Build Direction Research Articles

Assessment of the potential correlation between Smart Readiness Indicator and energy performance in a dataset of buildings in South Tyrol

The Energy Performance of Buildings Directive introduced the Smart Readiness Indicator (SRI), a common European system for assessing buildings’ smart readiness. While not mandatory across the European Union, some countries have initiated trial phases, and several studies already examined its application in different Member States. In this work, we present the findings of an extensive application of the SRI methodology on a sample of 59 recently constructed or recently renovated high-performance buildings in South Tyrol, Italy. Our research focused on two main objectives: (1) characterizing the level of smart readiness of state-of-the-art modern buildings in the Italian Alpine region of South Tyrol, and (2) discussing the potential correlation between the level of smart readiness and building energy performance class. Specifically, the HVAC and building systems with the most widespread adoption of advanced smart technologies were identified, as well as those configurations with traditional control solutions suggesting potential for improvement. The analysis proved that the different building categories present various levels of smart readiness, which is higher for the local office buildings and lower for the residential ones. No particular correlation was found between smart readiness and energy performance class, suggesting the need of adopting the SRI to give a more comprehensive characterization of the building performances.

Microstructure and mechanical properties of large Ti6Al4V components by electron beam powder bed fusion

Electron beam powder bed fusion (EB-PBF)-built Ti–6Al–4V(Ti6Al4V) has increasingly shown great potential for orthopedic implant and aerospace applications in recent years. Large components prepared by additive manufacturing (AM) have heterogeneous microstructures, defect size, and residual stress in the building direction due to the high temperature gradient. The samples with a height of 170 mm ware prepare via EB-PBF. The microstructure, mechanical properties, defect size, and residual stress along the building direction have been systematically study in this work. The grains epitaxial growth along the build direction as coarse prior β columnar grains. The residual compressive stress increases from the sample bottom to top. The max void size increases from 23.8 μm at the bottom to 108 μm at the top, and the mechanical properties gradually deteriorate along the building direction, which is related to the temperature gradient on the building direction of the sample. It is found that the ultimate tensile strength decreases from 916 ± 9 MPa at the bottom to 876 ± 7 MPa at the top, and the elongation to failure decreases from 9.13 ± 0.61 % to 6.49 ± 0.34 %. Meanwhile, the hardening ability is also weakened along the building direction. This study reveals the evolution process of the sample's microstructure, mechanical properties, and defects, providing data support for further control of material defects.

On the texture and strength of a 316L steel processed by powder bed fusion

The developed microstructures and textures and their effect on the tensile behavior of a 316L austenitic stainless steel produced by powder bed fusion (PBF) were studied. The material printed with one set of printing parameters was tensile tested in three different directions. The microstructural analysis was conducted using electron microscopy. Referring to the build direction (BD) and the side direction (SD), which are parallel/crosswise to the laser scanning direction, the texture can be characterized by two strong components of <011>//BD and <001>//SD. The obtained steel samples exhibit the yield strength of 550 MPa–590 MPa depending on the tensile direction. The strengthening contributors to the PBF material were considered separately. Considering the microstructural grain size between the high angle boundaries and taking the dislocations of cellular structure as a part of dislocation density, the dislocation density is considered being the main strength contributor while the Taylor factor variety from about 2.9 to 3.2 for different directions revealed the strength anisotropy as an attribute of the texture.

Mechanical and tribological characterization of wire arc additively manufactured SS308L component

The mechanical and tribological characterization of stainless steel 308 L, which was fabricated using wire arc additive manufacturing (WAAM), is presented in this work. Longitudinal tensile samples extracted along the deposition direction depict higher tensile strength than the transverse tensile samples. The reduction in microhardness along the build direction is associated with the temperature fluctuations the metal undergoes in the WAAM process. Ball-on-disc wear tests were performed on specimens from the top, middle, and bottom parts of the build at loadings of 20 N, 25 N, and 30 N. Furthermore; the wear analysis results showed that the top portion had the most wear at the highest load, while the bottom portion experienced the least wear under the lowest load.

Measuring fatigue crack growth using microscale specimens: Si-modified Inconel 939 alloy processed by laser powder bed fusion additive manufacturing

Quantitative assessment of fatigue crack growth (FCG) in a Si-modified Inconel 939 alloy, processed by laser powder bed fusion additive manufacturing (L-PBF AM), was conducted through cyclic bending of pre-notched cantilevers with a characteristic cross-sectional dimension of 25 μm × 25 μm. To the best of our knowledge, this work is the first to show that cyclic bending of such pre-notched microscale cantilevers can sense both the threshold regime and the Paris-law regime of FCG quantitatively, despite the small specimen size. The deliberate fabrication of such microscale test specimens enables control of the direction of fatigue crack propagation with respect to a given microstructure, while avoiding the inclusion of volumetric defects within the test volume. Significant differences in FCG behavior were observed when the direction of crack propagation was switched from being parallel to the AM build direction to being perpendicular to it. The present work demonstrates the efficacy of FCG assessment using microscale specimens, which can enhance our understanding of the influence of a given microstructure on crack growth behavior.

On the feasibility to obtain CuCrZr alloys with outstanding thermal and mechanical properties by additive manufacturing

The CuCrZr alloy combines high thermal conductivity and mechanical strength with stability at high-medium temperatures, making it a promising heat sink material for the EU-DEMO divertor and limiters. Additive Manufacturing (AM) technologies have proven effective in developing complex-shaped components with almost no constraints on geometry and minimal machining and welding requirements. This makes them particularly suitable for the production of heat exchangers featuring complex cooling channels with intricate inner structures.This study demonstrates the feasibility to obtain dense CuCrZr via Electron Beam Powder Bed Fusion (EB-PBF) with high thermal conductivity and enhanced mechanical strength compared to conventional routes. Gas atomization was used to produce spherical powders with a composition close to ITER specifications. By optimising the EB-PBF process parameters, relative density values of 99.7 % were achieved after HIP treatment, that removes the eventual residual porosity. The results underscore the importance of meticulous powder manufacturing to mitigate oxidation and microstructural defects in the final components. Achieving high relative densities in the EB-PBF process requires a focus on adopting high-energy absorption rates in the powders. This strategy can be accomplished by reducing the scanning speed and consequently the building rate of the process. The microstructural characterization revealed a complex hierarchical microstructure composed of grains and grain boundaries, solidification-enabled cellular-like subgrains elongated along the building direction and an ultra-fine precipitate state (already present in the as-built condition) mainly consisting of Cr-rich nanoprecipitates, although Zr-rich precipitates were also found at the melt pool boundaries. The thermal conductivity, hardness, mechanical strength at room temperature and high-medium temperatures were measured and correlated with the EB-PBF process parameters and the microstructure obtained after HIP treatment. The results indicate that it is possible to obtain CuCrZr with improved mechanical behaviour compared to conventional manufacturing technologies, while maintaining the thermal conductivity requirements for EU-DEMO.

Towards harmonising energy performance certificate indicators in Europe

Achieving the European Union's ambitious goal of transforming buildings into carbon-neutral assets is crucial for combating climate change and improving energy efficiency. The harmonization of Energy Performance Certificates (EPCs) plays a vital role in this effort. It can provide a standardized measure of building energy performance, which is crucial for benchmarking and improving energy efficiency across Member States. In the context of the recast Energy Performance of Buildings Directive (EPBD) of 2024, this study examines the progress made by EU Member States in standardizing EPCs. The research aims to evaluate the implementation of EPC indicators, focusing on data quality, calculation methods, and costs. The methodological procedure followed for the study led to the development of a dedicated Cross Comparative Matrix (CCM) to assess the implementation of EPC indicators across 27 EU Member States and their reading feature allowed the declination into three scenarios for different EPC data analysis: qualitative, quantitative and burden costs. The findings reveal significant disparities, particularly in areas such as thermal comfort and smart readiness, due to the lack of a common methodology and local regulatory differences. While key indicators like energy performance class and primary energy use are widely implemented, compliance with EU standards varies. The study concludes by recommending standardized methodologies and enhanced assessor training to improve EPC quality, harmonization, and effectiveness. This research contributes to policy discussions by offering a comprehensive framework for EPC evaluation and insights into improving data quality, reliability, and accessibility. The originality of this study lies in its cross-national analysis, highlighting the need for a unified EPC scheme to promote building sustainability across the EU.

Fracture behavior of a Ni-20 wt.%Cr binary alloy processed by Laser Powder Bed Fusion: Influence of the specimen building orientation and rotation angle between layers

This work provides a comparative study on the influence of the manufacturing process on the tensile and fracture properties of a Ni-20 wt.%Cr binary alloy produced by Laser Powder Bed Fusion (L-PBF). Two main processing parameters were investigated: the orientation of the samples with respect to the building direction (horizontal and vertical) and the rotation angle between layers (67° and 90°). Tensile and three-point bending tests were conducted to study the mechanical behavior. Monotonic tensile results suggest that the choice of the printing parameters affected the yield and ultimate tensile strength values, but was not influential to elongation. An increase in yield and ultimate tensile strengths of up to 15 % was noted for horizontal specimens compared to the vertical ones, and an increase of 10 % for an angle of 67° rather than 90°. Fracture toughness values remained in a range of 200 to 450 kJ/m2 regardless of the set of parameters considered. For a rotation angle of 67°, the fracture toughness was similar for both building orientations, but vertical specimens exhibited better resistance to crack propagation after initiation, with a tearing modulus increased by 50 % compared to horizontal ones. In contrast, building orientation was detrimental to specimens built with a rotation angle of 90°, as both fracture toughness and tearing modulus decreased drastically (up to 70 %) for a horizontal orientation rather than a vertical one. Microstructural observations highlighted mixed fracture modes for all L-PBF configurations, though crack propagation seemed mainly intergranular for horizontal specimens, and transgranular for vertical specimens. Fracture mechanisms were mostly governed by the grain orientation, size and morphology, while the crystallographic texture and the nano-oxides located in the dendrite arm spacing had a second-order influence. The pores and meltpool boundaries did not appear to play a significant role in crack propagation.

Additive manufacturing of functionally graded stellite6/17-4 PH fabricated via direct laser deposition

Multi-material structures with variable functionalities can lead to unique solutions for engineering problems compared to single-material structures. Additive manufacturing of Functionally Graded Materials (FGMs) using Direct Laser Deposition for the multi-material deposition of Stellite6 and 17–4 PH stainless steel has been investigated in this study. Process parameter design was successfully applied to achieve FGM structures with expected composition ratio and defect free. Results revealed that clads with insufficient laser power had unmelted 17-4 PH powders, while those with excessive power resulted in micro-cracks and disrupting the expected composition for the previous layer. Energy Dispersive Spectroscopy analysis results showed that the composition was almost as expected, with less than 10% deviation. The Stellite6 composition in FGM exhibits a minimum ratio near the substrate due to the penetration of 17-4 PH elements. Meanwhile, in multi-track clads, the Stellite6% decreases along the transverse direction due to increased heat input, multiple cladding tracks, higher dilution, and slower solidification rate. The results of the micro-hardness tests illustrated the gradual evolution of micro-hardness along the build direction starting from the base metal, which had a hardness of approximately 300 HV for 17-4 PH and for the compositions of 25%, 50%, 75%, and 100% Stellite6 showed increases of 10%, 39%, 43%, and 63% respectively, reaching up to 490 HV for fully Stellite6 at the top of the specimen.

Material Characterization and Electrochemical Properties of Titanium Alloy 5553 Prepared by Selective Laser Melting as Processed and after Abrading and Polishing.

The microstructure, Vickers microhardness, and electrochemical properties of an additive manufactured titanium alloy, Ti-5553 (Ti-5Al-5Mo-5V-3Cr wt %), are reported on. The alloy specimens were fabricated by selective laser melt processing. The surface morphology and electrochemical properties of the as-processed and surface-pretreated (abraded and polished) Ti-5553 specimens were investigated. The as-processed specimens had a nominal density of 4.62 ± 0.04 g/cm3. Based on comparison with the reported density for the die-cast alloy, the specimens were 99-100% dense with ca. 1% porosity. Optical microscopy and scanning electron microscopy revealed some micropores, balling features, and fusion pore defects across the surface of the alloy (XZ plane-orthogonal to the build direction). The nominal Vickers microhardness was 292 ± 2 HV. Detailed electrochemical characterization of the as-processed and surface-pretreated alloys revealed reproducible open-circuit potentials (OCPs), linear polarization resistances (R p), and potentiodynamic polarization curves for both specimen types in naturally aerated 3.5 wt % NaCl at room temperature. For the surface-pretreated alloys, the OCP was 225 mV more noble, the anodic current in the potentiodynamic polarization curves was 72× lower, the cathodic current was 8× lower, and R p was larger by 426× than the values for the as-processed specimens. The collective electrochemical data revealed that the surface-pretreated alloys exhibit greater corrosion resistance than the as-processed alloys due to a reduction of the real area and the formation of a more passivating oxide layer.

Effects of Building Direction, Process Parameters and Border Scanning on the Mechanical Properties of Laser Powder Bed Fusion AlSi10Mg.

The variability arising from the LPBF process, the multitude of manufacturing parameters available, and the intrinsic anisotropy of the process, which causes different mechanical properties in distinct building directions, result in a wide range of variables that must be considered when designing industrial parts. To understand the effect of these variables on the LPBF manufacturing process, the performance of the AlSi10Mg alloy produced through this technique has been tested through several mechanical tests, including hardness, tensile, shear, and fracture toughness. The results have been correlated with the microstructure, together with manufacturing parameters, building directions, border scanning strategy, and layer height. Significant differences were observed for each mechanical behavior depending on the configuration tested. As a result, an anisotropic material model has been developed from tested samples, which allows to numerically model the alloy and is unique in the current literature.

Influences of grain orientation on high-cycle fatigue performance of laser powder bed fused Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy at room temperature and 500℃

The fatigue performance of titanium (Ti) alloys fabricated by laser powder bed fusion (LPBF) is a crucial factor influencing the structural safety in service. The high-cycle fatigue (HCF) of LPBF Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy at the room temperature and 500 °C was tested. Compared with the room-temperature samples, the fatigue strength of fatigue samples tested at 500 °C is reduced by about 55.8 % after 106 fatigue cycles. Crack initiation on the surface is mainly related to fatigue after fewer cycles under high stress, while interior cracks initiate after a longer fatigue life under low stress. Electron back scattering diffraction (EBSD) was adopted to characterize the orientations of grains on the crack propagation paths and the activated slip systems. All prismatic oriented grains were found to activate prismatic slip systems, the activation of which achieves symmetric slips surrounding crack tips, forms ductile striations, and increases energy absorption during crack propagation. These characteristics are conducive to improved fatigue performance. About half of the basal oriented grains activate prismatic slip systems. These activated prismatic slip systems not only have a high Schmid factor (SF) but also need to have a high geometrical compatibility factor with slip systems activated by adjacent grains. The residual β phase and α phase are aligned according to the Burgers orientation relationship (BOR), so the β phase does not alter the direction of crack propagation. The results were used to predict the fatigue crack propagation paths in LPBF Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy during loading along building and transverse directions were predicted. This, to some extent, provides a basis for comparing fatigue performance of LPBF Ti alloys in different directions.

Tensile Properties and Fracture Analysis of Duplex (2205) and Super Duplex (2507) Stainless Steels, Produced via Laser Powder Bed Fusion Additive Manufacturing

Additive manufacturing of duplex (DSS) and super duplex stainless steel (SDSS) has been successfully demonstrated using laser powder bed fusion (LPBF) in recent years. Owing to the high cooling rates, as-built LPBF-processed DSS and SDSS exhibit close to 100% ferritic microstructures and require heat treatment at 1000–1300 °C to obtain the desired duplex microstructure. In this work, the mechanical properties of DSS and SDSS processed via LPBF were investigated in three building directions (vertical, horizontal, diagonal) and three processing conditions (as-built, stress-relieved, annealed, and quenched) using uniaxial tensile testing. As-built samples exhibited tensile and yield strength greater than 1000 MPa accompanied by less than 20% elongation at break. In comparison, the water-quenched samples and samples annealed at 1100 °C exhibited elongation at break greater than 34% with yield and tensile strength values less than 950 MPa. Stress relief annealing at 300 °C had a negligible impact on the mechanical properties. Austenite formation upon high-temperature annealing restored the reduced ductility of the as-built samples. The as-built and stress-relieved SDSS showed the highest yield and tensile strength values in the horizontal build direction, reaching up to ≈1400 and ≈1500 MPa (for SDSS), respectively, as compared to the vertical and diagonal directions. Fractographic investigation after tensile testing revealed predominantly a quasi-ductile failure mechanism, showing fine size dimple formation and cleavage facets in the as-built state and a fully ductile fracture in the annealed and quenched conditions. The findings in this study demonstrate the mechanical anisotropy of DSS and SDSS along three different build orientations, 0°, 45°, 90°, and three post-processing conditions.

Experimental analysis of failure behaviour of PA12 specimens manufactured by SLS as a function of wall thickness and build direction

PurposeThis paper aims to investigate and explain the dual fracture behaviour of PA12 specimens sintered by selective laser sintering (SLS) as a function of wall thickness and build direction with a powder mixture 30:70. To achieve this objective, research related to chemical, thermal and structural behaviours as a function of the input variables was carried out to describe and explain why ductile-fragile behaviour occurs during fractures under uniaxial tension manufactured via a methodology of material analysis and manufacturing processes.Design/methodology/approachThe factorial design 32 relates the fracture of PA12 tensile specimens to the horizontal, transverse and vertical build directions at 2.0, 2.5 and 3.0 mm thicknesses, respectively. Fractographic images revealed the fracture surfaces and their dual ductile-fragile behaviour related to the specimens’ measured crystalline, thermal, surface and chemical properties.FindingsThe study showed that thermal property variables differ depending on the input variables. The wall thickness variable affected this morphology the most, showing the highest percentage of the ductile area, followed by the transverse and vertical directions. It was determined that the failure in the vertical direction is due to crystalline gradients associated with the layer-by-layer construction process. The pore density may be closely related to generating ductile and brittle areas.Originality/valueIn this paper, fracture characterisation is performed based on the mechanical, chemical, structural, thermal and morphological properties of PA12 manufactured by SLS. In addition, a heatmap of porosities in cross-sections is constructed using a machine learning model (k-means) related to dual fracture behaviour. This research revealed significant differences in the fracture type according to the build direction. In addition, thin-section fractography provides a more detailed explanation of the fragile behaviour of the vertical direction associated with crystalline changes due to the direction of the sintering layers.

Pulsed TIG wire arc additive manufactured 17-4 PH stainless steel: Effect of Cu-rich precipitates and δ-ferrite on the mechanical properties

Thin-wall samples of 17-4 PH stainless steel were prepared by pulsed TIG wire arc additive manufacturing technology (P-TIG WAAM), and the microstructure and mechanical properties of the samples in different regions (bottom, middle, top) were studied. The results show that the microstructure of the thin-wall samples are mainly consisted of martensite matrix embedded by worm-like (bottom) and strip-shaped (top) δ-ferrite, with a small amount of austenite. The δ-ferrite content gradually decreases along the building direction, resulting in a gradual increase in microhardness from the bottom to the top. Along the building direction, the precipitation density and size distribution of nano-scale CRPs (Cu-rich precipitates) in δ-ferrite and martensite, as well as at the δ-ferrite/martensite interface are significantly different: the CRPs in δ-ferrite is precipitated with lower density, larger size, and inhomogeneous distribution at the bottom region, while that in martensite is precipitated with higher density, smaller size, and homogeneous distribution. At the bottom region, a chain of large size fcc-CRPs (∼65 nm) is precipitated along the δ-ferrite/martensite interface to coordinate the strain between them and improve the strength and ductility simultaneously, thus excellent mechanical properties (tensile strength = 1356 ± 24 MPa, elongation = 15.16 ± 2.6 %) are obtained. The relationship between the evolution of CRPs and the intrinsic heat treatment (IHT) during P-TIG WAAM is also discussed.

Mechanical characterization of lattice structures fabricated by selective laser melting via an image-based finite cell method with a damage model

Lattice structures fabricated by the selective laser melting (SLM) additive manufacturing process hold great potential for diverse applications. However, their actual mechanical behaviors often deviate from their counterparts with the as-designed geometries due to manufacturing defects. In this study, we presented an in-depth mechanical characterization of imperfect octet lattice structures via an image-based finite cell method (FCM) in combination with the multi-level hp refinement scheme for resolving the local defects and a Lemaitre damage model to conduct the damage analysis. Micro-computed tomography scanning was utilized to scan six SLM-fabricated octet lattice cells to obtain their as-built geometries. Based on the obtained geometry, the force-displacement curves and the damage distribution of the octet lattice cells and struts under given loads were predicted. The numerical results indicate that external defects significantly affect the struts' damage distribution, while internal voids have a lesser influence due to their low volume fraction. It is identified that the SLM-fabricated octet lattice cell presents better elastoplastic behavior along the loading direction perpendicular than parallel to its build direction. These insights into the mechanical performance of imperfect octet lattice cells underscore the defects' adverse effects and advance the understanding of their significance in SLM components.

Compressive Properties of Additively Manufactured Metal-Reinforced PLA and ABS Composites.

The development of multi-material filaments has enabled fused filament fabrication-based additive manufacturing to address demand for high-performance lightweight multifunctional components. In this study, polylactic acid (PLA) and acrylonitrile butadiene styrene based filaments with metallic reinforcements of magnetic iron (MI), stainless steel (SS), bronze (Br), copper (Cu), Bismuth (Bi), and Tungsten (W) were investigated to elucidate their complex processing-structure-property relationships. The microstructure of 3D-printed materials were characterized by microscopy and analyzed to determine the metal cross-sectional area percentage and the relationship between metal reinforcement, the polymer matrix, and porosity. Compression testing was conducted in directions parallel and perpendicular to the build direction in order to evaluate the effect of orientation and metal reinforcement on the mechanical properties. 3D-printed specimens experienced either fracture through print layers or layer-wise interfacial rupture for loads applied perpendicular and parallel to the print layers, respectively. A dependence of yield strength on loading orientation was observed for Br-PLA, Cu-PLA, SS-PLA, Bi-ABS, and W-ABS; however, MI-PLA and pure ABS specimens did not exhibit this sensitivity. Metal reinforcement also influenced the magnitude of compressive yield strength, with MI-PLA and SS-PLA demonstrating increased strength over Br-PLA and Cu-PLA, while ABS demonstrated increased strength over Bi-ABS and W-ABS. These results demonstrate the importance of considering orientation in printing and applications, the trade-off between various metallic reinforcements for added multifunctionality, and the potential of these tailored polymer composites for novel 3D-printed structures.

In situ tailoring of precipitation behavior and improving mechanical properties of (Ti2AlC+Y2O3) reinforced TiAl alloy produced by directed energy deposition

A (Ti2AlC + Y2O3) synergistically reinforced Ti–48Al–2Cr–2Nb alloy was prepared by directed energy deposition with in situ tailoring of precipitate formation by induction preheating and thermal cycle. The influence of C and Y2O3 coaddition on the microstructure and high-temperature compressive properties was systematically investigated. The results indicated that Ti2AlC was formed by adding elemental C, and the Ti2AlC phase was mainly distributed in two forms: long rod-shaped Ti2AlC with a micron scale that distributed uniformly in the matrix, and lenticular Ti2AlC particles with nanometer size that distributed along the (α2/γ) lamellar interface. The Y2O3 particles were randomly distributed in the matrix. Columnar grains in vertical cross section along the building direction were completely eliminated by adding C and Y2O3. The high temperature compressive strength increased from 597 MPa to 758 MPa at 850 °C by adding C and Y2O3. Finally, the precipitation mechanism of nano-Ti2AlC was discussed in detail. This work provided a valuable reference for the preparation of high-performance TiAl alloys by in situ tailoring of the precipitates during the DED process.

Evaluation of microstructure and mechanical properties of additively manufactured Ti–5V–5Mo-5 Al-3 Cr alloy

Ti–5V–5Mo–5Al–3Cr (Ti-5553) is a near-beta titanium alloy commonly used in aerospace applications. It is currently being explored for additive manufacturing (AM), but the fatigue behavior of this AM alloy needs to be well-understood for adoption. This paper explores the tensile and high-cycle fatigue behavior of laser powder bed (LPBF) manufactured Ti-5553 that has been post-print heat treated with a beta anneal and age (BAA), with a focus on the microstructural evolution and effects of surface roughness and print defects. Fatigue lives of as-LPBF and BAA material are nearly identical and both are far below fatigue lives of conventionally manufactured Ti-5553. As-built samples contain columnar β grains with a [001] texture in the build direction with a negligible fraction of α phase confirmed by electron backscatter diffraction (EBSD). The BAA material contains HCP alpha-phase precipitates: grain boundary α, primary α, and secondary Widmanstätten α. Fatigue samples were printed in the vertical direction and tested with an as-printed and machined surface. Both the as-LPBF and BAA samples exhibit similar fatigue strengths despite their vastly different microstructures. Machined surfaces led to an increase in tensile strength, ductility, and fatigue strength. This work emphasizes the importance of heat treatment and minimization of flaws inherent to AM processing of near-beta Ti-5553.

Dynamic Response of Ti-6Al-2Zr-1Mo-1V Alloy Manufactured by Laser Powder-Bed Fusion.

Titanium parts fabricated by additive manufacturing, i.e., laser or electron beam-powder bed fusion (L- or EB-PBF), usually exhibit columnar grain structures along the build direction, resulting in both microstructural and mechanical anisotropy. Post-heat treatments are usually used to reduce or eliminate such anisotropy. In this work, Ti-6Al-2Zr-1Mo-1V (TA15) alloy samples were fabricated by L-PBF to investigate the effect of post-heat treatment and load direction on the dynamic response of the samples. Post-heat treatments included single-step annealing at 800 °C (HT) and a hot isotropic press (HIP). The as-built and heat-treated samples were dynamically compressed using a split Hopkinson pressure bar at a strain rate of 3000 s-1 along the horizontal and vertical directions paralleled to the load direction. The microstructural observation revealed that the as-built TA15 sample exhibited columnar grains with fine martensite inside. The HT sample exhibited a fine lamellar structure, whereas the HIP sample exhibited a coarse lamellar structure. The dynamic compression results showed that post-heat treatment at 800 °C led to reduced flow stress but enhanced uniform plastic strain and damage absorption work. However, the HIP samples exhibited both higher stress, uniform plastic strain, and damage absorption work owing to the microstructure coarsening. Additionally, the load direction had a subtle influence on the flow stress, indicating the negligible anisotropy of flow stress in the samples. However, there was more significant anisotropy of the uniform plastic strain and damage absorption. The samples had a higher load-bearing capacity when dynamically compressed perpendicular to the build direction.