Enhancing the mechanical property and thermal stability through the combination effect of La and Y in ODS-Cu alloys prepared by powder metallurgy

In this work, Cu-1.5 wt%Y (Cu-Y) and Cu-0.75 wt%Y-0.75 wt%La (Cu-Y-La) were prepared by mechanical alloying combined with spark plasm sintering and hot rolling, followed with annealing at different temperatures. The effects of the introduction of La and annealing temperatures on the microstructures, mechanical properties, electrical conductivity and thermal stability of Cu-Y alloys were investigated. Both Cu-Y and Cu-Y-La obtain the heterogeneous mixed grain structures composed of coarse grains and fine grains, and oxide nanoparticles are uniformly dispersed in Cu matrix. With the introduction of La, the grains and oxide nanoparticles are refined, and LaYO3 nanoparticles with the coherent interfacial structure can be observed in Cu-Y-La. After annealing at 500 degree celsius, both Cu-Y and Cu-Y-La obtain the most excellent comprehensive tensile properties and highest electrical conductivity (63 %IACS for Cu-Y and 62 %IACS for Cu-Y-La). Benefited from effectively enhanced grain boundary strengthening and particle strengthening mechanisms induced by the combination effect of La and Y, Cu-Y-La shows higher strength than that of Cu-Y (after annealing at 500 degree celsius, 244 MPa of yield strength for Cu-Y and 300 MPa for Cu-Y-La). Meanwhile, benefited from improved dynamics stability of the Cu matrix induced by significantly refined precipitates and the formation of LaYO3 nanoparticles with the coherent interfacial structure after introducing La, the better softening resistance is achieved by Cu-Y-La in comparsion with Cu-Y, and almost 100 degree celsius improvement of the softening temperature is achieved (966 degree celsius for Cu-Y-La and 870 degree celsius for Cu-Y).