Additively manufactured CoCrFeNiMn high-entropy alloy via pre-alloyed powder

Highlights: • This is the first detailed report regarding the EBM-built single-phase high entropy alloy (HEA) parts. • Gas atomized HEA powder is proved to be suitable for powder-bed-fusion additive manufacturing to develop new material. • Deformation mechanism of the EBM-built HEA is dominated by dislocation with limited contribution of mechanical twinning. • The cellular structure does not contribute the strength without the pre-existing surrounding dislocation network. • HEA parts with complex geometry and good mechanical properties can be obtained using EBM process and gas atomized powder. -- Abstract: An equiatomic CoCrFeNiMn high-entropy alloy (HEA) powder is produced by vacuum induction melting gas-atomization with argon gas. A detailed characterization reveals that gas atomized HEA powder is suitable for powder-bed-fusion additive manufacturing (PBFAM). Therefore, the powder with size ranging from 45 to 106 μm is applied in one of PBFAM, electron beam melting (EBM). The final EBM part is strongly affected by the feedstock. The entrapped gas pores result in a high porosity of EBM-built parts, requesting extra efforts to eliminate the pores for processing parameters optimization. After the optimization, the highly dense EBM-built parts with a hierarchical microstructure and a strong 100 texture are obtained. The hierarchical microstructure displays long columnar grains containing intragranular cellular structure (dendrites) along build direction. Deformation mechanism of the EBM-built CoCrFeNiMn HEA is dominated by dislocation with limited contribution from mechanical twinning. Experimental results reveal that the cellular structure (dendrites) does not contribute the strength without the pre-existing surrounding dislocation network. As a result, EBM-built CoCrFeNiMn HEA parts exhibit comparable tensile properties to their conventional cast counterparts. It is suggested that the EBM process and gas atomized HEA powder can be employed for fabricating single-phase HEA parts with complex geometry and good mechanical properties.