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

The mechanical properties and microstructural features of Al-Cu-Mg alloys 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 velocity of 1/2 cm/s. Usually an increasing hardness with increasing laser scan velocities is reported in the literature. This remarkable property could be explained based on the microstructural features observed by transmission 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 precipitation, induced by shot peening afterwards is most striking at a high concentration of alloying elements in solid solution. Since this is the case in samples treated at a low scan velocity (i.e. an increased homogenization time) as well as in samples treated at a high scan velocity samples (high quench rates), the parabola shape is maintained even after shot peening.