Microstructure Evolution and Properties of an In-Situ Nano-GdO/Cu Composite by Powder Metallurgy.

Gadolinia (GdO) is potentially attractive as a dispersive phase for copper matrix composites due to its excellent thermodynamic stability. In this paper, a series of 1.5 vol% nano-GdO/Cu composites were prepared via an internal oxidation method followed by powder metallurgy in the temperature range of 1123-1223 K with a holding time of 5-60 min. The effects of processing parameters on the microstructure and properties of the composites were analyzed. The results showed that the tensile strength and conductivity of the nano-GdO/Cu composite have a strong link with the microporosity and grain size, while the microstructure of the composite was determined by the sintering temperature and holding time. The optimal sintering temperature and holding time for the composite were 1173 K and 30 min, respectively, under which a maximum ultimate tensile strength of 317 MPa was obtained, and the conductivity was 96.8% IACS. Transmission electron microscopy observations indicated that nano-GdO particles with a mean size of 76 nm formed a semi-coherent interface with the copper matrix. In the nano-GdO/Cu composite, grain-boundary strengthening, Orowan strengthening, thermal mismatch strengthening, and load transfer strengthening mechanisms occurred simultaneously.