This open-source LAMMPS script simulates the laser welding mechanism of aluminum plates through molecular dynamics, providing detailed insights into the atomistic behavior during the welding process. The script models a moving laser heat source that sequentially heats discrete zones along the weld seam, reaching temperatures of 2500K to induce localized melting and fusion between two butt-jointed plates. The mechanism captures the complete thermal cycle: laser heating, melt pool formation, and controlled cooling through multiple temperature stages (2500K→800K→400K→300K), mimicking real welding conditions. The simulation tracks critical physical phenomena, including stress field evolution through von Mises stress calculations, temperature distribution via kinetic energy analysis, and microstructural changes through centro-symmetry parameters. Edge thermostats simulate heat dissipation boundaries while the moving laser creates realistic thermal gradients. This tool enables researchers to understand fusion zone formation, heat-affected zone characteristics, residual stress development, and potential defect formation at the atomic level, supporting optimization of welding parameters and prediction of joint quality without expensive experimental trials.

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This open-source LAMMPS script investigates the melting mechanism of a spherical aluminum powder particle on a substrate, simulating conditions relevant to powder-based additive manufacturing and powder metallurgy. The script models a 15-unit radius aluminum sphere positioned above a rigid substrate, with the substrate acting as a frozen heat sink to represent a build platform. The melting mechanism occurs through controlled heating: the sphere is equilibrated at 300K, then gradually heated to 950K (above aluminum's melting point of 933K) over 40 picoseconds, and maintained at this temperature to observe complete phase transformation from solid to liquid. The frozen substrate creates asymmetric heat transfer, causing the sphere to melt while maintaining contact with the solid base, mimicking real powder sintering or melting processes. This simulation enables analysis of wetting behavior, contact angle evolution, melt pool spreading dynamics, and substrate-particle interactions at the atomic scale. The tool provides insights into powder consolidation mechanisms, interfacial bonding formation, and thermal management in additive manufacturing, helping optimize process parameters like substrate temperature and heating rates without costly experimental iterations. 

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This open-source LAMMPS script simulates the laser sintering mechanism of two spherical aluminum powder particles positioned adjacent to each other on a frozen substrate. The mechanism begins with two 12-unit radius spheres in near-contact, representing loose powder particles. A focused laser beam targets the neck region between the particles, delivering localized energy through heat deposition (150 eV/ps) and raising the temperature to 1800K, approaching aluminum's melting point of 933K. This creates a narrow heat-affected zone where atomic diffusion becomes active. The simulation progresses through distinct phases: rapid laser heating of the neck region, steady-state sintering where atoms at the interface undergo diffusion and rearrangement to form bonds, extended holding time for neck growth and strengthening, followed by gradual cooling that allows the newly-formed neck to solidify with minimal residual stress. The frozen substrate acts as a continuous heat sink, creating realistic temperature gradients that drive the sintering process. Throughout the simulation, coordination numbers track atomic bonding (increasing from ~8 in loose powder to ~12 in consolidated material), centro-symmetry parameters identify grain boundaries and defects at the interface, and stress analysis reveals mechanical properties of the sintered bond. This atomistic approach captures neck formation kinetics, interfacial bonding mechanisms, and microstructural evolution during laser-driven powder consolidation. 

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