Characterization of the density fluctuations existing in amorphous alloys

对于各种非晶合金（a-合金），我们研究了电脉冲作用下的结晶，Young's模量ε_t和f的函数，E(ε_t, f)，以及电流对E（ε_t, f）的影响，其中ε_t为应变幅值，f为频率。当I_<d0>高于阈值I_<d0,c>和I_<d0,c>是τ的函数时，电脉冲进行结晶，其中电脉冲是通过电容器放电进行的，初始电流密度I_<d0>为10^9 a /m^2，衰减时间τ在2 - 0.1 ms之间。在电脉冲作用下，温度的最大升高小于结构弛豫温度，说明电脉冲作用下的结晶不是热搅拌引起的。此外，电脉冲后可以发现新的晶相。认为电脉冲激发了许多原子的共振集体运动，也改变了相的热力学自由能。作为f的函数测量的E（10…More ^<-6>,f）通常显示在10^1 Hz到10^4 Hz的频率范围内从E_0减小，在10^2 Hz附近和10^3到10^4 Hz之间的局部最小值，其中E_0是准静态拉伸试验中发现的杨氏模量。ε (ε_t, 10^2 Hz)随ε_t的增大而增大，最终在ε_t为2 ~ 4 × lO^<-3>时达到饱和。我们推测在非晶合金中存在密度波动，其中高密度区经历共振集体运动产生共振非弹性应变，并且高密度区在尺寸上呈分布。由于电流导致的E（10^<-6>,10^2 Hz）的增加通常在各种a合金中观察到，这表明电流由于电迁移力的集中而引起内应力。通过比较由电流引起的（10^<-6>,10^2 Hz）的增加和随着ε_t的增加而增加的E(ε^t, 10^2 Hz)，我们估计了测量电迁移力浓度的有效电荷数Z^*。在各种A合金中发现的Z^*的数量级为10^5，这表明与10^2 Hz激发的集体运动相关的原子数在10^3到10^4之间。本工作还表明，电脉冲后可以找到一种新的材料，其特有的弹性性能可以应用于机电器件。少

For various amorphous alloys (a-alloys), we investigated the crystallization under electropulsing, the Young's modulus as a function of ε_t and f, E(ε_t, f), and an effect of electric current on E(ε_t, f), where ε_t is a strain amplitude and f is a frequency. The crystallization proceeds during electropulsing when I_<d0> is higher than the threshold I_<d0,c> and I_<d0,c> is a function of τ, where electropulsing was made by means of discharge of a condenser with the initial current density, I_<d0>, of the order of 10^9 A/m^2 and the decay time, τ, between 2 - 0.1 ms. The maximum increase in temperature during electropulsing is lower than the structural relaxation temperature, suggesting that thermal agitation is not responsible for the crystallization under electropulsing. Further, a new crystalline phase can be found after electropulsing. It is suggested that electropulsing excites a resonant collective motion of many atoms and modifies the thermodynamic free energy of phases too. E(10 … More ^<-6>,f) measured as a function of f commonly shows a decrease from E_0 in a frequency range of 10^1 Hz to 10^4 Hz, and local minimums near 10^2 Hz and between 10^3 and 10^4 Hz, where E_0 is the Young's modulus found in quasi-static tensile tests. E(ε_t, 10^2 Hz) increases with increasing ε_t and finally saturates at ε_t of 2 to 4 x lO^<-3>. We surmise that density fluctuations exist in amorphous alloys, where a high density region undergoes a resonant collective motion producing a resonant anelastic strain, and the high density regions show a distribution in dimension. An increase in E(10^<-6>,10^2 Hz ) due to an electric current is commonly observed for various a-alloys, suggesting that an electric current induces an internal stress due to an electromigration force concentration. We estimate the effective charge number, Z^* measuring the electromigration force concentration after a comparison between an increase in (10^<-6>,10^2 Hz ) due to an electric current and an increase in E(ε^t, 10^2 Hz) with increasing ε_t. A value of Z^* found is the order of 10^5 for various a-alloys, suggesting that the number of atoms associated with the collective motions excited at 10^2 Hz is between 10^3 and 10^4. The present work also suggests that a new materials can be found after electropulsing and the characteristic elastic properties may be applied to an electro mechanical device. Less