Effect of heat treatment on the microstructure and mechanical properties of yttrium metal

Abstract Rare earth oxides prepared by magnetron sputtering of rare earth metal targets are ideal high k gate dielectric materials. The production of targets has drawn more and more attention. In this work, the yttrium (Y) metal target is subjected to cold rolling, resulting in an accumulated deformation of 40%. Subsequently, the deformed Y was heat-treated at various temperatures. Microstructural and mechanical characteristics of Y subjected to deformation and heat treatment were systematically examined utilizing an electron backscatter diffractometer and a hardness tester. The main coarse grains of rolled Y metal were replaced by fine grains with heat treatment temperatures of 550, 650, and 750 °C. Heat treated at 750 °C, grain size distribution was quite homogeneous and the grain growth was not obvious. As for recovery and recrystallization processes, the recovery process occurred after 450-°C heat treatment. And the recrystallized process is fully completed at 750 °C. Besides, the High-Angle Grain Boundaries (HAGB) fraction increased with a rise in heat treatment temperatures from 550 to 750 °C. The microhardness decreased with the heat treatment temperatures increased until 650 °C, then remained stable. This work can provide an important reference for the optimal heat treatment temperature of Y target materials.