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Outline
This study investigates the characteristics and formation mechanisms of pore defects in TC4 titanium alloy fabricated via selective laser melting （SLM） through numerical simulation and industrial computed tomography （CT） analysis. Numerical simulations find that the temperature at the laser beam spot is high， while the temperature away from the laser beam spot is low. After printing， microstructural characterization reveals well-overlapped melt tracks； however， both spherical and irregularly shaped pores are observed within the consolidated material. Using the same parameters as the simulation， the TC4 alloy prepared by SLM has a density of 97.7%. Microstructural analysis shows that the grains along the scanning direction and building direction are equiaxed and columnar crystals， respectively， and the microstructure is composed of primary β-Ti and α'/α-Ti. Metallographic structure， SEM images， and industrial CT reconstruction images demonstrate the presence of spherical and irregular pores in the material that are similar to the numerical simulation results. The appearance of spherical pore defects is due to the vapor pressure difference between the molten pool and the solid metal surface， which causes the gas at the interface to be carried into the molten pool without overflowing， ultimately remaining inside the material； the appearance of irregular pores is due to the uneven temperature distribution that makes it difficult for the pores enclosed inside the material to be completely filled by the liquid phase when the melt track passes over each other.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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