1991 Fiscal Year Final Research Report Summary
HIGH TEMPERATURE DEFORMATION OF POLYCRYSTALS WITH FEW EQUIVALENT SLIP SYSTEMS
| Project/Area Number |
01460218
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
OIKAWA Hiroshi TOHOKU UNIV.,FAC.OF ENG.,PROFESSOR, 工学部, 教授 (30005243)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Hiroyuki TOHOKU UNIV.,FAC.OF ENG.,INSTRUCTOR, 工学部, 助手 (10225998)
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| Project Period (FY) |
1989 – 1991
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| Keywords | High Temperature Deformation / Creep / Solid Solution / Cottrell Effect / Magnesium / Aluminum / Simulation / Plastic Anisotropy |
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| Research Abstract |
High temperature plastic deformation behavior of magnesium-aluminum solid solutions has been investigated. The materials are a model whose primary slip systems are fewer than five,i.e. the least number of independent slip systems required for plastic deformation of polycrystals. There are two temperature-ranges where the temperature dependence of strain rate is different. The stress dependence of strain rate is also different in each temperature range. Gradual change between two stress-ranges, where the stress dependence of strain rate is different, was observed at lower temperature range. The differences of concentration dependence are also observed at each stress and temperature range.
TEM observations of the dislocation structures after deformation show that the burgers vector of dislocations differ at each temperature range. The a and a+c dislocations are mainly observed at lower and higher temperature range, respectively. The change in shape of dislocations at lower temperature ran
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ge suggests that the break-away stresses of dislocations from solute atmosphere on different slip planes are different from each other. The transition conditions of high temperature deformation behavior, obtained by experiments, are proved quantitatively by means of the numerical simulations of dragging force and solute distribution based on the model including crystalline structure, slip plane and anisotropy of diffusion. The effects of stressing direction on the transition of creep behavior of magnesium-aluminum-alloys, which have strong texture, are also determined experimentally. It is concluded that the gradual change between two stress-ranges at lower temperature is caused by the gradual break-away of dislocations from solute atmosphere.
As a conclusion, the aspects of macroscopic deformation of polycrystalline solid solutions, which have few numbers of equivalent primary slip systems, are different from that of cubic solid solutions. It is caused by the difference of interactions between solute atoms and dislocations on different slip planes. Less
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