Mesoscale modeling of jet initiation behavior and microstructural evolution during cold spray single particle impact

• Published in: Acta materialia Vol. 182; pp. 197 - 206
• Main Authors: Suresh, Sumit, Lee, Seok-Woo, Aindow, Mark, Brody, Harold D., Champagne, Victor K., Dongare, Avinash M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2020
• Subjects: Cold spray; Jetting; Mesoscale; Molecular dynamics; Particle impact; Recrystallization; Jetting; Molecular dynamics; Mesoscale; Particle impact; Cold spray; Recrystallization
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2019.10.039

Quasi-coarse-grained dynamics (QCGD) simulations are carried out to investigate the mesoscale deformation behavior during the impact of a 20 µm pure aluminum particle onto a substrate of pure aluminum at time and length scales relevant to cold spray deposition. A rigorous analysis of the evolution of pressure, temperature, strain, flow stress and microstructure is carried out to investigate the jetting mechanisms over a range of process parameters (impact velocity and particle temperature). The QCGD simulations identify a critical role of the pressure wave propagation in the initiation of a jet, i.e. outward flow of material at the particle/substrate interface periphery (edge). Jetting is observed to initiate when the shock wave interacts with the edge and results in localized softening of the metal in this region. This localized softening enables outward flow of the material and is accompanied by a release of the pressures in the particle and the substrate at the interface. Observations of final splat microstructures of systems that showed jetting revealed several new “small” grains in the range of 2–4 µm. These grains are mainly found at the interface, suggesting that recrystallization is favored in cold sprayed impacts of aluminum. The temporal evolution of pressure in a thin vertical section through the center of the particle is plotted in Fig. 2 for an impact velocity of 1300 m/s, where “jetting” is observed. The contour levels are chosen to provide a clear visual inspection of the propagation of a compressive shock wave generated as shown in (a), interaction with the particle edge as shown in (b), if any, and its role in initiating a jet. In this case the shock wave arrives the particle edge at t = 2.9 ns as shown in Fig. 2 (c), that results in outward flow of the materials and a particle jet is initiated. [Display omitted]