MECHANICAL-PROPERTIES AND MICROSTRUCTURE OF LASER TREATED AL-CU-MG ALLOYS

The mechanical properties and microstructural features of Al-Cu-Mg all oys were investigated, as exposed to laser treatments at various scan velocities. As far as the mechanical property is concerned a striking observation is a minimum in the hardness value at a laser scan velocit y of 1/2 cm/s. Usually an increasing hardness with increasing laser sc an velocities is reported in the literature. This remarkable property could be explained based on the microstructural features observed by t ransmission electron microscopy. After subsequent shot peening, in all cases the formation of precipitates was observed, independent of the laser scan velocities originally applied. This phenomenon of precipita tion, induced by shot peening afterwards is most striking at a high co ncentration of alloying elements in solid solution. Since this is the case in samples treated at a low scan velocity (i.e. an increased homo genization time) as well as in samples treated at a high scan velocity samples (high quench rates), the parabola shape is maintained even af ter shot peening.