摘 要
本文采用光學(xué)顯微鏡、掃描電鏡、X射線衍射、差示掃描量熱儀和室溫壓縮試驗(yàn)等研究了Co元素對Ni-Mn-Sn合金的組織結(jié)構(gòu)、馬氏體相變行為和力學(xué)性能等的影響，探討Co摻雜對Ni-Mn-Sn合金相變行為和力學(xué)行為的影響規(guī)律。
試驗(yàn)結(jié)果表明，Co摻雜顯著改變了Ni-Mn-Sn合金的顯微組織，在合金基體上形成了富Co相；Ni50Mn37Sn13合金的顯微組織為單一固溶體，加Co后合金室溫下的顯微組織由基體相和富Co相組成；Co的加入不僅能夠明顯細(xì)化Ni-Mn-Sn合金的晶粒尺寸，還抑制了熱處理過程中合金晶粒的長大。
在冷卻和加熱過程中Ni-Mn-Sn-Co合金只發(fā)生一步馬氏體相變，隨著Co含量增加， Ni-Mn-Sn-Co合金的相變溫度升高，Co的加入降低了Ni-Mn-Sn合金的相變滯后，但是隨Co元素含量變化，相變滯后度基本保持不變。隨Co含量增加，Ni-Mn-Sn-Co合金中馬氏體的晶體結(jié)構(gòu)由10M轉(zhuǎn)化為14M結(jié)構(gòu)。
壓縮試驗(yàn)表明，Co摻雜顯著提高了合金的斷裂應(yīng)力和斷裂應(yīng)變。隨Co含量增多，合金的斷裂應(yīng)力和斷裂應(yīng)變均呈增大趨勢。合金的斷口形貌表明，隨Co含量提高，合金的斷裂方式從典型的沿晶脆斷逐漸轉(zhuǎn)變?yōu)榛品蛛x性延性斷裂，說明合金韌性得到了顯著的改善。

關(guān)鍵詞：Ni-Mn-Sn-Co合金；磁性形狀記憶合金；顯微組織；馬氏體相變；
力學(xué)性能

Abstract
The characteristics of martensite transformation，microstructure of Ni-Mn-Sn alloys were investigated by means of optical microscope，SEM，XRD，DSC as well as compression test at room temperature. The influence of Co dopping on the phase transformation behavior and mechanical properties was studied.
The experimental results show that the microstructure of Ni-Mn-Sn alloy is obviously changed by Co addition, and there are Co-rich phases formed in the matrix of Ni-Mn-Sn alloy. The microstructure of Ni50Mn37Sn13 alloy is single solution, however the Co-rich phase and the matrix consists of the microstructure of Ni-Mn-Sn-Co alloy. Co addition not only refines the grain size of Ni-Mn-Sn alloy evidently but also retards the grain growth during heat treatment process.
Ni-Mn-Sn-Co alloy exhibits one-step martensitic transformation during the process of cooling and heating. With Co content increasing, the martensitic transformation temperatures increase while the hysistersis decreases. The crystal structure of martensite of Ni-Mn-Sn-Co alloy is changed from 10M to 14M with the increase of Co content.
Compression test results show that Co addition improves the mechanical properties. The compressive strength and compressive strain of Ni-Mn-Sn alloy both invreases with Co content increasing. The fracture type of Ni-Mn-Sn changes from intergranular crack to gliding separated ductile fracture with Co addition, which indicates the improvement of ductility.

Keywords：Ni-Mn-Sn-Co alloy, Magnetic shape memory alloy, Microstructure, Martensitic transformation, Mechanical behavior
目 錄
摘 要 I
Abstract II

第1章 緒論 1
1.1 引言 1
1.2 形狀記憶合金分類 2
1.2.1 傳統(tǒng)溫控記憶合金 2
1.2.2 新型磁驅(qū)動記憶合金 3
1.3 Ni-Mn-Sn合金的晶體結(jié)構(gòu) 5
1.4 選題意義和研究內(nèi)容 7
1.4.1 選題意義 7
1.4.2 主要研究內(nèi)容 8
第2章 材料制備和實(shí)驗(yàn)方法 9
2.1 Ni-Mn-Sn-Co材料制備及熱處理 9
2.2 組織性能 10
2.2.1 金相組織觀察 10
2.2.2 掃描電鏡分析 10
2.2.3 X射線衍射分析 10
2.3 相變溫度測試 11
2.4 力學(xué)性能測試 11
第3章 Ni-Mn-Sn-Co合金的顯微組織 12
3.1 引言 12
3.2 Ni-Mn-Sn-Co合金的顯微組織 12
3.2.1 鑄態(tài)Ni50Mn37Sn13-xCox合金的顯微組織 12
3.2.2 熱處理后Ni50Mn37Sn13-xCox合金的顯微組織 12
3.2.3 Ni-Mn-Sn-Co合金固溶處理態(tài)的SEM形貌和成分分析 14
3.3 本章小結(jié) 17
第4章 Ni-Mn-Sn-Co合金的馬氏體相變 18
4.1 引言 18
4.2 Ni-Mn-Sn-Co合金的晶體結(jié)構(gòu) 18
4.3 Ni-Mn-Sn-Co合金的馬氏體相變 20
4.4 本章小結(jié) 25
第5章 Ni-Mn-Sn-Co合金的力學(xué)行為 26
5.1 引言 26
5.2 Ni-Mn-Sn-Co合金的壓縮變形行為 26
5.3 Ni-Mn-Sn-Co合金斷口組織觀察 30
5.4 本章小結(jié) 31
結(jié) 論 32
致 謝 33
參考文獻(xiàn) 34
附錄1 36
附錄2 41