Effect of initial surface topography on the surface status of LY2 aluminum alloy treated by laser shock processing

Samples manufactured by LY2 aluminum (Al) alloy with different initial surface topography were treated by laser shock processing (LSP), and then the surface topographies before and after LSP were carefully investigated with a non-contact optical profiler (NCOP). Moreover, the residual stress and microhardness were also examined. Results showed the following three aspects: (a) Initial surface topography will influence the surface roughness of LY2 when treated by LSP. The values of surface roughness of all the tested samples would tend to be stable after one LSP impact, and there was an ultimate value for the surface roughness after multiple LSP impacts, which was about 0.58 mu m. (b) With the increase of initial surface roughness, the compressive residual stress decreased when subjected to one LSP impact. The surface residual stress of all the samples tended to be saturated after three LSP impacts, and the saturated value was nearly equal. (c) With the increase of initial surface roughness, the microhardness of all the samples increased when subjected to one LSP impact. (C) 2012 Elsevier Ltd. All rights reserved.