Deformation-driven precipitate evolution in cold sprayed age-hardenable aluminum alloys

Abstract

Recent advances in laser assisted cold spray have shown great promise in addressing the limitations of particle plasticity and bonding strength in conventional processes, especially for difficult-to-deposit hard metal materials. In the present study, we enhanced the plastic deformation capability of cold sprayed high strength age-hardenable aluminium (Al) alloy particles by applying laser assisted heating, which enabled effective particle deposition at lower velocities. We investigated the deformation behavior of individual particles under varying velocities and temperatures through single particle simulations and controlled experiments. The results demonstrated a strong correlation between simulation and experimental data, showing that particle deformation increases with velocity. High-resolution transmission electron microscopy revealed excellent bonding at the interface between laser treated particles and the substrate, with no visible demarcation. In contrast, the interface of untreated particles exhibited a nanometer-thick oxide layers of 15–25 nm. Additionally, with the increase of severe plastic deformation, a large amount of η/η’-MgZn<inf>2</inf> precipitates appeared in the multi-particle bonding regions of the deposits, which are attributed to the high dislocation density and local thermal effects promoting the rapid nucleation of precipitates at dislocation positions. The concurrent increase in precipitate formation contributed to the strengthening of the deposit, as reflected by an elevated nanoindentation hardness of up to 3.5 GPa. Vacuum heat treatment confirmed that intense plastic deformation during in situ laser-assisted deposition generates high dislocation densities and drives microstructural evolution, which are key to accelerating precipitation and improving interfacial bonding quality. These findings provide mechanistic insights and practical guidance for tailoring particle bonding and microstructural evolution in laser assisted cold spray of high-strength alloys.