Study On Deformation Mechanism Of Ti-10Mo-1Fe Alloy

Titanium alloy has been widely used in aerospace,energy,chemical and biomedical fields due to its high specific strength,significant corrosion resistance and better biocompatibility.Ti-Mo-based titanium alloy have mechanical property matching and excellent machining performance due to its special plastic deformation mechanism at room temperature.After various heat treatments,the initial microstructures of the titanium alloys before deformation are different,resulting in the difference between deformation mechanism at room temperature.Herein,the microstructure evolution of a nearβtitanium Ti-10Mo-1Fe alloy deformed under room temperature was analyzed.The influence of grain size,the initial microstructure before deformation and the stress loading method on the deformation mechanism and mechanical properties were studied.The main deformation mechanism of alloy after solution-treated followed with water cooling(WQ alloy)is{332}<113>twinning and stress-induced martensiteα"phase.The stress-inducedωphase,{112}<111>twinning,dislocation slip can also be detected in the deformed samples.The yield strength of the WQ alloy is acceptable,and the elongation is excellent.The excellent performance of the elongation is mainly due to the dynamic refinement of grain by the generation of{332}<113>twinning.The tensile/compressive strength of the alloy solution-treated above T_βfollowed with water quenching is affected by the grain size and the appearance of the{332}<113>twinning.When solution treated at 810℃and 840℃,the grain were fine enough to improve the strength,while the average grain size for these samples was not suitable for the formation of{332}<113>twinning.On the contrary,when solution treated at 900℃,the contribution of grain refinement was small while the strengthening effect of{332}<113>twinning was remarkable.The strengthening of grain size and twinning matches well while the alloy solution-treated at870℃.Therefore,the compression/tensile strength of the alloy is higher than solution-treated at other temperatures.Compared with the alloy solution-treated above T_β,the strength of the alloy increases and the elongation decreases when solution-treated at780℃.The existence of primaryαphase makes the distribution of intergranular twinning more unequal.The compression cracks can be observed in the 45°direction at the boundary between primaryαphase andβphase under serious deformation.The deformation mechanism of the tensile alloy is similar to the compression one.The volume fraction of the stress-inducedα"martensite is higher,and the coexistence of various deformation mechanisms is more complex than the compression alloy.Compared with the WQ alloy,the strength of the alloy increases and the elongation decreases when solution-treated above T_βfollowed with air cooling(AC alloy).Because a large number of nanoscale isothermalωphase precipitated in theβgrains during air cooling,which can improve the strength and hardness of the alloy.However,the isothermalωphase also suppressed the TWIP/TRIP effect in the alloy.The deformation mechanism of the alloy solution-treated above T_βfollowed with air cooling(AC alloy)were{332}<113>twinning and dislocation slip.The mechanical properties of the alloy are affected by combination of deformation modes(twinning and dislocation slip).Compared with the water quenching samples,the volume fraction of the{332}<113>twinning is lower,the width of the twinning is larger,the distortion of twinning boundary under severe deformation is more serious,and the dislocation slip makes more contribution to the deformation.The stress-inducedα"phase,the stress-inducedωphase and{112}<111>twinning can also be detected in the deformed air cooling samples.The strength and the elongation of the alloy solution-treated above T_βfollowed with furnace cooling(FC alloy)were lower than that for WQ alloy.Because more than 52%ofα_s phase precipitated in theβphase.It is evident that theβdomain size decreased because the formation ofαcan separate theβgrains and reduce the area of the matrix to the nanometer level.Consequently,the formation of twinning and stress-inducedα"martensite will be difficult.The strengthening effect ofα_s phase in the FC alloy is weaker than that of theωphase in the AC alloy,and is not as good as the strengthening effect of twinning in the WQ alloy,resulting in the lower compressive strength of the FC alloy.