Microstructure evolution of copper/steel gradient deposition prepared using electron beam freeform fabrication

[Display omitted] •Copper and 304 stainless steel (SS) gradient materials were obtained using electron beam freeform fabrication (EBF3).•Nanoscale FeCu4 metastable phases were found in the deposition.•The microstructure evolution of copper/SS depositions were revealed. Additive manufacturing of copper and steel gradient materials by electron beam freeform fabrication is a novel exploration. T2 copper was deposited on AISI-304 stainless steel in the experiment and the gradient depositions were obtained successfully. The results showed that the distribution of iron element was more uniform with the increase of copper layers. No iron-rich α phase could be found when the number of copper layer was greater than three. The supersaturated ε phases precipitated in globular α phases while there was no ε phase found in dendritic one. FeCu4 metastable phases were found in the depositions duo to low cooling rate and ordering transformation.