Engineering topics
Matthews, Manyalibo
Publications and source records attributed to Matthews, Manyalibo.
Laser pre-sintering for denudation reduction in the laser powder bed fusion additive manufacturing of Ti-6Al-4V alloy
As a fundamentally different process for creation of complex parts, laser powder bed fusion (LPBF) additive manufacturing exhibits complex behavior at the melt pool that has a direct influence on the macroscopic properties of the final material. Powder denudation, a previously studied deleterious phenomenon, is the displacement of powder due to entrainment in a jet of rapidly vaporized metal created by the process laser. To minimize the effect of denudation and inspired by methods in adjacent fields, a laser pre-sintering (LPS) method was studied in an effort to reduce denudation. LPS was found to be most effective in the 1–4 J/mm3 volumetric energy density processing regimes, minimizing the common experimentally observed problems with the LPBF process. Scanning electron microscopy of the LPS-treated powder bed revealed insight into the accelerating effect morphological irregularities along the powder particle surface have in the pre-sintering process. To further understand the process, an estimation of the sintered neck sizes necessary to eliminate denudation in LPS is made, qualitatively affirming the low energy densities needed to prevent denudation. Here, the results presented in this work represent an initial step towards understanding and implementing LPS as a quality-enhancing step in LPBF.
Microstructural characterization of L-PBF stainless steel 316L as-built and in situ during plastic deformation
This document gathers the data obtained as of December, 13 th 2019 by SEM/EBSD, S/TEM/EDS, and mechanical testing of a stainless steel 316L additively manufactured by L-PBF using the Fraunhofer system with build parameters: 100 μm Gaussian beam, 350 W laser power, 219 mm/s scan speed, 100 μm hatch spacing, and 90º scan rotation between layers.