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hslining木虫 (正式写手)
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JMR最近文章--自由体积对应变软化的影响
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作者首先采用界面连接技术，分别对cast及relax样品打界面显微压痕。然后采用纳米压痕技术，研究显微压痕后变形区的压痕硬度。发现无论是cast样，还是relax样，变形软化引起的硬度下降幅度均为12-15%。从而证明样品初始自由体积含量并不影响应变软化，尽管退火后的样品硬度升高，P-h曲线变得更加光滑。 Role of free volume in strain softening of as-cast and annealed bulk metallic glass Author(s): Byung-Gil Yoo, Kyoung-Won Park, Jae-Chul Lee, U. Ramamurty, Jae-il Jang Plasticity in amorphous alloys is associated with strain softening, induced by the creation of additional free volume during deformation. In this paper, the role of free volume, which was a priori in the material, on work softening was investigated. For this, an as-cast Zr-based bulk metallic glass (BMG) was systematically annealed below its glass transition temperature, so as to reduce the free volume content. The bonded-interface indentation technique is used to generate extensively deformed and well defined plastic zones. Nanoindentation was utilized to estimate the hardness of the deformed as well as undeformed regions. The results show that the structural relaxation annealing enhances the hardness and that both the subsurface shear band number density and the plastic zone size decrease with annealing time. The serrations in the nanoindentation load-displacement curves become smoother with structural relaxation. Regardless of the annealing condition, the nanohardness of the deformed regions is ~12–15% lower, implying that the prior free volume only changes the yield stress (or hardness) but not the relative flow stress (or the extent of strain softening). Statistical distributions of the nanohardness obtained from deformed and undeformed regions have no overlap, suggesting that shear band number density has no influence on the plastic characteristics of the deformed region. 上述结果对Li等在2008 J. Phys. D: Appl. Phys. 41,155415中的发现（cast与relax样具有相似的压痕尺寸效应），似乎提供了一个更加合理的解释。 [ Last edited by hslining on 2009-9-10 at 14:07 ] |
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hslining
木虫 (正式写手)
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3楼2009-06-02 15:24:46
2楼2009-06-02 15:07:23