Synthesis of Nanocrystalline Ti-Al powders by High Energy Ball Milling

摘要

Lightweight aerospace structures can benefit from the use of metallic foil products for high temperature applications such as thermal protection systems. Gamma TiAl alloys are strong candidates (with much lower density than the incumbent Ni-based superalloys), but they suffer from poor ambient temperature ductility. In an attempt to improve the ductility and obtain a suitable combination of properties, the microstructure has been varied via processing. The primary objective of this work was the production of material with a fine-grained, homogeneous microstructure using high-energy ball milling. Samples were obtained starting with both elemental and prealloyed powders and were then characterized using XRD, SEM and TEM. The effects of milling parameters such as milling tools, initial state of the powders and process control agents on the size and microstructural state of the milled powders were investigated. Consequently, two processing routes are proposed for synthesizing nanocrystalline powders with a high yield. It is intended that subsequent powder metallurgy consolidation processing will be used to produce foil product from these powders.