Abstract: In order to obtain the premixed water jet peening strengthening amplification effect, research the effects of premixed water jet peening on surface micro hardness, surface residual stress and fatigue life of 2A11 aluminum alloy and 45 steel. The micro hardness tester and X-ray stress analyzer are used to respectively determine peened surface micro hardness and surface residual stress. The scanning electron microscope is used to observe the fatigue fracture morphology, then the change rules of peened surface micro hardness and surface residual press stress with the change of peening pressure, scanning velocity and target distance. It is indicated that the premixed water jet peening can greatly improve the fatigue life of 2A11 aluminum alloy and 45 steel, the fatigue life of peened specimens can respectively improve 25.31 and 18.56 times in comparison to unpeened specimens when the stress amplitude of 2A11 aluminum alloy and 45 steel is respectively 155.7 MPa and 282 MPa. The fatigue cracks of unpeened specimens initiate from the surface of specimens; but for peened specimens, some fatigue cracks initiate from the surface of specimens, others from inside of specimens, when the fatigue source is inside the specimen, cracks initiate at the inclusion. Therefore, the premixed water jet peening is an effective method to improve the fatigue life of metallic componens.

Key words: Fatigue life, Micro hardness, Peening, Residual press stress, Water jet