The selective laser melted (SLM) Ti–6Al–4V cellular solid is a promising material in biomedical and other applications. The mechanical properties of the SLM Ti–6Al–4V cellular material are predominantly controlled by the design of the cellular structure. The objective of this study was to investigate the uniaxial compressive properties and compressive fatigue performance of the SLM Ti–6Al–4V cellular solid with a new cuboctahedron unit cell reinforced by four diagonal struts and two horizontal struts along the X and Y axes. The influences of hot isostatic pressing (HIP) on the various mechanical properties were also examined. The results showed a smoother stress–strain curve and fewer stress oscillations in the HIP specimen than in the SLM specimen. The HIP process slightly decreased the yield strength of the SLM sample from 55 to 52 MPa. Under uniaxial compressive stress, the SLM and HIP specimens exhibited layer-by-layer fracture and diagonal shear fracture, respectively. Furthermore, the HIP treatment significantly increased the fatigue performance and improved the fatigue endurance ratio at 10⁶ cycles from 0.15 to 0.35. The HIP treatment contributed to several positive effects, including phase transformation from brittle α′ to α + β, the elimination of strut porosity and residual stress, an increase in lath size, and a better combination of strength and ductility, thereby improving the fatigue performance. The effects of stress mode on the fracture mechanism were also clarified using in situ observation in combination with digital image correlation.

Graphic abstract

中文翻译：

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选择性激光熔化 Ti-6Al-4V 蜂窝结构的单轴压缩性能和压缩疲劳性能

选择性激光熔化 (SLM) Ti-6Al-4V 细胞固体在生物医学和其他应用中是一种很有前途的材料。SLM Ti-6Al-4V 蜂窝材料的机械性能主要由蜂窝结构的设计控制。本研究的目的是研究 SLM Ti-6Al-4V 多孔固体的单轴压缩性能和压缩疲劳性能，该多孔固体具有由四个对角支柱和两个沿 X 轴和 Y 轴的水平支柱增强的新立方八面体晶胞。还研究了热等静压 (HIP) 对各种机械性能的影响。结果表明，与 SLM 试样相比，HIP 试样的应力-应变曲线更平滑，应力振荡更少。HIP 工艺将 SLM 样品的屈服强度从 55 MPa 略微降低到 52 MPa。在单轴压应力作用下，SLM 和 HIP 试样分别表现出逐层断裂和对角剪切断裂。此外，HIP 处理显着提高了疲劳性能并提高了疲劳耐久比为 10从 0.15 到 0.35 ⁶个循环。HIP 处理产生了几个积极的影响，包括从脆性 α' 到 α + β 的相变，消除了支柱孔隙和残余应力，增加了板条尺寸，更好地结合了强度和延展性，从而提高了疲劳性能. 还通过原位观察结合数字图像相关来阐明应力模式对断裂机制的影响。

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