Investigation of Near Surface Stress Gradients in Shot Peened Ti 2.5Cu Measured by Mechanical and Diffraction Methods

Abstract

Mechanical surface treatments such as shot peening or ball burnishing lead to changes in the nearsurface material states. This is mainly the result of induced plastic deformation which results in workhardening and the generation of residual stresses. Residual compressive stresses are well known to enhance the fatigue performance and corrosion resistance of a number of metallic materials by retarding or even suppressing micro crack growth from the surface into the interior. Shot peening was performed on the alpha titanium alloy Ti 2.5Cu using cast steel shot S 330 having an average shot size of 0.8 mm. Peening was done to full coverage at Almen intensities of 0.11 and 0.20 mmA The shot peening induced residual stresses were evaluated by applying various methods including the incremental hole drilling technique, conventional X rays diffraction as well as Synchrotron radiation techniques. In addition, changes of the near surface crystallographic textures were evaluated by conventional X rays and Neutron diffraction. The residual stress depth profiles as determined by the various methods will be discussed and differences be interprete