In-situ dispersion hardened aluminum bronze/steel composites prepared using a double wire electron beam additive manufacturing

Electron beam additive manufacturing with simultaneously controlled feeding and melting of ER321 stainless steel and CuA19Mn2 bronze wires was carried out. The composite microstructure was formed consisting of homogeneously distributed ferrite and nickel-enriched bronze grains. Intensive intermixing and diffusion in the melted pool caused redistribution of nickel from stainless steel to the bronze and solidification of ferrite grains instead of the austenitic ones. Dispersion hardening of both ferrite and aluminum bronze grains occurred by core/shell beta'/AlNi and AlFe3 (kappa(iv)-phase) precipitates, respectively, that resulted in improving the ultimate tensile stress and increasing the microhardness of the composites depending upon the content of stainless steel introduced. Deformation was localized mainly in the bronze grains while ferrite grains retained their shape and were almost free of dislocations. The bronze grains allowed revealing only small regions containing the deformation microtwins. The tensile strength and microhardness of the composite samples were increased as compared to those of the pure bronze. No anisotropy was found during tensile testing.