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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/9541

Title: 高性能雙相鈦合金應用研究---高性能雙相鈦合金板材及銲件疲勞裂縫成長特性研究
Fatigue Crack Growth Behavior of High Performance Dual Phase Titanium Alloys and Welds
Authors: 蔡履文
Contributors: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
Keywords: Notched tensile strength;Fatigue crack growth rate;Laser welding
雷射銲接;缺口拉伸試驗;疲勞裂縫成長試驗;Ti-6Al-6V-2Sn
Date: 2007-08
Issue Date: 2011-06-28T07:09:28Z
Publisher: 行政院國家科學委員會
Abstract: 摘要:鈦合金基本上分為α、nearα、α-β及β四大類,其中α-β型鈦合金可經 由熱處理來改變其顯微組織,因而其機械性能隨著產生變化,因此高強度鈦合 金經常是選用α-β型,其中代表性合金為Ti-6Al-4V,但由於更高強度或較佳 成型性需求,SP 700 或高強度Ti-6Al-6V-2Sn 等已逐步取代原使用之Ti-6-4。 SP 700 有較佳之成型性,而Ti-6-6-2 銲道韌性則優於Ti-6-4。 本研究為針對三種α-β 型鈦合金,進行板材及銲件之疲勞裂縫成長特性試 驗,評估不同顯微組織對α-β 型鈦合金疲勞性能之影響。500℃以下鈦合金仍 保有優良之抗氧化性及比強度,工程材料具備優越之高溫疲勞裂縫成長特性, 亦為航太結構材料所需具備重要性質,因此本研究前兩年度主要進行高溫疲勞 裂縫成長試驗,採用電壓降比對法來量測裂縫長度,並於不同溫度進行疲勞裂 縫成長試驗,來測定α-β 鈦合金銲件之高溫疲勞性質。粗大組織ㄧ直是有害 於鈦合金之強度及延、韌性,本研究第三年度是針對粗大α-β 鈦合金銲道組 織予以微細化,細化製程為依據本研究群體吳教授前兩年度研究成果,在常溫 進行衝擊及疲勞裂縫成長試驗,以評估鈦合金微細組織對其機械性能之影響, 本年度研究有助於此研究群體之橫向研究整合及設備整合。
In this study, the influence of post-weld heat treatments on the mechanical properties and microstructure of Ti-6Al-6V-2Sn laser welds were investigated. Notched tensile tests were performed to evaluate the presence of notch on the tensile strength of Ti-6Al-6V-2Sn laser welds, which were post-aged at different temperatures. Ti-6Al-6V-2Sn laser welds showed notch brittleness except for the welds post-weld aged at 704℃. In case of the weld aged at 482℃, it had the highest hardness (Hv440) but shows notch brittleness. The same trend was also observed on impact tests. The coarsen columnar structure in a weld was preferred to exhibit brittle transgranular fracture. This characteristics could be due to the lack of extensive slip systems in titanium alloys, intergranular dimple fracture was seen for the presence of αat columnar grain boundary. Fatigue crack growth tests revealed base metal had a slightly higher fatigue crack growth rate than the welds. The fracture features showed all the specimens exhibited transgrainular fatigue fracture. The zigzag crack path in the fusion zone of Laser welds resulted in a reduced fatigue crack growth rate in comparison with the base metal.Keywords: Ti-6Al-6V-2Sn alloy, hydrogenation, grain refinement.
Relation: NSC96-2221-E019-018
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/9541
Appears in Collections:[材料工程研究所] 研究計畫

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