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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/34741

Title: Ti-15V-3Cr-3Sn-3Al母材與銲件之缺口拉伸性質及疲勞裂縫成長行為研究
Notched Tensile Fracture and Fatigue Crack Growth Behavior of Ti-15V-3Cr-3Sn-3Al Alloy and Weld
Authors: Shih-Tsung Chang
張世宗
Contributors: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
Keywords: 缺口拉伸強度;Ti-15V-3Cr-3Sn-3Al;時效熱處理;疲勞裂縫成長
Notched tensile strength;Ti-15V-3Cr-3Sn-3Al;Aging treatment;Fatigue crack growth
Date: 2012
Issue Date: 2013-10-07T02:46:02Z
Abstract: 本研究以Ti-15V-3Cr-3Al-3Sn合金板材及使用5KW二氧化碳雷射對板材進行銲接之銲件,探討板材與銲件比較分別經由371-593℃/8hr時效處理,在不同環境溫度下,其缺口拉伸性質及破斷面的變化情形,並且於常溫環境下,以Ti-15V-3Cr-3Al-3Sn經371-593℃/8hr時效處理之合金板材進行疲勞裂縫成長試驗,探討在不同的實驗應力比下(R=0.1 or 0.5),負載頻率為20Hz之疲勞裂縫成長行為。 Ti-15V-3Cr-3Al-3Sn經不同時效熱處理之板材與銲件,在室溫環境下,低溫時效試件會顯示高缺口脆化程度,使得強度與延展性皆不佳,破裂面呈現大量劈裂面及混些許窩穴狀破裂特徵,而高溫時效試件則是相對有較優異之強度與延展性能,破裂面大致呈現窩穴狀破裂特徵,但隨著環境溫度的提升,低溫時效試件之延展性及強度有顯著增加,而高溫時效試件則受到高溫軟化的影響,強度逐漸弱化,破裂形態以穿晶窩穴狀破裂為主,而原始板材在室溫下有較佳之強度,在高溫下則有弱化的現象。 Ti-15V-3Cr-3Al-3Sn在常溫疲勞裂縫成長試驗中,結果顯示疲勞裂縫成長速率隨著時效溫度的提升而遞減,整體而言,在不同的實驗應力比下,皆呈現371℃時效試件最慢,而426℃時效試件有最高之疲勞裂縫成長速率。觀察疲勞破裂面, 371℃時效試件,在0.1R時,隨△K的增加呈現大範圍的劈裂及深的溝狀破裂特徵,而在0.5R時,在高△K範圍,可觀察到大規模的梯狀劈裂破壞特徵,隨著時效溫度的提升,破裂特徵逐以穿晶破壞為主。
In this study, the Ti-15V-3Cr-3Al-3Sn alloys and its welds were used to investigate the effect of the various heat treatments ranging from 371-593℃ on the fatigue crack growth rates and notched tensile strength at different environment temperature. At room temperature, the Ti-15-3 plate sheet and welds show that the specimen with low aging treatment exhibit high notch brittleness, causing the decline in strength and elongation. The fracture morphology is composed of quasi-cleavage and small amount of dimple fracture. Instead, the specimen with high aging treatment possesses a superior strength, causing the fracture morphology has a trend to a tough dimple fracture. With the increasing of the elevated temperature, it has an inversely change at notch tensile strength for specimens via distinct heat treatment. The specimen with low aging treatment has a markedly increase in strength and elongation in comparison to the specimen with high aging treatment at a gradually rise of elevated temperature. It could be attributed that the high temperature causing the latter exhibited the deterioration with pronounced dimple fracture morphology. The fatigue crack growth rates of Ti-15-3 alloy was determined at room temperature in laboratory air. The effect of aging treatment over the temperature range from 371 to 593 oC on the FCGRs of the specimens was investigated. The results indicated the 371 oC aged specimen exhibited a serration in crack growth curve at the stress ratio (R) of 0.1. Moreover, the 371 oC aged specimen had a greater Paris law gradient than other specimens at 0.5 R. In addition, the 426oC aged specimen had higher FCGRs than other specimens, regardless of stress ratio. Increasing the aging temperature at/above 482 oC, the FCGRs of the specimens decreased gradually.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0019955010
http://ntour.ntou.edu.tw/handle/987654321/34741
Appears in Collections:[材料工程研究所] 博碩士論文

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