Research Progress in Manufacturing Technology of Functionally Graded Materials

Advanced equipment in aerospace, energy power and other fields puts forward high requirements for the service performance of components in the multiple extreme harsh environment. Functionally graded material, as an advanced material based on function and performance drive, breaks the material performance originally coupled together, allows one or more of them to be improved alone, and makes it possible for key components to have different functions and performances at different locations. At present, it has shown a strong development potential and a wide range of applications. In the aerospace field, it works for things such as rocket engine combustors, nozzles, reflectors, solar panels, turbine disks, and space shuttle heat insulation tiles; It's used in automotive components such as diesel engine pistons, cylinder liners, combustion chambers, race car brakes, drive shafts and flywheels; In the medical field, the pore gradient structure can be prepared according to the actual bone degree of the patient to realize the customization of the elastic modulus, which can eliminate the long-standing problems of stress shielding, poor interface bonding between the host tissue and the implant, and bone loss caused by wear; In the mechanical manufacturing field, gradient gears or tools can be prepared to greatly improve the friction and wear performance of the wear surface. This paper first introduced the gradient characteristics and advantages of functionally graded material, and summarizes the development of functional graded materials. Secondly, several commonly used preparation technologies of graded materials were discussed, including vapor deposition, thermal spraying, laser additive manufacturing, powder metallurgy and centrifugal casting. The current research progress of metal / metal and metal / ceramic graded materials with high research heat was summarized. Due to its unique technical characteristics, laser additive manufacturing technology has promoted the design and preparation of functionally graded materials, and promoted the development of gradient materials. At present, some gradient path design methods and microstructure control methods have been preliminarily proposed in terms of the connection of different gradient materials, and the mechanism of melting behavior of each material system has been studied. In the future, more effective studies on the composition and morphology of the gradient interface can be carried out to further study the formation and regulation mechanism of the gradient interface, so as to realize the application of functional gradient materials in more material systems. Finally, the key problems in the preparation of functional graded materials were pointed out, which were formation of intermetallic compounds, thermal-physical parameter mismatch and variation of dilution rates. How to solve the above problems is crucial for the development of gradient materials. In terms of the microstructure regulation of intermetallic compounds, thermodynamic model simulation can be used to find the optimal path in the space of different components to construct the gradient transition path, so as to effectively avoid intermetallic compounds. In terms of thermophysical parameter regulation, the transition can be carried out by setting the intermediate composite components, eliminating the sharp gradient interface, realizing the smooth transition of the material structure and elements, and then reducing the thermal stress. On the one hand, the adjustment of dilution rate should control the material composition of the transition layer on both sides of the binding interface. On the other hand, different process parameters should be optimized for different transition layer materials, and the two aspects should be combined to achieve the adjustment of dilution rate. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.