鋁合金7075-T73原材與陽極處理封孔後的疲勞性質影響對微結構的研究

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Title:	鋁合金7075-T73原材與陽極處理封孔後的疲勞性質影響對微結構的研究
Authors:	李庭豪;Lee,Ting-hao
Contributors:	機械工程學系
Keywords:	硫酸;陽極處理;旋轉樑疲勞試驗;電子背向散射;穿透式電子顯微鏡;7075-T73;Sulfuric acid;Anodization;Rotating bending fatigue test;EBSD;TEM;7075-T73
Date:	2013-07-29
Issue Date:	2013-08-22 12:14:51 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究探討鋁合金7075-T73熱處理後利用15wt%硫酸溶液的陽極處理進行10-12μm的陽極膜厚度之後熱水封孔。將原材試棒和陽極處理試棒進行旋轉樑疲勞試驗，並觀察和比較不同應力振幅的試片微結構差異。而鋁合金7075-T73熱處理(原材)的試片，在基地中存在一些次晶粒及二次相顆粒的微結構的探討。調查疲勞壽命的旋轉週數與應力振福的關係，比較7075-T73熱處理的原材和陽極處理封孔後的差異。原材的疲勞壽命為225MPa，而陽極處理封孔後的疲勞壽命為240MPa。利用電子背向散射(Electron back scattering diffraction；EBSD)實驗，發現原材在低取向差的角度晶界(low misorientation angle grain boundary)有顯著的增加(MAGB：<50)，而陽極處理封孔後則是在高取向差的角度晶界(High misorientation angle grain boundary)有顯著的增加(MAGB：>150)。加以討論疲勞試驗後原材低取向差的角度以及陽極處理封孔後的高取向差的角度所造成的原因。 A set of 7075-T73 alloy samples was prepared for running anodization in a 15wt% sulfuric acid solution to coat 10-12 micron in thickness of anodic aluminum oxide (AAO) film and then sealed in hot water. The samples with/without AAO film were removed for carrying out rotating bending fatigue test. The microstructure of different samples was observed and compared. The 7075-T73 (bare) samples showed some subgrains in together with some amounts of intermetallic compound particles in the matrix. Relations of number of cycles to failure versus stress amplitude were constructed for two sets of sample. The bare samples achieved fatigue limit (FL) at 225 MPa at 107 cycles and those with sealed AAO film yielded 240 MPa at 107 cycles. After electron back scattering diffraction (EBSD) pattern test, we found that the former samples showed an increased in the low misorientation angle grain boundary (MAGB:<5?) and the latter samples obtained a high fraction in the high MAGB (>15?) on the matrix of fractured sample. Reasons for increasing low MAGB in bare sample and for increasing high MAGB in anodized/sealed samples were discussed.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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