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研究生:李健綸
研究生(外文):Chien-Lun Li
論文名稱:真空熱壓燒結製程及Laves相TiCr2對鉻鈦合金其顯微組織與材料特性之研究
論文名稱(外文):Investigation of the Vacuum Hot-Press Sintering Process and TiCr2 Laves Phase on Microstructures and Material Characteristics of Cr-Ti alloys
指導教授:張世賢張世賢引用關係
指導教授(外文):Shih-Hsien Chang
口試委員:黃國聰吳明偉陳貞光
口試日期:2016-07-01
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:材料科學與工程研究所
學門:工程學門
學類:材料工程學類
論文種類:學術論文
畢業學年度:104
中文關鍵詞:電導率硬度粉末冶金熱壓燒結Laves相TiCr2鉻鈦合金
外文關鍵詞:Electrical ConductivityHardnessHot-Press SinteringPowder MetallurgyCr-Ti AlloyTiCr2 Laves Phase
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鉻鈦合金由於會形成Laves相TiCr2金屬間化合物,因此具有高熔點、抗腐蝕性與良好的高溫強度,是一種高溫結構材料,適合應用在航太零件上。另一方面,鉻鈦合金靶材透過濺鍍等方法製備的薄膜,具有高硬度、抗氧化性佳與高耐磨性,可應用在刀具或模具的保護層上,以延長刀具與模具的使用壽命。鉻鈦合金通常利用熔煉法或粉末冶金的方式進行製備,由於熔煉法會有成份偏析、組織不均勻與晶粒粗大的缺陷存在,因此,本研究將利用粉末冶金法之真空熱壓燒結製程製備鉻鈦合金。真空熱壓燒結是一種結合傳統燒結與加壓成形的複合式粉末冶金技術,在熱壓過程中,透過石墨模具直接將壓力傳遞至粉末,同時進行材料的壓製與燒結,此方法有助於在較低的燒結溫度下,形成較緻密的材料。
本研究係以真空熱壓燒結製備鉻鈦合金,添加不同含量的次微米(800 nm)鈦粉到微米(5 μm)與次微米(600 nm)鉻粉中,進行球磨混合,利用不同熱壓壓力(20、35和50 MPa)與不同的熱壓燒結溫度(1250、1300、1350和1400°C ),以尋求熱壓燒結對鉻鈦合金(Cr-50 wt% Ti與Cr-31.2 wt% Ti)之最佳參數,並探討顯微組織與材料特性之差異。
實驗結果顯示,Cr-50 wt% Ti合金的最佳熱壓燒結參數是溫度為1250°C、壓力20 MPa及持壓時間1小時,其相對密度可達95.67%,硬度和橫向破裂強度(TRS)分別為85.92 HRA與313.06 MPa,而電導率為1.35×104 S·cm-1。然而,由於鈦的活性高,容易與雜質元素反應,因此後續改變粉末配比為Cr-31.2 wt% Ti,並經由改變熱壓壓力(20→50 MPa),以研究壓力對合金之緻密度與性質之影響。研究結果顯示,在燒結溫度1250°C、壓力50 MPa及持壓時間1小時,其相對密度可達99.94%,硬度和橫向破裂強度(TRS)分別為81.90 HRA與448.53 MPa,以及電導率為1.58×104 S·cm-1,與Cr-31.2 wt% Ti合金在燒結溫度1400°C、壓力20 MPa及持壓時間1小時之相對密度及其他性質比較下,並無太大差異,此結果表示透過壓力的提升,有助於金屬之燒結行為,並在較低的燒結溫度下,即能有效地改善其性質。
Due to the usual formation of the TiCr2 Laves phase in a Cr-Ti alloy, it is considered to be a kind of high temperature structural material for use with aerospace components, having a high melting point, corrosion resistance and high strength at elevated temperatures. On the other hand, Cr-Ti thin films deposited by a sputtering process also possess the properties of high hardness, good oxidation resistance and high wear resistance. As a result, Cr-Ti thin films are widely used as hard coating layers on tools and molds to extend their lifetimes. Furthermore, Cr-Ti alloys are generally made by means of melting or powder metallurgy methods. However, ingredient segregation, heterogeneity and coarse grains defects in Cr-Ti alloys are frequently caused by the melting processes. Therefore, in this study, a Cr-Ti alloy was fabricated by means of the vacuum hot-press sintering process of powder metallurgy technology. Vacuum hot-press sintering is a complex method which combines the conventional sintering and pressing processes, whereby the material is directly pressed and sintered through a graphite mold to transmit the pressure onto the powder, which makes it possible to obtain a densified material at a relatively low sintering temperature.
In this study, Cr-Ti alloys were fabricated by vacuum hot-press sintering. Different amounts of submicron titanium powders (800 nm) were added into micron (5 μm) and submicron (600 nm) chromium powders, respectively. Then they were mixed by ball milling. The experiments utilized various hot-press pressures (20, 35 and 50 MPa) and hot-press sintering temperatures (1250, 1300, 1350 and 1400°C) to find the optimal parameters for Cr-Ti alloys (Cr-50 wt% Ti and Cr-31.2 wt% Ti), and simultaneously investigate the differences in microstructures and characteristics.
The experimental results show that the optimal parameters of hot-press sintering Cr-50 wt% Ti alloys were 1250°C at 20 MPa for 1 h. The relative density reached 95.67%, and the hardness and TRS reached 85.92 HRA and 313.06 MPa, respectively. Moreover, the electrical conductivity was 1.35×104 S·cm-1. However, since titanium possesses high activity and easily reacts with other impure elements, Cr-31.2 wt% Ti alloys were used for subsequent research. Consequently, the results show that when the pressure was increased to 50 MPa, the optimal parameters of Cr-31.2 wt% Ti alloys were obtained after 1250°C hot-press sintering for 1 h. Meanwhile, the relative density increased to 99.94%, and the hardness and TRS reached 81.90 HRA and 448.53 MPa, respectively. The electrical conductivity was 1.58×104 S·cm-1. It possessed similar relative density and properties compared with Cr-31.2 wt% Ti alloys after 1400°C at 20 MPa for 1 h hot-press sintering. According to the above discussion and results, enhancing the pressure is helpful for sintering behavior and effectively improves the properties at a relatively low-temperature sintering.
摘 要 i
ABSTRACT iii
誌 謝 v
目 錄 vi
表目錄 x
圖目錄 xi
第一章 緒論 1
1.1 前言 1
1.2 研究目的與動機 2
第二章 文獻回顧 3
2.1 Laves相合金[8] 3
2.1.1 Laves相金屬間化合物 3
2.1.1.1 Laves相TiCr2的性質 4
2.1.1.2 Laves相TiCr2的基礎研究 5
2.1.1.3 Laves相金屬間鉻化物的製備[21] 6
2.2 燒結原理 9
2.2.1 燒結概論 9
2.2.2 燒結過程與驅動力 9
2.2.3 燒結應力 10
2.2.4 固相燒結機制 12
2.2.5 影響燒結之因素 14
2.3 真空熱壓燒結(Vacuum Hot-Press Sintering)製程 16
2.3.1 真空燒結 16
2.3.2 熱壓燒結[34][37] 17
2.3.2.1 熱壓燒結原理 17
2.3.2.2 熱壓緻密化過程 18
2.3.2.3 熱壓燒結設備[47] 19
2.3.2.4 影響熱壓之因素 20
第三章 實驗流程與研究方法 22
3.1 實驗步驟與流程 22
3.1.1 真空熱壓燒結 24
3.1.1.1 球磨混合粉末 24
3.1.1.2 石墨模具組裝與粉末裝填 24
3.1.1.3 預壓成形 25
3.1.1.4 真空熱壓燒結製程 26
3.2 性質分析 26
3.2.1 粉末形貌分析 26
3.2.2 X-ray繞射分析 27
3.2.3 相對密度量測 28
3.2.4 視孔隙率量測 29
3.2.5 晶粒尺寸量測 30
3.2.6 SEM顯微結構及成份分析 30
3.2.7 硬度試驗 30
3.2.8 橫向破裂強度試驗 31
3.2.9 電性量測 32
第四章 結果與討論 34
4.1 球磨混合前後之Cr-Ti粉末形貌與粒徑大小 34
4.2 不同熱壓燒結溫度對Cr-50 wt% Ti合金之影響 37
4.2.1 Cr-50 wt% Ti合金顯微組織結構分析 37
4.2.1.1 X-ray 繞射分析 37
4.2.1.2 密度與孔隙率 39
4.2.1.3 金相顯微組織觀察與晶粒量測 41
4.2.2 真空熱壓燒結溫度對Cr-50 wt% Ti合金電性之影響 43
4.2.3 機械性質測試 45
4.2.3.1 硬度試驗 45
4.2.3.2 橫向破裂強度(TRS)試驗 46
4.2.3.3 破斷面觀察 47
4.2.4 不同熱壓燒結溫度對Cr-50 wt% Ti合金之影響小結 48
4.3 不同熱壓燒結溫度對Cr-31.2 wt% Ti合金之影響 49
4.3.1 不同溫度之Cr-31.2 wt% Ti合金顯微組織結構分析 49
4.3.1.1 X-ray 繞射分析 49
4.3.1.2 密度與孔隙率 51
4.3.1.3 金相顯微組織觀察與晶粒量測 53
4.3.2 真空熱壓燒結溫度對Cr-31.2 wt% Ti合金電性之影響 56
4.3.3 機械性質測試 57
4.3.3.1 硬度試驗 57
4.3.3.2 橫向破裂強度(TRS)試驗 58
4.3.3.3 破斷面觀察 59
4.3.4 不同熱壓燒結溫度對Cr-31.2 wt% Ti合金之影響小結 60
4.4 不同熱壓燒結壓力對Cr-31.2 wt% Ti合金之影響 61
4.4.1 不同壓力之Cr-31.2 wt% Ti合金顯微組織結構分析 61
4.4.1.1 X-ray 繞射分析 61
4.4.1.2 密度與孔隙率 62
4.4.1.3 金相顯微組織觀察與晶粒量測 65
4.4.2 真空熱壓燒結壓力對Cr-31.2 wt% Ti合金電性之影響 66
4.4.3 機械性質測試 68
4.4.3.1 硬度試驗 68
4.4.3.2 橫向破裂強度(TRS)試驗 68
4.4.3.3 破斷面觀察 69
4.4.4 不同熱壓燒結壓力對Cr-31.2 wt% Ti合金之影響小結 71
4.5 不同粒徑鉻粉對Cr-31.2 wt% Ti合金之影響 71
4.5.1 不同粒徑鉻粉之Cr-31.2 wt% Ti合金顯微組織結構分析 72
4.5.1.1 X-ray 繞射分析 72
4.5.1.2 密度與孔隙率 72
4.5.1.3 金相顯微組織觀察與晶粒量測 74
4.5.2 不同粒徑鉻粉對Cr-31.2 wt% Ti合金電性之影響 77
4.5.3 機械性質測試 78
4.5.3.1 硬度試驗 78
4.5.3.2 橫向破裂強度(TRS)試驗 79
4.5.3.3 破斷面觀察 79
第五章 結論 81
參考文獻 83
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