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Grain growth in IN718 superalloy fabricated by laser additive manufacturing
摘要： The grain growth mechanism of IN718 superalloy fabricated by selective laser melting (SLM) was studied. Epitaxial growth with the same crystallographic orientation or rotating by 90° across the melting pool boundary and competitive growth in the same melting pool were observed. Either of the two patterns of epitaxial growth can maintain the same grain across the melting pool boundary. Competitive growth is determined by both the heat flow direction and preferred crystallographic orientation. In SLM, the grains grow along the preferred crystallographic orientation owing to a high solidification rate. The smaller the deviation angles between the heat flow direction and the preferred crystallographic orientation, the faster the grain growth rate.
关键词： competitive growth,crystallographic orientation,selective laser melting,IN718,Epitaxial growth
更新于2025-09-23 15:19:57
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Microstructure control, competitive growth and precipitation rule in faceted Al2O3/Er3Al5O12 eutectic in situ composite ceramics prepared by laser floating zone melting
摘要： Microstructure control and competitive growth of Al2O3/Er3Al5O12 eutectic/off-eutectics are explored over wide ranges of solidification rates and compositions. Gradual transformation phenomenon of microstructure morphology from complete eutectic to eutectic + coarse Er3Al5O12 phase and to eutectic + Er3Al5O12 dendrite is observed and the corresponding influence factors are evaluated. Competitive growth between single-phase Al2O3 (or Er3Al5O12) dendrite and eutectic is analyzed and coupled growth zone is mapped through comparing interface temperatures of different patterns of microstructures. The complete eutectic microstructure could be obtained at Al2O3/Er3Al5O12 hypoeutectic (Al2O3-17.5 mol% Er2O3) under fast solidification rate and the onset growth rate (~0.94 × 104 μm/s) estimated from the measured eutectic spacing (~150 nm) fits well with the result calculated on the basis of competitive growth (~1.27 × 104 μm/s). Transformation of microstructure from irregular eutectic to regular eutectic and probable adjustment mechanism of eutectic spacings are discussed when the eutectic spacings refined from micron-scale (< 10 μm) to nano-scale (~20 nm).
关键词： Competitive growth,Directional solidification,Microstructure control,Precipitation rule,Oxide ceramic
更新于2025-09-19 17:13:59