Abstract
Metallic microparticles can acquire remarkable nanoscale morphologies after experiencing high velocity collisions, but materials science regarding the extreme events has been limited due to a lack of controlled experiments. In this work, collision dynamics and nonlinear material characteristics of aluminum microparticles are investigated through precise single particle collisions with two distinctive substrates, sapphire and aluminum, across a broad range of collision velocities, from 50 to 1,100 m/s. An empirical constitutive model is calibrated based on the experimental results, and is used to investigate the mechanics of particle deformation history. Real-time and post-impact characterizations, as well as model based simulations, show that significant material flow occurs during the impact, especially with the sapphire substrate. A material instability stemming from plasticity-induced heating is identified. The presented methodology, based on the use of controlled single particle impact data and constitutive models, provides an innovative approach for the prediction of extreme material behavior.
Highlights
High-velocity impacts of microparticles often occur in either natural or artificial environments
Despite the growing interest of cold spray (CS) as an additive manufacturing method for metals, the materials science underlying the extreme microscopic events in general has not been explicitly understood, primarily because the material response is in a nonlinear, non-equilibrium, and high- strain-rate (HSR) regime
When the particles are accelerated through a CS system, which is developed for bulk processing, individual particle’s impact velocity, mass, temperature, and shape can only be marginally estimated with various statistical errors
Summary
The aluminum 6061 particles were mixed with isopropanol and a single drop of the mixture was applied on the PDMS/gold-coated substrate. An individual Al-particle was placed near the focal point of the laser ablation on a PDMS/Au/glass substrate (Fig. 1b). A Ti:Sapphire oscillator (Mai Tai HP, Spectra-Physics) continuously provided laser pulses (a pulse duration
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