Ti-6Al-4V鈦合金電子束銲件之疲勞裂縫成長研究

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Title:	Ti-6Al-4V鈦合金電子束銲件之疲勞裂縫成長研究
Authors:	羅志明;Lo, Chih-Ming
Contributors:	機械工程學系
Keywords:	鈦合金;Ti-6Al-4V;電子束銲接;疲勞裂縫成長;變動振幅負載;titanium alloy;Ti-6Al-4V;electron beam welding;fatigue crack growth;variable amplitude loading
Date:	2018-08-20
Issue Date:	2018-08-31 15:04:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究以Ti-6Al-4V鈦合金為實驗材料，選擇對接型式進行電子束銲接(EBW)，並檢視鈦合金銲件在等負荷振幅及變動負荷振幅負載下之疲勞裂縫成長性質以及金相、硬度與拉伸之機械性質。研究結果顯示，金相方面，銲道金相組織為針狀α麻田散體，而熱影響區則由初晶α及針狀α麻田散體所組成。硬度結果顯示，銲道區針狀α麻田散體硬度最高，熱影響區次之。在拉伸性質方面，平滑試棒之拉伸強度為885.9 MPa，斷裂位於母材。在疲勞裂縫成長方面，由於銲道疲勞強度高於母材，導致疲勞裂縫實驗初期失敗，經過重新設計試片在試片的兩側開溝槽，以利裂縫沿銲道成長。在變動振幅疲勞裂縫成長實驗，成功利用柔性法及特殊分析方法測量得到裂縫成長數據。 ;In this study, the experimental material was T i-6Al-4V titanium alloy. Butt joint type was selected for electron beam welding (EBW). Fatigue crack growth rate of the titanium alloy weldment under both constant amplitude loading and variable amplitude loading were measured. Also, the microstructure, microhardness and tensile properties of the weldment were evaluated. The results showed that needle-like α-martensite appeared in the EBW weld. The microstructure in the heat-affected zone was composed of primary α and needle-like α martensite. The highest microhardness occurred in the fusion zone followed by the heat affected zone. Tensile strength of the smooth specimen was 885.9 MPa, and the broken position located at the base metal. With respect to the fatigue crack growth of Ti-6Al-4V EBW weldment under constant amplitude loading, the fatigue resistance of weld metal was higher than that of base metal. The valid fatigue crack growth test of weld metal was performed by using a side-grooved specimen. The fatigue crack growth of the weldment under variable amplitude loading was successfully measured by a compliance method.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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