Study On Deformation Mechanisms And Mechanical Properties Of Metastable ?-ZrTiAlV Alloy At Room Temperature

Zr and Zr alloys have excellent anti-irradiation,good anti-genic erosion and good dimensional stability in alternating temperature fields,and have potential to be used as moving components material in spacecrafts and deep-sea detectors.However,traditional Zr alloys are normally with low strength and toughness,and it is difficult to meet the requirements as moving component materials.The new Zr Ti Al V series alloys have high strength,good plasticity and good dimensional stability,is a strong competitor for moving components material in spacecrafts and deep-sea detectors.However,the current researches on the Zr Ti Al V alloys mainly focus on the composition control,preparation process and mechanical properties,and the martensitic transformation,twinning and dislocation slip and the effects of these deformation mechanisms on the mechanical properties in the deformation process of Zr Ti Al V alloys,especially in metastable?-ZrTiAlV alloys have never been systematically studied.In this paper,the deformation mechanisms and mechanical properties of metastable?-ZrTiAlV alloy during deformation with different deformation modes,different strains,different initial?grain size and different?phase content were systematically studied and the intrinsic link between deformation mechanisms and mechanical properties have been explored.Therefore,the deformation behavior of?-ZrTiAlV alloys is more deeply understood,and the experimental data and theoretical support for the performance improvement and future service of the new Zr Ti Al V alloys are provided.In this paper,the metastable?-ZrTiAlV alloy was used.Electron backscatter diffraction(EBSD),transmission electron microscopy(TEM)technologies and X-ray diffraction(XRD)were carryed to characterize the deformation microstructures.The deformation mechanisms and mechanical properties of the?-ZrTiAlV alloy under different deformation modes,different strains,different initial?grain size and different?content were systematically studied.The main conclusions are summarized below:(1)The deformation-induced??and???martensitic transformation and internal{1012}_??twinning coexist in the compressed metastable?-ZrTiAlV alloy.Such a combination of deformation mechanisms was observed in metastable?Zr or Ti alloys for the first time.The deformation mechanisms during tensile were deforamtion-induced????martensitic transformation,kinking bands and{1011}_??twinning.The{1012}_??and{1011}_??internal twining are the secondary deformation products of??martensite which is related to the accommodation of local plastic strains or transformation strains generated in??plates during deformation.(2)The morphology evolutions of deformation-induced??,???martensite and retained?phase with increasing deformation strains were systematically studied in metastable?-ZrTiAlV alloy for the first time.Three types of deformation-induced??martensite have been observed during deformation,namely,twinned??martensite,untwinned??martensite and paired??martensite.Transitions in morphology of twinned??martensite from thin plate to twinned plate and to widened twinned plate,eventually to{1012}_??twin-related domains and of untwinned??martensite from thin plate to widened plate to domain have been observed with increasing deformation strains.The paired??martensite is undergone a process in which the??martensite impacted grain boundaries stimulating the nucleation of new??martensite in neighboring grains,and then leading to martensite growth on both sides grow simultaneously.With progressive deformation,the nano-size deformation-induced???martensite changes from long thin plate to ladder-shaped plate to 90°rotation domains.The average hardness increased with increase in deformation strains,owing to the martensitic transformation strengthening along with dislocation multiplication strengthening.(3)In metastable?-ZrTiAlV alloy,the triggering stress increases,the total elongation and tensile strength decreases and the double yielding phenomena gradually disappears when the initial?grain size increases from 36?m to 267?m.Meanwhile,the work hardening rate curve changes from an obvious parabolic evolution to a monotonically decreasing evolution and the work hardening effect is gradually reduced.Although the deformation mechanisms in all samples are kinking bands,deformation-induced??martensite and{1011}_??internal twinning as the initial?grain size increases.However,increasing the initial?grain size will increase the size of deformation products,reducing the occurrence of special boundaries and weakening the dynamic Hall-Petch effect.(4)In metastable?-ZrTiAlV alloy,the double yielding phenomena gradually disappears,the triggering stress increases,the total elongation decreases and the tensile strength did not change significantly when the?phase fraction increases from 0%to42.4%.Meanwhile,the work hardening rate curve changes from an obvious parabolic evolution to a monotonically decreasing evolution and the work hardening effect is gradually reduced.As the?phase fraction increases,the stability of the?phase increases gradually and the size of the?domain gradually decreases,the deformation mechanisms evolve from the coexistence of kinking bands,deformation-induced??martensite and{1011}_??internal twinning at 0?17.5%?phase fraction to completely suppressed at 42.4%?phase fraction.