Nb-Ni-Ti-Co-Mo-Fe高熵合金系統之微結構及特性研究

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Title:	Nb-Ni-Ti-Co-Mo-Fe高熵合金系統之微結構及特性研究 A study on the microstructures and Characteristics of Nb-Ni-Ti-Co-Mo-Fe high-entropy alloys
Authors:	林文晟
Contributors:	材料科學與奈米科技研究所
Keywords:	高熵合金微結構樹枝狀微結構熱處理韌性熔配特性
Date:	2006
Issue Date:	2014-06-04 10:09:33 (UTC+8)
Abstract:	本論文為延續陳岳鋒學長之研究，將原子尺寸差異較大之元素熔配成合金，共計熔配NbNiTi、NbNiTiCo、NbNiTiCoMo及NbNiTiCoMoFe等四個合金，觀察這些元素對合金性質的影響，同時亦研究熱處理對此系列合金之微結構及機械性質的影響。　在TGA的研究結果顯示，除了NbNiTi合金的抗氧化性質較差以外，另外三種合金系統具有相當良好的抗氧化性。而這些合金的硬度也因為合金成份的增加，而原子大小的差異愈明顯，使之強度也愈增。由破斷韌性可以發現NbNiTi與NbNiTiCoMo合金因時效而硬化，NbNiTiCo合金因熱處理而軟化。　　經由金相觀察及XRD分析結果顯示，此四種合金均為樹枝狀組織，經過1000°C下24hrs之熱處理後，仍然維持類似的結構。其樹枝結構為HCP相，而樹枝間結構則因合金之不同而有差異。NbNiTiCoMo合金的樹枝間結構為BCC相，其他三種合金的樹枝間結構則為FCC相。另外，NbNiTiCoMo合金經過熱處理後觀察到富Ti析出相散佈於基地中。 According to the previous study of our group, four alloys of NbNiTi, NbNiTiCo, NbNiTiCoMo and NbNiTiCoMoFe were prepared by arc-melting. The elements of these alloys were selected because of their atomic sizes were large difference, they were thereby chosen for investigating the effects of these different elements on the properties of the alloys. The effects of heat treatment on the microstructures and mechanical properties of these alloys were also examined. The results indicated that the NbNiTiCo, NbNiTiCoMo and NbNiTiCoMoFe alloys possessed good high-temperature oxidation resistance by TGA, but NbNiTi alloy easily oxidized at high temperature. The hardness of these alloys increased with increasing the number of the elements, because atoms with different sizes increased. In addition, the fracture toughness of NbNiTi and NbNiTiCoMo alloys decreased after annealed, but that of NbNiTiCo alloy increased after annealed. These four alloys had similar dendritic microstructures by SEM observation. They still kept almost the same
Appears in Collections:	[Department of Chemical & Materials Engineering] thesis

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