Microstructure Evolution and Mechanical Properties of TA1 Pure Titanium Plate with Deformation Degree AITranslate

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Basic Information:

DOI：10.13373/j.cnki.cjrm.XY25030016

Chinese Library Classification Number:TG146.2

Citation Information:

The study focused on TA1 pure titanium as the research object. The electron back scatter diffraction （EBSD） technology and tensile testing were used to characterize the microstructure，texture，and mechanical properties of TA1 pure titanium plates rolled under different deformation regimes. The microstructure evolution process of TA1 pure titanium plates during hot rolling and the influence of deformation degree on mechanical properties were analyzed. In terms of microstructural evolution during hot rolling，at the initial stage of deformation，plastic deformation mainly occurred through twinning and slip. Most grains exhibited plastic deformation，with a large number of low-angle grain boundaries （LAGBs） and twins generated inside the grains. Meanwhile，fine recrystallized grains emerged at the grain boundaries. As the deformation degree increased，the equiaxed structure was flattened，and the dynamically recrystallized grains gradually increased. With small deformation，both slip and twinning participated in plastic deformation，and the proportion of twin boundaries was relatively high. However，with the increase in deformation，the proportion of twin boundaries decreased，and dislocation slip became the main mode of coordinating plastic deformation. Additionally，internal stress promoted the transformation of LAGBs into high-angle grain boundaries （HAGBs），leading to the formation of recrystallized grains. Mainly because at small deformations，the dislocation density was low，and there were relatively few slip systems that could be activated，so twinning was required to coordinate the deformation. As the deformation increased，the initially formed twin boundaries underwent torsion and tilting，and transformed into ordinary HAGBs，which destroyed the specific orientation relationship between the twins and the matrix. At the same time，the increase in dislocation density promoted the activation of more slip systems，leading to the formation of a large number of LAGBs. At this time，the main way to coordinate plastic deformation was dislocation slip. Additionally，as the deformation increased，the internal stress increased，which promoted a large number of LAGBs to grow into HAGBs，resulting in the formation of fine recrystallized grains. Regarding texture evolution，significant changes were observed in the {0001} pole-figure texture during hot rolling. In the small deformation stage，the initial three-peak texture disappeared，and part of the {0001}∥transverse direction （TD） texture transformed into {0001}∥ rolling direction （RD） texture，forming a two-peak texture. With further deformation，the {0001}∥RD texture vanished，and a strong single-peak {0001}∥TD texture was formed，with the texture strength increasing. The inverse pole figures showed that the main texture types during hot-rolling deformation were <01$\overline{1}$0> ∥RD texture and <0001> deviated by 30° parallel to normal direction （ND） texture. The main difference laid in the change of strength. At small deformations，the <01$\overline{1}$0> ∥RD texture developed into the main texture，and then the strength of this texture and the ∥ND texture alternated. For the mechanical properties at room temperature，as the hot-rolling deformation degree increased，the tensile and yield strengths of the plates increased，while the elongation after fracture decreased. This was mainly due to grain refinement，an increase in dislocation density，and work hardening during deformation，which led to an increase in strength and a decrease in plasticity. This was mainly because as the degree of deformation increased，the original recrystallized equiaxed structure was fully fragmented，and the grains were fully refined，thus increasing the strength of the plate. At the same time，with the increase of cumulative deformation，the dislocation density increased，which promoted the distortion of the crystal lattice，leading to an increase in the internal energy of the material and an increase in internal stress. As a result，the plasticity of the plate decreased，and work hardening also increased the strength of the plate. During the process of plastic deformation，the stress concentration formed by the dislocation pile-up would promote the initiation of cracks，while the grain boundaries would hinder the propagation of cracks. Therefore，cracks were likely to propagate on the coarse grains. In addition，the coarser structure was conducive to the continuous occurrence of slip，which in turn led to uneven deformation. The deformation twins generated in the initial stage would cause the crystal to rotate，enabling the slip to continue，thereby releasing stress，weakening the initiation of cracks，and exhibiting better plasticity. The plates hot-rolled at 750 ℃ had the same texture type，which was mainly the cylindrical texture parallel to RD. Moreover，during the room-temperature tensile test along the TD，the {10$\overline{1}$0}<11$\overline{2}$0> prism plane slip system was relatively easy to activate. Therefore，for the plates obtained at the same deformation temperature，the influence of the texture on the mechanical properties was basically the same. The mechanical properties of the plates obtained at the same deformation temperature were mainly affected by the grain size. This research provided crucial theoretical support for the optimization of the processing technology of TA1 pure titanium，which was of great significance for improving the performance and quality of TA1 pure titanium products in practical applications.