| In this paper, a series of experiments on TC4, TB10 and TB8 alloys were carried out by split Hopkinson pressure bar(SHPB) in different strain rates. Microscope observation and analysis were carried out on samples by optical microscopy, SEM, TEM and XRD techniques, etc. The effect of microstructures and texture property on dynamic mechanical property and adiabatic shear sensitivity of titanium alloy was discussed. And the effect of impact-induced phase transformation on the adiabatic shear sensitivity of TB10 alloy was analyzed. The main results are as follows:The effect of microstructures of titanium alloy on dynamic mechanical property is lager. The energy absorbed by bimodal microstructure of TC4 alloy before adiabatic shear failure happening is the most, which of equiaxial microstructure of TC4 alloy, solution treated and aging microstructure of TB10 alloy and solution treated and diplex aging microstructure of TB10 alloy is less, and widmanstatten microstructure of TC4 alloy is more sensitive to the adiabatic shearing。With the increasing of primary a-phase in bimodal microstructure of TC4 alloy, the dynamic strength is slightly lower, and uniform dynamic plastic strain is enlarge. The dynamic plastic strain matches the uniform dynamic plastic strain better when solution treated below the phase transformation 50℃(the content of primary a-phase is about 38%). At this moment the energy absorbed before failure by the TC4 sample is the most, the adiabatic shear sensitivity is weaker and the ability to resist adiabatic shear failure is stronger.Exuiaxal a and intergranular (3 microstructure of TC4 alloy solution treated below the phase transformation 50℃and furnace cooling has excellent compatibility of deformation because the orientation between exuiaxal a-phase and matrix is random, which can compatibility the inhomogeneity effectively in the process of plastic deformation, and then has low adiabatic shear sensitivity and excellent ability to resist adiabatic shear failure.The failure law of TC4 bars ofΦ30 mm,Φ165 mm andΦ350 mm at high strain rate is generally consistent. However on the same loading condition the shear deformation and destruction of the samples were relatively more serious with the increase in bar size.With high strain rate, the transition zone between shear band and matrix of TB10 alloy by solution treated and aging is composed of grains of 20～50 nm in width with high dislocation density, and the grains were elongated along the shear direction. The center of shear band consists of a number of recrystallized grains with diameters of 50～100 nm and low dislocation density. The recrystallization is the result of grain mechanical fragmentation, crystal boundary migration and subgrain coarsening. With high strain rate loading, impact-induced phase transformation happened to the TB10 alloy treated ofβsolution, which calibrated to be martensite phase a". Because some shock energy was absorbed in the process of impact-induced phase transformation, it didn't reach the critical condition of constitutive destabilization to formation adiabatic shear band. Therefore the deformation of grain is uniform at 3500 s-1 and there is no adiabatic shear localization phenomenon.The TC4 plate rolled in 950℃has no remarkable texture, and the difference of adiabatic shear sensitivity in rolling direction(RD), transverse direction(TD) and normal direction(ND) is obscure. The main texture of TC4 plate rolled at 900℃is {1219} <12 3 9 1>±30°RD whose intensity value is 10.577. And the main texture of plate rolled at 1050℃is {T219}(1010) whose intensity value is 15.333. TC4 rolled plate shows significantly anisotropic when texture intensity is high:The dynamic strength of TD is the highest, which of ND is lower and which of RD is the lowest. The energy absorbed before adiabatic shear failure occurring of RD is the biggest, which of ND is smaller, and which of TD is the least. And this indicates that the direction of RD has the lowest adiabatic shear sensitivity and excellent ability to resist adiabatic shear failure.
|
PDF Full Text Request