CrCoNi medium-entropy alloy thin-walled parts manufactured by laser metal deposition: Microstructure evolution and mechanical anisotropy

摘要

Laser metal deposition (LMD) shows outstanding advantages in manufacturing complex parts. In practice, some formed parts usually require directional properties in order to obtain better service performance in its use. This study has comprehensively analyzed the microstructure, texture and porosity of CrCoNi medium-entropy alloy thin-walled parts manufactured by LMD process, as well as the effect of these factors on its mechanical anisotropy. The results show that the yield strength in the building direction is slightly higher than the scanning direction and the uniform elongation is about 1.5 times. Meanwhile, the fracture morphology and microcrack characteristics of the tensile samples in these two directions have also been studied. The results reveal that cross-slip microcracks and microcrack deflection appeared in the scanning direction and building direction, respectively. In addition, it has also been made clear that initial dislocations can contribute to the yield strength of thin-walled samples. The work provides guidance for the design freedom and scanning strategy of engineering parts with directional performance by the LMD process.