The Residual Stress Analysis Of Tial-Based Alloy And Composite Sheet

TiAl-based alloys have been considered as the most promising new lightweight high-temperature structural materials because of their advantageous properties. The preparation of the sheet is one of the key techniques for its wide applications, especially in the aerospace and aircraft industry with much emphasis on the lightweighting. However, it's difficult to prepare the TiAl sheet because of its limited ductility and work ability at room temperature.In this thesis, the TiAl-based alloys sheet and Al2O3P/TiAl composites sheet with 150mm×100mm×0.4mm were prepared by electron beam-physical vapor deposition (EB-PVD) technique. The residual stresses of the sheet were tested by x-ray stress analyzer.In order to instruct the manufacturing process of the sheet, the reasons and effecting factors on generation of residual stresses were analyzed theoretically. The analytical results indicate that the residual stresses are mainly formed on cooling, the change of temperature and the mismatch of material parameters are major reasons of their generation. Thermal stress models of TiAl-based alloys sheet, Al2O3P/TiAl composites and Al2O3P/TiAl composites sheet were established. The thermal stresses of them were numerically simulated by ANSYS finite element software.Results of numerical simulation show that the thickness of substrate exercise little influences upon the stresses of sheet in the system of TiAl-based alloys sheet/ceramic layer/substrate. However, the values of effective elastic modulus, thermal expansion coefficient and Poisson's ratio of Al2O3P/TiAl composites sheet are all in between those of its component materials. The thermal residual stresses near the boundary between grain and matrix evidently increase with the volume percentage of Al2O3 particles.