Particle deformation and microstructure evolution during cold spray of individual Al-Cu alloy powder particles

Abstract

This paper examines the single particle impact process for a series of Al-Cu alloy powder particles with 2–5 wt% copper, performed using a low-pressure cold spray system with helium as the carrier gas. The cold spray deposition process is fundamentally controlled by the deformation processes, which occur during single particle impacts. Single particle depositions on steel substrates were produced for each composition over a range of gas temperatures (225–325 °C). Cross sections from single, impacted particles were produced using focused ion beam methods. The deformation microstructure in individual cold sprayed particles was studied using precession electron diffraction (PED) and transmission Kikuchi diffraction (TKD) techniques. For Al-Cu alloy particles, the amount of deformation estimated using a compression ratio did not show a significant difference with varying copper alloy additions. The single particles experienced large deformation upon impact, and ultrafine grains were formed at the particle/substrate interface via dynamic recrystallization. The particles were bonded to the steel substrate via a thin amorphous layer at the interface.