Study on the microstructure and mechanical properties of Nd:YAG pulsed laser beam weld of UNS-C17200 copper beryllium alloy

摘要

In this study, the microstructure of Nd:YAG pulsed laser welding of copper beryllium sheet has been investigated by tensile and hardness tests, optical and scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SEM images reveals three distinct solidified structures due to various thermal gradients occurred in the fusion zone. The XRD patterns show that the preferred solidification directions are like other FCC materials. Tensile strength of the weld metal is lower than that of the base metal since the CuBe phase precipitates during solidification. The effects of pulsed laser parameters on the weld pool dimensions were also studied. The results show that by applying constant pulse energy, focused beam diameter should be kept as low as possible to obtain the weld pool with the highest penetration and the least width. Moreover, the effect of passive layer on the reflectivity of surface by incident beam was investigated. It was found that weld pool increases when the laser energy is high due to multiple internal reflections.