Three dimensional (3D) printing is considered as an advanced manufacturing technology because of its additive nature. Electron beam melting (EBM) is a widely used 3D printing processes for the manufacturing of metal components. However, the products printed via this process generally contain micro porosities which affect mechanical properties, especially the fatigue property. In this paper, two types of EBM printed samples of the Ti-6Al-4V alloy, one with a round cross section and the other with a triangle cross section, were employed to investigate the existence of porosities using computed tomography (CT). Statistical analyses were conducted on the number, volume, shape, and distribution of pores. The results show that small pores (less than 0.000 2 mm 3) account for 80% of all pores in each type of samples. Additionally, to some extent, the shape of sample has influence on the number of micro porosities in EBM made Ti-6Al-4V. The sphericity of the pores is relatively low and is inversely proportional to pore volume. It is found that re-melting on the free surface effectively reduce pore density near the surface. This study may help produce a medical implant with better fatigue resistance.
三维（3D）打印技术因其增材制造特性被认为是一种先进的制造技术，其中电子束烧结技术（EBM）是一种广泛应用的金属 3D 打印工艺。该工艺打印的金属构件因常含有微观孔洞缺陷而降低了力学性能，特别是疲劳性能。本文针对电子束烧结工艺打印的两种不同形状的植入体 Ti-6Al-4V 合金试样，利用计算机断层扫描技术（CT）对试样内的孔洞进行了测量，统计并分析了孔洞的数量、体积、形状以及空间分布情况。结果表明形状差异在一定程度上影响了电子束烧结 Ti-6Al-4V 合金的微观孔洞缺陷数量，但不同试样的孔洞均以小于 0.000 2 mm 3 的小体积孔洞为主，占孔洞总数的 80%。反映试样孔洞奇异性的球度值较小，孔洞体积与球度值呈反比。对自由面的强化烧结有效降低了试样近表面的孔洞密度。本文结论对利用该工艺制备具有较好抗疲劳性能的医用植入体有一定参考价值。.
Keywords: distribution of porosities; electron beam melting; material defects; pores density; sphericity.