Characterization of the density fluctuations existing in amorphous alloys

我们研究了各种非晶态合金(a-合金)在电脉冲作用下的晶化过程，杨氏模数与ε_t和f，E(ε_t，f)的关系，以及电流对E(ε_t，f)的影响，其中ε_t是应变幅度，f是频率。在电脉冲过程中，当It；d0，c&gt；高于阈值It；lt；d0，c&gt；且It；d0，c&gt；是τ的函数时，电脉冲是通过放电电容器进行的，初始电流密度It；d0&gt；数量级为10^9A/m^2，衰减时间τ在2-0.1ms之间。电脉冲过程中的最大温升低于结构松弛温度，表明热搅拌不是电脉冲下结晶的主要原因。此外，在电脉冲作用下，可以发现新的晶相。结果表明，电脉冲激发了许多原子的共振集体运动，同时也改变了相的热力学自由能。E(10…作为f的函数测量的More^lt；-6，f)通常在10^1~10^4赫兹的频率范围内从E_0减小，局部极小值在10^2赫兹和10^3~10^4赫兹之间，其中E_0是在准静态拉伸试验中发现的杨氏模数。E(ε_t，10^2 Hz)随ε_t的增大而增大，在ε_t为2~4×10~(-3)~(-3)时达到饱和。我们推测在非晶态合金中存在密度涨落，其中高密度区经历共振集体运动产生共振滞弹性应变，并且高密度区在尺寸上呈现出分布。电流引起的E(10^&lt；-6&gt；，10^2 HZ)在各种a合金中是很常见的，这表明电流由于电迁移力的集中而引起内应力。通过比较电流引起的(10^~(-6)，10^2赫兹)和E(ε^t，10^2赫兹)随ε_t的增加，我们估算了电迁移力浓度的有效电荷数Z^*。对于各种a合金，Z^*值是10^5的数量级，这表明在10^2赫兹激发的集体运动所伴随的原子数目在10^3到10^4之间。本工作还表明，电脉冲后可以发现一种新的材料，这种特征的弹性性质可能应用于机电器件。较少

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