Microstructure evolutions induced by electron beam melting of a sintered Cu-25Cr composite

Cu-Cr alloys are used as electrical contacts for medium voltage applications because of their desirable trade-off between electrical, thermal, and mechanical properties. However, few studies have investigated the microstructural evolutions caused by an electrical arc during an electrical breakdown. Herein, electron beam melting of a Cu-25Cr (wt.%) composite fabricated by solid-state sintering is used to mimic the thermal conditions of an electrical arc. The microstructure before and after melting was characterized using synchrotron x-ray computed microtomography and directly correlated with post-mortem electron microscopy observations. The melt pool consists of different zones: a fusion zone characterized by the complete melt of both Cu and Cr phases, and a partially melted zone where only the Cu phase is melted. Pores in the matrix or at the Cu/Cr interfaces are healed upon melting. Tracking large Cr-particles reveals significant spatial evolutions attributed to convective flows.