Laser powder b e d fusion of copper matrix iron particle reinforced nanocomposite with high strength and high conductivity

Liquid-liquid phase separation,and the resulted solute segregation,during conventional solidification have been a long-term challenge to produce copper(Cu)-iron(Fe)immiscible composites with high strength and high conductivity.The present work reports an effective solution to this issue through laser powder bed fusion(L-PBF)in-situ alloying of Cu-8 wt.%Fe.Microstructure observation showed that the fast cooling within micron-scale melt pools fully eliminated the Fe segregation and therefore the L-PBF fabricated nanocomposite achieved the homogeneous microstructure,which featured equiaxed fine grains around 1μm in size.Ageing of the nanocomposite at 600℃for 1 h enabled precipitation of two types of nanoparticles.One is coarser Fe nanoprecipitates with body-centered cubic(BCC)structure and diam-eter of 100-300 nm,mainly distributing along grain boundaries.The other is smaller Fe nanoprecipitates with face-centered cubic(FCC)structure and diameter of 10-35 nm,being observed within the grains and having coherent interfaces with the Cu matrix.As a result,the aged Cu-Fe nanocomposite achieved tensile strength of 462.9±6.6 MPa with 30.4%±1.7%elongation to failure and 74.5%IACS(International Annealed Copper Standard)electrical conductivity.The formation mechanisms of the nanoprecipitates and the strengthening mechanisms of the nanocomposite are discussed.