Mapping the Tray of Electron Beam Melting of Ti-6Al-4V: Properties and Microstructure

Abstract

Using an electron beam melting (EBM) printing machine (Arcam A2X, Sweden), a matrix of 225 samples (15 rows and 15 columns) of Ti-6Al-4V was produced. The density of the specimens across the tray in the as-built condition was approximately 99.9% of the theoretical density of the alloy, ρT. Tensile strength, tensile elongation, and fatigue life were studied for the as-built samples. Location dependency of the mechanical properties along the build area was observed. Hot isostatic pressing (HIP) slightly increased the density to 99.99% of ρT but drastically improved the fatigue endurance and tensile elongation, probably due to the reduction in the size and the distribution of flaws. The microstructure of the as-built samples contained various defects (e.g., lack of fusion, porosity) that were not observed in the HIP-ed samples. HIP also reduced some of the location related variation in the mechanical properties values, observed in the as-printed condition.

Tailoring Microstructure and Mechanical Properties of Additively-Manufactured Ti6Al4V Using Post Processing

“…Increasing utilization of additive manufacturing (AM), enables the fabrication of stronger and lighter parts with more intricate geometries. AM processes yield parts with high density, commonly higher than 99.5% of the theoretical density [ 4 , 5 ]. Two main AM methodologies exist, the addition of material by melting wire or sprayed powder, or melting powder laid on a base plate in a layer-by-layer fashion, known as the powder bed fusion (PBF) method.…”

Wire-Based Additive Manufacturing of Ti-6Al-4V Using Electron Beam Technique

“…However, as seen in Figure 8 b there is an excellent agreement between the measured ε y and the values calculated as—ν. ε x based on the assumption of a uniaxial stress in the x-direction (where ν = 0.317 is Poisson’s ratio [ 21 ]). Consequently, only strain and stresses in the x -direction are considered hereafter.…”

“…Under the assumption of a uniaxial stress state, the stress–strain relationships simplify to σ x = E × ε x , and σ y = σ z = 0. The Young’s modulus, E, for this alloy is 120.4 GPa [ 21 ]. Figure 8 c shows the resulting residual stresses as a function of height in the wall.…”

“…and σ y = σ z = 0. The Young's modulus, E, for this alloy is 120.4 GPa [21]. Figure 8c shows the resulting residual stresses as a function of height in the wall.…”

“…During additive manufacturing, defects are mainly related to porosity affected by the process parameters and the type of adding material [ 17 , 18 , 19 ], cracks formation due to residual stresses generated during the process and delamination due to incomplete melting [ 18 ]. Insufficient bonding—e.g., lack of fusion as the major defect—has a negative effect on the static and dynamic mechanical properties of AM parts [ 20 , 21 ]. The variety of microstructure has a significant role in the mechanical properties of components made by titanium alloys [ 22 , 23 ].…”