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Effects of homogeneous and heterogneous structures on properties of sintered steels
COMPOSITION CONTROL OF STAINLESS STEEL IN LINED STEEL PIPE L. Hoyi et al. (University Science and Technology, Beijing, China.) PM Technologv Vol 14, No 1, 1996, 14-18. (In Chinese.) It is reported that a centifrugal process and reactive synthesis had been used to line a steel pipe with stainless steel. Control of composition of the lining is discussed. TENSILE CHARACTERISTICS OF NITROGEN ENHANCED INJECTION MOULDED 316L STAINLESS STEEL J. Rawers et al. (Bureau of Mines, USA) Powder Metallur&‘ol 39, No 2, 199, 125. 129. It is reported that a change in sintering of MIM 316L stainless steel had resulted in reduced costs. N was used instead of inert gas which gave some nitriding. N is shown to increase mechanical properties. USE OF MASTER ALLOYS TO PREPARE PREMIXED HARDENABLE PM STEELS D.W. Hall. (Ford Motor Co, Dearborn, USA) Powder Metallurgv;Vol 39, No 2, 1996, 130. 137. Liquid phase sinterlng of steels, made from atomized Fe powders and atomized master alloy powders, was investigated. The master alloys were Mn-Cu-Ni and Mn-Ni-CrMO-Fe alloys with the lowest and narrowest melting ranges. After sinterlng and forging the hardenabilities were 75 to 90% of calculated values for conventional steels. These were improved by additions of Si and rare earths to enhance diffusion. Good tensile and impact properties are reported. Effects of individual alloy elements are discussed. It was concluded that LPS gave best densification and warm compaction gave good hardenability. EFFECTS OF HOMOGENEOUS AND HETEROGNEOUSSTRUCTURESON PROPERTIES OF SINTEBED STEELS H. Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Japan Sot. Powder and Powder Metallurgv, Vol42, No 3, 1995, 378-382. (In Japanese.) It is reported that 4600 steels had been made by MIM. The structures were containing bainite, heterogeneous, martensite and retained austenite, which is attributed to segregation of Ni. Efforts to improve the heterogeneity, in which prealloyed powders and elemental powder mixtures were compared, are described. As sintered, the prealloyed powders gave a fine homogeneous microstructure of ferrite and pearlite. The mixed powder gave the heterogeneous structures of bainite and martensite. Ductilities and toughnesses were similar but the strength was higher for the elemental powder specimens due to bainite and martensite. Differences were reduced by heat treatment.
CARBON CONTROL OF INJECTION MOULDED STRUCTURAL ALLOY STEEL M. Tomita. (Industrial Research Inst. of Kanagawa Prefecture, Yokohama, Japan.) J.Japan Sot. Powder and Powder Metallurgv, Vol 42, No 3, 1995, 402-407. (In
Japanese.) Investigations of control of C content in MIM steels are described. During sintering C was controlled by composition and flow rate of CHI-H atmospheres, sintering time and temperature.
Magnesium EXTRUSION RATIO AND MECHANICAL PROPERTIES OF EXTRUDED MACHINED MAGNESIUM ALLOY CHIPS K. Higashi et al. (University of Osaka prefecture, Sakai, Japan.) J. Japan Sot. Powder and Powder Metallurgy, Vol 42, No 3, 1995, 373-377. (In Japanese.) Investigations of the effects of extrusion ratio on mechanical properties of AZ91 Mg alloys, made from machining chips, is described. Good properties are reported when the ER exceeded 4.9 in comparison with hit pressed chips. This is attributed to bonding between chips, heavy plastic deformation and structure refinement. With an ER of 44 a strength of 373 MPa was attained. Above this recovery processes reduced strength.
TENSILE PROPERTIES OF INJECTION MOULDED AND SINTERED TITANIUM K Kusaka et al. (Daido Steel Co. Ltd., Nagoya, Japan.) J. Japan Sot. Powder and Powder Metallurgs Vo142, No 3, 1995,383387. (In Japanese.) The sintered properties of MIM Ti, made from blends of a range of powders, were investigated. It is reported that the strength increased with the proportion of hydride/ de-hydride powder in the mix with atomized Ti and is related to the 0 content. Highest elongation was found at BO%H/D-H Ti powder, (0.3%0). Tensile strenmgth of 640 MPa and 21% elongation are reported. MICROSTRUCTURAL DEVELOPMENT OF GAS ATOMIZED AND HOT PRESSED TITANIUM ALLOY R. Xu et al. (Harbin Inst. of Technology, Harbin, China.) Metallurgical Trans. A, Vol 27A, No 8, 1996, 2221-2228. The effects of a range of heat treatments on structure of Ti-25%Al-10%Nb-3°%V-l%Mo, made from gas atomized powders by hot pressing, were investigated. According to process conditions structures observed included p, 8, 8 + w and c1a+ po.
Tungsten A PROGRAM FOR QUANTITATIVE
Nickel EFECT OF NITROGEN AND OXYGEN ON SYNTHESIS OF NICKEL ALUMINIDE BY CRYOMILLING MJ. Luton et al. (State University of New Jersey, USA) Nanostructured Materials, Vol 5, No 6, 1995, 631-642. Milling of Ni-BOat%Al in liquid N was investigated. Opposing mechanisms, formation and decomposition of B2 NiAl are reported, with synthesis of AIN and y AlzOs having a role. Effects of annealing are considered. AlN and ~AlzOs are shown to impede grain growth.
Titanium FORMATION AND HARDENING EFFECTS IN NANOCRYSTALLINE TITANIUM-NITROGEN ALLOYS T.D. Chen, C.C. Koch. (North Carolina State University, USA) Nanostmctured Materials, Vol 5, No 6, 1995, 615-629. It is reported that mechanical alloying in a protective atmosphere had been used to prepare nanocrystalline ‘f-N powders. The powders were characterized for relationships between solute content, grain size and microhardness. Relationship between TiN and ‘I-N solid solution was discussed. Strong solid solution hardening was detected.
X-RAY DIFFRACTION ANALYSIS OF LOW CRYSTALLINITY
TUNGSTEN
B. Ziemer, HJ. Lunk. (Humboldt University, Berlin, Germany.) Int. J. Relkactoq Metals and Hard Materials, Vol 14, No 4,1996,279287. Quantitative X-ray analysis of low crystallinity intermediate products found in the manufacture of non-sag W was investigated. Sample preparation and computing methods are described. Application of a computer program, QUADIF, written in PASCAL for MS Windows, is demonstrated for different W oxides.
Ceramic materials STUDY OF SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS OF p SILICON CARBIDE MATERIALS
W. Tiejun, W. Shenghong. (Central Iron and Steel Research Inst., Beijing, China.) PM Technology, Vol 14, No 2, 1996, 92-95. (In Chinese.) Synthesis of PSiC from Si and C powders was investigated theoretically and by a range of techniques. The particle size of the powder was analysed. It is reported that a more cost effective and technically improved method of synthesizing Sic had been developed.
MPR February 1997 35
CARBON CONTROL OF INJECTION MOULDED STRUCTURAL ALLOY STEEL M. Tomita. (Industrial Research Inst. of Kanagawa Prefecture, Yokohama, Japan.) J.Japan Sot. Powder and Powder Metallurgv, Vol 42, No 3, 1995, 402-407. (In
Japanese.) Investigations of control of C content in MIM steels are described. During sintering C was controlled by composition and flow rate of CHI-H atmospheres, sintering time and temperature.
Magnesium EXTRUSION RATIO AND MECHANICAL PROPERTIES OF EXTRUDED MACHINED MAGNESIUM ALLOY CHIPS K. Higashi et al. (University of Osaka prefecture, Sakai, Japan.) J. Japan Sot. Powder and Powder Metallurgy, Vol 42, No 3, 1995, 373-377. (In Japanese.) Investigations of the effects of extrusion ratio on mechanical properties of AZ91 Mg alloys, made from machining chips, is described. Good properties are reported when the ER exceeded 4.9 in comparison with hit pressed chips. This is attributed to bonding between chips, heavy plastic deformation and structure refinement. With an ER of 44 a strength of 373 MPa was attained. Above this recovery processes reduced strength.
TENSILE PROPERTIES OF INJECTION MOULDED AND SINTERED TITANIUM K Kusaka et al. (Daido Steel Co. Ltd., Nagoya, Japan.) J. Japan Sot. Powder and Powder Metallurgs Vo142, No 3, 1995,383387. (In Japanese.) The sintered properties of MIM Ti, made from blends of a range of powders, were investigated. It is reported that the strength increased with the proportion of hydride/ de-hydride powder in the mix with atomized Ti and is related to the 0 content. Highest elongation was found at BO%H/D-H Ti powder, (0.3%0). Tensile strenmgth of 640 MPa and 21% elongation are reported. MICROSTRUCTURAL DEVELOPMENT OF GAS ATOMIZED AND HOT PRESSED TITANIUM ALLOY R. Xu et al. (Harbin Inst. of Technology, Harbin, China.) Metallurgical Trans. A, Vol 27A, No 8, 1996, 2221-2228. The effects of a range of heat treatments on structure of Ti-25%Al-10%Nb-3°%V-l%Mo, made from gas atomized powders by hot pressing, were investigated. According to process conditions structures observed included p, 8, 8 + w and c1a+ po.
Tungsten A PROGRAM FOR QUANTITATIVE
Nickel EFECT OF NITROGEN AND OXYGEN ON SYNTHESIS OF NICKEL ALUMINIDE BY CRYOMILLING MJ. Luton et al. (State University of New Jersey, USA) Nanostructured Materials, Vol 5, No 6, 1995, 631-642. Milling of Ni-BOat%Al in liquid N was investigated. Opposing mechanisms, formation and decomposition of B2 NiAl are reported, with synthesis of AIN and y AlzOs having a role. Effects of annealing are considered. AlN and ~AlzOs are shown to impede grain growth.
Titanium FORMATION AND HARDENING EFFECTS IN NANOCRYSTALLINE TITANIUM-NITROGEN ALLOYS T.D. Chen, C.C. Koch. (North Carolina State University, USA) Nanostmctured Materials, Vol 5, No 6, 1995, 615-629. It is reported that mechanical alloying in a protective atmosphere had been used to prepare nanocrystalline ‘f-N powders. The powders were characterized for relationships between solute content, grain size and microhardness. Relationship between TiN and ‘I-N solid solution was discussed. Strong solid solution hardening was detected.
X-RAY DIFFRACTION ANALYSIS OF LOW CRYSTALLINITY
TUNGSTEN
B. Ziemer, HJ. Lunk. (Humboldt University, Berlin, Germany.) Int. J. Relkactoq Metals and Hard Materials, Vol 14, No 4,1996,279287. Quantitative X-ray analysis of low crystallinity intermediate products found in the manufacture of non-sag W was investigated. Sample preparation and computing methods are described. Application of a computer program, QUADIF, written in PASCAL for MS Windows, is demonstrated for different W oxides.
Ceramic materials STUDY OF SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS OF p SILICON CARBIDE MATERIALS
W. Tiejun, W. Shenghong. (Central Iron and Steel Research Inst., Beijing, China.) PM Technology, Vol 14, No 2, 1996, 92-95. (In Chinese.) Synthesis of PSiC from Si and C powders was investigated theoretically and by a range of techniques. The particle size of the powder was analysed. It is reported that a more cost effective and technically improved method of synthesizing Sic had been developed.
MPR February 1997 35