Surface Morphologies and Mechanical Properties of Copper Foil Following Microscale Laser Dynamic Flexible Forming
Y-P. Fan, Z-B. Shen, Y-Y. Wang, K. Liu, Y-Y. Lin, G-Y. Zhou, Y. Wang, P. Li, H-X. Liu and X. Wang
Microscale laser dynamic flexible forming (μLDFF) is a new kind of high velocity forming (HVF) process. After the laser beam irradiates an ablative medium the rubber obtains shockwave energy to load the sample into the microdie so that the inner surfaces of sample contact with the rubber, while the outer surfaces of sample contact with the microdie. For the outer surfaces of sample, the outer wall surface slide contact with the microdie, while the outer bottom surface impacts with the microdie. This work investigates the different surface morphologies of the different forming regions under different laser energies. The roughening phenomenon was observed on the inner wall surface, and this is because that the rubber does not keep in contact with the sample during forming. When laser energy ranges from 450 to 1550 mJ, increasing laser energy can improve forming accuracy. When laser energy is 1800 mJ, partial fracture occurred at the entrance of the microdie, and oxidation layer was formed on the outer wall surface due to the high speed sliding friction. When laser energy is 1900 mJ, complete fracture occurred at the entrance of the microdie. This work also investigates the mechanical properties of the sample. The results of nanoindentation tests show that the values of nanohardness and elastic modulus in forming regions were obviously increased.
Keyword: Nd:YAG laser, ablative medium, rubber, microdie, microscale laser dynamic flexible forming (μLDFF), surface morphology, roughening, oxidation, nanohardness