Microstructure evolution and properties of novel AZ31B/SiCps composites prepared based on wire-arc directed energy deposition

The novel AZ31B/SiCps composite was prepared by wire-arc directed energy deposition (DED-Arc) method. The effects of SiCps content in the range of 1.0–3.0 wt% on grain orientation, average grain size, grain boundary angle distribution, and mechanical properties of AZ31B magnesium alloy were studied. The results showed that SiCps, as a reinforcing phase uniformly dispersed in the matrix, could effectively reduce the free energy of the α-Mg matrix, and promoted non-uniform nucleation as a heterogeneous nucleation point. At the same time, SiCps was also pushed to the grain boundary by the solid-liquid interface, hindering the columnar grain of epitaxial growth, which helped to reduce the subcooling of components at the grain growth front (ΔTcs = ΔTn-min). With the increase of SiCps mass fraction, the transformation of columnar crystals to equiaxed crystals was realized. The average grain size of the deposited specimen and the texture strength of the crystal face of the α-Mg matrix (0001) gradually decreased. Finally, the AZ31B magnesium alloy with a mass fraction of 2.0 wt% SiCps exhibited excellent mechanical properties with a tensile strength of 233.35 MPa and an elongation of 24.04%. The anisotropy of the deposited sample was converted to isotropy.