effects of nanoglass process factors on its microstructure: a molecular dynamics study

Metallic glasses (mgs), typically produced through the rapid quenching of corresponding metal (alloy) melt, are characterized as amorphous solids without any long-range order or defects. for that reason, controlling their properties by means of modifying their microstructural features, in a way comparable to crystalline materials, seems to be infeasible at the first glance. in contrast to typical amorphous solids, nanoglasses (ngs) are considered as the most prominent and newest efforts in production of the amorphous materials with controllable and modifiable microstructures. the characteristics and structural features of ngs differ noticeably from those of mgs made by rapid quenching of the metal melt. this study aimed to analyze effects of the cu-zr-based ng process factors on its resulting structural features including its morphology as well as governing short-range order by adopting molecular dynamics simulations in the lammps package. it should be mentioned that experimentally, the ng is produced by consolidation of the amorphous nanoparticles, mainly prepared by the inert-gas condensation (igc) method. however, due to the computational costs consideration in our study, the glassy nanoparticles are cut from the rapidly-quenched bulk of corresponding mg and then annealed at glass transition temperature (tg) to mimic the nanoparticles generated from the igc method. so all things considered, the factors involved in the process of ng formation can be considered as the initial bulk mg quenching rate, the temperature, and the pressure of the consolidation phase. begin with the prepared glassy nanoparticles, a close inspection of their chemical structure revealed a core-shell structure of nanoparticles with different chemical compositions, which originated from the surface segregation of cu atoms. it is worth noting that the core-shell structure of the glassy nanoparticles leads to the formation of the ng microstructure, which is characterized by glassy regions connected by the interface regions that originated from the shell portion of the initial glassy nanoparticles. moreover, to get a precise insight into the structural order of the resulting ng, the voronoi tesselation analysis is carried out. implementing the voronoi analysis, it is found that the cu-centered full icosahedra [0,0,12,0] voronoi polyhedra is predominant in the short-range order of ng structure. another key point to remember is that the process factors have significant consequences on the governing short-range order of the structure, which itself is responsible for the mechanical properties of the ng. the findings shed light on the governing process-structure linkages in ng structure, which enables the engineers to modify the microstructure by controlling the process parameters.