Fabrication And Microstructure Of Ti-43Al-9V-1Y Alloy Honeycomb Structure Wiyh Prefabricated Vacancy

TiAl-based alloys have the advantages of high specific strength,oxidation resistance and corrosion resistance,and excellent creep resistance.The honeycomb structure formed by TiAl-based alloy can further reduce the weight of high-temperature components and improve the structural strength of components,making it an aerospace field.One of the most promising high-temperature lightweight structures.Due to the difficulty in preparation of domestic TiAl-based alloy sheets and poor forming properties,it is difficult to fabricate TiAl-based alloy honeycomb structures by conventional forming methods.In view of this,this paper proposes a new process for fabricating TiAl-based alloy planar/curved honeycomb structures by the pull forming method.Large-sized honeycomb structures are obtained by drawing and forming small-sized sheets,which is of great significance for solving the problem of manufacturing large-sized and lightweight structures of TiAl-based alloys,and provides a basis for the manufacture of difficult-to-deform alloy honeycomb structures.Firstly,the finite element analysis of the deformation process of different vacant size sheets was carried out by ANSYS software.The influence of the size and distribution of the hollow position on the overall shape change of the sheet was studied.The results show that with the increase of the vacancy length,the shape of the vacancy is more uniform after deformation,and the maximum tensile strain position is transferred from the vacancy intersection to the vacancy fillet.The forming performance is better.With the increase of the width,the vacancy shape gradually becomes more and more In a circular shape,the deformation of the honeycomb unit tends to be uneven.In summary,the optimal aspect ratio of the preset vacancy is determined to be 7.5.On this basis,the verification test of the 5083 aluminum alloy was carried out,and it was found that the tensile strain at the upper end of the sheet was the largest and the crack occurred.By optimizing the outer edge of the sheet and increasing the arc,it can effectively avoid cracking at the fillet of the vacancy and increase the elongation of the sheet.The numerical simulation and verification test of the curved honeycomb structure shows that the square sheet material can solve the problem of uneven lateral and longitudinal deformation of the sheet during deformation,and obtain better forming effect.Ti-43Al-9V-1Y?at%?alloy was prepared by pre-alloying powder hot pressing sintering process.The experimental results show that the powder particle size is normally distributed and the powder microstructures of different particle sizes are different.The Ti-43Al-9V-1Y?at%?prealloyed powder was subjected to hot press sintering at a sintering temperature of 1150?,a sintering pressure of 30 MPa,and a holding time of 2 h,and the obtained alloy structure was fine and uniform.The XRD results of the alloy show that the main phase composition is?phase,?/B2 phase and a small amount of YAl₂ phase.The high temperature tensile test of Ti-43Al-9V-1Y?at%?alloy shows that the elongation of the alloy increases remarkably with the decrease of strain rate and the deformation temperature.At 990?,the strain rate is 1×10^-3s^-1.Under the condition,the elongation reaches 100%.The observation of high temperature tensile fracture shows that the fracture of the sample is mainly caused by the boundary defect of the original powder.Due to the lower sintering temperature,the sintering pressure is smaller and the powder particle size is uneven,the strength between the powder interfaces is lower,and the crack process is prone to crack source.,causing a break.The tensile test of the planar honeycomb structure of Ti-43Al-9V-1Y?at%?alloy was carried out at a temperature of 990?and a strain rate of 1×10^-3s^-1.The elongation of the sheet reached 112%.The alloy is plastic at this temperature and strain rate.The macroscopic deformation of the whole sheet is formed by the accumulation of small deformations of various vacancies,and no cracks are formed in the drawn parts.The experimental results of the Ti-43Al-9V-1Y?at%?alloy curved honeycomb structure under the same deformation conditions show that the curved honeycomb structure is well formed and the forming depth reaches 14mm.Finally,the Ti-43Al-9V-1Y?at%?alloy flat-drawn honeycomb structure sheet was brazed by TiCuNi brazing filler metal,and the welded joint interface was better without obvious defects.