Microstructure of laser bent aluminium alloy Alclad 2024-T3

A set of optical and SEM micrographs of the Aluminium Alloy Alclad 2024-T3 microstructure, which has been bent by means of a CO₂-laser beam, are presented showing the changes occurring to the grain structure as a consequence of this laser induced process. The laser bending variables used are: power (P), scanning velocity (v), beam diameter (D) and number of passes (N), all of them arranged into a parameter, $NS⋅PD⋅v$⁠, called Accumulated Energy Density (AED in J/mm²). For AED values below 25 J/mm² the microstructure of the material showed presence of subgrain structures and incomplete recrystallization of small size grains in the upper region of the sheet. Higher AED values, in between 25 and 133 J/mm², caused recrystallization to take place fully, contrasting with the elongated crystal structure of the as-received material. In that AED range segregation of dispersoids at the grain boundaries occurred as well as partial melting of previously recrystallized grain. For AED values near to 133 J/mm² melting and resolidification of the upper region of the sheet, underneath its Alclad layer, took place leaving a cellular-dendritic structure. AED values ranging from 133 up to 250 J/mm², caused the Alclad layer to fuse together with the substrate.