| WSTi3515S alloy is a full beta burn-resistant titanium alloy,which has excellent burn-resistance properties and good comprehensive properties.However,due to its high temperature deformation resistance,titanium alloy is easy to crack limiting its large-scale engineering application.Therefore,it is very important to explore and develop the plastic processing characteristics and to study the hot deformation process of WSTi3515S titanium alloy.In this paper,the WSTi3515S burn-resistant titanium alloy annealing after forging is used as the object.The isothermal simulation compression test is carried out to study the mechanical behavior and microstructure evolution of the alloy under different hot deformation conditions.And the corresponding constitutive equations,hot processing map and dynamic recrystallization kinetics models of deformation conditions were established.The main research contents and results are as follows:By analyzing the mechanical behavior of WSTi3515S burn-resistant titanium alloy during hot deformation,it is found that the flow stress reduced with the increase of deformation temperature and the decreases of strain rate;When the strain rate is small (5×10-4?1×10-2s-1),the stress-strain curve exhibits a dynamic recrystallization type.With a large strain rate(0.1?10s-1),the flow stress curve shows a dynamic recovery type;The Arrhenius constitutive equation is established,and the hot deformation activation energy of WSTi3515S alloy is 252.445 KJ/mol.The equation can be used to describe the steady flow phase of hot deformation of the alloy.According to the dynamic material model?DMM?and based on the Prasad instability criterion,the hot deformation processing map of WSTi3515S burn-resistant titanium alloy was established.The instability deformation zone appears in the deformation range of 800?840?,1×10-2?10s-1,and should be avoided in the actual production process;the low energy dissipation zone is concentrated at 800?840?,5×10-4?1×10-2s-1 and 840?920?,1×10-2?10s-1 deformation zone.Although it is in the safe zone,which can not be conducive to the dynamic recrystallization;The peak energy dissipation rate appears in the higher temperature and low strain rate region(840?920?,5×10-4?1×10-2s-1),and the dynamic recrystallization is fully carried out,which can obtain excellent comprehensive mechanical properties.It is the best deformation zone.Through the analysis of the microstructure evolution of WSTi3515S flame retardant titanium alloy during hot compression deformation,it is found that:With the increase of deformation temperature,the initial equiaxed?grains of WSTi3515S alloy are gradually replaced by new grains formed by dynamic recovery and dynamic recrystallization;When the strain rate is 10?0.1s-1,the large strain rate causes the original?grain to be distorted,the grain boundary is broken,and the microstructure is gradually occupyed by the dynamic recovery of the original grain of the polygon and large number of dynamic recrystallized nuclei with the strain rate decreases;At low strain rates of 1×10-2?5×10-4s-1,fine and uniform recrystallized equiaxed grains are obtained due to the growth of the dynamic recrystallization.The critical strain equation of dynamic recrystallization of WSTi3515S titanium alloy under hot deformation conditions is established.The results show that the critical strain and critical stress of dynamic recrystallization of WSTi3515S alloy increase with the increase of Zener-Holomon parameter equation;The dynamic recrystallization dislocation density evolution model is established based on the KM equation.It is shown that the dislocation density shows a trend of increasing when hot deformation,and finally remaining unchanged after decreasing.And the dislocation density get lower with the increasing of deformation temperature and the decreasing of strain rate.The recrystallization volume fraction model of WSTi3515S alloy is established,and when reaches the critical strain,the dynamic recrystallization volume fraction(XDRX)growth rate under different deformation conditions increases rapidly with the increase of true strain until full dynamic recrystallization is achieved. |
PDF Full Text Request