Effect Of Rolling Microstructure And Recrystallization Microstructure On Adiabatic Shear Behavior Of TA2 Pure Titanium

Adiabatic shear is a common form of deformation and failure of materials under highspeed impact loading.It generally exists in high-speed deformation processes such as highspeed impact,stamping forming,projectile penetration,high-speed cutting,and explosive crushing.Studies of the adiabatic shearing behavior of the material microstructure has important scientific significance and the influence of engineering reference value.In this paper,TA2 pure titanium plate with different microstructure was prepared by rolling and incomplete crystallization annealing.Dynamic impact tests were carried out on hat-shaped specimen using split Hopkinson pressure bar device and limit ring technology.The effect of rolling and recrystallization microstructure on adiabatic shear behavior of TA2 pure titanium was studied combining with material microstructure analysis technology.The following main conclusions were obtained:(1)In the dynamic shear experiment with the same shear strain and strain rate,the hatshaped specimens with rolling deformation of 40% 、 50% 、 60% and 70% will undergo deformation localization earlier with the increase of rolling deformation,which makes the adiabatic shear band and crack easier to nucleate and expand.At the same time,the mechanical properties in different sampling directions show differences.The rheological stress of TD hat-shaped specimen is the largest,the rheological stress of RD-45° hat-shaped specimen is the second,and the rheological stress of RD hat-shaped specimen is the smallest.The law of the difficulty of the formation of the corresponding adiabatic shear band is that the TD hat-shaped specimen is the most easy to form,the RD-45° hat-shaped specimen is the second,and the RD hat-shaped specimen is the least easy to form.(2)Recrystallized grains as softening point will make the material form softening zone in the shear region,resulting in the nucleation and expansion of adiabatic shear band.With the increase of recrystallization degree in the matrix before shear deformation,the width of the central region of the shear band gradually decreases,and the increase of the proportion of recrystallized grains induces the nucleation and propagation of shear band and crack.The adiabatic temperature rise in the later stage of shear band development will promote secondary recrystallization in the shear band,improve the toughness of materials in the shear band and delay the development of shear band to crack.(3)There are differences in the localization evolution process of adiabatic shear deformation between rolling structure and recrystallized structure.With the increase of shear strain,the hat-shaped specimen of rolling structure first forms cracks at both ends of the shear area,which reduces the bearing capacity of the sample,and then the deformation localization of the sample occurs.Because of the existence of recrystallized grains as the softening point,the deformation localization first occurs at both ends of the shear area,and then further induces the deformation localization in the shear area.The obvious adiabatic temperature rise effect appeared in the later stage of the development of the shear band,which promoted the formation of secondary recrystallization in the shear band.Adiabatic temperature rise may not be the main factor for the formation of shear band.On the contrary,the formation of shear band makes the specimen strain highly localized,resulting in temperature rise.