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

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 Cu ₂O 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 Y ₄Al ₂O ₉ nanoparticles homogeneously distributed in Cu(Al) solid solution matrix was successfully fabricated. It is found that a crystallographic orientation relationship of ( 3 1 ¯ 2 ) Y 4 A l 2 O 9 ∥ ( 1 1 ¯ 1 ) C u ( A l ) was formed between Y ₄Al ₂O ₉ nanoparticles and Cu(Al) matrix and the lattice mismatch was 0.337%. The small lattice mismatch reduced the nucleation barrier for Y ₄Al ₂O ₉ nanoparticles so a mean particle size of 4.8 nm and a number density of 2.16×10 ²⁴ 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 Y ₄Al ₂O ₉ nanoparticles. In addition, the thermal conductivity of Cu-1Y-9Al-0.3Cu ₂O alloy is close to other copper alloys as the volume fraction of Y ₄Al ₂O ₉ nanoparticles is limited. Cu-1Y-9Al-0.3Cu ₂O alloy provides a good overall performance, which may be used as heat sink materials under severe conditions.