Microstructure reconfiguration of duplex high entropy alloy/BCC ferrite bimetallic interface under electropulsing

Abstract

Additive manufacturing of multi-materials is one of the effective pathways to enrich the performance diversity of metallic materials, and it is generally acknowledged that the bimetallic interface is the weakest position because of stress concentration and compositional mutation. Here it was found that the stress concentration along the BCC + FCC duplex Al-Co-Cr-Fe-Ni high entropy alloy/BCC ferrite bimetallic interface can be significantly released by electropulsing, and the compositional mutation region was also reasonably widened from 2 μm to 10 μm. Meanwhile, the neighboring grains rotated to form High Angle Grain Boundaries, which can reduce the Gibbs free energy of the system. Additionally, the nano-scale second phase including spherical BCC NiAlFe and rod-like B2 NiAl particles was generated at the interface. The BCC NiAlFe phase is coherent with the matrix and has numerous crystal defects inside the precipitates, whereas the B2 NiAl phase has a stable structure without stress fluctuation because of its greater maturation degree.