臺灣博碩士論文加值系統

鎳鋁介金屬化合物具有高熔點、低密度、極佳的抗氧化性等優點，因此其在高溫結構的應用方面十分具發展之潛力，但是NiAl室溫脆性及低的抗潛變性等缺點仍有待進一步去克服。為了改善NiAl的機械性質，引入第二相強化物以形成介金屬基複合材料的方式是一可行的研究方向。以往的研究中有以預先氧化的方式來製作NiAl/Al2O3複合材料的報導，以此法所製備之NiAl/Al2O3複合燒結体具有較NiAl更優異的室溫機械性質，值得再進一步研究。
本研究中吾人以球磨的方式分別對起始之NiAl粉末與經氧化後之NiAl/Al2O3複合粉末進行長時間的乾磨，之後再將粉末以真空熱壓燒結的方式燒結緻密，並檢討球磨處理對NiAl/Al2O3複合粉末以及對其熱壓燒結体之微結構與機械性質的影響。
實驗結果顯示，NiAl起始粉末與經預先氧化之NiAl/Al2O3粉末於球磨後，粉末會發生氧化、細化、與形變的現象，且粉末的粒徑呈現雙峰分布(bimodal distribution)。經真空熱壓燒結後，NiAl/Al2O3複合燒結体內顆粒狀的α-Al2O3是分散於NiAl晶界上以及晶粒內部。隨著粉末球磨時間的增長，燒結体之晶粒會細化，其內部所含之α-Al2O3的量會增加，其破壞方式會由延晶破壞逐漸轉成穿晶破壞的模式。NiAl/Al2O3燒結体之室溫機械性質(彎曲強度、硬度以及破壞韌性)亦隨之增加。

The intermetallic compound NiAl has potentials as a high temperature structural material because of its high melting point, low density, and excellent oxidation resistance. However, some disadvantages of NiAl which needs solving are brittleness at room temperature and low creep resistance. To improve the mechanical properties of NiAl, adding second phase to from intermetallic matrix composites is a practicable direction . It has been reported on "Pre-Oxidation Method", which shows NiAl/Al2O3 composites have better room temperature mechanical properties than that of NiAl. So it is worth studying further.
In this study, as received NiAl powder and oxidized NiAl/Al2O3 powder were dry ball milled for a long time, and then hot-pressed in vacuum. The effects of ball milling on the NiAl/Al2O3 composite powder and the microstructures and mechanical properties of the hot pressed NiAl/Al2O3 composites were investigated.
The results of the experiment show that both as received NiAl powder and pre-oxidized NiAl/Al2O3 powder oxidizes, refines, and strains after ball milling , and their particle size distributions are bimodal distributions. α-Al2O3 disperses in the grain boundary and within the grain of the NiAl/Al2O3 composites. As the ball milling time increases, NiAl/Al2O3 composites show refinement of grain size and increase in the content of α-Al2O3. Fracture mode of NiAl/Al2O3 transforms from intergranular mode to transgraular mode as the content of α-Al2O3 increases, and it benefits to increase the room temperature mechanical properties of NiAl/Al2O3 composites.

中文摘要*************************I
英文摘要 ************************II
目錄*..*************************IV
表目錄*************************VII
圖目錄*..***********************VIII
第一章 前言..***********************1
第二章 理論基礎*********************..3
2.1 NiAl的基本性質*****************.*.3
2.2 NiAl之氧化理論*****************..*4
2.3 燒結理論..***********.**********5
2.4 顆粒強化型複合材料..****************.6
2.5 殘留應力韌化理論************.*****..7
第三章 實驗步驟及方法 *****************.14
3.1燒結粉末之製備****************..**14
3.1.1起始原料..********************.14
3.1.2氧化處理NiAl粉末****************.14
3.1.3球磨.**********************..14
3.2球磨後NiAl/Al2O3複合粉末之性質**********..15
3.2.1粉末表面型態之觀察*.*************..*15
3.2.2粉末結晶相分析.*****************..15
3.2.3粉末粒徑分布之檢測.***************..15
3.3真空熱壓燒結*******************..16
3.4燒結体微結構分析與觀察.**************16
3.4.1結晶相分析..*******************16
3.4.2微結構分析.******************.*.16
3.4.3高解析穿透式電子顯微鏡觀察.***********..17
3.4.4晶粒大小.********************..17
3.4.5燒結体組成成份分析..***************.17
3.5 NiAl/Al2O3熱壓燒結体之性質.************.18
3. 5.1密度的測定.*******************..18
3.5.2硬度的測定.*******************..18
3.5.3彎曲強度的測定.*****************..19
3.5.4破壞韌性的測定.*****************..19
第四章 結果與討論..*******************..23
4.1氧化處理後之NiAl/Al2O3複合粉末**********..23
4.2球磨後之NiAl/Al2O3複合粉末.************..23
4.2.1粉末表面形態..******************.23
4.2.2粉末之結晶相分析***************.*..24
4.2.3粉末之粉徑分佈**********.*******..25
4.3燒結体之微結構及組成分析*********.****.25
4. 3.1結晶相與組成分析****************..25
4.3.2燒結体的微結構***************.**..27
4.4燒結体之性質*******************..28
4.4.1密度*******************.**..*28
4.4.2硬度***..*******************.28
4.4.3彎曲強度********************...29
4.4.4破壞韌性*.*******************..31
第五章 結論***********************74
參考文獻**********************.**.75

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