Study On The Forming Features And Process Of Large Scale TA15 Titanium Alloy Aviation Structural Parts

Titanium alloy, as the most important selectable structural material in modern aircraft, its application level in design even become the most important mark to measure the extent of advanced in selection of aircraft structural material. Titanium alloy can play the role that other metals can not match on such aspects, to decrease the total weight of aircraft, to raise the design efficiency of aircraft structure, to improve the structural reliability, to enhance the life of aircraftbody, to meet the requirements that worked under high temperature, high load and corrosive condition. At present the application of titanium aircraft structural parts are moving in the overall and large-scale direction. Forging process is the most applied forming method to titanium alloy; it can change the microstructure and mechanical properties accurately by deformation and heat treatment. So, it has the most practical significance to research the forming features and process of large-scale titanium alloy aircraft structural parts.TA15 titanium alloy whole frame die forging part was the typical large scale titanium alloy aircraft structural part. By study on the hot deformation features and combined with the reaserch on forging process parameters optimization, it can provide the base pudution data and process experience to die forging process of this type of large scale titanium alloy structural part.To study the hot deformation features of TA15 titanium alloy, a series of hot compression tests which were tested on Gleeble-1500D material thermal / power simulation test machine were carried out. In the test, TA15 titanium alloy pecimence were compressed under the heating temperature of 800℃,850℃,900℃,950℃,1000℃and 1050℃by strain rates of 0.01s-1,0.1 s-1,1 s-1,10 s-1 respectively. By the hot compression test results data, the high temperature rheological behavior of TA15 were analysised and the constitutive equation based on Arrhenius flow model and Fields-Backofen flow stress model were established. The constitutive equation were verified and discussed.Based on the theory of dynamic material modeling (DMM), processing map of TA15 were established with the hot compression test data that the strain were 0.2,0.4,0.6 respectively. The hot deformation ability of this alloy was analysised and the hot working process parameters were optimized.Plastic finite element analysis software DEFORM-2D was apllied to simulate the TA15 titanium alloy hot compression test plan. The hot process performance of it was discussed in terms of material critical damage factor by study on the mechanical behavior of ductile damage with numerical simulation. The law that the material critical damage factor varied with the deforming temperature and strain rate changing was established.With the large scale TA15 titanium alloy whole frame die forging, numerical simulation technology was carried out to study its hot forming process. The optimized scheme of forging blank piece was obtained by study on the outline and size of it. Forging temperature, stroke speed, and deformation power effect on the forging forming process were anlysised comprehensively, the reasonable parameters of titanium alloy whole frame part forging process were obtained. The reliability of the constitutive model that eatablished using hot compression test data was verified by using it in whole frame forging part numerical simulation research.The large scale TA15 titanium alloy whole frame die forging was trialed on 1MJ counter-blow hammer based on the study of basic theory and numerical simulation. The process of forging blank piece and parameters of die forging were verified in the trial. The microstructure and mechanical properties of the finished forging were tested and evaluated; the results show that the forging had reached the demand of standards. The trial verified the results of numerical simulation and flow stress model which established by hot compression test also. The site production quality control technology of large titanium forging were summaried, that is the critical control of the process"microstructure preparation+coordination and control of forging deformation and forming temperature+microstructure monitoring"is the important guarantee for the successful development of large scale titanium alloy forging. In the trial process, the die steel H13 was researched in terms of carbides. The research results are instructive to the development of large-scale forging on hammer.