Research On Dynamic Response Of Meta-stable βTi-5553Alloy Under Shock Wave Loading

In this paper,the metastable beta Ti-5553alloy was systemically investigated.Theeffects of heat treatment on the quasi static mechanics performances and dynamicalperformances were explored through quasistatic and dynamic compression and tensile tests.Structure damage and failure mechanism, dynamic mechanical properties and phasetransformation were invsstigated by light gas gun and Split Hopkinson PressureBar(SHPB).with optical microscope(OM),scanning electronic microscope(SEM)andtransmission electronic microscope(TEM).The major conclusions are as follows.Quasi static and dynamical compression tests was carried out to obtain four kindsmicrostructures:dimodal structure(T1,T2),basket weave structure (T3), widmanstattenstructure (T4).The results show that with the solid solution temperature increase in heattreatment, the percentage reduction of area is reduced as well as the plastic.With theoriginal beta grain not quite big, the tensile strength of widmanstatten structure at roomtemperature was similar with other groups,but was low plasticity.Under1000s-1~3000s-1strain rateloading,dimodal microstructure was not obvious strain rate hardening but mainlythe strengthening mechanism of strain-hardening. The true stress-strain curve of Ti-55553alloy with two phases structures (basket weave and widmanstatten) under different strainrates exhibited strain rate hardening effect. Under high strain rate dynamic compression, thestress induce martensite phase transformationβ-α〞, needle and parallelα" phase insubstrate.With high solid solution temperature, the secondaryα〞phase volume fractionincreasand the strain rate decreas as the material was fracture.The beta single-phase Ti-5553alloy structurewas investigated by SHPB loadingcompression.Under the condition of high strain rate (1000s-1-3000s-1),Ti-5553alloy do notshow obvious strain harding effect.Under the condition of high strain rate(3000s-1),adiabatic shear failure andmartensite phase transformation β-α〞occurre inTi-5553alloy.The titanium alloy of beta single-phase was investigated through light gas gun andSHPB dynamic compression to investigate the effect on the mechanical properties.After theshock wave loading, the plasticity and strength is reduced.With the increase of impactvelocity, the yield strength first decrease and then increased.With the improvement of impact velocity, phase transformation β-α〞happene under the tensile shock wavesloading.The increase of the content of beta phase make shock waves alloy " softening"effect. By the light gas gun of low speed (360m/s) and medium speed (430m/s,480m/s)impact, adiabatic shear band occured at strain rate of the2000s-1.The adiabatic shearband was the same strain rate;Under higher impact velocity of560m/s, the strain rate ofemergence of adiabatic shear band to improve to the3500s-1.High temperature Hopkinson bar with synchro assembly system was carried out toinvestigated Ti-5553alloy of beta single-phase for charactering the mechanical propertiesand microstructure evolution under high temperature and high strain rate.The rate of strainrate sensitivity of beta single-phase structure decreas gradually along with the increase oftemperature or becomes negative. Above400℃,Ti-5553alloy of beta single-phase is notsensitive to strain rate.The temperature sensitivity of beta single phase at first increaseswith rising temperature and later decrease.At400℃,the temperature sensitivity reached themaximum.With rising temperature,the temperature sensitivity increased slightly. At400℃and600℃,martensite phase transformation occurred in Ti-5553alloy with beta single-phaseGleeble-3500was carried out to investigated Ti-5553alloy of beta single-phase.Withrising strain rate,the stress of the alloy increased slightly under every temperature.At200℃,the stress ofTi-5553alloy showed the same regularizes under three strain rates.At600℃,with rising strain rate,the average stress incressed.The microstructure evolutionregularity in Ti-5553alloy with the increase of temperature was the fact that secondaryalpha happened at grain boundaries and defects for having more energy here.