Powder production PLASMA ATOMIZATION PRODUCTION POWDERS
OF FINE SPHERICAL
R.A.LDrew et al. J.of Metals, Vol 48, No 6, 1996, 53-55. It is reported that a new process, plasma atomization, yields fine spherical powders 40 pm in size. The process uses multiple DC plasmas to accelerate the atomization gas and metal wire is fed into the apex. The wire is melted and atomized in a single step.
Fundamentals PACKING CHARGCTERISTICS MONO-SIZED
R.P.Zou, AB.Yu. [University of New South Wales, Sydney, Australia.) Powder Technoiogr: Vol 88, No 1, 1996, 71-79. Loose and dense packing of mono-sized non-spherical shaped particles were investigated to determine the effects of particle shape. It is shown that the equivalent packing diameter is only affected by shape and is not sensitive to evaluation methods or packing and mixing techniques. The results are shown to predict porosity of non-spherical powders.
AIuminirrm EFFECT OF POWDER AND EXTRUSION VARIARLES ON EXTRUSION PRESSURE FOR ALUMINIUN
HJones et al. (University of Sheffield, Sheffield, UK) Powder Metallura Vol 39, No 2, I996, 143-149. Extrusion of AR atomized Al-5%Cr-2%Zr powders was investigated for effects of extrusion variables and powder characteristics on extrusion pressure. At low ram speeds and temperatures the integrity of the rapidly solidified powder was retained. The results are discussed in the light of conditions. MICROSTRUCTURE OF GAS ATOMIZED ALUMINIUM-SILICON-IRON POWDERS Y.S.Choi, H.Y.Ra. (National University of Seoul, Seoul, Korea.) J. Korean Inst. of Metals, Vol 34, No 2, 1996, 230-235. (In Korean,) Charaterization of gas atomized Al-(20 to 30)wt%Si-(3.5)XFe powders are
described.The RS powders consisted of 6 phase (AlaFeSiZ), Si and Al solid solution, with a ternary eutectic present. The 6 decomposed on heating being replaced by a p phase, (AlsFeSi). It is anticipated that materials made from these powders will show property improvements compared with binary Al-Si alloys,
AND GRAIN GROWTH
DURING SINTERING ALUMINIUM
M.Udaka et al. (Neturen Ltd., Hiratsuka, Japan.) J. Japan Inst. of Metals, Vol 60, No 6, 1996, 607-615. (In Japanese.) It is reported that Cu-AlN compacts had been made from 90 nm Cu and 54 nm AlN powders. Sintering and densfication characteristics were investigated. It is shown that the Cu grain size increased with sintering time and stabilized. The stable grain size was in inverse proportion to the %AlN. AlN retarded grain growth but impeded densiflcation.
Iron and steel INJECTION
J.Rawers et al. (Department of Energy, Albany, Oregon, USA) Int. J.Powder Metallurgv, Vol 32, No 4, 1996, 319-322. It is reported that a small change in sintering of MIM 316L stainless steel gave increased tensile properties and reduced costs. Tensile strength was increased above 375 MPa by addition of N. MICROSTRUCTURE AND TENSILE PROPERTIES OF MECHANICALLY ALLOYED COMPACTED IRON ALUMINIUM J.Rawers et al. (Department of Energy, Albany, Oregon, USA) Met&. and Mater. Tram A, Vol27A No 10, 1996, 3126-3134. Problems in determination of mechanical properties of nano-crystalline materials are identified as small quantity of material, for testing, and inability to retain nano-crystalline structures during processing. Studies of Fe-2wt%Al, which had been attrition milled, mechanically alloyed and vacuum hot pressed to full density are described. The structure is shown to comprise Fe microsub-grains and Fe-Al nanogram clusters. A tensile strength approaching 1 GPa is reported.
EFFECTS OF ATMOSPHERE ON PHASE FORMATION AND MAGNETIC PROPERTIES
S.E.Lee et al. (Seoul National University, Seoul, Korea.) J. Korean Inst. of Metals, Vol 34, No 3, 1996, 289-295. (In Korean.) Effects of atmosphere, N or Ar, on phase evolution and magnetic properties during mechanical alloying of Fe-Zr powders were investigated. The structures contained an amorphous phase and aFe. Amorphization was retarded in N and this is attributed to hardening of the aFe by dissolved N. Relationships between magnetic properties and milling time were discussed. HIGH DENSITY OF SINTERED IRON MATERIALS BY ROTARY COLD PRESSING S.Stolarz et al. (Inst. Metali Niezelaznych, Gliwice, Poland.) Metal. Proszkow, Vol 29, No 1, 1996, 12-23. (In Polish.) Rotary cold pressing, to attain high density, in sintered Fe base alloys is described. Properties were determined, and optimum process conditions established for a range of steels with different alloy contents. POROSITY CHARACTERISTICS OF SINTERED IRON-COPPER AND IRON-PHOSPHORUS JLezanski. (Akademia Gorniczo-Hutnicza, Krakow, Poland.) Metal. fioszkow, Vol 29, No 1, 1996, 24-29. (In Polish.) Properties of green and sintered Fe-Cu and Fe-P compacts were investigated as functions of powder morphology and process conditions. Particular emphasis was placed on porosity and capilliary morphology. MICROSTRUCTURE AND PROPERTIES OF QUENCHED AND TEMPERED PM HOT-WORKING TOOL STEELS N.Tsujii et al. (Sanyo Special Steel Co. Ltd., Himeji, Japan.) JXapan Sot. Powder and Powder Metallurm, Vol42, No 4, 1995,481484. (In Japanese.) A comparative study of PM and cast/ wrought 5%Cr-0.35%C-MO-V hot working tool steels is described. Effects of heat treatment temperatures of structures and properties were determined. The PM steel had a fine uniform microstructure but the IM steels were banded. Hardness of quenched and tempered PM steels was slightly lower and grain growth was less in the PM steels. MPR March