Variation in the Mechanical properties of Extruded Al-2099 after laser shock peening

Abstract

Laser shock peening (LSP) is an industrial process which creates rapid pressure rise in material surfaces giving rise to shock waves by using a high energy laser pulse. It offers 10 times increased life time as compared to the traditional mechanical shot peening. In other to understand how strengthening precipitates are distributed in aluminum 2099 after been treated with Laser Shock Peening (LSP), hardness test was applied to an axially extruded T-shape of Al-2099. The result obtained from the hardness test showed variation in the hardness values of specimens extracted at different sections of the T shaped Al 2099. The initial average hardness value of the flange was 140Hv while that of the web was 130 Hv. That was before laser shock peening was applied. After the application of laser shock peening, the initial softer part (Web) showed a higher value of hardness value of up to 170 Hv. The flange which was initially harder than the web before laser shock peening showed a hardness increment value of up to 160Hv. By implication, it means the softer web developed more residual stress meaning better response to laser shock peening. The findings also showed that Al 2099 extruded T shaped exhibit different crystallographic textures at differing locations within the extruded cross section. This was reflected in the hardness variation. There was evidence of fibrous texture in the web and rolling texture in the flange. Inhomogeneous texture showed influence on mechanical properties such as hardness value. An average depth of laser shock penetration based on the peened condition for Al 2099 was recorded at 2 mm from the surface in to the material. Approximately 18 % and 21 % increment in maximum surface hardness was recorded for the flange and web specimens respectively after treating them with Laser shock peening. Hence, the users of software's solvers such as finite element analysis and eigen strain analysis for modelling should bear in mind the assumption of such geometry as continuum and assumption of homogeneous material properties and assumption of homogeneous material properties.

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