陳鈞臺灣大學：材料科學與工程學研究所鍾偉志Chung, Wei-ChihWei-ChihChung2007-11-262018-06-282007-11-262018-06-282007http://ntur.lib.ntu.edu.tw//handle/246246/55180本研究係針對SP-700鈦合金，探討母材之麻田散體相變態及其後續熱處理的組織變化。此外，藉由雷射銲接及不同條件之銲後熱處理，進行SP-700銲件顯微組織的探討，同時亦進行相關銲件之缺口拉伸及衝擊試驗，並分析試片之破斷面及顯微組織。 實驗結果顯示SP-700母材在β轉換溫度（900˚C）以上淬火，β將會完全變態為HCP的α′；固溶溫度略低於β轉換溫度（約890˚C）時，水淬後α′會與斜方晶格的麻填散體α″同時存在；當固溶溫度介於880˚C及800˚C之間時，β相在水淬後將會變態為α″相（或有部份β殘留）；若在低於800˚C固溶後水淬，β相不再變態為麻田散體，可完全殘存至室溫。α″相之晶體結構為Base-centered orthorhombic（底心原子位於垂直 軸的平面），其晶格常數為The microstructural evolution and heat treatment of SP-700 titanium alloy, in particular the martensitic transformation, have been investigated. The emphasis of this study was also placed on the influence of the post-weld heat treatment (PWHT) on the microstructure and related mechanical properties of SP-700 laser welds. Notched tensile and impact tests of the laser welds with various PWHTs were evaluated. Detailed microstructural and fractographic analyses were conducted on distinct specimens and the results were discussed. Martensitic transformation studies of SP-700 titanium alloy indicated that β (BCC) was transformed completely into α′ (HCP martensite) after solution treating at a temperature higher than β-transus (approximately 900˚C) and water quenched. The co-existence of α′ and α″ (Orthorhombic martensite) could be observed upon quenching from a temperature which was slightly below β-transus, e.g. 890˚C, of the alloy. Quenching from the intermediate temperature range of 880˚C to 800˚C, the transformation of β to α″ with or without some retained β was resulted according to the solution temperature employed. For a solution temperature of less than 800˚C, β was remained unchanged after rapidly cooling to room temperature. The crystal structure of α″ has been identified as base-centered orthorhombic (centered on C-faces) with誌謝 i 中文摘要 ii 英文摘要 iii 第一章 前言 1 第二章 文獻回顧 2 2-1 鈦合金之簡介及發展 2 2-1-1 鈦金屬的晶體結構 2 2-1-2 溶質元素對鈦合金之影響 2 2-1-3 鈦合金的分類 6 2-1-4 α β雙相鈦合金之熱處理條件與顯微組織的關係 7 2-1-5 SP-700的簡介與其性質 10 2-2 雷射銲接技術 12 2-2-1 雷射的原理 12 2-2-2 CO2雷射銲接 15 2-2-3 雷射銲接參數 17 2-2-4 鈦合金的銲接特性 25 第三章 實驗方法與設備 27 3-1 實驗材料與流程 27 3-2 雷射銲接 27 3-3 銲後熱處理與時效處理 31 3-4 金相觀察與硬度量測 31 3-5 顯微組織觀察 35 3-5-1 SEM觀察 35 3-5-2 TEM觀察 35 3-6 機械性質測試 35 3-6-1 缺口拉伸試驗 35 3-6.2 衝擊試驗 38 第四章 結果與討論 41 4-1 SP-700之母材顯微組織 41 4-2 SP-700之淬火組織探討 41 4-2-1 熱處理溫度對麻田散體相變態的影響 41 4-2-2 SP-700之α″相的晶體結構 53 4-2-3 SP-700之麻田散體的時效硬化 60 4-3 SP-700之As-welded雷射銲件顯微組織 73 4-3-1 銲道的顯微組織 73 4-3-2 熱影響區的顯微組織 77 4-4 熱處理程序對顯微組織的影響 77 4-4-1 不同熱處理溫度後水淬之顯微組織 80 4-4-2 不同熱處理溫度後空冷之顯微組織 80 4-4-3 不同熱處理溫度後爐冷之顯微組織 90 4-4-4 冷卻速率對銲道顯微組織的影響 90 4-5 SP-700雷射銲件之機械性質 95 4-5-1 缺口拉伸試驗 95 4-5-2 衝擊試驗 95 第五章 結論 103 第六章 參考文獻 10515234953 bytesapplication/pdfen-USSP-700鈦合金雷射銲接銲後熱處理顯微組織SP-700 titanium alloylaser beam weldingheat treatmentmicrostructuremechanical propertiesthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/55180/1/ntu-96-R94527020-1.pdf