Estimation of microstructure and corrosion properties of peened nickel aluminum bronze

In this study, the effects of shot peening on the residual stress, microstructure and corrosion properties of nickel aluminum bronze were evaluated by using X-ray stress analyzer, X-ray diffraction profile analysis, transmission electron microscopy and electrochemical tests. Shot peening improved the hardness and compressive residual stress of the surface layer. A thin layer of nanometer-scaled domain formed at the top surface and the domain size raised constantly with depth until it reached nearly the value of matrix. The micro-strain and dislocation density dropped gradually with the increasing distance toward interior. Moreover, the samples treated by shot peening with different intensities all showed superior corrosion resistance than that of unpeened ones. However, further improving the peening density resulted in a poor corrosion performance, which was mostly ascribed to the increased surface roughness due to the raised deformation.