Influence of Severe Shot Peening on the Surface State and Ultra-High-Cycle Fatigue Behavior of an AW 7075 Aluminum Alloy
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JMEPEG DOI: 10.1007/s11665-017-2692-9
Influence of Severe Shot Peening on the Surface State and Ultra-High-Cycle Fatigue Behavior of an AW 7075 Aluminum Alloy Libor Trsˇko, Mario Guagliano, Otakar Boku˚vka, Frantisˇek Novy´, Michal Jambor, and Zuzana Florkova´ (Submitted January 24, 2017; in revised form March 23, 2017) The ever more pressing and concurrent requirements of light design, increased performances and reliability, energy savings together with acceptable costs, is always pushing researchers and engineers toward the definition and application of new materials and treatments, able to guarantee superior properties and adequate repeatability and reliability. This means that one step beyond the definition of a potentially successful solution, a complete characterization of the new materials is needed, in order to get the right data and use them in the design process. A promising severe plastic deformation surface treatment to improve the fatigue properties of materials and metal parts is considered in this paper. The used treatment is called the severe shot peening, and it is derived from the conventional shot peening but with use of unusually high peening parameters. It was proven that it is able to generate a nanostructured surface layer of material, which results in superior fatigue properties when applied to many structural materials. The severe shot peening is applied to an AW 7075 Al alloy, widely used in mechanical and aeronautic constructions and the effects of such a treatment on this material are investigated in this paper, with particular emphasis on the ultra-high-cycle fatigue behavior. The results address the choice of the correct treatment parameters for getting an evaluable advantage of this treatment and are critically discussed for a complete understanding of the mechanisms leading to the modified fatigue behavior, in view of the future developments and research in the field. Keywords
AW 7075 aluminum alloy, fatigue life, grain refinement, residual stress, severe shot peening
1. Introduction The ever-increasing demand of light design, increased performances and reliability, energy savings together with acceptable costs, is pushing researchers and engineers toward the definition and application of new materials and treatments, able to guarantee superior properties and adequate repeatability. This means that one step beyond the definition of a potentially successful solution, a complete characterization of the new materials is needed, in order to get the right data to use in the design process. Among the methods used to improve the mechanical characteristics of materials, the so-called severe plastic deformation treatments proved to be able to generate the grain refinement down to nanoscale, with grains with dimension of the order of 40-100 nm (Ref 1). The materials treated in this
Libor Trsˇko and Zuzana Florkova´, Research Centre of the University of Zˇilina, Univerzitna´ 8215/1, 010 26 Zˇilina, Slovak Republic; Mario Guagliano, Department of Mechanical Engineering, Politecnico di Milano, Via La
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