Fatigue behaviour of Ti-6Al-4V titanium alloy fabricated by selective laser melting (3D printing)

• Main Author: Tan, Chng Kiat
• Other Authors: Li Peifeng
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering::Aeronautical engineering::Materials of construction
• Online Access: http://hdl.handle.net/10356/68367
• Institution: Nanyang Technological University

Manufacturing technology has made significant progress over the years and additive manufacturing technology, specifically selective laser melting (SLM), is becoming increasingly popular with many industries. In the aviation industry, Ti-6Al-4V titanium alloy is one of the most widely used material due to its excellent mechanical properties. Although SLM optimizes the usage of material and has the ability to produce parts with geometrical flexibility, the inherent process-related defects such as porosities and voids have resulted in mechanical inferiorities. Therefore, the project aims to evaluate the fatigue behaviour of Ti-6Al-4V titanium alloy fabricated by SLM. As-built SLM Ti-6Al-4V with circular cross-sections were subjected to constant amplitude uniaxial fully reversed fatigue loading and fractographic analyses were conducted using a scanning electron microscope. In general, the SLM Ti-6Al-4V specimens demonstrated considerably lower fatigue performance as compared to those from reference literatures. This is mainly attributed to the SLM defects as fatigue cracks were observed to be initiated at voids and unfused regions. The fracture surfaces of the high cycle specimens were characterized by crack initiation, propagation and final rupture and an apparent endurance limit was encountered. In contrast, the low cycle specimens displayed no features of a fatigue failure. Future projects can incorporate specimens with different build orientations so that the effects of different build orientations on the fatigue behaviour can be studied and compared.