Effects of laser irradiations on layers condition in three-layered sheet metals

Stainless-steel SUS430/copper C11000/stainless-steel SUS430 three layered sheets have been exposed to different number of Ytterbium fiber laser irradiations. Five specimens are prepared with 0, 10, 20, 30 and 40 laser passes. The steel and copper layers boundary conditions are evaluated after laser forming and tensile test by metallography and SEM, respectively. The microstructure of unirradiated SUS430 consists of ferrite and dispersed carbide particles. Microstructure of specimens with laser irradiation in the HAZ is consisting of martensite and oriented ferrite with smaller grain size. Copper has microstructure of a solid solution of copper containing twins in all specimens. Boundary of layers of the specimens does not show any separation and mixing after laser forming. The reason for this is low penetration depth in the material in the HAZ which only includes a small portion of the steel layer exposed to the laser. Evaluation of the fracture surface using SEM showed dimples in steel and copper layers. No separation is found in layers boundary of the tensile test specimen.