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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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Microstructure development, tribological property and underlying mechanism of laser additive manufactured submicro-TiB2 reinforced Al-based composites
摘要： Al-based composites reinforced with submicro-TiB2 particles were manufactured by selective laser melting (SLM) of powder mixture under different laser powers. The microstructure evolution and tribological property of SLM-processed AlSi10Mg/TiB2 composites were investigated. Al-based composites with high manufacturing quality and uniform dispersion of TiB2 particles throughout the matrix were obtained. The EBSD results showed that incorporation of TiB2 reinforcements imposed no appreciable influence on the crystallographic orientation and average grain size, while the grain size distribution was distinctly narrowed as a result of limitation on grain growth by addition of ceramic particles. The SLM-processed composites exhibited a continuous tendency of increasing microhardness and decreasing coefficient of friction (COF) along with wear rate with a laser power increasing from 350 to 450 W. The composites showed high microhardness of 126 HV0.2, exceeding over those of the Al-Si alloys and composites processing by conventional techniques. A low COF of 0.65 and wear rate of 5.2×10?4 mm3N-1m-1 were obtained for bulk-form composites at 450 W due to the combined effects of high manufacturing quality, microstructure homogeneity, and sound interfacial bonding.
关键词： Tribological property,Microstructure development,Selective laser melting (SLM),Al-based composite
更新于2025-09-16 10:30:52