Microstructure and properties of homogeneous Cu90Fe10 immiscible composites with nanotwins by laser powder deposition: Effect of spot size

To select the reasonable spot size during laser powder deposition (LPD), the homogeneous Cu90Fe10 immiscible composites were produced by LPD with different spot sizes (2 mm and 4 mm in diameter). The LPD-produced Cu90Fe10 immiscible composites deposited with different spot sizes display a similar microstructure composed of α-Fe/γ-Fe and e-Cu phases. A large amount of nanoscale Fe-rich particles is uniformly embedded within the Cu-rich matrix and the Cu-rich particles with nanotwins are distributed within the Fe-rich particles due to secondary liquid phase separation (SLPS). Moreover, some nanoscale FeCr grains (∼20 nm) are precipitated within the Fe-rich particles. Both the averaged diameter and grain size of Fe-rich particles reduce with decreasing the spot size due to higher cooling rate. The immiscible composite produced with spot size of 2 mm exhibits higher microhardness and elastic modulus (1.9 GPa and 143.5 GPa respectively) than the corresponding ones for the counterpart with spot size of 4 mm (1.8 GPa and 142.6 GPa respectively) and Brass. As a result, the LPD-produced Cu90Fe10 immiscible composite deposited with spot size of 2 mm exhibits higher wear and corrosion resistance compared to that deposited with spot size of 4 mm.