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

采用室温电脉冲和液氮中电脉冲的方法，研究了（a-）Cu_<50>Ti_<50>，a-Cu_<50>Zr_<50>，a-Pd_<80>Si_<20>和a-Zr_<60>Cu_<30>Al_的共振电脉冲诱导低温晶化（r-e-LTC）<10>。共振（r-）电脉冲是通过电容器的放电产生的，电容器的特征在于初始电流密度i<a0>和衰减时间τ，其中r-电脉冲的主傅立叶组成分量的频率为1/2πτ。i_的范围<a0>在10^8 A/m^2和10^<10>A/m^2之间，τ的范围在0.05 ms和20 ms之间。对于所有的α-合金，r-e-LTC都发生在i_<a0>高于阈值电流密度i_<a0>，c（i_，<a0>c是τ的函数）的单次r-电脉冲过程中。r-e-LTC期间的最高样本温度为，例如，在RT和LN_2中分别为400 K和200 K，表明r-e-LTC与 ...更多信息 无热过程在<a0>液氮_2中发现的r-电脉冲的i_c对τ的依赖关系与在室温下观察到的r-电脉冲的i_c对τ的依赖关系基本相同，表明与共振集体运动有关的密度涨落是r-e-LTC在玻璃化转变温度下冻结的密度涨落。透射电子显微镜观察显示，由r-e-LTC形成的微晶显示出彼此的晶体学对准，并且微晶的尺寸为，例如，10 nm的量级。取向结晶的一种可能的机制是相对高密度区域（RHDR）到结晶相的直接转变，其中许多原子的协同运动，诸如原子的光学声子样运动应该发生。换句话说，在共振集体运动期间的位移幅度应该是原子种类的函数，并且该区域中的组成波动也应该在所形成的结晶相的允许范围内。为了实现RHDR的这种协同运动，在相对低密度区域中的滞弹性应变的能力应该相当大。纳米晶金属的滞弹性研究支持了这一观点。本工作论证了非晶态合金中多原子集体运动激发的实现和应用。少

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