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Excitation of collective motion of many atoms in amorphous alloys : Realization and application

非晶合金中多原子集体运动的激发：实现与应用

基本信息

批准号：
14350338
负责人：
MIZUBAYASHI Hiroshi
金额：
$ 11.01万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The resonant-electropulsing-induced low temperature crystallization (r-e-LTC) of amorphous (a-) Cu_<50>Ti_<50>, a-Cu_<50>Zr_<50>, a-Pd_<80>Si_<20> and a-Zr_<60>Cu_<30>Al_<10> was investigated by means of electropulsing at RT and that in liquid nitrogen (LN2). Resonant (r-) electropulsing was made by means of discharge of a condenser which is characterized by the initial current density, i_<a0>, and the decay time, τ, where the frequency of the principal Fourier constitutional component of r-electropulsing is 1/2πτ. The range of i_<a0> was between 10^8 A/m^2 and 10^<10> A/m^2 and that of τ was between 0.05 ms and 20. ms. For all the a-alloys, the r-e-LTC took place during single r-electropulsing with i_<a0> higher than the threshold current density, i_<a0>,c, where i_<a0>,c was a function of τ. The maximum specimen temperature during the r-e-LTC was, e.g., 400 K for r-electropulsing at RT and 200K for r-electropulsing in LN_2, respectively, indicating that the r-e-LTC is associated with … More an athermal process. The dependence of i_<a0>,c, on τ found for r-electropulsing in LN_2 was essentially the same to that observed for r-electropulsing at RT, indicating that the density fluctuation associated with the resonant collective motion responsible for the r-e-LTC was that frozen at the glass transition temperature. The transmission electron microscopy observation revealed that crystallites formed by the r-e-LTC showed crystallographic alignment with each other and the size of the crystallites was, e.g., the order of ten nm. A possible mechanism for the aligned crystallization is a direct transformation of the relatively high density region (RHDR) to a crystalline phase, where cooperative motions of many atoms such as an optical phonon like motions of atoms should take place. In other words, the amplitude of displacement during the resonant collective motion should be a function of atomic species and the compositional fluctuation in this region should be inside in a permissible range for the crystalline phase formed too. In order to realize such cooperative motion of RHDR, a capacity for the anelastic strain in the relatively low density regions should be considerably large. The anelasticity study of nanocrystalline metals supported this point of view. The present work demonstrated the realization and application of excitation of collective motion of many atoms in amorphous alloys. Less

通过室温和液氮中的电脉冲研究了非晶（a-）Cu_<50>Ti_<50>、a-Cu_<50>Zr_<50>、a-Pd_<80>Si_<20>和a-Zr_<60>Cu_<30>Al_<10>的谐振电脉冲诱导低温结晶（r-e-LTC）（液氮2）。谐振(r-)电脉冲是通过电容器放电来实现的，其特征在于初始电流密度i_<a0>和衰减时间τ，其中r-电脉冲的主要傅里叶构成分量的频率为1/2πτ。 i_<a0>的范围在10^8 A/m^2到10^<10> A/m^2之间，τ的范围在0.05 ms到20. ms之间。对于所有 a 合金，r-e-LTC 发生在单次 r 电脉冲期间，i_<a0> 高于阈值电流密度 i_<a0>,c，其中 i_<a0>,c 是 τ 的函数。例如，r-e-LTC 期间的最大样品温度分别为 RT 下 r-电脉冲的 400 K 和 LN_2 中 r-电脉冲的 200K，这表明 r-e-LTC 与无热过程相关。 LN_2 中 r 电脉冲的 i_<a0>,c 对 τ 的依赖关系与在 RT 下观察到的 r 电脉冲基本相同，表明与负责 r-e-LTC 的共振集体运动相关的密度波动在玻璃化转变温度下被冻结。透射电子显微镜观察表明，由r-e-LTC形成的微晶显示出彼此的晶体排列，并且微晶的尺寸为例如10nm的量级。排列结晶的一种可能机制是相对高密度区域（RHDR）直接转变为结晶相，其中应该发生许多原子的协作运动，例如原子的光学声子运动。换句话说，集体共振运动期间的位移幅度应该是原子种类的函数，并且该区域的成分波动也应该在形成的晶相的允许范围内。为了实现RHDR的这种协作运动，相对低密度区域中的滞弹性应变的容量应该相当大。纳米晶金属的迟弹性研究支持了这一观点。目前的工作展示了非晶合金中许多原子集体运动激发的实现和应用。较少的