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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/30669

Title: Ti-15-3合金加工製程及特性研究-Ti-15-3合金板材及銲件缺口拉伸及疲勞特性研究
Notched Tensile and Fatigue Crack Growth Properties of Ti-15-3 Alloy and Its 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: Taiwan concrete (TAICON);Mix design;High performance concrete (HPC);Rebar corrosion;Workability
台灣混凝土;配比設計;高性能混凝土;鋼筋腐蝕;工作性
Date: 2011-08
Issue Date: 2012-04-13T01:17:17Z
Publisher: 行政院國家科學委員會
Abstract: β 及 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顯微組織不同而產生明顯變化,尤其是 β 型合金之高硬化能,使其易於時效後達成硬化,且 β 型鈦合金由於其穩定之結構,未經時效處理前有良好之成型性,而時效後其強度則可大幅提升,因此 β 型鈦合金之用量呈現快速成長,其中以Ti-15V-3Cr-3Al-3Sn (Ti-15-3) 為典型代表合金,而且其價格較其它 β 型合金低廉;但一般 β 型鈦合金添加大量合金元素,因此銲接性較其他鈦合金差。本兩年期研究為針對 Ti-15-3 合金,評估板材及銲件經不同時效處理後,其缺口拉伸及疲勞裂縫成長特性,探討不同顯微組織對缺口脆化及疲勞特性之影響。 第一年 使用二氧化碳雷射,進行板材不加填料雷射銲接,將銲後銲件及板材施行時效處理,實驗進行試件硬度量測、缺口拉伸試驗,並將板材及銲件獲致之結果相互比較,另一方面,將試件升溫至各不同溫度,探討測試溫度對缺口強度之影響,並與 Ti-6-4 合金進行比較,並以掃描式電子顯微鏡觀察各不同試件之破壞特微。 第二年 本年度研究是利用本研究群體研究成果,子計畫吳建國教授以先行充氫再脫氫方式,來達成鈦合金晶粒細化之目的,利用此計劃的發展之技術,來細化鈦合金雷射銲道組織,進而評估這些細化組織之缺口拉伸強度及疲勞裂縫成長特性,並與粗大銲道特性進行比較。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。
It is well known that the microstructures of α-β and β titanium alloys can be altered through heat treatment. Therefore, the mechanical properties of α-β and β titanium alloys will undergo a great change, depending on the inherent microstructures. The high forming ability together with high strength after aging treatment make β titanium alloys increasing its usage in different fields. Ti-15V-3Cr-3Al-3Sn, the typical β titanium alloy, is one of the most widely used β titanium alloys. The demand of the Ti-15-3, in aircraft applications, is even over Ti-6Al-4V. Thus, further investigation of this alloy needs to be performed. Besides, the high alloy contents of β titanium alloy are found to deteriorate its inherent weldability. In this work, the notched tensile and fatigue crack growth behaviors of Ti-15-3 alloy plate and welds, with and without postweld heat treatment or ageing treatment, will be evaluated, especially pay attention to the effects of notch brittleness and temperature dependence on the mechanical properties of the specimens. The change in microstructures of the specimens will be examined carefully by transmission electron microscope (TEM). Moreover, the variation in fatigue crack growth behaviors will be correlated with the microstructures in distinct specimens. The first year of the project will focus on the influence of elevated temperature on the notched tensile strength (NTS) of the alloy and welds. The notched tensile strength of postweld-heat-treated welds will be determined and compared with the counterpart base metal. Moreover, the NTS of mill-annealed Ti-6Al-4V will also be measured and compares to that of Ti-15-3. Coarse structures are known to damage the mechanical properties of Ti-15-3 alloy in comparison with the fine grained one. In the second year of the investigation, a special hydrogen-charging procedure developed by Professor Wu will be used to refine the coarse microstructure of the welds. The influence of coarse solidified microstructures on notched tensile strength and the fatigue crack growth rate of various specimens will be evaluated with the counterpart specimens with fine grained size. Fatigue fracture appearance of various specimens were examined by scanning electron microscopy (SEM) to identify typical fracture features and correlated with fatigue crack growth characteristics.
Relation: NSC100-2221-E019-031
URI: http://ntour.ntou.edu.tw/handle/987654321/30669
Appears in Collections:[材料工程研究所] 研究計畫

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