The microstructure, mechanical-thermal properties and softening resistance of Y4Al2O9 dispersion-strengthened Cu alloy

•ODS-Cu alloy containing a high number density (2.16×1024 m−3) of uniformly dispersed nanoscale Y4Al2O9 particles (mean particle size: 4.8 nm) was fabricated.•Coherent interface between Y4Al2O9 nanoparticles and Cu(Al) solid solution matrix was formed with an orientation relationship of (31¯2)Y4Al2O9∥(11¯1)Cu(Al) and a small lattice mismatch of 0.337%.•The microhardness of the ODS-Cu alloy was enhanced to 228.6 HV. A relatively high thermal conductivity of 269 W m−1 K−1 at 600 °C for the ODS-Cu alloy was maintained. The softening temperature of the ODS-Cu alloy was more than 1000 °C. Oxide dispersion-strengthened copper (ODS-Cu) alloys with yttrium oxide nanoparticles are promising heat sink materials in fusion reactor due to their high strength, thermal conductivity and thermodynamic stability. The particle size and number density of oxide nanoparticles can be improved via addition of microalloying element. In this study, the atomized Cu-Y alloy, Al and Cu2O were used as the Y source, the microalloying element and the oxidant material, respectively, to fabricate ODS-Cu alloy by mechanical alloying method. After spark plasma sintering and annealing, a ODS-Cu alloy with a microstructure containing Y4Al2O9 nanoparticles homogeneously distributed in Cu(Al) solid solution matrix was successfully fabricated. It is found that a crystallographic orientation relationship of (31¯2)Y4Al2O9∥(11¯1)Cu(Al) was formed between Y4Al2O9 nanoparticles and Cu(Al) matrix and the lattice mismatch was 0.337%. The small lattice mismatch reduced the nucleation barrier for Y4Al2O9 nanoparticles so a mean particle size of 4.8 nm and a number density of 2.16×1024 m−3 were obtained in the alloy. Consequently, the microhardness was enhanced via Hall-Petch strengthening, dislocation strengthening and dispersion strengthening. The softening temperature of ODS-Cu alloy was improved to higher than 1000 °C due to the thermodynamic stability and the pinning effect of Y4Al2O9 nanoparticles. In addition, the thermal conductivity of Cu-1Y-9Al-0.3Cu2O alloy is close to other copper alloys as the volume fraction of Y4Al2O9 nanoparticles is limited. Cu-1Y-9Al-0.3Cu2O alloy provides a good overall performance, which may be used as heat sink materials under severe conditions.