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Computational Assessment of Thermokinetics and Associated Microstructural Evolution in Laser Powder Bed Fusion Manufacturing of Ti6Al4V Alloy
摘要： Although most of the near non-equilibrium microstructures of alloys produced by laser powder bed fusion (LPBF) additive manufacturing (AM) are being reported at a rapid rate, the accountable thermokinetics of the entire process have rarely been studied. In order to exploit the versatility of this AM process for the desired properties of built material, it is crucial to understand the thermokinetics associated with the process. In light of this, a three-dimensional thermokinetic model based on the finite element method was developed to correlate with the microstructure evolved in additively manufactured Ti6Al4V alloy. The computational model yielded the thermal patterns experienced at given location while building a single layer through multiple laser scans and a whole part through multiple layers above it. X-ray analysis of the resultant microstructure confirmed the presence of acicular martensitic (α′) phase of (002) texture within the build-plane. Computationally predicted magnitude of the thermal gradients within the additively manufactured Ti6Al4V alloy in different directions (X, Y, and Z) facilitated the understanding about the evolution of grain morphology and orientation of acicular martensite in prior β grains. The scanning electron microscopy observations of the alloy revealed the distinct morphology of phase precipitated within the martensitic phase, whose existence was, in turn, understood through predicted thermal history.
关键词： Thermokinetics,Additive manufacturing,Microstructural evolution,Laser powder bed fusion,Ti6Al4V alloy
更新于2025-09-23 15:21:01
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Thermodynamics analysis and rapid solidification of laser polished Inconel 718 by selective laser melting
摘要： This paper presents thermodynamics analysis and rapid solidi?cation of laser polishing technology for selective laser melting (SLM) Inconel 718 superalloy. Signi?cant porosity reduction has been examined in the laser polished layer, where the surface porosity is reduced by 65.7% compared with that of the as-fabricated SLM surface. The results show that the temperature in the polished zone is over 1683 K, and the cooling rate is approximately up to 2.46 × 106 K/s. Besides, the polished layer consists of equiaxed grain and columnar grain with average grain size of 10 ± 2.4 μm and 5 ± 1.2 μm, respectively, and tiny cell grains with average size of 3.5 μm in the heat-a?ected zone (HAZ). Moreover, the transmission electron microscope (TEM) results show that the orientation relationship (OR) between the γ matrix and Laves phase is found to be Burgers OR [0 1 1] ‖[0 1 1ˉ 2] Laves on the as-received layer and [1ˉ 1 1] ‖[1 2ˉ 1 3ˉ] Laves on the polished layer.
关键词： Inconel 718 superalloy,Microstructural evolution,Crystallographic orientation,Selective laser melting,Laser polishing
更新于2025-09-16 10:30:52
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The effect of different scanning strategies on microstructural evolution to 24CrNiMo alloy steel during direct laser deposition
摘要： 24CrNiMo alloy steel is a low-alloy high strength steel and was used to fabricate engine components and brake discs. In the current study, Direct Laser Deposition (DLD) was used to additively manufacture 24CrNiMo alloy steel samples with high strength and ductility. The microstructural evolution, texture and mechanical properties of deposited samples can be affected by changing inter-layer time intervals and scanning strategy between deposited layers. The granular bainite (GB) and lath martensite (LM) inside deposited samples were obtained by inter-layer successive deposition and 2-minute intervals deposition, respectively, because of the different cooling rates of different inter-layer time intervals. The occurrence of 2-minute intervals between cladding layers leads to higher cooling rates, resulting in finer grain size. In addition, the relatively strong textures could be transformed into the weak ones since the columnar dendrites were fragmented by the different heat transfer directions resulting from a scanning strategy of 90°-rotation between cladding layers. Less inclusions and un-melted powders inside deposited samples were obtained when a scanning strategy of 90°-rotation between deposited layers was applied. The experimental results indicate that a deposited sample with excellent tensile properties and microhardness was fabricated by an optimized laser scanning strategy. The optimized scanning strategy mainly include inter-layer 2-minute intervals and 90°-rotation between deposited layers. Deposited samples fabricated by the optimized scanning strategy have comparable tensile strength and ductility to those of other forged low-alloy high strength steel. Therefore, this optimized laser scanning strategy can be applied to manufacture low-alloy steel with high tensile properties.
关键词： microstructural evolution,scanning strategy,direct laser deposition,mechanical properties,24CrNiMo alloy steel
更新于2025-09-11 14:15:04