08/07/19: Prof. Lee gives a talk at NATAS 2019

2019 46th Annual North American Thermal Analysis Society (NATAS) Conference

August 5-8, 2019 Newport, RI

Laser-induced projectile impact testing (LIPIT) for extreme material science in cold spray

Swetaparna Mohanty1, Carmine Taglienti1, Wanting Xie1,2, Victor K. Champagne3, and Jae-Hwang Lee1*

1Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, Massachusetts 01002, USA.
2Department of Physics, University of Massachusetts, Amherst, Massachusetts 01002, USA.
3Unitied States Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA.
*E-mail: leejh@umass.edu

In cold spray (CS),[1] various ductile metals are deposited on a substrate below their melting temperatures, and powdered forms of the metals are sprayed through a de Laval nozzle at supersonic speeds using a pressurized carrier gas. Due to the exclusive advantages in sold-state deposition without considerable recrystallization, oxidation, and thermal stresses, CS has attracted attention from industries targeting high-performance coating and additive manufacturing. Although various numerical approaches have been expected to facilitate the fundamental understanding of the extreme deformation mechanisms, their results are still limited due to the lack of referenceable experimental results with precise experimental parameters. Here, we introduce the laser induced single particle impact test (LIPIT) experiments[2] to study the extreme dynamics of aluminum 6061 particles.

For the temperature-dependent deformation characteristics of the aluminum 6061 particles, LIPIT experiments were conducted at elevated temperatures (23°C, 100°C, 200°C, and 300°C). Sapphire was used as the rigid target substrate. Since the entire plastic deformation occurred solely on aluminum spheres due to the high modulus of sapphire, aluminum-sapphire collisions provided a very simple environment for numerical simulations and referenced data. For in-situ characterization, we measured the rebound speeds of the aluminum particles as a function of its impact speeds and temperatures. In addition, rebound particles were captured to help understand how temperature affects the deformation of particles. Furthermore, it has been generally understood that the oxide layer plays a significant role in the bonding process of a metallic particle to a metallic surface. As a model system, aluminum 6061 substrates with three different thicknesses (5, 15, 25 nm) of aluminum oxide layers were prepared using atomic layer deposition. The dynamic behavior of the single microparticles was quantified by LIPIT. In the experiments, aluminum 6061 microparticles (~ 20 µm diameter) were accelerated to controlled high speeds (50 – 1,100 m/s) and impacted with the substrate. Rebound speeds after impact/collision and coefficients of restitution were precisely quantified using an ultrafast microscopic imaging technique. Moreover, critical velocities of different oxide thicknesses were measured.

This research was supported by the U.S. Army Research Laboratory under contract W911NF-15-2-0026 (Program Manager: Aaron Nardi).