The low cycle fatigue（LCF） tests were carried out using symmetrical cyclic loading under total strain amplitude control conditions.The present paper is devoted to investigating the cyclic deformation response of Ti...The low cycle fatigue（LCF） tests were carried out using symmetrical cyclic loading under total strain amplitude control conditions.The present paper is devoted to investigating the cyclic deformation response of Ti–6Al–4V titanium and the electron-beam-welded（EBW） joint in the following aspects,i.e.,cyclic deformation behavior,fatigue life and fatigue fracture behavior.The results show that the softening of the joint is significant at larger strain ranges,while not obvious at smaller strain ranges.The joint shows shorter fatigue life at larger strain ranges and equivalent fatigue life at smaller strain ranges compared with Ti–6Al–4V base metal.A fatigue crack of the joint not only originates at the surface or subsurface,but also at defects in the fusion zone（FZ）.The crack propagation zone of Ti–6Al–4V base metal shows ductile fracture mechanism,while the joint shows brittle fracture mechanism.In all the fatigue fracture zones many dimples appear,showing the typical ductile fracture.展开更多
Ti–Al surface alloy was fabricated using a cyclic pulsed liquid-phase mixing of predeposited 100 nm Al film with a-Ti substrate by low-energy high-current electron beam. Electron probe micro-analysis（EPMA）,grazing ...Ti–Al surface alloy was fabricated using a cyclic pulsed liquid-phase mixing of predeposited 100 nm Al film with a-Ti substrate by low-energy high-current electron beam. Electron probe micro-analysis（EPMA）,grazing incidence X-ray diffraction analysis（GIXRD）,transmission electron microscopy（TEM）, and nanoindentation were used to investigate the characterization of Ti–Al surface alloy. The experimental results show that the thickness of alloy layer is ＊3 lm, and the content of Al in the ＊1 lm thickness surface layer is ＊60 at%. The tetragonal TiAl and TiAl2intermetallics were synthesized at the top surface, which have nanocrystalline structure.The main phase formed in the ＊2.5 lm thick surface is TiAl, and there are few TiAl2and Ti3Al phase for the alloy.Dislocation is enhanced in the alloyed layer. The nanohardness of Ti–Al surface alloy increased significantly compared with a-Ti substrate due to the nanostructure and enhanced dislocation. Since the e-beam remelted repeatedly, the Ti–Al surface alloy mixed sufficiently with Ti substrate. Moreover, there is no obvious boundary between the alloyed layer and substrate.展开更多
基金financially supported by the HiTech Research and Development Program of China(No.2012AA052102)the Program of International Science Technology Cooperation of China(No.2013DFA61590)
文摘The low cycle fatigue（LCF） tests were carried out using symmetrical cyclic loading under total strain amplitude control conditions.The present paper is devoted to investigating the cyclic deformation response of Ti–6Al–4V titanium and the electron-beam-welded（EBW） joint in the following aspects,i.e.,cyclic deformation behavior,fatigue life and fatigue fracture behavior.The results show that the softening of the joint is significant at larger strain ranges,while not obvious at smaller strain ranges.The joint shows shorter fatigue life at larger strain ranges and equivalent fatigue life at smaller strain ranges compared with Ti–6Al–4V base metal.A fatigue crack of the joint not only originates at the surface or subsurface,but also at defects in the fusion zone（FZ）.The crack propagation zone of Ti–6Al–4V base metal shows ductile fracture mechanism,while the joint shows brittle fracture mechanism.In all the fatigue fracture zones many dimples appear,showing the typical ductile fracture.
基金financially supported by the National Natural Science Foundation of China and the Russian Foundation for Basic Research (No. 11011120081)Large Scientific Facilities of the National Natural Science Foundation of China and of the Chinese Academy of Sciences (No. 11079012)the National Natural Science Foundation of China (No. 10875021)
文摘Ti–Al surface alloy was fabricated using a cyclic pulsed liquid-phase mixing of predeposited 100 nm Al film with a-Ti substrate by low-energy high-current electron beam. Electron probe micro-analysis（EPMA）,grazing incidence X-ray diffraction analysis（GIXRD）,transmission electron microscopy（TEM）, and nanoindentation were used to investigate the characterization of Ti–Al surface alloy. The experimental results show that the thickness of alloy layer is ＊3 lm, and the content of Al in the ＊1 lm thickness surface layer is ＊60 at%. The tetragonal TiAl and TiAl2intermetallics were synthesized at the top surface, which have nanocrystalline structure.The main phase formed in the ＊2.5 lm thick surface is TiAl, and there are few TiAl2and Ti3Al phase for the alloy.Dislocation is enhanced in the alloyed layer. The nanohardness of Ti–Al surface alloy increased significantly compared with a-Ti substrate due to the nanostructure and enhanced dislocation. Since the e-beam remelted repeatedly, the Ti–Al surface alloy mixed sufficiently with Ti substrate. Moreover, there is no obvious boundary between the alloyed layer and substrate.
