Research On High Temperature Deformation Behaviors And Application Of Bti-62421s Alloys

The high temperature mechanical behavior, strain hardening behavior andmicrostructures of a new near α high temperature titanium alloy BTi-62421S were studied byhot compression simulation, plane strain compression tests. For the titanium complexstructure, the theory of integral forming process with multi-direction loading was analyzedusing numerical simulation, moreover practical processing was performed to veitify thefeasibility. The research has important significances on both enriching the plastic processingtheory of titanium alloy and improving the manufacturing level of weapons equipment. Themain research contents and conclusions are the following:(1) In this investigation, isothermal compression tests were carried out on Gleeble-3800system at constant strain rate with the deformation of70%. The influences of deformationtemperature and strain rate on the high temperature flow stress and microstructure ofBTi-62421S alloy were analyzed. The dynamic deformation mechanisms were revealedthrough deformation activation energy calculation and microstructure observation. Theconstitutive equation of this alloy in (α+β) two-phase region during hot deformation wasestablished, which can provides a theoretical basis for equipment selection and finite elementsimulation.(2) The influences of thermal processing parameters on the mechanical properties ofBTi-62421S alloys were studied by plane strain compression tests. The results showed that, inthe (α+β) two phase region, the tensile strength can be significantly improved by thedeformation with equivalent strain greater than or equal to0.80; while the tensile strengthwas decreased in β single-phase region or in the (α+β) two phase region with the equivalentstrain less than0.8. At the same time, it was also found that the hardness of the deformedalloys was higher than the as-cast one.(3) The microstructures of specimens after hot compression simulation experiments andplane strain compression test were observed, and the influences of thermal processingparameters on the evolution of microstructure were also analyzed. The results can establishthe foundation for controlling the microstructures of the components for further improvementtheir mechanical properties. When deformed in the (α+β) phase region, the lamellarstructure were mainly equiaxed evolved, for BTi-62421S alloy, the kinking of lamellarstructure promoted equiaxed processes. Meanwhile it was found that the globularization oflamellar structure need a certain deformation degree and deformation temperature, the criticalequivalent strain was0.8and the critical temperature was900℃. For obtaining uniform fineequiaxed microstructures, the deformation process should be held at higher temperature in the(α+β) phase region with larger deformation degree.(4)"theε&-T-cracking figure of compress deformed BTi-62421S alloy" was establishtedwith the combination of the crack specimens after hot compression simulation. According tothe results of plane strain compression tests,"the relationship among the deformation temperature–deformation degree-tensile strength of BTi-62421S Alloy" was establishted,In order to improve the performance and ensure the quality of the formed workpiece.(5) For a kind of monolithic component, in this study, rational shape and size ofroughcast were designed and three schemes of integral forming process with multi-directionloading were proposed. With the help of numerical simulation, a conclusion was drawn that,compared with other schemes, the forming process with first axial compression then lateralextrusion was the best for less loading, short duration of maximum load, little influences ondie life, uniform deformation, smallest injury and least likely of crack.(6) The die was designed for the monolithic component, and the forming process wascarried out in this work. The monolithic component made by BTi-62421S alloy was full filledwith no folding, tearing and other defects, besides the accuracy of shape and size can meetthe technical requirements.more results indicate that the forming process of "precast-heating-isothermal integral forming process with multi-direction loading" was feasible for titaniumcomplex components. Furthermore, material utilization through direct forming is morethen80%, together the cost of production is reduced for the decreasing of forming load and theimprovement of mechanical properties.Through the research, the key technical issues oftitanium complex monolithic component were solved, the forming theory for the titaniumalloy was enriched, witch lay the foundation for the engineering applications of titaniummonolithic component.