Composition dependence of open-volume relaxation in Zr-Cu-Al bulk amorphous alloys studied by positron annihilation
Composition dependence of open-volume relaxation in Zr-Cu-Al bulk amorphous alloys studied by positron annihilation
复制标题
DOI：
10.1016/j.jallcom.2016.12.416
复制
发表时间：
2017-06
影响因子：
6.2
通讯作者：
F. Hori;A. Ishii;T. Ishiyama;A. Iwase;Y. Yokoyama;T. Konno
中科院分区：
文献类型：
--
作者：
F. Hori;A. Ishii;T. Ishiyama;A. Iwase;Y. Yokoyama;T. Konno
采用正电子湮没技术（正电子寿命和符合多普勒展宽（CDB））、x射线衍射（XRD）、差示扫描量热法（DSC）和体积密度测量研究了Zr-Cu-Al三元体非晶合金（过共晶：zr45cu45al10和Zr49Cu41Al10，共晶：Zr50Cu40Al10，次共晶：zr55cu35al10和Zr60Cu30Al10）在玻璃化转变温度（Tg）下等温退火过程中的结构弛豫行为。退火使正电子的寿命由于弛豫而减小。而共晶合金的正电子寿命在退火10 k后下降最大。并证实了亚共晶和过共晶合金正电子变化的成分依赖性不同。特别是过共晶合金的开体积很难通过退火来改变。我们发现正电子寿命Δτ随Zr浓度的变化趋势与堆积密度的变化不一定一致。另一方面，退火过程中的正电子寿命服从拉伸的指数弛豫函数。Zr浓度不同，表明开体积弛豫分布活化能的松弛参数β也不同。
Structural relaxation behavior of various composition for Zr-Cu-Al ternary bulk amorphous alloys (hyper-eutectic: Zr45Cu45Al10and Zr49Cu41Al10, eutectic: Zr50Cu40Al10, hypo-eutectic: Zr55Cu35Al10and Zr60Cu30Al10) during isothermal annealing below glass transition temperature (Tg) has been investigated by positron annihilation techniques (positron lifetime and coincidence Doppler broadening (CDB)), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and bulk density measurements. The annealing makes the positron lifetime decrease owing to the relaxation. However, maximum decreasing of positron lifetime after 10 ks annealing for eutectic alloy was observed. And different composition dependence of positron change between hypo- and hyper-eutectic alloys was confirmed. Especially, open-volume in hyper-eutectic alloys is hard to change by the annealing. We found that the trend of positron lifetime change Δτ with Zr concentration is not necessarily correlated with the change in bulk density consistently. On the other hand, the positron lifetime during annealing obeys a stretched exponential relaxation function. Also we found the relaxation parameterβ, which indicates the distribution activation energy for open-volume relaxation, varies in Zr concentration.