Mechanical behavior of a near α titanium alloy under dynamic compression: Characterization and modeling

Dynamic compression tests under strain rates from 870 s(-1) to 2100 s(-1) were conducted for a near alpha Ti-8Al-1Mo-1V titanium alloy with equiaxed microstructure. Compression behavior, adiabatic shearing and band microstructure were investigated via characterization and calculation. The results demonstrate that all dynamic constitutive curves exhibited obvious stress fluctuation phenomenon with double increase-decrease changing stages at the primary stage of compression. The dislocation multiplication theory can be used to explain this phenomenon. After the stress fluctuation period, work hardening coexisted with the thermal softening, resulting in the slow hardening tendency in constitutive curves. J-C model was utilized to quantify the dynamic constitutive curves. The deviations between the predicted and experimental curves under high strain rates may be attributed to the over-consideration of thermal softening effect in J-C model. Adiabatic shearing band (ASB) began to form under the strain rate of 2100 s(-1). A total shearing strain of 8.1 within ASB achieved in 8.9 mu s, corresponding to a local strain rate of about 9.1 x 10(5) s(-1) and is over 430 times of the macro strain rate. Post annealing was conducted on ASB before EBSD characterization. Due to the static recrystallization during annealing, the alpha phase within ASB generally presented as ultra-fine grains less than 1 mu m in diameter.