Investigation of nanostructured Al-10 wt.% Zr material prepared by ball milling for high temperature applications

Abstract

Ground chips of as-cast Al-10wt.% Zr alloy were subjected to mechanical alloying (MA) with 5vol.% of nanodiamond addition in a high energy planetary ball-mill. The aim of this work was to investigate the microstructure, phase transformation and mechanical properties of the material both after MA and after subsequent annealing. Optical and transmission electron microscopes were used for morphological and microstructural analysis. The effect of milling time on powder microhardness, Al lattice parameter, lattice microstrain and crystallite size was determined. It was shown that mechanical alloying of as-cast Al-10wt.%Zr alloy during 20h leads to a complete dissolution of the primary tetragonal Al3Zr crystals in aluminum. At the same time, the powder microhardness increases to 370HV. Metastable cubic Al3Zr phase nanoparticles precipitate from the Al solution due to its decomposition after annealing, however, the Al solid solution remains supersaturated and nanocrystalline. Compression tests at room temperature and at 300°C showed that the strength values of the hot-pressed samples reach 822MPa and 344MPa, respectively.