Towards Quantitative Understanding of Melting and Erosion Caused by Hypervelocity Impacts

If a material experiences a high-rate impact with enough kinetic energy, the resulting plasticity and adiabatic heat generation can lead to local melting. Such melting is a source of erosive wear, because liquid is easily ejected from the impact site, and can also facilitate the removal of solid matter. Our recent works have aimed at understanding the melt-induced erosion process during hypervelocity impacts of microparticles. With impactors including hard particles as well as soft metals, we explore the heating, melting, and ejection of matter for microparticles launched and imaged with a laser system. In-situ videography provides insight on the development of ejecta during the impact event, as well as the kinetic energy associated with plasticity. Ex-situ quantitative measurements of impact sites provide accurate assessment of the volume of ejected matter. By combining in- and ex-situ quantitative measurements, we are able to conclude that only a small amount of liquid formation is needed to achieve remarkable phenomenological changes in erosion behavior.