Crack analysis in Ti-6Al-4V alloy produced by selective laser melting

Quality and property control have become one of the critical problems for the metallic parts produced by selective laser melting. In this paper, the crack spontaneously formed in the Ti-6Al-4V alloy by selecting laser melting is investigated. The crack is C-shape without branching in macro view. In micro view, the crack originates from and propagates toward the selective laser melting (SLM) processing defects. The crack surface topography shows that the crack is typical dimple cleavage. A few heads of martensitic alpha ' laths appear at the bottom of the dimple. And the secondary crack nucleates and grows up near by the martensitic alpha ' laths. A lot of spatters and cavities formed at the top surface of the SLM body and the residual stress accumulated in the SLM body is up to 640 MPa, which confirms that the SLM processing defects and the residual stress induced the origination and propagation of the crack. The research results indicate that preventing spatter and controlling residual stress are important to SLM processing.