*Article* **Effect of Porosity on Dynamic Response of Additive Manufacturing Ti-6Al-4V Alloys**

**Yihang Cui <sup>1</sup> , Jiacheng Cai <sup>2</sup> , Zhiguo Li <sup>1</sup> , Zhenyu Jiao <sup>3</sup> , Ling Hu <sup>1</sup> and Jianbo Hu 1,3,\***


**Abstract:** Additive manufacturing is a rapidly developing manufacturing technology of great potential for applications. One of the merits of AM is that the microstructure of manufactured materials can be actively controlled to meet engineering requirements. In this work, three types of Ti-6Al-4V (TC4) materials with different porosities are manufactured using selective laser melting using different printing parameters. Their dynamic behaviors are then studied by planar impact experiments based on the free-surface velocity measurements and shock-recovery characterizations. Experimental results indicate that the porosity significantly affects their dynamic response, including not only the yield, but also spall behaviors. With the increasing porosity, the Hugoniot elastic limit and spall strength decrease monotonically. In the case of TC4 of a large porosity, it behaves similar to energy-absorbing materials, in which the voids collapse under shock compression and then the spallation takes place.

**Keywords:** additive manufacturing; Ti-6Al-4V; dynamic behaviors; porosity; spall
