Rejuvenation and plasticization of metallic glass by deep cryogenic cycling treatment
Rejuvenation and plasticization of metallic glass by deep cryogenic cycling treatment
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DOI：
10.1016/j.intermet.2017.11.015
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发表时间：
2018-02-01
期刊：
影响因子：
4.4
通讯作者：
Saida, Junji
中科院分区：
文献类型：
--
作者：
Guo, Wei;Yamada, Rui;Saida, Junji
Zr基金属玻璃经过30个循环的低温至室温循环处理。尽管处理后的结构保持其整体无定形结构，但与未处理的铸态样品相比，处理后的样品表现出再生行为，包括更高的弛豫焓和更低的密度。由于循环过程中产生的内应力，原子级核-壳异质微观结构被认为有助于再生。内应力引起的核心区域的微观变形可能相当于外部应力引起的宏观剪切带变形，这导致了核心区域的演化和过量自由体积的增加。与未处理的样品相比，处理过的样品还表现出更低的硬度和更好的塑性。较低的剪切面形成能和较大的剪切转变区体积和尺寸被认为促进剪切带形成并产生更多的多个剪切带以适应塑性变形。深冷循环处理被认为是使金属玻璃焕发活力并提高机械性能的可行且非破坏性的方法。
A Zr-based metallic glass is treated by a cryogenic-to room-temperature cycling treatment with 30 cycles. Though the structure after treatment maintains its monolithic amorphous structure, the treated sample exhibits a rejuvenation behavior contrasting with that of an untreated as-cast sample, including a higher relaxation enthalpy and a lower density. The atomic level core-shell heterogeneous microstructure is considered to contribute to the rejuvenation because of the internal stress generated during cycling. The microscopic deformation of the core region by the internal stress may be equivalent to the macroscopic shear band deformation by the external stress, which induces the evolution of the core region and an increased amount of excess free volume. The treated sample also exhibits lower hardness and better plasticity than the untreated sample. A lower shear plane formation energy and larger shear transformation zone volume and size are considered to promote shear band formation and to generate more multiple shear bands to accommodate the plastic deformation. The deep cryogenic cycling treatment is believed to be a feasible and non-destructive way to rejuvenate metallic glass and improve the mechanical properties.