Improving Structural Stability and Thermal Stability of Copper Alloy by Introducing Completely Coherent Ceramic Dispersoids

Abstract

When ceramic particles are incoherent with copper matrices, or when large coherent strains exist due to the differences between their crystal structure and lattice parameters in traditional dispersion-strengthened copper alloys, the strengthening effect of dispersoids at high temperatures is reduced. In the present work, a Cu-0.48Al-3.5Yb2O3 alloy was fabricated by mechanical alloying and spark plasma sintering. The investigation results prove that completely coherent inert ceramic particle YbAlO3 without coherent strains is introduced into the copper matrix. The microstructural evolution and thermal stability of the alloy after annealing at high temperatures are investigated and discussed, and it is found that the alloys exposed at 600~800 °C for 3 h exhibit excellent thermal stability and exceptional structural stability. The exceptional resistance to grain growth in the alloy can be attributed to the Zener pinning effect provided by the fine dispersion of YbAlO3 particles. High-density geometrically necessary dislocation (GND) is retained in the alloy even after annealing at 800 °C for 3 h, as is the presence of parallel GND rows because they do not easily react with opposite rows to annihilate the dislocation. At the same time, dispersed YbAlO3 acts as a strong obstacle to moving the GND. The present work proves that the structural stability of copper can be significantly improved by introducing completely coherent dispersed particles.