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Molybdenum
Difficulty in processing nanostructured materials, stabilized by hard phases, is discussed. It is shown that liquid enhanced plasticity is a means of overcoming this. Experiments on Cu-(4, i0 or 14)at%Mg12w)l%TiC are described. Mechanical alloying, HIP and hot rolling, making use of partial liquidation at an atomic fraction of 0.5% which gave an elongation of 200%, were used to prepare specimens for mechanical testing. Melting promoted diffusion bonding. Grain sizes of 30 nm were measured.
Iron and steel Fabrication of stainless steels with composite structures by sintering inN K.Kataoka et al (KTu~hu Uniw~rsiLy, Fukuoka, J~#~an.)J. Jpn Soc. Powder/PowderMeral[, Vo146, No 11, 1999, 1 t36-1142. (In Japanese.)
It is reported that ferritic stainless steels, with 12 to 23wt%Cr, had been made by pressing and sintering in N at 1200 °C to yield composite N based 0~ and y martensitic structures. The steels absorbed 0.3%N at I2%Cr and 1.0% at 23%Cr. Mechanical tests showed that both strength and elongation increased with %Cr due to a less brittle form of martensite at higher %Cr,
Effect of Cr content on mechanical properties of iron-chromium alloys K.Kobayashi e~ al (Natioru~l Industrial Research Inst., Nagoya, Japan.) J. Jpn Soc. Powder/PowderMetall, Vol 46, No I ~,, 1999, 1179-1184. (In Japanese.)
Elemental Fe-(28, 38, 48, 58 and 68)at%Cr alloys were mechanically alloyed in Ar for 100 hours. The powders were spark plasma sintered and tensile samples ground from the sintered alloys, Strength increased and ductility decreased with %Cr. Cast Fe-68%Cr was too hard to be ground but the sintered alloy had a tensile strength of 1500 MPa. The optimum %Cr was considered to be 48% and this had a tensile strength of 1125 MPa and 5% elongation.
MIM of stainless steel with small addition of boron J.Takekawa. (Senshu UniversiU, Ishinomaki, Japan.) J. Jpn Soc. Powder/PowderMetall, 'v'~~146,No 11, 1999, 1201H 206. (In Japanese.)
A n investigation of the effects of 0.4wt%B, added to 316L stainless steel, is described. The B was dispersed in the powder by ball milling. The steel was injection moulded, debound and sintered. Samples debound at 300 °C sintered to near fifll density at 1190 °C. Debinding at 330 °C required 1240 °C to attain ful~ density, which also gave a larger grain size.
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Properties of low alloy steel injection moulded by Quick-Set technique
S.~xkaki et a[. (Kyushu University, Fukuaka, Japan.) 1. Jpn Soc. Powder/PowderMetall., Vo146, No I2, I999,
H.Miura et al. (Kumam~)to University, Kumamoto, Japan.) J. Jpn S(~c. Powder/Powder Metall, V~146, No I 1, I999, 1207-121 t. (InJapanese.)
0,8%C steel powder was mechanically alloyed, packed in stainless steel cans and hot rolled. Mechanisms during consolidation were investigated by tensile tests at consolidation temperature, 600 °C. The structure was Fe3C + 0~Fe with a grain size of 0.3 )am. Deformation stress was 1700 MPa at 25 °C and 80 MPa at 600 °C. Few dislocations were found and it is deduced the deformation was by grain boundary sliding.
It is reported that a new injection moulding technique, the Quick-Set process had been developed to enable production of larger parts than had been possible using thermoplastic based binder systems. Mechanical properties of low alloy steel parts, made by this process, are described. Two steels, of similar compositions but differing particle size distributions, were studied and comparison is made between Quick-Set and conventional PM parts.
Production of parts from water atomized cast iron powders M.Takita et al. (Nagoya University, Nagoya, Japan.) J. Jpn Soc. Powder/PowderMetall, Vo146, No ] 1, I999, 1212-12. (In Japanese.)
Magnesium Synthesis of magnesium-iron alloys by mechanical alloying K.Kobayashi et al. (National Industrial Research Inst., Nagoya, Japan.) J. Jpn Soc. Powder/PowderMetall., Vol 46, N() I0, ~999, 1068-1072. (in Japanese.)
An investigation of injection moulding of parts from atomized cast iron powders is described. Oxidation was minimized by use of powder with a tow % 0 and by solvent debinding. Tensile strength of sintered cast iron is similar to that of ductile cast iron but the damping capacity is higher. The higher damping capacity is attributed to pores and fine graphite particles in the structure.
It is reported that Mg-(0, 5, 10 and 20)wt% Fe alloys had been processed by mechanical alloying from elemental powders. The milled powders were composites of Mg and Fe. Powder morphology is described. The Mg-15%Fe was considered most suitable for further processing and was pulse current sintered at 500 °C and I9 MPa. The sintered microstructure was a fine dispersion of Fe in Mg matrix.
Ultra grain refinement of iron by mechanical milling
Molybdenum
Y.Kimura, S.Takaki. (Kyushu Urm,ersity, Fukuoka, Japan.) J. Jpn Soc. Powder/PowderMetall., \&146, No I2, •999, 1235-1241. (In English.)
Low temperature fracture of elongated coarse grained Mo sheets
tt is reported that mechanical alloying had been used to heavily deform Fe powder. A Vickers hardness of 950 and a nm grain size were attained. Grain growth in the powder was by growth of the nano-sized grains without conventional recrystal[ization and a Hall-Petch relationship was found. The powder could be consolidated to filll density at 650 °C with oxide particle inhibiting grain growth. 0.2% proof stress was about 1.6 GPa due to grain refinement strengthening,
T.Takida et al. (Toky~ Tungsten Co Lid, Toyama, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo146, No 10, t999, I025-I030. (tn Japanese.)
Fabrication of high nitrogen stainless steel by PM S.Takaki et al (Kyushu University, Fukuoka, Japan.) J. Jpn Soc. Powder/PowderMetal[., Vo146, No I2, 1999, 1249-1255. (In Japanese.)
It is reported that powders, high in N, such as CrxN, had been blended with N free 16 and 23%Cr-steel powders to prepare steels with l%N. Powders were canned in steel, hot rolled and homogenised at 1200 °C for 30 minutes. The resulting structures are described.
Consolidation of mechanically milled eutectoid steel powder
MPR April 2ool iii
1256-1260. (In Japanese.
Low temperature fracture of two Mo1.0wtLa203, with elongated spindle-like grains or stacked plate-like grains, and pure Mo with equiaxed grains, was investigated. Bend tests were used at -i96 to 25 °C. It is reported that the material with spindle-like grains had higher fracture strength than the pure Mo. Some samples had surface zones of equiaxed grains in which cracking was initiated.
Tensile properties of fine grained Mo with carbide dispersoids T.Takida et al. (Tok'~o Tungsten Co Lid, Toyama, Japan.) J. Jpn Soc, Powder/PowderMetall., Vo146, No 10, 1999, 1031-I036. (In Japanese.)
Fine grained Mo alloys, with 0.8mo1% ZrC or TaC, were prepared by mechanical alloying and spark plasma sintering. Tensile properties were investigated at ambient temperature and at 900 to 1500 °C. The dispersoids increased the strength in comparison with pure Mo. Mo-ZrC showed 120% elongation at i500 °C. The properties are attributed to fine structure and dispersoids.
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Iron and steel Fabrication of stainless steels with composite structures by sintering inN K.Kataoka et al (KTu~hu Uniw~rsiLy, Fukuoka, J~#~an.)J. Jpn Soc. Powder/PowderMeral[, Vo146, No 11, 1999, 1 t36-1142. (In Japanese.)
It is reported that ferritic stainless steels, with 12 to 23wt%Cr, had been made by pressing and sintering in N at 1200 °C to yield composite N based 0~ and y martensitic structures. The steels absorbed 0.3%N at I2%Cr and 1.0% at 23%Cr. Mechanical tests showed that both strength and elongation increased with %Cr due to a less brittle form of martensite at higher %Cr,
Effect of Cr content on mechanical properties of iron-chromium alloys K.Kobayashi e~ al (Natioru~l Industrial Research Inst., Nagoya, Japan.) J. Jpn Soc. Powder/PowderMetall, Vol 46, No I ~,, 1999, 1179-1184. (In Japanese.)
Elemental Fe-(28, 38, 48, 58 and 68)at%Cr alloys were mechanically alloyed in Ar for 100 hours. The powders were spark plasma sintered and tensile samples ground from the sintered alloys, Strength increased and ductility decreased with %Cr. Cast Fe-68%Cr was too hard to be ground but the sintered alloy had a tensile strength of 1500 MPa. The optimum %Cr was considered to be 48% and this had a tensile strength of 1125 MPa and 5% elongation.
MIM of stainless steel with small addition of boron J.Takekawa. (Senshu UniversiU, Ishinomaki, Japan.) J. Jpn Soc. Powder/PowderMetall, 'v'~~146,No 11, 1999, 1201H 206. (In Japanese.)
A n investigation of the effects of 0.4wt%B, added to 316L stainless steel, is described. The B was dispersed in the powder by ball milling. The steel was injection moulded, debound and sintered. Samples debound at 300 °C sintered to near fifll density at 1190 °C. Debinding at 330 °C required 1240 °C to attain ful~ density, which also gave a larger grain size.
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ill
Properties of low alloy steel injection moulded by Quick-Set technique
S.~xkaki et a[. (Kyushu University, Fukuaka, Japan.) 1. Jpn Soc. Powder/PowderMetall., Vo146, No I2, I999,
H.Miura et al. (Kumam~)to University, Kumamoto, Japan.) J. Jpn S(~c. Powder/Powder Metall, V~146, No I 1, I999, 1207-121 t. (InJapanese.)
0,8%C steel powder was mechanically alloyed, packed in stainless steel cans and hot rolled. Mechanisms during consolidation were investigated by tensile tests at consolidation temperature, 600 °C. The structure was Fe3C + 0~Fe with a grain size of 0.3 )am. Deformation stress was 1700 MPa at 25 °C and 80 MPa at 600 °C. Few dislocations were found and it is deduced the deformation was by grain boundary sliding.
It is reported that a new injection moulding technique, the Quick-Set process had been developed to enable production of larger parts than had been possible using thermoplastic based binder systems. Mechanical properties of low alloy steel parts, made by this process, are described. Two steels, of similar compositions but differing particle size distributions, were studied and comparison is made between Quick-Set and conventional PM parts.
Production of parts from water atomized cast iron powders M.Takita et al. (Nagoya University, Nagoya, Japan.) J. Jpn Soc. Powder/PowderMetall, Vo146, No ] 1, I999, 1212-12. (In Japanese.)
Magnesium Synthesis of magnesium-iron alloys by mechanical alloying K.Kobayashi et al. (National Industrial Research Inst., Nagoya, Japan.) J. Jpn Soc. Powder/PowderMetall., Vol 46, N() I0, ~999, 1068-1072. (in Japanese.)
An investigation of injection moulding of parts from atomized cast iron powders is described. Oxidation was minimized by use of powder with a tow % 0 and by solvent debinding. Tensile strength of sintered cast iron is similar to that of ductile cast iron but the damping capacity is higher. The higher damping capacity is attributed to pores and fine graphite particles in the structure.
It is reported that Mg-(0, 5, 10 and 20)wt% Fe alloys had been processed by mechanical alloying from elemental powders. The milled powders were composites of Mg and Fe. Powder morphology is described. The Mg-15%Fe was considered most suitable for further processing and was pulse current sintered at 500 °C and I9 MPa. The sintered microstructure was a fine dispersion of Fe in Mg matrix.
Ultra grain refinement of iron by mechanical milling
Molybdenum
Y.Kimura, S.Takaki. (Kyushu Urm,ersity, Fukuoka, Japan.) J. Jpn Soc. Powder/PowderMetall., \&146, No I2, •999, 1235-1241. (In English.)
Low temperature fracture of elongated coarse grained Mo sheets
tt is reported that mechanical alloying had been used to heavily deform Fe powder. A Vickers hardness of 950 and a nm grain size were attained. Grain growth in the powder was by growth of the nano-sized grains without conventional recrystal[ization and a Hall-Petch relationship was found. The powder could be consolidated to filll density at 650 °C with oxide particle inhibiting grain growth. 0.2% proof stress was about 1.6 GPa due to grain refinement strengthening,
T.Takida et al. (Toky~ Tungsten Co Lid, Toyama, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo146, No 10, t999, I025-I030. (tn Japanese.)
Fabrication of high nitrogen stainless steel by PM S.Takaki et al (Kyushu University, Fukuoka, Japan.) J. Jpn Soc. Powder/PowderMetal[., Vo146, No I2, 1999, 1249-1255. (In Japanese.)
It is reported that powders, high in N, such as CrxN, had been blended with N free 16 and 23%Cr-steel powders to prepare steels with l%N. Powders were canned in steel, hot rolled and homogenised at 1200 °C for 30 minutes. The resulting structures are described.
Consolidation of mechanically milled eutectoid steel powder
MPR April 2ool iii
1256-1260. (In Japanese.
Low temperature fracture of two Mo1.0wtLa203, with elongated spindle-like grains or stacked plate-like grains, and pure Mo with equiaxed grains, was investigated. Bend tests were used at -i96 to 25 °C. It is reported that the material with spindle-like grains had higher fracture strength than the pure Mo. Some samples had surface zones of equiaxed grains in which cracking was initiated.
Tensile properties of fine grained Mo with carbide dispersoids T.Takida et al. (Tok'~o Tungsten Co Lid, Toyama, Japan.) J. Jpn Soc, Powder/PowderMetall., Vo146, No 10, 1999, 1031-I036. (In Japanese.)
Fine grained Mo alloys, with 0.8mo1% ZrC or TaC, were prepared by mechanical alloying and spark plasma sintering. Tensile properties were investigated at ambient temperature and at 900 to 1500 °C. The dispersoids increased the strength in comparison with pure Mo. Mo-ZrC showed 120% elongation at i500 °C. The properties are attributed to fine structure and dispersoids.
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