對多晶材料而言，當晶粒徑由微米尺度下降到微奈米尺度時，強度會提升，但是普遍延展性不佳，甚至出現明顯應變集中的現象，因此近年來許多研究聚焦在如何提升微奈米材料的延展性，其中雙峰晶粒徑分佈被認為是方法之一。本實驗利用電鍍製作具備雙峰晶粒徑分佈特性的純鎳與鎳鈷合金試片，研究機械性質與顯微組織的關係，並與具單一晶粒徑分佈的鎳鈷合金進行比較。透過Hall-Petch關係的分析顯示，降伏強度的高低主要取決於材料中小晶粒的平均粒徑，而抗拉強度則由平均晶粒徑大小決定。當小晶粒所佔面積的比例r2小於30%或是大於70%的試片，其延展性較佳。推測原因是在r2小於30% 的情形，大晶粒亂數分佈於小晶粒當中，機械性質由小晶粒主導，而大晶粒能夠增加延展性，造成強度高延展性相對好的材料；r2大於70%時，機械性質由大晶粒主導，小晶粒能夠增加強度，造成延展性好強度相對高的材料。

The strength of polycrystalline materials increases with decreasing grain size. The increase of strength is usually associated with deterioration of ductility, especially for materials having sub-micrometer or nanometer in grain size. It has bee suggested that the ductility of submicro- or nano- grained materials can be improved significantly by introducing a bimodal distribution of grain sizes. The purpose of the present study aims at clarifying the microstructural parameters of the bimodal distribution, such as area ratio and size difference, on the strength and ductility of pure nickel and nickel-cobalt specimens produced by electrodeposition. The microstructural parameters were determined from orientation imaging mapping technique using electron backscatter diffraction. Results indicated that the yield strength is mainly determined by the average size of the fine grains, whereas the tensile strength has a good relation with the average grain size in total. Moreover, it was showed that samples having a area ratio of the fine grains lower than 30% or higher than 70% possess a better ductility. The possible mechanism is discussed in detail.

一、前言 1
二、文獻回顧 3
2-1 微、奈米材料的機械性質 3
2-1-1強度 3
2-1-2提升微奈米材料延展性的方法 4
2-1-3雙峰晶粒徑分佈與延展性 7
2-1-4晶界和延展性 9
2-1-5應變硬化率與延展性 10
2-2鎳鈷合金的機械性質 12
2-2-1鎳鈷合金的強度 12
2-2-2鎳鈷合金的延展性 13
2-3. 電鍍原理 14
2-3-1 法拉第定律 14
2-3-2 極化 14
2-3-3 脈衝電鍍 16
2-3-4 電鍍鎳鈷合金 17
2-3-5 異常共鍍 18
三、實驗方法 19
3-1實驗總流程 19
3-2電鍍製程 19
3-3橫截面硬度測量 20
3-4鍍層成分分析 20
3-5 X-ray分析 20
3-6熱退火處理 20
3-7拉伸實驗 21
3-8 EBSD分析 21
四、實驗結果 22
4-1試片成分、微硬度與X-ray繞射分析 22
4-1-1試片成分與微硬度分析 22
4-1-2 X-ray繞射分析 22
4-2 機械性質分析 23
4-2-1純鎳機械性質 23
4-2-2 Co-15機械性質 24
4-2-3 Co-40機械性質 24
4-2-4退火試片機械性質 25
4-3 EBSD分析 26
4-3-1純鎳EBSD分析 26
4-3-2 Co-15 EBSD分析 28
4-3-3 Co-40 EBSD分析 28
4-3-4退火試片EBSD分析 29
五、討論 31
5-1 晶粒徑與應力 31
5-2 實驗結果討論 32
5-3 強度與延展性 33
六、結論 35
七、文獻回顧 36

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