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Study of microscopic mechanism of plastic deformation in inorganic materials with non-periodic structure

非周期结构无机材料塑性变形微观机理研究

基本信息

批准号：
12450261
负责人：
TAKEUCHI Shin
金额：
$ 9.22万
依托单位：
Tokyo University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

It has been clarified that quasicrystals and metallic glasses, both having non-translational symmetry structure, can undergo plastic deformation by slip process. The purpose of the research is to elucidate the microscopic slip deformation mechanisms in these materials of non-translational symmetry, by means of experiments over a wide deformation conditions and of computer simulations(1) As a result of high temperature deformation experiments on various quasicrysmtals, the following facts have been clarified:(a) any quasicrystal can be plastically deformed only above 0.75Tm (Tm: melting point), and the yield stress decreases rapidly with increasing temperature, (b) quasicrystals commonly exhibit pronounced work-softening, and (c) the work-softening is concluded to occur as a result of decreasing activation enthalpy. Based on the computer simulation of dislocations in model quasicrystals, the dislocation glide in a quasicrystal is exerted by a resistance due to a phason wall production s … More uperimposed by that due to a quasiperiodic Peierls potential, and its rate is controlled by kink-pair formation at high temperatures. The deformation behavior is well explained by the model where on the phason-free quasicrystal the dislocation mobility is governed by kink-pair formation at large Peierls potentials, while as phason- defect density increases with plastic deformation it is governed by that at small Peierls potentials(2) Deformation experiments of bulk metallic glasses over a wide temperature range have been shown that their yield stresses are almost temperature independent down to near zero Kelvin. In order to elucidate what kink of dislocation glide governs the slip in metallic glasses, computer simulation studies have been performed. A realistic model binary metallic glass has been constructed by means of the inverse Monte Carlo method and by use of interatomic potentials for a Ni-Nb alloy. It has been classified that dislocation is stable only when its Burgers vector is larger than about 3A. The slip deformation model for the dislocation of the minimum Burgers vector is tentatively assumed, but the final deformation model has not been established yet, since the simulation for the dislocation glide has not been completed Less

人们已经阐明，准晶体和金属玻璃都具有非平移对称结构，可以通过滑移过程发生塑性变形。本研究的目的是通过广泛变形条件下的实验和计算机模拟来阐明这些非平移对称材料的微观滑移变形机制（1）通过对各种准晶进行高温变形实验，澄清了以下事实：（a）任何准晶只能在0.75Tm（Tm：熔点），屈服应力随着温度升高而迅速降低，（b）准晶通常表现出明显的加工软化，（c）加工软化被认为是由于活化焓降低而发生的。基于模型准晶体中位错的计算机模拟，准晶体中的位错滑移是由相子壁产生的阻力施加的，再加上准周期 Peierls 势的阻力，其速率由高温下扭结对的形成控制。该模型很好地解释了变形行为，其中在无相子准晶上，位错迁移率受大 Peierls 势下扭结对形成的影响，而当相子缺陷密度随塑性变形增加时，它受小 Peierls 势下的影响 (2) 大块金属玻璃在较宽温度范围内的变形实验表明，它们的屈服应力几乎与温度无关，低至接近零开尔文。为了阐明位错滑移的扭结控制金属玻璃中的滑移，已经进行了计算机模拟研究。通过逆蒙特卡罗方法并利用 Ni-Nb 合金的原子间势构建了真实的二元金属玻璃模型。据分类，只有当位错的 Burgers 矢量大于约 3A 时，位错才是稳定的。暂时假设了最小Burgers矢量位错的滑移变形模型，但由于位错滑移的模拟尚未完成，最终的变形模型尚未建立。