Cracking behavior of newly-developed high strength eutectic high entropy alloy matrix composites manufactured by laser powder bed fusion

A novel AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) composite doped with SiC particles was designed and fabricated by laser powder bed fusion (LPBF). Its microstructure characteristic, tensile properties, and metallurgical defects, with an emphasis on cracking behavior, have been investigated. The results showed that the addition of SiC particles into the AlCoCrFeNi2.1 matrix enabled the development of a {100} texture and highly elongated columnar grains, which were the main contributors to mechanical behavior anisotropy. The ultimate tensile strength of 1466 ± 26 MPa and elongation of 9% ± 3% achieved in the as-deposited EHEA composite surpassed those of advanced metal alloys subjected to additive manufacturing processes. Unfortunately, severe horizontal and longitudinal cracks, as well as a few micro-cracks were observed in the as-deposited bulk samples. Micro-cracks were verified to be associated with the aggregation of carbon and oxide particles. They formed in the final stage of solidification owing to insufficient liquid feeding ability and solidification contraction. The formation of macroscopic cracking was induced by the tensile stress accumulations at sample edges, and the stress concentration areas where microcracks and pores were located were the predominant propagation location. This work provides guidelines for defect control in SiC-reinforced EHEA, assisting in the high-performance design and integrated manufacturing of EHEA composite components.