Compression Property, Deformation Behavior, and Fracture Mechanism of Additive-Manufactured Ti-6Al-4V Cellular Solid with a New Cuboctahedron Structure

Abstract

Laser powder bed fusion is a major additive manufacturing process for manufacturing cellular metallic materials. The main objective of this study was to clarify the influences of microstructure on the compressive deformation behavior and fracture mechanism of selective laser melted (SLM) cellular Ti-6Al-4V alloy with a new cuboctahedron structure using in-situ observation in combination with the digital image correlation technique. The results indicated that the compressive stress–strain curve of the SLM specimen was serrated in the plateau regime due to the brittle struts with α′-martensite. Nevertheless, hot isostatic pressing (HIP) at 1000 °C/150 MPa transformed the microstructure from brittle α′-martensite to ductile α + β dual phases. In the HIP specimen, the struts plastically collapsed layer-by-layer with increasing compressive strain and were then extruded into the surrounding pores, resulting in a smooth stress–strain curve. Furthermore, the HIP treatment also improved the energy absorption at 50 pct strain from 68.1 to 77.4 MJ/m3 and maintained the uniformity in the width of the cellular material. These effects are advantageous to energy absorbing applications and alleviating the risk of biomedical implants.