Residual stresses and hardening phases in aluminum-copper alloy surfaces produced by laser

Laser surface treatments can increase mechanical behaviour, in particular h ardness and wear resistance, by formation of new alloys. Alloying elements are here predeposited on the aluminium surface: this precoating technique g ives the best results concerning microhardness, microstructural homogeneity and porosity elimination. With aluminium - copper alloys, we obtain homoge neous layers with a hardness of 60 to 300 Hv(0.2) for 5 to 45 percent in ma ss concentrations. Hardness contributes to wear resistance but it is necess ary to gel more information about residual stresses and about the nature of the metallurgical phases in the laser track : for this purpose X-Ray diffr action is an appropriate and efficient method which shows that the microstr ucture is composed of fine a primary and intermetallic Al2Cu phases, depend ing of the copper concentration and that compression residual stresses are present at the surface of the tracks.