Effect of Laser Energy Density on Microstructure and Properties of High Strength and Magnetic Cu-Fe-P Immiscible Alloys Fabricated by Laser Selective Melting

Abstract

By adding the third component phosphorus (P), the magnetic phase with nanotwin structure was formed in situ, the Cu-Fe-P immiscible alloys with integrated structure and function were obtained by using selective laser melting (SLM). The microstructure is mainly composed of the magnetic heterogeneous Fe-P-rich phase (Fe2P mixed with a small amount of Fe3P), distributed in the ε-Cu Cu-rich matrix alternately with two forms of “fiber-layer” and “particle-shape” structures. Some α-Fe was precipitated in the fibrous Fe2P, and high-density nanotwinned Cu (nt-Cu) particles were precipitated in both the “fiber-layer” and “particle-shape” structures Fe-P-rich phase. By adjusting the laser energy density, the microstructure density and structural characteristics of Cu-Fe-P immiscible alloys were improved, so as to improve the mechanical and magnetic properties. With the increase of laser energy density, the microstructure density increases first and then decreases. When the laser energy density is 53 J/mm3, the microstructure of Cu-Fe-P immiscible alloy has the highest relative density (98%). The effects of laser energy density on the mechanical properties and soft magnetic properties of Cu-Fe-P immiscible alloys were investigated. The results show that the compact Cu-Fe-P immiscible alloys have good compression mechanical properties and soft magnetic properties. The ultimate compressive stress and failure strain can reach 890.5±20 MPa and 20.5±2%, respectively. The coercivity is as low as 20.0 Oe, the magnetic saturation strength is as high as 93.5 emu/g, and the residual magnetization is 1.1 emu/g.

Keywords: selective laser melting, immiscible composite, magnetic property, mechanical property, nanoscale twins