION DURING HOT ISOSTATIC PRESSING OF TITANIUM ALLOY
D.P.Delo, H.R.Piehler. (Carnegie-Mellon University, Pittsburgh, USA.) Acta Mater., Vol47, No 9,1999,2841-2852. Ti-G%Al-4%V compacts were HIPed to a range of density to identify mechanisms in the initial stages of compaction. The HIPed compacts were examined by optical and stereo-pair scanning electron microscopy. Particle movement is shown to contribute to densification. Preferential deformation of smaller particles is shown to lead to increased density. Tensile fractures provided evidence of cooperative movement in clusters of particles. There was agreement between experiment and mechanistic models for powder compaction. STRUCTURE AND PROPERTIES OF TITANIUM-SILICON COMPACTS MADE BY HIGH PRESSURE CONSOLIDATION
A.Matsumoto et al. (National Industrial Research Inst. of Nagoya, Nagoya, Japan.) J. Jpn Sot. Powder Powder Metal., Vol 45, No 12, 1998, 1211-1215. (In Japanese.) Ti-37.5at%Si powder was mechanically alloyed in Ar. The powder was amorphous and had nano-sized particles. The powders were consolidated at high pressure (5.4 GPa) and at 400°C to give a fully dense compact with retention of non-equilibrium structures. Compressive strength at ambient temperature was 2.5 GPa. NITRIDING OF TITANIUM UNDER MICROGBAVITY - MICROSTRUCTURE
Y.Kaieda. (National Research Inst. for Metals, Tsukuba, Japan.) J. Jpn Sot. Powder Powder Metal., Vol 46, No 1, 1999,9-15. (In Japanese.) Ti wire was nitrided under normal and microgravity, in a drop shaft that gives 10 seconds of microgravity, in order to simulate the effects of microgravity on powder/gas reactions. Effects on microstructure were studied. The nitriding reaction is shown to be enhanced by microgravity due to