| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1987: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
PROPERTIES OF MATERIALS CAN BE MODIFIED BY A CONTROL OF THE MICROSTRUCTURE AS WELL AS AN APPROPRIATE SELECTION OF THE COMPONENTS. REFINEMENT OF THE MATRIX GRAIN SIZE USUALLY RESULTS IN THE IMPROVEMENT ON ITS MECHANICAL, MAGNETIC AND OTHER PROPERTIES. THERE ARE WELL KNOWN MERHODS FOR THE REFINEMENT OF THE MATRIX GRAIN SIZE SUCH AS STRAIN-ANNEALING, RAPID SOLIDIFICATION AND ANNEALING OF AMORPHOUS MATERIALS. BESIDES THESE, THERE IS A SINTERING METHOD OF ULTRAFINE POWDERS. A BASIC STUDY HAS BEEN CONDUCTED BY THE PRESENT AUTHOR TO FIND OUT THE FABRICATING CONDITIONS FOR OBTAINING FINE GRAINED METALS AND ALLOYS BY THE SINTERING OF ULTRAFINE METAL POWDERS. IN THIS STUDY, THE LOWEST SINTERING TEMPERATURE (T^c_ FOR COMPLETE DNESIFICATION OF Fe, Co, Ni AND Cu ULTRAFINE METAL POWDERS (AVERAGE PARTICLE SIZE, 0.02-0.05 m; OXYGEN CONTENT, 6-15 mass%) WAS INVESTIGATED UNDER THE PRESSURE UP TO 400 MPa IN H_2 GAS, AND THE CRYSTAL GRAIN SIZE AND HARDNESS OF THE DENSE SINTERED COMPACTS WERE INVESTIGATED. IT WAS FOUND THAT T^c_ UNDER 400 MPa FOR Fe, Co, Ni AND Cu POWDERS WERE ABOUT 620, 670, 470 AND 470K, RESPECTIVELY, WHICH WERE 350-600K LOWER THAN THOSE UNDER O MPa. THE MINIMUM AVERAGE CRYSTAL GRAIN SIZES OF Fe, Co, Ni AND Cu DENSE SINTERED COMPACTS WERE AS SMALL AS ABOUT 0.08, 0.21, 0.12 AND 0.40 m, RESPECTIVELY. THE HIGHEST VALUES OF HARDNESS (Hv) OF THE SINTERED COMPACTS WERE ABOUT 600, 550, 550 AND 130, WHICH WERE EXTREMELY HIGH COMPARED WITH USUAL COARSE-GRAINED METALS. THE HALL-PETCH LINEAR RELATIONSHIP BETWEEN Hv AND THE INVERSE OF SQUARE ROOT OF GRAIN SIZE HOLD FOR EACH ELEMENT.
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