Modeling of selective laser sintering of single-component metal powders

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Selective Laser Sintering (SLS) is a rapid prototyping technology which enables freeform fabrication of complex-geometry components directly from three-dimensional CAD data and is widely applied to the processing of single-component metal powders in the past years in order to manufacture functional metal components layer by layer. Laser sintering of single-component metal powders is a process in which a high-energy laser beam scans, melts, shrinks and consolidates a metal powder. This complex process includes physical effects such as heat transfer into the powder articles, radiative and convective boundary conditions, shrinkage phenomena caused by the density change, moving boundary of the melt/solid interface with phase change, fluid flow caused by surface tension and buoyancy and mass transportation in the molten pool. The inherent complexity of this process requires the construction of increasingly sophisticated models to enable a fundamental understanding of the important physical parameters such as laser intensity, scanning velocity and spacing, subcooling parameter, initial porosity and so on. For better understanding physical mechanisms during laser sintering of single-component metal particles, this dissertation develop models to investigate the physical mechanisms of selective laser sintering of single-component powders under different conditions including rapid melting, partial melting, and complete melting processes and simulate the manufacturing processes during the laser sintering processes in single-line and multiple-line scanning manners. The parametric effects on the surface temperature distribution, various interfaces in the molten pool and mushy zone, velocity distribution in the molten pool and melt/solid fraction profiles in the mushy zone are extensively analyzed.