Explosive formation of titanium and zirconium oxide during milling under O_2 Gas

摘要

It has been found that when Ti and Zr powders are milled in reactors under O_2 gas, at some point during the milling process a sudden combustion of the metal powder leads to the near complete transformation to the oxide state occurs as detected by a sudden pressure drop in the reactor d ue t9 O_2 absorption into the solid state. However, the nearly instantaneous explosive reaction occurs suddently after milling times of the order of 10~5 s. We have examined powder samples removed just after the reactions in order to understand the mechanism and timing of these self-sustanined explosive reactions. It is discovered that a fast-type oxidation reaction propagates through the grain boundaries, cracks and internal surfaces and thus can occurafter a critical degree of deformation-induced grain-refinement and multiple fracture events.