Grain refinement in a single titanium powder particle impacted at high velocity

Titanium powder particles were deposited at high velocity on a steel substrate by a process called warm spraying. Extremely fine grains, several tens of nanometers in size, were observed along the interfacial boundary of the deposited particles known as splats and the substrate, where the most severe deformation had taken place. A schematic model to explain the mechanism of grain refinement of titanium powder is presented, in which dynamic recrystallization caused by adiabatic shear instability plays the major role. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.