Multiscale Study Of Deformation Localization Of Industrial Pure Titanium Under Uniaxial Tension

Industrial Commerical pure titanium has been widely used in the fields of national defense,biomedicine and chemical industry due to its excellent corrosion resistance,good mechanical properties and low density.During servive,commercial pure titanium often deforms under external loads.In order to clarify the relationship between the deformation behavior of commercial pure titanium at different spatial scales,three speckles in different sizes are prepared on the surface of commercial pure titanium.The microstructure evolution of commercial pure titanium under uniaxial tension is characterized with in situ scanning electron microscope(SEM)and electron backscattering diffraction(EBSD),and the multiscale deformation fields are obtained via digital image correlation(DIC)analysis.The relationship between macroscale deformation localization and microstructure is established,and the failure behavior of commercial pure titanium is predicted effectively.Speckles in three different sizes are prepared on the surface of commercial pure titanium specimens,referred to as microscale,mesoscale and macroscale speckles.Spray painting is used to prepare the macroscale speckles,using black paint as the primer and spraying white paint to make random speckles.The microscale and mesoscale speckles are fabricated by different electro-polishing procedures.Uniaxial tension of pure titanium samples with diferent speckles are performed with homemade miniature materials test systems.During tension,the images of deformed samples are captured with optical camera and SEM,and the deformation fields at different spatial scales are derived.For the microscale speckle case,the crystallographic structure of the sample is also collected by EBSD characterization.Multiscale deformation fields of commercial pure titanium at different plastic strains are obtained.The experimental results show that massive {1012} extension twins are activated,strain localization tends to form at grain boundaries and inside deformation twins,especially at the large-angle grain boundaries,and the amplitude and rate of strain accumulation at grain boundaries are higher than inside deformation twins at the microscale.The strain fields at three spatial scales show obvious deformation localization.The microscale strain-localized regions dispersed at grain boundaries and within deformation twins present themselves as the strain concentration bands observed with the macroscale speckles,and both the strain localization regions and strain concentration bands are at ±45°with the tensile direction.