Shock consolidation of mechanically alloyed amorphous Ti-Si powders

Mechanical alloying was used to synthesize amorphous 5Ti-3Si atomic ratio powders in a SPEX mill under Ar atmosphere. X-ray diffraction analysis revealed formation of a single-phase amorphous compound after approx24 h of milling. High-resolution transmission electron microscopy (TEM) showed that the milled powder still contained nanocrystallites of Ti and Si among regions of generally amorphous compound. The mechanically alloyed amorphous powder was shock consolidated, using a plate impact assembly, to produce bulk compacts. The compaction resulted in a significant amount of crystallization, forming 30- to 40-nm crystals of TiSi sub 2 and Ti sub 5 Si sub 3 intermetallic compounds. The compacts were subsequently annealed above the crystallization temperature, measured to be approx640 deg C using differential thermal analysis. The compacts annealed at 800 deg C for 1 h showed only limited grain growth to approx50-nm crystallite size. Microhardness of the shocked amorphous alloy compacts was approx1100 KHN, which increased to approx125- KHN upon subsequent annealing, with the formation of a more homogeneous nanocrystalline microstructure.