Titanium alloys are widely used in aerospace and other fields because of their excellent properties such as low density, high specific strength and creep resistance. Titanium alloys have the characteristics of low ductility, high deformation resistance and obvious anisotropy. Therefore, titanium alloys are very sensitive to hot deformation process parameters.
Application of Simulation Technology in Hot Machining of Titanium Alloys
Titanium alloys usually need to be hot-worked in beta single-phase region or alpha beta two-phase region to obtain products with certain structure and properties. The choice of hot working parameters has an important influence on the processing properties and microstructures of titanium alloys. In recent years, more and more research has been done in the field of hot working of titanium alloys in China. Thermal simulation technology and numerical simulation technology are particularly prominent in the application of hot deformation mechanism and microstructure evolution of titanium alloys.
Typical application of thermal simulation technology
Many scholars have carried out hot compression deformation experiments on different types of titanium alloys using thermal/mechanical simulator, and obtained the flow stress curve, i.e. the stress-strain relationship. The flow stress curve reflects the intrinsic relationship between flow stress and deformation process parameters, and it is also the macroscopic manifestation of the changes in the internal structure of materials. Xu Wenchen et al. carried out constant strain rate compression deformation tests on a thermal simulator to study the dynamic hot deformation behavior of TA15 titanium alloy, calculated the deformation activation energy Q and observed the hot deformation structure. Dynamic recrystallization is the main softening mechanism in the alpha phase region, while dynamic recovery is the main softening mechanism in the beta phase region.
Typical application of numerical simulation technology
Because the numerical simulation technology can make the hot working process of titanium alloy reappear on the computer truly, the enterprise producers and scientific researchers use this technology to study the relationship between the ideal process parameters and the corresponding structure and mechanical properties, so as to optimize the current production process and reduce the research of new products, new processes and new materials. The purpose of making cost. Shao Hui [11] et al. studied the alpha phase evolution of TC21 titanium alloy with lamellar structure during forging in two-phase zone. DEFORM software was used to simulate and analyze the change rule of temperature field and strain field in forging process, and the morphology change of alpha phase was quantitatively analyzed. The smaller the Feret Ratio is, the more spheroidized the morphology is. The results show that the strain field and temperature field influence the evolution of flake phase. Under lower strain conditions, the temperature at the edge of forging material decreases rapidly, the recrystallization is sufficient, and the temperature at the center of forging material is higher.
Simulation of Microstructure Evolution
The diversity of titanium alloy microstructures is regularly related to the multi-process production process and the diversity of each process. This complex relationship makes it difficult to predict and control the structure and properties of titanium alloys by traditional methods. With the development of computer and numerical simulation technology in recent years, the numerical simulation method of micro-structure has become a powerful tool to obtain the quantitative relationship between the influence of main process parameters on the macro and micro-structure of hot-formed workpiece. Using numerical simulation technology to reproduce the evolution process of microstructures can not only deepen the understanding of the mechanism of microstructural change and promote the development of existing theories, but also improve the structure of materials and optimize the preparation process, so as to obtain the expected mechanical properties of materials.
Compared with the traditional process trial-and-error method, simulation technology can shorten the development cycle, reduce production costs and optimize production process, thus achieving the purpose of improving production efficiency and increasing economic benefits. Because of its high price and long production cycle, simulation technology is urgently needed to open up a shortcut for titanium alloys, and overcome the difficult problems of narrow hot working temperature range and complex process-structure-performance relationship.
Thermal simulation technology and numerical simulation technology have been used to study the hot deformation mechanism and microstructure evolution of titanium alloys at home and abroad. The relationship between force and energy parameters, process parameters and microstructure has been obtained, which can optimize production process and improve product quality. However, due to the inaccurate data of material properties, the difficulty of approaching the actual boundary conditions and friction parameters, and the absence of micro-structure changes in macro-variables, the simulation results have some errors compared with the actual production.
In order to study the mechanism of hot deformation and the evolution of microstructure of titanium alloys in the future, physical simulation and numerical simulation techniques should be combined organically to establish a macro-finite element model more in line with the actual production process and to couple it with the micro-structure evolution model so as to provide theoretical basis for on-site production. Moreover, it can guide the field process quantitatively, and finally achieve the goal of real-time tracking the deformation process and controlling the product quality.