TiB2- and Fe2P with nanotwins-reinforced Cu-based immiscible composites fabricated by selective laser melting: Formation mechanism and wear behavior

Abstract

To restrain the collision and coarsening of Fe-rich droplets within supercooled Cu-Fe immiscible melt, the TiB2 particles as inoculants are introduced to produce the TiB2 and Fe2P with nanotwins-reinforced Cu-based immiscible composites by selective laser melting (SLM). The Cu-based immiscible composite with heterogeneous structure is characterized by nano-/micro-scale Fe2P particles and micron fibrous Fe2P dispersed within the ε-Cu matrix. Moreover, some nanotwinned Cu (nt-Cu) particles and a high density of nanotwins are embedded within these nano-scale Fe2P particles, whereas some irregular α-Fe precipitated within these fibrous Fe2P. The addition of TiB2 particles can refine the size of Fe2P and promote their homogeneous distribution within the ε-Cu matrix. As a result, the hardness and wear resistance of the TiB2 reinforced Cu-based immiscible composite are significantly improved by the combined strengthening mechanisms of twin boundaries (TBs) strengthening, refinement strengthening, dispersion strengthening and precipitation strengthening.