## 1 Introduction  
Direct metal laser sintering (DMLS) is in the additive manufacturing (AM) category of powder bed fusion (PDF) and produces solid parts from 3D CAD models in a layer-by-layer manner by melting metal powders with a focused high energy laser beam. This technology was developed by Electron Optical System (EOS) GmbH of Munich, Germany and has been available commercially since 1995 [1]. Initially the metals and alloys produced by this technology were limited, however more materials options are currently being produced by the DMLS process. These include steel, stainless-steel, tool steel, aluminium, bronze, cobalt-chrome, and titanium-based alloys [2]. Among these materials Ti6 Al4V is the most widely applied AM alloy. This is mainly due to its range of applications in the aerospace and the biomedical industries, which is based on by its array of desirable properties, such as good fracture toughness, high specific strength, and biocompatibility [3, 4, 5]. Traditionally, turbine-engine fan blades of jet engines have been made from forged Ti6 Al4V attached to a forged disk that was usually made of the same material [4]. Small-diameter engines use solid Ti6 Al4V blades, whereas larger diameter engines use hollow blades of Ti6 Al4V alloy [4]. Conventional processes, such as forging, involve deformation at room temperature or even at high temperatures to obtain better mechanical propertiesby breaking up the \(\alpha\)-lamellar microstructures and decreasing the size of recrystallized grains. Mechanical working of the AM parts may not be necessary, as the technology aims at producing near net shape components with minimal machining. Other benefits of AM have been identified over forging and other traditional manufacturing processes such as machining and casting. These include reduced material usage, no requirements of hard tooling, manufacturing of parts with complex geometries such as internal cooling passages, and reduced lead time [4; 5; 6; 7]. Due to the advantages offered by AM technology, it is being pursued globally by material scientists and engineers as a potential alternative to conventional manufacturing processes. It is worth noting that the current state of research is not essentially about influencing the choice of AM over conventional manufacturing methods, but rather to establish how the AM process may be implemented at different stages in production, where it is deemed advantageous. Although AM technology offers the noted advantages, the mechanical properties of AM Ti6 Al4V are not always as good as those achieved by traditional manufacturing processes. This is mainly because AM results in microstructures that typically differ from those produced by these traditional processes. Additive manufacturing produces a fine microstructure commonly referred to as acicular martensite, which is attributed to rapid solidification because of rapid heat conduction from the localized molten zone towards the surrounding environment. Post-process heat treatment has been routinely applied to these as-built parts to modify the microstructure and consequently optimize their mechanical properties [8; 9; 10]. Aircraft components are exposed to complicated loadings during flights. During steady-state conditions, static loads act on structural components. However, dynamic loads are very prominent during the flight phases such as landing [11]. In addition, aircraft structures are expected to respond to extreme conditions of impact such as bird strike and damage from gravel stones during bump taxing or take-off [12]. While considering the mechanics of an aircraft during landing, the vertical component of its velocity is normally reduced to zero in a very short time and thus this deceleration introduces inertia loads over the structures. Vibration may also be excited by the impact loading through the landing gear, especially in large aircraft with heavy engines installed in the wings. These vibrations also introduce additional inertia loads.