Molecular dynamics study on CuZr nanoglass produced by controlling SLM parameters

Amorphous metals are formed by rapid quenching of metallic melts. The atoms have no opportunity to form a crystalline lattice and solidify in a disordered manner. Since the phase transformation from liquid to solid is suppressed in this process, no crystallization nuclei are formed during solidification. This class of materials, called metallic glass (MGs), possesses a short range order rather than the long-range one available in their crystalline counterpart. Moreover, the absence of grain boundaries in these structures brings them an ultrahigh strength and excellent wear and corrosion resistance. This fact has turned the MGs as promising materials that their structure and mechanical properties are needed to be investigated comprehensively. The most important drawback of the MGs is their brittleness. In other words, blocking the deformation mechanisms in MGs has led to small elongation before failure in these structures. In order to eliminate this weakness, Nanoglasses (NGs) are introduced, which offer higher deformability, more flexibility, and a wider plastic behavior compared to metallic glasses. These structures consist of two distinct areas: the core and the shell. The core of a NG has a structure similar to that of the MGs obtained by rapid cooling of the melt. It is surrounded by a shell, which consists of amorphous interfaces characterized by a decrease in density. The structure of the shell is more ductile than the core, which means an improved ductility in the NG rather than MGs. The NG is produced by consolidation of nano-sized particles of MGs. Selective laser melting (SLM) is a widely used additive manufacturing method for producing MG structures. This method involves placing amorphous nanoparticles, produced by various metallurgical processes, next to each other. By applying laser energy, particle merge into each other and the MG structure forms. However, this process destroys the primary structure of nanoparticles, which consists of a hard core and a relatively softer shell. To address this issue, here in this work, the laser parameters are investigated. in fact, it is aimed to prevent the removal of the core and shell areas in the final structure by controlling the laser energy delivered to the nanoparticles. By doing so, the outcome of the process would be NG instead of the MG structure. For this purpose, amorphous CuZr nanoparticles are adopted as the primary constitutes. In order to simulate the SLM process, Molecular Dynamics (MD) simulations using the Large Scale Atomic/Molecular Parallel Mass Simulator (LAMMPS) software has been employed. In order to qualify the structural evolutions, some geometrical indicators of the final structure are extracted and by studying the process of its changes during the production process, an approximation of the quality of the produced product can be obtained. The results show the high impact of laser parameters such as scanning speed and laser power on the structural properties of the NG.