3D printing results in anisotropy in the microstructure and mechanical properties. The focus of this study is to investigate the structure, texture and phase evolution of the as-printed and heat treated IN718 superalloy. Cylindrical specimens, printed by powder-bed additive manufacturing technique, were subjected to two post-treatments: homogenization (1100 • C, 1 h, furnace cooling) and hot isostatic pressing (HIP) (1160 • C, 100 MPa, 4 h, furnace cooling). The Selective laser melting (SLM) printed microstructure exhibited a columnar architecture, parallel to the building direction, due to the heat flow towards negative z-direction. Whereas, a unique structural morphology was observed in the x-y plane due to different cooling rates resulting from laser beam overlapping. Post-processing treatments reorganized the columnar structure of a strong {002} texture into fine columnar and/or equiaxed grains of random orientations. Equiaxed structure of about 150 µm average grain size, was achieved after homogenization and HIP treatments. Both δ-phase and MC-type brittle carbides, having rough morphologies, were formed at the grain boundaries. Delta-phase formed due to γ -phase dissolution in the γ matrix, while MC-type carbides nucleates grew by diffusion of solute atoms. The presence of (Nb 0.78 Ti 0.22 )C carbide phase, with an fcc structure having a lattice parameter a = 4.43 Å, was revealed using Energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) analysis. The solidification behavior of IN718 alloy was described to elucidate the evolution of different phases during selective laser melting and post-processing heat treatments of IN718.

El modelo presentado resulta una herramienta de gran potencial para el diseño y fabricación de cascos de combate debido a la versatilidad de aplicación que posee, permitiendo ajustar el número de capas exacto atendiendo al nivel de protección a alcanzar.

This work focuses on the combination of two complementary non-destructive techniques to analyse the final deformation and internal damage induced in aramid composite plates subjected to ballistic impact. The first analysis device, a 3D scanner, allows digitalising the surface of the tested specimen. Comparing with the initial geometry, the permanent residual deformation (PBFD) can be obtained according to the impact characteristics. This is a significant parameter in armours and shielding design. The second inspection technique is based on computed tomography (CT). It allows analysing the internal state of the impacted sample, being able to detect possible delamination and fibre failure through the specimen thickness. The proposed methodology has been validated with two projectile geometries at different impact velocities, being the reaction force history on the specimen determined with piezoelectric sensors. Different loading states and induced damages were observed according to the projectile type and impact velocity. In order to validate the use of the 3D scanner, a correlation between impact velocity and damage induced in terms of permanent back face deformation has been realised for both projectiles studied. In addition, a comparison of the results obtained through this measurement method and those obtained in similar works, has been performed in the same range of impact energy. The results showed that CT is needed to analyse the internal damage of the aramid sample; however, this is a highly expensive and time-consuming method. The use of 3D scanner and piezoelectric sensors is perfectly complementary with CT and could be relevant to develop numerical models or design armours.

Integration of additive manufacturing into traditional manufacturing processes presents the future of engineered components with similar or superior performance levels to wrought or cast materials. In this work, the hot deformation behavior and the microstructural changes of heat-treated SLMprinted IN718 specimens are investigated. Samples having the same shape and size were 3D-printed, homogenized (1100 °C, 1h and furnace-cooled) and hot-compressed, using a Gleeble ® 3800 physical simulator at 1000 and 1050 °C and 0.1 and 0.01 s-1 strain rates. A 3D diagram shows the effect of temperature and strain rate on the flow stress behavior of IN718 during hot deformation is plotted. The dynamic recrystallization (DRX) mechanism was dominant in all specimens tested at 0.1 s-1 , while dynamic recovery (DRV) dominated in 0.01 s-1 tests. Changing the strain rate from 0.01 to 0.1 s-1 at 1000 °C increased the peak stress from 150 to 290 MPa (93%), while with a temperature decrease from 1050 to 1000 °C at 0.1 s-1 , the peak stress increased by 45%. Thus, the mechanical behavior was found to be more dependent on the strain rate than on the temperature. The DRX structure showed new grains developing at the boundaries of the original grains, whereas with the DRV structure, new grains grew within the original grains. A phenomenological model based on the Zener-Hollomon parameter was proposed in order to predict the size of recrystallized grains during hot deformation of the SLM-printed IN718 superalloy. The thermal softening due to recrystallization was compensated by precipitation hardening, as was revealed by phase analysis.

This paper presents and analyses the behaviour of aramid composite plates subjected to low and medium impact energies. In order to study the material behaviour under impact loading, experimental tests have been performed using a drop-weight tower and a pneumatic gas gun within the range of impact energies (20 J E imp <<600 J). The plates are impacted by hemispherical impactor and spherical projectile for drop-weight and impact tests, respectively. The influence of areal density is also evaluated in terms of absorption energy. Energy Profile Diagrams (EPD) are used to identify the penetration and perforation thresholds enabling the definition of the nopenetration, penetration and perforation zones. The results revealed that there is a greater energy absorption capacity in thin plate than in thick plate for low impact energy values. However, areal density is relevant in the energy absorption capacity for high impact energy values.