However, there are some problems in the hot - plastic forming process of this alloy. The hot - deformation behavior and the microstructure evolution of the dual - phase alloy are relatively complex. In current manufacturing, due to improper matching and control of process parameters, many problems such as plastic instability, low forming accuracy, and non - uniform microstructure often occur. Therefore, it is very important to study its high - temperature plastic deformation behavior.
In order to deeply study the hot - deformation behavior of Ti - 6.5Al - 3.5Mo - 1.5Zr - 0.3Si alloy, isothermal constant - strain - rate hot - compression experiments were carried out. Under different deformation conditions, the true stress - true strain curves of this alloy show different characteristics. In the α+β phase region with a deformation temperature of 1173 - 1273K, the true stress - true strain curves show obvious dynamic recrystallization characteristics. At this time, the flow stress will increase sharply to a peak value with the increase of strain due to work hardening, and then tend to decrease due to the action of dynamic recovery and dynamic recrystallization softening mechanisms. In the β phase region with a deformation temperature of 1323K, the true stress - true strain curves conform to the significant characteristics of the dynamic recovery type. The flow stress first increases sharply to a peak value with the increase of strain, and then gradually decreases or tends to be stable.
This indicates that the change in the flow stress of Ti - 6.5Al - 3.5Mo - 1.5Zr - 0.3Si alloy is the result of the competition between work hardening and dynamic softening during the hot - plastic deformation process. In the early stage of hot deformation, work hardening plays a dominant role; as the hot - plastic deformation progresses, work hardening and dynamic softening reach a balance, and even the dynamic softening mechanism may dominate.
In order to better study the law of flow stress during the hot - plastic deformation process of this alloy, the constitutive relationship under any flow stress was established by using the modified Arrhenius constitutive equation. The constructed Arrhenius constitutive equation does not contain the strain parameter. By introducing the expressions of relevant material constants and strain into the equation, the accuracy of the constitutive equation is improved. By comparing the model - predicted data with the actual experimental data, it is found that under different deformation conditions, the prediction accuracy of the Arrhenius constitutive equation coupled with strain is different. When the deformation temperatures are 1173K and 1273K, the constitutive equation shows a relatively high prediction accuracy.
In addition, the hot - plastic deformation behavior of the alloy was analyzed by establishing a hot - working map. Based on the dynamic material model, the material is regarded as a non - linear energy - dissipating body during the hot - plastic deformation process, and the energy - dissipation - efficiency η value is calculated to reflect the microstructure deformation mechanisms in different strain - rate and deformation - temperature ranges. The high - energy - dissipation regions of plastic deformation of Ti - 6.5Al - 3.5Mo - 1.5Zr - 0.3Si alloy are mainly concentrated in the medium - and - high - temperature regions at low strain rates.
According to the hot - working map constructed based on the Babu instability criterion, the plastic - instability regions of this alloy are the low - temperature region and the medium - and - high - temperature regions at medium - and - high strain rates. The energy - dissipation regions with higher η values are the medium - and - high - temperature regions at low strain rates, and its optimal hot - plastic - deformation - process - parameter window is: deformation temperature 1230 - 1323K, strain rate 0.1 - 0.816s⁻¹.
Through the analysis of the microstructure in the instability regions in the hot - working map of Ti - 6.5Al - 3.5Mo - 1.5Zr - 0.3Si alloy, it can be known that adiabatic shear bands are likely to appear in the process regions with low temperature and high strain rate, and the deformation mechanisms of local plastic flow and adiabatic shear bands are the same, only the degree of local deformation is slightly smaller.
In summary, the research on the high - temperature plastic deformation behavior of Ti - 6.5Al - 3.5Mo - 1.5Zr - 0.3Si alloy provides a theoretical basis for determining its reasonable plastic - deformation - process parameters and solving the forming - technology problems of typical difficult - to - form parts, and has important guiding significance for the hot - working process of this alloy.