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The role of side-branching in microstructure development in laser powder-bed fusion
摘要： In-depth understanding of microstructure development is required to fabricate high quality products by additive manufacturing (for example, 3D printing). Here we report the governing role of side-branching in the microstructure development of alloys by laser powder bed fusion. We show that perturbations on the sides of cells (or dendrites) facilitate crystals to change growth direction by side-branching along orthogonal directions in response to changes in local heat flux. While the continuous epitaxial growth is responsible for slender columnar grains confined to the centreline of melt pools, side-branching frequently happening on the sides of melt pools enables crystals to follow drastic changes in thermal gradient across adjacent melt pools, resulting in substantial broadening of grains. The variation of scan pattern can interrupt the vertical columnar microstructure, but promotes both in-layer and out-of-layer side-branching, in particular resulting in the helical growth of microstructure in a chessboard strategy with 67° rotation between layers.
关键词： microstructure development,additive manufacturing,thermal gradient,side-branching,epitaxial growth,laser powder bed fusion,3D printing
更新于2025-09-19 17:13:59
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Investigation on Ti6Al4V laser metal deposition using Taguchi based grey approach
摘要： An optimization of laser metal deposition process considering tensile strength, clad hardness, clad grain size and clad porosity as performance characteristics were investigated. The influence of laser power and laser scan speed on the thermal gradient and cooling rate with regard Ti6Al4V powder coating on Ti6Al4V substrate was focused. Taguchi’s experimental design approach is employed for planning the experiments and analyzing the dependency of input variables on desired performance measures such as micro hardness, tensile strength, porosity and grain size. The laser scan speed is found as the dominant factor on the clad hardness while laser power has the influencing effect on grain size of the substrate. GRA is opted for determining the multi performance machining characteristics of laser metal deposition process. The experimental outcomes reveal that the proposed method of multi objective optimization considerably enhances the multi performance machining characteristics.
关键词： Laser metal deposition,Ti6Al4V,Grain size,Thermal gradient,Grey relational approach,Laser scan speed
更新于2025-09-12 10:27:22