Influence of Inherent Surface and Internal Defects on Mechanical Properties of Additively Manufactured Ti6Al4V Alloy: Comparison between Selective Laser Melting and Electron Beam Melting

Abstract

Additive manufacture (AM) appears to be the most suitable technology to produce sophisticated, high quality, lightweight parts from Ti6Al4V alloy. However, the fatigue life of AM parts is of concern. In our study, we focused on a comparison of two techniques of additive manufacture—selective laser melting (SLM) and electron beam melting (EBM)—in terms of the mechanical properties during both static and dynamic loading. All of the samples were untreated to focus on the influence of surface condition inherent to SLM and EBM. The EBM samples were studied in the as-built state, while SLM was followed by heat treatment. The resulting similarity of microstructures led to comparable mechanical properties in tension, but, due to differences in surface roughness and specific internal defects, the fatigue strength of the EBM samples reached only half the value of the SLM samples. Higher surface roughness that is inherent to EBM contributed to multiple initiations of fatigue cracks, while only one crack initiated on the SLM surface. Also, facets that were formed by an intergranular cleavage fracture were observed in the EBM samples.

Encapsulation of Electron Beam Melting Produced Alloy 718 to Reduce Surface Connected Defects by Hot Isostatic Pressing

“…Three types of defects were observed, i.e., lack of fusion, shrinkage porosity, and gas porosity, and they are visualized in Figure 3. Such defects have also been previously observed by Goel et al [3], and the influence of the defects on mechanical properties has been elaborated elsewhere [16,17]. Round-shaped gas porosities (refer Figure 3a) were randomly distributed, and they are attributable to entrapped gas inside the virgin powder, which could have found its way into the EBM build [1].…”

Tensile and Creep Properties Improvement of Ti-6Al-4V Alloy Specimens Produced by Electron Beam Powder Bed Fusion Additive Manufacturing

“…In general, this results in higher tensile properties, even if manufactured products are affected by microporosity causing a decrease of elongation respect to wrought products. Nevertheless, the use of various energy sources requires different processing conditions and subsequently produces distinct characteristic features [12]: L-PBF process is performed in an inert gas atmosphere, while EB-PBF in vacuum conditions to avoid the electron beam deflection. During L-PBF, powder particles absorb heat energy from photons, while the electron beam penetrates inside powder converting its kinetic energy into thermal energy.…”

Current advances in solid free-form techniques for osteochondral tissue engineering

“…In this sense, SLS can be a good alternative not only for OC tissue engineering, but also for the fabrication of bio-inspired multilayer scaffolds with well-designed architecture and gradient composition. Furthermore, a recent study performed by Fousová et al [22] showed the comparison of other two laser-assisted techniques in the scaffold's production. In this work, the authors compared the architecture and mechanical performance of solid free-form scaffolds composed by a Ti6Al4 V alloy.…”