The invention relates to a hot extrusion forming method for a titanium alloy fastener, in particular to a hot extrusion forming method for an inner hexagonal bolt blank of a titanium alloy, which belongs to the technical field of plastic processing and forming for metal pieces. The hot extrusion forming method for an inner hexagonal bolt blank of a titanium alloy comprises the following technological processes of: (1) feeding; (2) heating the blank; (3) preheating a heading mould; (4) heading; (5) preheating a punching mould; and (6) punching. The hot extrusion forming method for an inner hexagonal bolt blank of a titanium alloy can effectively solve the problem that an inner hexagonal bolt blank of a titanium alloy with a larger length-to-diameter ratio is difficult to form by plastic processing, and can meet the needs of the mass production of the inner hexagonal bolt blank of a titanium alloy.

The compression tests of TiC-Ni alloy were carried out by Gleeble-2000 simulator, and the flow stress data were obtained at different temperature, strain rates and various true strain. Based on the experimental datas and network knowledge, an artificial neural network with back propagation algorithm was established and knowledge based on constitutive relations model was developed after training. Error analysis shows that the artificial neural network model for constitutive relationship has higher predicted precision, and it can be used for guiding the reactive hot press process and applying in finite element simulation of TiC-Ni.

By employing latest developed corrosion-resistant metal-ceramic electrode and using trailing peening to achieve the densification of coating by TIG,the bead welding layer of TiCNi cermet on the surface of steel was obtained.The analysis of microstructure and XRD indicates that the bead welding is of good densification and has high combination strength.Regarding the defects occurring at the ends of the ceramic lining pipes,many repairing tests were carried out,in which different kinds of cermet electrodes were used.It is found that the best structure of bead welding is composed of TiCNi and Fe/Al2O3/TiC.The best process parameters of the bead welding follows: electric current 80～120 A,voltage 50～60 V.When the cermet electrode contains Fe/Al2O3,the good welding with the ceramic lining pipe can be got;and when the cermet electrode contains Ni,the good welding can be got.In the end,a method was raised to repair the partly destroyed ceramic lining pipes.

Using TiC-Ni ceramic metal electrode which was made by means of SHS,the ceramic coat was prepared on the surface of steel by TIG.The mathematical models and physical models for temperature and stress field of TiC-Ni coat were built.The distribution of the temperature and residual stress field,the changes of temperature field in surfacing layer in the deposition process were analysed through finite element analysis software.Meanwhile,the continuity and thermal relaxation of the coating were checked through analysing the residual stress changes.The rules of the residual stress fields were simulated and analyzed.

The design research for thermal stress relaxation coating of TiCNi/Fe was done. A new method of coating structure design was put forward. The high density TiCNi/Fe ceramic coating was produced on the surface of Fe by self-propagating high-temperature synthesis method combined with hot pressing. The wear-resistant properties were examined through ball-on-disk wear tester. The microstructure of TiCNi/Fe ceramic coating was investigated. The results show that TiCNi/Fe ceramic exhibits an excellent wear-resistant property. There is little mass loss after 40 min wear test under 30 N load and dry sliding condition. The main wear mechanism can be described by the following stages: sticking friction, abrasion and stripping of hard phase.

In recent years, Nitinol, near-equiatomic nickel-titanium alloys, have found growing applications in medical technology and joining technology, due to their special characteristics such as shape memory, superelasticity and biocompatibility. The production of Nitinol tube cost-effectively remains a technical challenge. In this paper, we describe a hot drawing process for Nitinol tube production. A Nitinol tube blank and a metal core are assembled together. The assembly is hot drawn for several passes to a final diameter. The metal core is then plastically stretched to reduce its diameter and removed from the tube. Hot drawing process has been applied to Ni50.7Ti and Ni47Ti44Nb9 alloys. Nitinol tubes of 13.6 mm outer diameter and 1 mm wall thickness have been successfully produced from a tube blank of 20 mm outer diameter and 3.5 mm thickness.

The technology process of TiC-Ni functional gradient coating prepared by reactive flame spraying was introduced. The mathematical models and the physical models for temperature field and stress field of TiC-Ni functional gradient coating were built. The distribution of temperature field and residual stress field during the deposition process was analysed using finite element analysis software. The effects of experiment conditions on the temperature field was analysed. Meanwhile, the continuity and the thermal relaxation of the coating were checked through analysing the residual stress changing along the direction of the coating thickness. Different residual stress fields in different spraying speeds were simulated and compared. The results show that different spraying speeds affect little the distribution of stress field.

In order to study the high temperature thixo-forming rules of TiC-Ni cermet,the thixo-forming mechanical behavior of the TiC-Ni cermet was studied on the Gleeble-2000 material thermo-simulation machine.The visco-plastic thixo-forming constitutive model of the stress-strain at 950 ℃,1000 ℃and 1050 ℃ was set up through the regression analysis,and the regression equation was examined by mathematical statistics,its examination indexes were approved in confidence interval of 95%.

Based on the principle of the self-propagating high-temperature synthesis (SHS) reaction of Ti and C powders, a Ti CNi cermet composite coating was prepared successfully on LY12 alloy substrate by means of laser cladding. The good technical parameters such as laser power, scanning velocity, beam diameter, overlap ratio and so on were gotten. The OM, XRD, EDS techniques were employed to study the phases of the coating. The results show that the top coating is a layer of TiCNi, below which is the Ni-Al intermetallic fusion layer and the substrate, and the coating's microstructure is dense and pure. Elements are diffused mutually at both sides of the interface and a metallurgical bonding interface. The heating of the reaction coarsens the grain size of the substrate near the interface. The formation mechanism of the layer is explained. It involves a series of SHS reactions, including the reactions between Ti and Ni, Ti and C, Ni and Al. Good interfacial bonding is achieved at the fusion layer, TiCNi interface and the fusion layer/ LY12 alloy substrate. The thermal shock experiment was employed to study the thermal shock properties of the coating at different elevated temperature. The results show that the thermal shock property of the coating is fine.