The EM3 Lab uses experiments, analytical theory, and computer simulations to understand the structure-property relation in structural materials, with particular emphasis on the extreme conditions of plastic strain, deformation rate, pressure, temperature, energetic particle/photon fluxes, etc. The EM3 Lab also exploits such extreme conditions for advanced processing and solid-state additive manufacturing:
Solid Particle Erosion
Solid particle erosion is the ablation of matter caused by being physically struck by another object. It occurs, for instance, during abrasive water jet cutting, or when space dust particles impact the space vehicles and satellites. While this phenomenon is known, it is empirically challenging to study mechanistically because of the short timescales and small length scales involved. We have recently resolved supersonic impact erosion in-situ with micrometer- and nanosecond-level spatiotemporal resolution and find that erosion in normal impact of ductile metallic materials is melt-driven. Moving forward, we plan to develope numerical models to describe material conditions when damage/melting take place during the deformation.
Solid-State Additive Manufacturing
Among more than 5500 metallic alloys in use today, only a few can be reliably 3D-printed. The majority presently faces major challenges such as compositional/structural inhomogeneity, distortion, tensile residual stresses and cracking—all emerging at high temperatures or during rapid solidification.
We explore the fundamentals of a solid-state approach, namely cold spray, that eliminates the need for high temperature fusion or sintering in additive manufcaturing. In cold spray we exploit kinetic energy rather than thermal energy to achieve bonding. We develop the process-structure-property relationships for in cold spraying metals, alloys, and composites.
Energetic particles have sufficient kinetic energy to dislodge substantial numbers of atoms in structural materials and ablate their surface layers. Research is underway to study damage mechanisms and to quantify the extent of radiation damage for a given set of radiation parameters.
Surface Mechanical Attrition
Nanocrystalline materials are viewed as critical future materials owing to their outstanding mechanical properties. The technological application of nanocrystalline materials, however, has been limited so far, largely due to the challenges encountered in their processing. Here we use surface mechanical attrition to make a gradient structure with nano-scale grains on the top surface of metallic materials. Since most material failures (fatigue, wear, corrosion, etc.) are very sensitive to the structure and properties of a material’s surface, surface nanocrystallization is a promising process to engineer materials against failures.