| Titanium alloy is one of the important structural materials,which is used in the structure of aircraft and aircraft engines.During the service,the structure of the aerospace titanium alloy is bearing complex loads and the service environment is also complicated.In recent years,air pollution is increasingly serious and the atmospheric acid components have gradually increased.These environments can cause corrosion,which will damage titanium alloy structure.In the service process,the aeronautical structure usually bears the alternating load,which can creating fatigue problems and corrosion damage.That can weaken the carrying capacity of the structure and shorten the structure's fatigue life.Therefore,the corrosion and fatigue properties of the titanium alloy structure are attracting more and more attention.TC17 titanium alloy is a kind of titanium alloy used in aviation structure.It has a great engineering value to study the corrosion and fatigue characteristics of TC17 titanium alloy.In this paper,the corrosion behavior of TC17 titanium alloy under different corrosive environments is studied.The corrosion damage morphology of the specimen with corrosion is observed by optical instrument.The effect of corrosion damage on the fatigue properties is analyzed by fatigue experiment.The influence of corrosion damage on the surface stress concentration of the specimen is simulated by finite element method.The main contents include:(1)The corrosion behavior of TC17 titanium alloy under different corrosion conditions is studied.The geometrical morphology and size of corrosion damage of titanium alloy are observed by metallurgical microscope and super-depth microscope.The results show that titanium alloy has good corrosion resistance to some corrosive environments.But it has obvious corrosion damage in corrosive environment containing HNO3 acid and HCl acid.In the HNO3 acid corrosion environment,the corrosion damage of TC17 titanium alloy is mainly pitting.But the pitting size is small.In the corrosive environment of HCl acid,the corrosion damage of TC17 titanium alloy is mainly gully shape corrosion.(2)The effects of corrosion time,temperature and corrosion concentration on corrosion damage are studied.The corrosion damage of TC17 titanium alloy under different corrosive environments is observed.The results show that the corrosion damage of TC17 titanium alloy is increasing with the increase of corrosion time,which indicates that the corrosion time is an important factor.The corrosion damage of TC17 titanium alloy under different temperature and different concentrations of HCl acid corrosion is observed.The results show that the higher corrosion temperature and the higher concentration of HCl acid aggravate the corrosion damage of TC17 titanium alloy,which reflects the corrosion environment temperature and the concentration of corrosive solution are also two important factors.(3)Fatigue life of TC17 titanium alloy without corrosion and with corrosion are studied by experimenting.The fatigue experiment of TC17 titanium alloy after corrosion with different environments is carried out by using high frequency fatigue testing machine,and the fatigue test results of TC17 titanium alloy with no corrosion damage are analyzed.(4)Micro-mechanism of fatigue damage caused by pre-corrosion damage is analyzed.Based on the results of corrosion damage observation and fatigue fracture analysis,the microcosmic mechanism of corrosion damage of TC17 titanium alloy on fatigue properties is studied.The results show that,since the size of the pitting corrosion being so small as to reach the micron level,the fatigue fracture and non-corrosive fatigue fracture is no essential difference and fatigue cracks mainly appear in the surface processing defects.As for the gully shape corrosion appearing in the HCl acid environment,fatigue cracks appear in the corrosion layer and the matrix at the junction.(5)The finite element method is used to study the influence of different sizes of the surface corrosion of the TC17 titanium alloy specimen and different distances between the two corrosion pits on the stress concentration,which is simulated by ABAQUS software. |
PDF Full Text Request