Month: June 2020

Tyler’s paper was published at Journal of Materials & Design!

Tyler’s paper was published at Journal of Materials and Design! Many Congratulations! This work is the collaboration with multiple groups (Mark Aindow (UConn), Avinash Dongare (UConn), Cyril Williams (US Army Research Laboratory)).


Tyler J. Flanagan, Sriram Vijayan, Sergey Galitskiy, Jacob Davis, Benjamin Bedard, Avinash Dongare, Mark Aindow, Cyril L. Williams, Seok-Woo Lee, “Shock-induced deformation twinning and softening in magnesium single crystals,” 194, 108884, Materials & Design (2020) [PDF] [web]



Magnesium is widely regarded as an excellent structural material, primarily because it forms the basis for a range of light-weight high-strength alloys. Recently, high-strain rate deformation of magnesium has received a great deal of attention due to the complicated deformation modes that involve combinations of dislocation slip and deformation twinning. In this study, single crystal magnesium samples were shock-compressed along the c- and a-axis, then released back to ambient conditions. Post-mortem transmission electron microscopy revealed that extension twins developed for both c- and a-axis shock loading. Also, the nanoindentation hardness values for these shocked samples were compared to those for samples compressed under quasi-static conditions; it was found that the hardness decreased with increasing strain rate for both c- and a-axis loading. Molecular dynamics simulations were performed to elucidate the detailed mechanisms of deformation twinning in terms of inertial confinement of sample geometry and different stress relaxation speed between impact and lateral directions. The conversion from work-done to heat was discussed to explain the influence of shock-induced heating on the residual hardness. These results give new insights into the residual mechanical response in shock-compressed materials and may help to develop a more fundamental understanding of shock phenomena in metallic materials.

Jessica’s paper was published at Journal of Materials & Design!

Jessica’s paper was published at Journal of Materials & Design. Many Congratulations!!!

  • Jessica M. Maita, Gyuho Song, Mariel Colby, Seok-Woo Lee, “Atomic arrangement and mechanical properties of amorphous boron,” – Materials & Design193, 108856 (2020) [PDF] [web]


Amorphous boron can be synthesized by chemical vapor deposition (CVD) onto a tungsten wire substrate, and this core-shell fiber has been widely used in high-performance composites due to its superior mechanical properties. Although the amorphous boron coating makes a significant contribution to the high fracture strength, its mechanical properties have not been studied rigorously due to its thin thickness and strong adhesion to the substrate. Furthermore, the medium-range atomic ordering of CVD amorphous boron has not been clearly understood, and the determination of the closest crystalline structure has been a challenge. In this study, high-resolution transmission electron microscopy (HRTEM), nanoindentation, and in-situ micropillar compression were performed to investigate the atomic arrangement and mechanical properties. Electron diffraction and autocorrelation function analysis revealed α-rhombohedral boron ordering as the closest crystalline structure. Micropillar compression displayed near-ideal yield strength (~13 GPa), but nanoindentation a relatively moderate Young’s modulus (~320 GPa), leading to a modulus of resilience (2.64 × 108 J/m3) unprecedentedly higher than most advanced engineering materials. Our structural and mechanical data will be discussed in terms of lattice point spacing and the influence of surface defects on fracture strength, respectively. Our results will be potentially useful to improve mechanical properties of amorphous boron core-shell fibers and related composites.