Co-Fe-Ni-Ti快速凝固微結構及性質之影響

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Title:	Co-Fe-Ni-Ti快速凝固微結構及性質之影響 A study on the microstructures and characteristics of casting and rapidly-solidified Co-Fe-Ni-Ti alloys
Authors:	周志儒
Contributors:	材料科學與奈米科技研究所
Keywords:	多元合金高熵合金 alloys
Date:	2006
Issue Date:	2014-06-24 14:37:20 (UTC+8)
Abstract:	本論文是以清華大學材料系葉均蔚教授所提出等莫耳多元合金為概念，選取Co、Fe、Ni及Ti等四種元素配製等莫耳比之合金。利用真空電弧熔煉爐熔製成等莫耳合金為主要研究材料，進行微結構觀察、熱性質分析、硬度量測等分析。部份試片再使用急冷旋鑄機製造急冷薄帶，以觀察急速凝固對此合金之影響。實驗結果顯示，因為合金的原子尺寸的差異大所造成的晶格應變與固溶硬化等效應，使等莫耳多元合金比傳統合金有較高的硬度值，同時在原始鑄件的狀態下，其非等莫耳Co31.6Fe27.4Ni21.2Ti19.8合金高於等莫耳CoFeNiTi合金。兩種合金的耐氧化性質並不佳。經由快速凝固的方法將合金噴製成急冷薄帶後，再藉由TEM觀察其結構，可以觀察到合金內具有奈米晶存在，晶粒大小約為數個nm至數十nm。 This paper was based on the Prof. Yeh’s concept of equal mole multi-element alloys and selected four elements of Co, Fe, Ni and Ti to prepare the master alloys. Two compositions of CoFeNiTi and Co31.6Fe27.4Ni21.2Ti19.81 alloys were made by arc-melting in Ar atmosphere, followed by microstructures observation, thermal properties analysis and hardness testing. In addition, some of the rapidly-solidified ribbons were made by melt-spinning technology to study the rapid solidification effect on these alloys. Results indicated that these alloys had high hardness because of the effects of lattice distortions and solid solution. These two effects were due to these elements had large differences in atomic sizes. Moreover, the hardness of Co31.6Fe27.4Ni21.2Ti19.8 alloy was higher than that of CoFeNiTi alloy. The oxide resistances of these two alloys were not good enough after exposure at 1000℃ for 24 hours in atmosphere. Additionally, the nano-sized grains were observed in the microstructures of rapidly solidified CoFeNiTi ribbons by TEM.
Appears in Collections:	[Department of Chemical & Materials Engineering] thesis

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