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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/13574

Title: 麻田散鐵變態與敏化對AISI 316L不□鋼銲件疲勞裂縫成長之影響研究
Authors: Jyun-Jie Chen
陳俊傑
Contributors: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
Keywords: 疲勞裂縫成長;不□鋼銲件
Fatigue crack growth;Stainless steel weld
Date: 2006
Issue Date: 2011-06-30T07:23:15Z
Abstract: 摘 要   本研究目的為探討316L不□鋼板材,以及經固溶熱處理之銲件,比較敏化熱處理前後,在大氣及氫氣環境下之疲勞裂縫成長特性。 316L板材無論敏化熱處理前後,大氣環境下呈現相似的疲勞裂縫成長特性,將R值提升,疲勞裂縫成長速率也相對提升,而在氫氣環境下,敏化板材其疲勞裂縫成長速率會稍低於未敏化板材。隨測試條件及熱處理程序不同疲勞破斷面會有程度不一的應變誘發麻田散鐵生成,隨R值增加及材料經過敏化熱處理,都會有較多之應變誘發麻田散鐵生成。從破斷面觀察,大氣環境中,板材與敏化板材大多呈現穿晶破裂特徵,氫氣環境中,板材之疲勞特徵則以Quasi-cleavage為主要破裂方式,而敏化板材為部分Quasi-cleavage伴隨沿晶破裂及沿雙晶破裂,由於破裂特徵不同,導致板材在敏化熱處理前後產生疲勞裂縫成長速率些許差異。 經固溶熱處理之316L銲件,其X-光繞射結果與板材有相同的趨勢,隨R值上升及經過敏化熱處理後,應變誘發麻散鐵變態量都有增加之現象,但銲件整體變態量低於板材。銲件在大氣或氫氣環境下,無論敏化熱處理與否,都呈現一致疲勞裂縫成長特性,隨R值增加,疲勞裂縫成長速率也相對提升。銲件和板材其疲勞裂縫成長速率,於大氣環境下呈現相似的疲勞裂縫成長特性,而氫氣環境中,銲件則會稍低於板材,這與銲件具有較大破斷面粗糙度有關。空氣中的敏化銲件及未敏化銲件破斷面以穿晶破裂為主,氫氣環境大多為Quasi-cleavage,之破裂特徵,並無沿雙晶破裂之特徵。
ABSTRACT The fatigue crack growth behaviors of AISI 316L stainless steel plates in air and gaseous hydrogen were evaluated, and further compared with the welds that were postweld-treated at the same conditions. The results indicated that sensitized and unsensitized steel plates have the same fatigue crack growth characteristic in the air, so as the welds. Changing the testing environment from air into gaseous hydrogen, hydrogen enhanced crack growth occurred for all the specimens but to different degrees. Rasing the R ratio from 0.1 to 0.5 increases the FCGR of the specimens over the testing K range. . For all the steel plates tested in air, fatigue fracture appearance of various specimens exhibited mainly transgranular fatique fracture feature together with few intergranular fracture and twin boundary separation. For the welds, transgranular fatigue fracture covered all the entire fracture surface of the specimens. In case of the steel plate and its weld tested in hydrogen, hydrongen-accelerated crack growth was accompanied with extensive quasi-cleavage fracture with lath morphology on their fracture surface. Additionally, increased extent of twin boundary separations and intergranular fracture were found in the sensitized base metal. The results of X-ray diffraction pattern of 316L stainless steel revealed that on the crack surface just partial transformation of austenite to martensite occured. Overall, the amount of strain-induce martensite will increasing accompany with rasing the R ratio and heat treatment.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M94550010
http://ntour.ntou.edu.tw/ir/handle/987654321/13574
Appears in Collections:[材料工程研究所] 博碩士論文

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