Research on a different method to reach the saturate limit of titanium aluminide alloy surface mechanical and fatigue properties by laser shock process

Abstract

Laser shock peening is one of the best method to enhance the mechanical and fatigue properties of titanium aluminide alloys. Most research depends on the pressure model produced by Professor Fabrro, based on Von-Mise stress yield standard, when the pressure is 2 Hugoniot elastic limit (HEL), the plastic deformation reaches the maximum limit and when the pressure is 2.5HEL The stress release from the edge of laser shock area, This research discussed the titanium aluminide alloys surface mechanical and fatigue properties after reducing the pressure of laser shock and inducing the repetitions of laser shock properly. When the pressure reached HEL the material began plastic deformation, in the experiment environment there are several factors affect the results, so the pressure should be more than 1HEL and less than 2HEL-2.5HEL. As the same repetitive times the effective of 2HEL-2.5HEL pressure is better than the less pressure but with the repetitive times rise the 2HEL-2.5HEL pressure specimens would be cracked and the less pressure specimens mechanical and fatigue properties still increase. The results show that with inducing the repetitions and reducing the pressure the material surface hardness improved nearly 25% and the fatigue life increase nearly 40% in high fatigue cycle, the microstructure is similar but the less pressure more repetitive times specimens contains dislocation cells. It indicates that with 2HEL-2.5HEL pressure (the maximum plastic deformation) the mechanical and fatigue properties reached to its peak after 3 times LSP and with 1.5 HEL pressure 8 times repetitive laser shock can reach to the saturate limit of the material itself, that means with less pressure and more repetitive laser shock is more accurately to get close to the saturate limit of the material.