冷軋對鋯基塊狀非晶質合金之機械性質與顯微組織的影響

Effect of cold rolling on mechanical properties and microstructures of Zr-based bulk amorphous alloys

陳秉棋(Ping-Chi Chen)

指導教授 ： 謝佩汝

義守大學/理工學院/材料科學與工程學系/碩士(2015年)

https://doi.org/10.6343/ISU.2015.00123

摘要

由於非晶質合金其擁有高強度，但缺乏延展性與塑形能力等基礎性質上的缺陷，亦發展出多樣的性質提升方法。例如，添加微量元素或熱處理使其晶體內部產生相變化、相析出、相分離等等，亦或是利用外部加工的方式，如軋延與摩擦等方式，對材料施加外加應力使晶體內部產生部分結晶，來增加材料本身之機械性質。
依據先前之研究，Zr53Cu30Ni9Al8非晶質合金具有較好的玻璃形成能力(Glass Forming Ability)，其 γm值約0.752並擁有寬廣的過冷液相區(ΔTx)約80K。而本實驗針對Zr53Cu30Ni9Al8非晶質合金板材以冷軋方式探討其機械性質影響效果。研究指出冷軋對非晶質合金在室溫下的塑性變形能力則有顯著的改善，其壓縮破裂強度與壓縮塑性應變量從基材試片之2032MPa和4.6％增加至冷軋試片的2266MPa和20.1％。經由冷軋過後的非晶質合金板材之破裂強度與塑性能力的大幅度提升可以歸咎於冷軋時所導入之雙向預剪切帶，其預剪切帶的導入可有效阻礙壓縮時所產生主剪切帶的行進，並產生多重剪切帶，進而達到加工硬化之效果，因此該非晶質合金展現出較佳之機械性質改善效果。

關鍵字

非晶質合金 ； 冷軋 ； 加工能力 ； 機械性質

並列摘要

Bulk metallic glasses (BMGs) have attracted attention due to their high strength and outstanding thermal properties. However, the low workability at room temperature of BMGs limited their applications. Different methods have been developed to solve the problem of poor room temperature ductility. For example, the methods of the minor addition of element, thermal treatments, and hot rolling are used to improve the mechanical properties of BMGs by the formation of phase transformation. It has been reported that the method of the plasticity improvement by rolling process is a possible way to increase the room temperature plasticity. Zr53Cu30Ni9Al8 bulk metallic glasses has high glass forming ability (γm is about 0.752) and wide supercooled liquid region (ΔTx is about 80K) are the base alloys in this study. Room temperature rolling process was used to study the mechanical properties and the workability of Zr53Cu30Ni9Al8 bulk metallic glasses with various rolling strain.
The results revealed that the brittle Zr53Cu30Ni9Al8 BMGs was plastically deformed at room temperature by the introducing of rolling process before the compression test. Room temperature compressive fracture strength and strain increased form 2032MPa and 4.6% (the base alloy) to 2266MPa and 20.1% (cold-rolled specimen with 5% rolling strain). The great enhancement of plastic strain can be attributed to the formation of pre-introduced shear bands (called pre-shear bands and secondary pre-shear bands) after the pre-rolling process. Dense dispersion of pre-introduced shear bands impeded the propagation of primary shear bands during the compression test and made the formation of multiple shear bands, indicating a typical ductile fracture behavior and the improved of plasticity of alloys with increasing rolling strains (up to 5%).

並列關鍵字

bulk metallic glasses ； cold rolling ； workability ； mechanical properties

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