On Defect Evolution in EBM Additively Manufactured Ti-6Al-4V via In Situ Investigations

TL;DR

This study examines how defects in 3D-printed titanium alloy evolve and cause fractures under tension, using in situ testing.

Contribution

The paper introduces in situ observations of defect evolution and fracture mechanisms in additively manufactured Ti-6Al-4V.

Findings

Spherical defects evolve into ellipses under tensile loading due to stress concentration.

Defects lead to increased slip band density and localized stress, promoting crack initiation.

Irregular defect shapes during fracture are caused by micro-void-induced multi-axial stress.

Abstract

This study concerned the in situ investigation of the defect evolution and fracture mechanism of additively manufactured (AM) Ti-6Al-4V under uniaxial tensile tests. In order to achieve this, microstructure characterization was initially carried out in order to identify the defects within the matrix of the candidate material. In situ testing was then performed, focusing on the spherical defect to observe its evolution under tensile loading. It was found that, before the fracture stage, the geometric evolution of the spherical defect towards an ellipse shape was dominated by the load in the tensile direction. In addition, the slip band density was found to be aggravated near the spherical defect due to the geometric discontinuity-induced stress concentration. During the fracture process, the defect geometry evolved as an irregular shape, which was mainly attributed to the micro-void-induced localized multi-axial stress state. The fracture analysis indicated that defects play a key role in crack initiation, leading to the fracture of LPBF materials.

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