臺灣博碩士論文加值系統

摘 要
鎳矽介金屬合金 (Ni3Si，有序之面心立方 L12結構)為一種有別於其他金屬之特殊結構，尤其在高溫環境時，其優良的抗侵蝕、抗氧化，及降伏強度隨溫度之上升而升高的特性 (最大之降伏強度發生於 700℃)，使此合金在高溫應用上優於其他金屬；然而，鎳矽二元合金相似於鎳鋁合金，在室溫環境下有著脆性破壞的現象；以至於如何增加晶界之契合性使合金提升延性，達到多用途的應用成為尚待解決的問題之一。
本實驗以鎳矽鈮基介金屬合金，應用巨量合金法（元素添加量大於1000 p.p.m.）以化學計量之方式同時添加硼與鉻元素，在氬氣氣氛保護之下，使用電弧熔煉、墜落式鑄造法製造成鑄塊胚料，續以真空退火爐進行鑄塊 1080℃、四小時均質化與700℃、十小時時效化處理後，一部份製成標距平行區3mmx2mmx20mm之拉伸試片，分別於大氣(14000ppm H2O vapor)真空、水氣(850ppm H2O vapor)各種氣氛下，分別進行25℃、500℃、600℃、700℃及800℃之拉伸試驗，另一部份進行成份分析驗證；並藉由其組織、破斷面之光學顯微鏡、掃瞄式電子顯微鏡及穿透式電子顯微鏡觀察，與微硬度之機械行為等變化，以獲得改善該合金材料脆性之最佳合金鉻元素之添加值。
本實驗之研究結果證實，當合金成份為Ni-18Si-3Nb-0.15B-1.0Cr時，該合金有最佳之機械性質組合。添加鉻元素確實可以增加高溫延性(800℃真空中延性可達到23﹪)且較不受環境因素影響(水氣中達16﹪)其原因為添加鉻元素可使氫原子吸附於表面上，防止氫原子的滲入，且會在表面形成氧化鉻層，對於抗腐蝕性及抗氧化有極大之改善，進而增加高溫延性有抑制環境脆化的效果。

Abstract
Intermetallic compounds based on Ni3Si (ordered fcc L12 structure) offer a number of interesting properties for structural applications in aggressive environments at elevated temperature. These interesting properties include the excellent corrosion and oxidation resistance at both ambient and elevated temperatures, good specific strength in comparison with other materials, increasing yield strength as a function of temperature, and a peak yield strength occurring at about 700℃. However, similar to the Ni3Al, binary Ni3Si suffers from grain boundary embrittlement at room temperature. Therefore, how to improve its grain boundary adhesion will be the critical point of increasing the ductility and widespread the applications of Ni-Si intermetallic alloys.
According to the pre-studies, we select the Ni-19Si-3Nb alloy as the based alloy to investigate the effect of adding boron and Chromium by means of arc melting and drop casting under argon atmospheres, and then homogenizing and aging in a vacuum annealing furnace with atmosphere of 5×10-5 torr at 1080℃ for 4 hours and 700℃ for 10 hours respectively.
The main part of heat-treated ingots were machined into the tensile test specimen with the gauge dimension of 3mmx2mmx20mm..Then the specimen were tensile test under different atmosphere, [such as air (14000ppm H2O vapor), vacuum(2×10-4torr),and pure water vapor(850ppm)] at different temperature(25℃、500℃、600℃、700℃、800℃). The evolution of microstructure change and mechanical properties of the Ni-19Si-3Nb-0.15B-XCr alloys were characterized by x-ray diffraction, SEM, TEM, EPMA, microhardness test, Vickers hardness test, and tensile tests.
According to the result of this study. The optimum condition of the mechanical properties occurs at the composition of Ni-18Si-3Nb-0.15B-1.0Cr. It can improve elongation on high temperature due to add Cr. The elongation reaches 23﹪for the specimen tested under the vacuum at 800℃ temperature.
This reason that with Cr additions the hydrogen atoms were adsorption on the alloy surface increased the possibility of adsorption of hydrogen species onto the surface. Furthermore it can form a chromium oxide layer to enhance corrosion and oxidation resistance. The results of this study showed that with Cr addition can improves ductility and suppress environment embitterment on high temperatures.

目錄
中文摘要……………………………………….…… …………………….Ⅰ
英文摘要……………………………….….……………………………….Ⅲ
致謝….……………………………….…………………………………….Ⅴ
目錄….……………………………….…………………………………….Ⅵ
表目錄…….…………………………….………………………………….Ⅶ
圖目錄…….…………………………….………………………………….Ⅷ
第一章 前言………………………………….……………………………..01
第二章 研究背景…………….…………………….……………………...03
第三章 理論基礎………………….……………….……………………. .06
3-1 影響鎳矽基合金延性之因素……………………..………...06
3-2 鎳矽基合金之延韌性改善………………………….……....12
3-3 鎳矽基合金與鎳矽鈮基合金…………………..……….…..13
3-4 鎳基介金屬化合物高溫晶界破壞…………….…..………..19
3-5 添加硼於鎳矽基介金屬之影響………………….……………22
3-6 添加鉻於鎳矽基介金屬之影響………………...…….………23
第四章 實驗步驟……………………………………………………………25
4-1合金試片之先前準備………………….………………….…..25
4-1-1 合金之組成……………….……………………….….25
4-1-2 電弧熔解與墜落式鑄造…………………………….…25
4-1-3 熱處理(均質化與時效) ……………………………..31
4-1-4 試片取樣……………………………………………….31
4-2 微觀組織分析……………………….…………………………36
4-2-1 輝光放電成份分析(GDS)………………………………36
4-2-2 光學顯微鏡 (OM)…………….…………………...…36
4-2-3 掃瞄式電子顯微鏡 (SEM) 觀察與 EDS元素分析……37
4-2-4電子微探儀 (EPMA)分析……………………………….37
4-3 相的鑑定……………………………………………………….37
4-3-1 X光繞射 (XRD)……………..………………………..37
4-3-2 熱差分析儀…………………………………………….38
4-3-3 穿透式電子顯微鏡 (TEM) 與擇域繞射 (SAD)…....38
4-4機械性質的分析…………………………………………………39
4-4-1 硬度值量測……………………….…………………..39
4-4-2 拉伸測試………………………………….…………..39
第五章 結果與討論………………………………….………………………42
5-1觀光放電分析(G.D.S)與碳硫分析量測……………….……..42
5-2 X光繞射分析(XRD)………………………………………………42
5-3 掃描式電子顯微鏡觀察(SEM)與EDS…………….…..……..42
5-3-1 合金經鑄造及熱處理後之觀察……………………….47
5-3-2 合金在添加不同比例的鉻、矽元素後，其微觀組織的.47
5-3-3 EDS成份分析………….……………………………...55
5-4 電子微探儀分析(EPMA)…….…………………………………55
5-5穿透式電子顯微鏡(TEM)與擇域繞射(SAD)……………………63
5-6 硬度測試……………………………………………………….63
5-7 拉伸性質……………………………………………………….64
5-7-1 常溫拉伸測試………………….………………….….64
5-7-2 高溫拉伸測試………………….……………………..68
5-8 拉伸破斷面之SEM觀察…………………………………………73
第六章 總結…………………………………………………………………88
參考文獻………………………………...………………………………..89
表目錄
表2-1近代發展一覽表………………………………………………………05
表4-1鎳矽鈮合金內各組成元素之比例……………………………..……30
表4-2 拉伸環境之參數………………………….………………………..41
表 5-1鎳-矽-鈮基介金屬合金添加不同鉻之輝光放電分析(GDS)分…..43
表 5-2各種成份第三相比例………………………………………………..56
表5-3各種成份經均質化4小時、時效十小時後之EDS鑑定……..…...59
圖目錄
圖 3-1 (a) Ni3Si 之 L12 有序 f.c.c. 結構
(b) 硼或碳格隙型原子於 Ni3Si 之位置………………….………07
圖 3-2 鎳矽二元相圖與主要之結晶結構……………….….…………….15
圖 3-3 鎳-鈮二元相圖………………………………………………………16
圖 3-4 鈮-矽二元相圖………………………………………………………16
圖 3-5 鎳-矽-鈮三元相圖…………………………….………………....17
圖 3-6 鎳-19矽基合金添加不同比例鈮元素後對 X光繞射之影響….…20
圖 3-7 鎳-19矽基合金添加不同比例鈮元素後對晶格常數之改變….…20
圖 3-8 鎳-19矽基合金之 TEM 影像與擇域繞射圖………………………21
圖 4-1 實驗流程…………………………………………………………….26
圖4-2製作示意圖……………………………………………………………27
圖4-3 (a)氬焊機外觀圖、(b)電弧熔解爐…………………………………28
圖4-4 電弧熔解爐結構圖………………………….………………………29
圖4-5 墜落式鑄造爐結構圖………………….…………………………..32
圖 4-6 石英管之管狀真空退火爐結構圖………………………………….33
圖4-7 鑄件剖斷面……………..………………………………………...34
圖 4-8拉伸試片之標準示意圖……………………………………..…….35
圖4-9 Hung TA Instrument 靜態拉伸試驗機之主機及電腦控制系統……41
圖4-10 高溫拉伸時使用之可氣氛控制高溫爐及其控制器….………….41
圖5-1 各成份之X-ray分析……………………………………………….46
圖 5-2 鎳-19矽-3鈮-0.15硼-1.0鉻介金屬掃瞄式電子顯微鏡觀察……48
圖 5-3 鎳-19矽-3鈮-0.15硼-1.5鉻介金屬掃瞄式電子顯微鏡觀察……49
圖 5-4 鎳-19矽-3鈮-0.15硼-2.0鉻介金屬掃瞄式電子顯微鏡觀察……50
圖 5-5 鎳-19矽-3鈮-0.15硼-2.5鉻介金屬掃瞄式電子顯微鏡觀察……52
圖 5-6 鎳-19矽-3鈮-0.15硼-3.0鉻介金屬掃瞄式電子顯微鏡觀察……52
圖 5-7 鎳-18矽-3鈮-0.15硼-1.0鉻介金屬掃瞄式電子顯微鏡觀察….53
圖 5-8 鎳-17矽-3鈮-0.15硼-2.0鉻介金屬掃瞄式電子顯微鏡觀察……54
圖5-9鎳基介金屬合金各成份經時效後之EDS成份取樣地方
(A)析出物 (B)第三相 (C)基地…………………….……………..58
圖5-10鎳-19矽-3鈮-0.15硼-1.0鉻之EPMA觀察…….…………………60
圖5-11鎳-19矽-3鈮-0.15硼-3.0鉻之EPMA觀察…………………………61
圖5-12鎳-18矽-3鈮-0.15硼-1.0鉻之EPMA觀察…………………………62
圖5-13 鎳-18矽-3鈮-0.15硼-1鉻之TEM影像
(a) 基地明視野影像(b)擇域繞射圖……………………………..65
圖5-14 鎳-18矽-3鈮-0.15硼-1鉻之TEM影像
(a) 基地暗視野影像(b)擇域繞射圖……………………………..66
圖5-15 各成份之維氏硬度值……………………….…………………….67
圖5-16 各成份經時效後之微小維氏硬度值……….…………………….67
圖5-17不同成份之常溫拉伸機械性質………………….………………..69
圖5-18 鎳-18矽-3鈮-0.15硼-1鉻真空環境
不同溫度之拉伸機械性質…………………………..……………..69
圖5-19 鎳-18矽-3鈮-0.15硼-1鉻水氣環境(850ppm)
不同溫度之拉伸機械性質………………………………..………..70
圖5-20 鎳-18矽-3鈮-0.15硼-1鉻大氣環境(14400ppm)
不同溫度之拉伸機械性質………………………………..………..70
圖5-21 有、無添加鉻真空和水氣之強度值之比較…………….…………71
圖5-22 有、無添加鉻真空和大氣之強度值之比較……………….………71
圖5-23 鎳矽基介金屬合金在大氣環境拉伸破斷後之SEM觀察………….75
圖5-24Ni-18Si-3Nb0.15B-1.0Cr基介合屬合金在(a)25、(b)500、(c)600、(d)700、(e)800℃真空環境拉伸破斷後之SEM觀察……………….………81
圖5-25 Ni-18Si-3Nb0.15B-1.0Cr基介合屬合金在(a)25、(b)500、(c)600、(d)700、(e)800℃水氣環境拉伸破斷後之SEM觀察………………….……84
圖5-26 Ni-18Si-3Nb0.15B-1.0Cr基介合屬合金在(a)25、(b)500、(c)600、(d)700、(e)800℃大氣環境拉伸破斷後之SEM觀察……………………….87

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