PSI - Issue 69

Mohammadjavad Abdollahzadeh et al. / Procedia Structural Integrity 69 (2025) 2–19

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Fig.7: Experimental and numerical result comparison (Power 150 W - Scan speed 115 cm/s). The error between experimental and numerical was less than 2.8 % (Height), and 3.1 % (Width) in this case which shows us a good agreement between experimental and numerical study

Fig.8: Comparison of simulation results with experimental data in LPBF-AM. (a) Shows the relationship between width and scan speed of the melt pool. (b) Displays depth versus scan speed of the melt pool. In both subfigures, the different lines represent simulations at different power levels. Experimental data from Chernyshikhin et al. is also included for validation. As shown, our model closely aligns with the experimental data, demonstrating its accuracy. 3.2. Thermal Behavior of the Melt-Pool and its Morphology The temporal evolution of the temperature field on the melt pool's surface is illustrated in Figure 9. These results, obtained from numerical simulations with laser parameters set to P = 150 W and v = 115 cm/s, reveal significant changes in surface geometry over time. The distinct thermal properties of NiTi, such as its thermal conductivity, set it apart from materials like AlSi10Mg [43]. For AlSi10Mg, the melt pool retains a circular shape, whereas for NiTi, the morphology transitions from circular to elliptical and eventually stabilizes into a comet-like shape as the laser heat source moves. This difference is driven by higher thermal conductivity at the tail of the melt pool, resulting from solidified material, compared to the liquid front. As the melt pool advances, the front material remains molten, while the tail cools and solidifies, driving these dynamic morphological changes. At 15 μs (Fig.9(a)), laser activation initiates phase transition, melting the powder particles and forming a circular melt pool. As time progresses to 120 μs (Fig.9(b)), the pool transitions to an elliptical shape due to slower heat transfer influenced by thermal conductivity, convective heat transfer, and thermal gradients. A clear gradient is observed, with the center hotter than the periphery. At 600 μs, the laser is deactivated, triggering the solidification process. These thermal dynamics, including energy absorption, reflection, and particle interaction, significantly influence melt pool behavior and final morphology.