Laser powder bed 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 1 mu m in size. Ageing of the nanocomposite at 600 degrees C 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 10 0-30 0 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. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.