1999 Fiscal Year Final Research Report Summary
The Mechanism of Plastic Deformation in Quasicrystals
| Project/Area Number |
10450236
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Science University of Tokyo |
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Principal Investigator |
TAKEUCHI Shin Science University of Tokyo, Dept.Mater.Sci.& Tech., Professor, 基礎工学部, 教授 (60013512)
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| Co-Investigator(Kenkyū-buntansha) |
EDAGAWA Keiichi University of Tokyo, Inst.Industrial Science, Assoc.Professor, 基礎工学部, 助教授 (20223654)
SUZUKI Takayoshi University of Tokyo, Inst.Industrial Science, Professor, 生産技術研究所, 教授 (70013208)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Quasicrystal / plastic deformation / dislocation / phason strain / Peierls mechanism |
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| Research Abstract |
The purpose of the present research is to ellucidate the microscopic mechanism of plastic deformation of quasicrystals by analyzing the elementary process of dislocatin glide. We deformed single quasicrystals at high temperatures, and performed thermal-activation analysis of plastic deformation and electron microscopy observation. The main results for Al-(Cu, Ni)-Co decagonal quasicrystals are : 【encircled1】the yield strength depends sensitively on the quality of the sample : those of high quality samples are twice as high as those of low quality samples ; 【encircled2】the yield stress for slip in periodic direction is not much different from that in quasiperiodic direction, 【encircled3】dislocations introduced are straight. The main results for Al-Pd-Mn icosahedral quasicrystals are : 【encircled1】the dragging stresses for the dislocation glide due to phason defect production, which have been estimated from the stress-relaxation tests, are in the range of 20 to 50% of the flow stress, 【encircled2】true-stress vs true-strain analysis shows that after exhibiting maximum the true stress continuously decreases towards minimum at around the true strain of 0.5 and then changes to gradual hardening at higher strain, 【encircled3】activation analysis showed that the maximum flow stress and minimum flow stress are governed by different activation enthalpies. Based on these results, we propose the following microscopic deformation mechanism : 【encircled1】glide resistance to dislocation glide consists of athermal component due to phason strain production and thermal component due to Peierls potential, 【encircled2】due to the quasiperiodicity of the lattice the kink-pair formation enthalpy is not unique, 【encircled3】in the perfect quasilattice the dislocation glide velocity is governed by the large kink-pair formation enthalpy while in phason-defected quasilattice it is governed by small kink-pair formation enthalpy since kink migration is much easier than the kink-pair formation.
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