Build Direction Research Articles

Additive friction stir deposition of super duplex stainless steel: Microstructure and mechanical properties

Additive Friction Stir Deposition (AFSD) is an emerging solid-state metal additive manufacturing (AM) process that offers several key benefits, including high deposition rates and wrought-equivalent mechanical properties even in the as-deposited condition. The work presented is the first study to report on the development of microstructure and mechanical properties of AFSD-processed duplex stainless steel (DSS2507). The banded microstructure of the starting material was remarkably affected by AFSD processing; the austenite grains exhibited a refined and equiaxed morphology, while the ferrite grains appeared slightly larger and elongated. Microstructural observations revealed that the potential mechanism of microstructure evolution in austenite was discontinuous dynamic recrystallization (DDRX), while in ferrite, it was continuous dynamic recrystallization (CDRX). The occurrence of multiple thermal cycles during the AFSD process resulted in σ phase precipitation, which in turn led to considerable variation in mechanical properties with respect to the build direction. The top region of the as-built part with an insignificant σ phase fraction showed improved tensile strength and ductility combination compared to the as-received DSS2507 as well as other AM-processed DSS2507 alloys.

A novel magnetic field assisted powder arc additive manufacturing for Ti60 titanium alloy: Method, microstructure and mechanical properties

Due to the rapid heating-cooling process and unstable keyhole, pore defects are easily formed during the high energy beam-powder additive manufacturing (AM) process, posing great challenges to the high-performance manufacturing of aerospace components. Using an arc with lower energy density as a heat source can effectively avoid these defects, but its matching raw materials are limited to wire. In this paper, a novel magnetic field assisted powder arc additive manufacturing (MFA-PAAM) method has been proposed, which combines arc heat source and powder raw material to achieve dense metal parts. A transverse magnetic field (TMF) was introduced to solve the powder spattering problem which impacts the stability of the PAAM process, by regulating the direction of the arc plasma flow and the arc pressure. The unique melting behavior of the powder under arc heating was captured by a high-speed camera, which can be summarized into two steps: balling and adsorption by the molten pool. And the well-formed and fully dense Ti60 high-temperature titanium alloy wall components were successfully manufactured using the self-developed equipment. The microstructure of the thin-wall component is dominated by basket-weave distributed α laths and few β sheets remaining at their boundaries. A layered periodic distribution along the building direction was observed, which is mainly distinguished from the content and morphology of the β phase. The average ultimate tensile strength (UTS) and elongation to failure in the travelling direction are 1003.2 MPa and 15.1%, while the average UTS and elongation along the building direction are 1009.3 MPa and 16.6%, respectively. The fracture morphologies in both directions are characterized by ductile fracture. The MFA-PAAM technique shows great potential for fabricating materials that are difficult to be drawn into wires with high efficiency and performance.

Multi-scale microstructure manipulation of an additively manufactured CoCrNi medium entropy alloy for superior mechanical properties and tunable mechanical anisotropy

Laser beam powder bed fusion (PBF-LB) additive manufacturing (AM) technology has become a versatile tool for producing new microstructures in metal components, offering novel mechanical properties for different applications. In this work, enhanced ductility (∼55% elongation) and tunable mechanical anisotropy (ratio of ductility along vertical to horizontal orientation from ∼0.2 to ∼1) were achieved for a CoCrNi medium entropy alloy (MEA) by multi-scale synergistic microstructure manipulation (i.e., melt pool boundary, grain morphology and crystallographic texture) through adjusting key PBF-LB processing parameters (e.g., laser power and scan speed). By increasing the volumetric energy density (VED) from 68.3 to 144 J/mm3, the melt pool size enlarges, and the crystallographic texture transitions from <100>//BD to <110>//BD due to the maximum thermal flux direction changing for different melt pool dimensions, which affects the proportion of grains that have different growth directions. Moreover, excellent mechanical properties of 890 MPa ultimate tensile strength and ∼55% elongation to failure can be achieved for loading perpendicular to the build direction with only a ∼15% reduction in properties for loading along the build direction. The superior combination of mechanical properties is achieved by processing parameter-controlled strengthening of melt pool boundary interfaces, heterogeneous deformation induced strengthening through bimodal grain structures, and favorable grain orientation for dislocation slip and twinning formation, which was significantly more activated in the <110>//BD texture than in the <100>//BD. This study offers new insights into achieving multi-scale synergistic microstructure manipulation via PBF-LB for desired strength, ductility, and mechanical anisotropy in a CoCrNi MEA.

Crystal plasticity approach for predicting mechanical responses in wire-arc directed energy deposition of NbZr1 refractory alloy

The refractory alloy, such as Niobium-1 wt% Zirconium (NbZr1) alloy, is a promising candidate for diverse applications in extreme environments. This study investigates an integrated experimental and computational methodology that can predict the mechanical properties of wire-arc directed energy deposited (DED) refractory NbZr1 alloy. The effect of large columnar grains with strong texture induced by the wire-DED process has been successfully incorporated into the representative volume element (RVE). Performing crystal plasticity (CP) simulation on RVE of NbZr1, deformation behavior and stress-strain relationship are predicted to explore the process-structure-property (PSP) relationship. The RVE has been created in synthetic microstructure generation software utilizing the grain statistics derived from electron backscatter diffraction (EBSD) analysis, capturing essential microstructural features. A phenomenological constitutive model and appropriate boundary conditions have been applied and solved, using the CP fast Fourier transform method. The CP model has been calibrated and validated utilizing the tensile test data along the build direction and deposition direction, respectively. The error in predicting yield strength and ultimate tensile strength is 0.91% and 0.67%, respectively, for the calibration simulation, whereas these values are 2.51% and 1.81% for the validation simulation. The results suggest strong agreement between the simulation and experimental observation. Even though global deformation behavior remains consistent across multiple RVEs with the same microstructural features, local stress-strain values vary, indicating structural anisotropy, which is also consistent with the digital image correlation (DIC) result. It is proven that this proposed CP method can effectively predict the mechanical responses of components with large grains and strong textures resulting from the wire-arc DED.

D retention in e-beam powder-bed fused (3-D printed) tungsten exposed to high-flux deuterium plasma in Pisces-RF

Tungsten targets produced by the additive manufacturing (AM) method of electron-beam powder-bed fusion, or 3-D metal printing, are exposed to high flux D plasma in the Pisces-RF linear plasma device with the plasma-exposed surface normal to the AM build direction. D retention was measured by thermal desorption mass spectrometry following exposure to D plasma with an associated ∼50eV D+ ion flux. D+ fluence, and operational temperature, in the ranges 5×1024–5×1026 m−2 and 400–1000 K, are explored. D retention values for the AM W are compared to identically plasma exposed ’conventional’ sintered W and it is found that total D retention is similar. However, the D thermal release is notably different. Desorption from the AM W shows reduced D retention in traps typical of sintered W, and moderately increased trapping in defect types of higher trap release energy. The dependence of D retention on fluence is also different for the AM W, revealing an uptake slower than expected from Fickian diffusion, while that for sintered W is consistent and in agreement with previous poly-crystalline W results from Pisces-B. Hydrogen transport modeling of the fluence dependence suggests that interconnected pathways for D release back to the surface during plasma-exposure can account for the slower D uptake in the AM W.

Ultrasonic characterization of material anisotropy in additively manufactured AlSi10Mg

Metal additive manufacturing (AM) based on laser powder bed fusion (LPBF) generates components by melting metal powder on a layer-by-layer basis. The melting and cooling process often generates samples with a preferred material symmetry aligned with the build direction. This anisotropy affects mechanical performance and can be challenging to characterize nondestructively. Here, LPBF was used to create samples of AlSi10Mg with specific geometries to affect the overall anisotropy. In addition, the hybrid AM process of interlayer milling was used to impact the microstructure and residual stress of some samples. Ultrasonic measurements were used to characterize the samples using both coherent wave and diffuse wave experiments to capture the anisotropic nature of the wave speed and scattering. The material symmetry and morphology of the grains affect the wave speed, attenuation, and backscatter with respect to direction. Furthermore, spatially resolved acoustic spectroscopy was used to provide insight regarding the localized wave speeds with respect to sample location and propagation direction. The experimental data were used collectively to quantify differences between the AM processes used to create the samples. Such information can be used to guide AM process parameters to optimize sample performance. Finally, prospects for characterization of residual stresses will be discussed.

Impact of Different Heat Treatments on the Mechanical Properties and Microstructure of Precipitation-Hardened Stainless Steel Fabricated by Laser Powder Bed Fusion

The mechanical properties of additively manufactured metal parts are often considered inferior to those of their traditionally manufactured counterparts. These inferior mechanical properties are primarily attributed to prevalent defects inherent in additive manufacturing processes, leading to reduced performance and durability. Researchers have extensively studied processing parameters and post-processing techniques to determine optimal conditions for improving the mechanical properties of laser powder bed fusion. This study investigates the densification and microstructure characteristics of laser powder bed fusion 15-5 precipitation-hardened stainless steel. The effects of three developed post-heat treatments and three build directions are examined. The results reveal that heat treatment schedules influence material strength and hardness at the cost of reduced ductility, while the fabrication build direction impacts surface porosity. Prolonged heat treatment procedures resulted in the highest hardness values due to enhanced homogenization.

Characterization of Microstructural and Mechanical Properties of 17-4 PH Stainless Steel by Cold Rolled and Machining vs. DMLS Additive Manufacturing

The 17-4 PH stainless steel is widely used in the aerospace, petrochemical, chemical, food, and general metallurgical industries. The present study was conducted to analyze the mechanical properties of two types of 17-4 PH stainless steel—commercial cold-rolled and direct metal laser sintering (DMLS) manufactured. This study employed linear and nonlinear tensile FEM simulations, combined with various materials characterization techniques such as tensile testing and nanoindentation. Moreover, microstructural analysis was performed using metallographic techniques, optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results on the microstructure for 17-4 PH DMLS stainless steel reveal the layers of melting due to the laser process characterized by complex directional columnar structures parallel to the DMLS build direction. The mechanical properties obtained from the simple tension test decreased by 17% for the elastic modulus, 7.8% for the yield strength, and 7% for the ultimate strength for 17-4 PH DMLS compared with rolled 17-4 PH stainless steel. The FEM simulation using the experimental tension test data revealed that the 17-4 PH DMLS stainless steel experienced a decrease in the yield strength of ~8% and in the ultimate strength of ~11%. A reduction of the yield strength of the material was obtained as the grain size increased.

Synchrotron based investigation of anisotropy and microstructure of wire arc additive manufactured Grade 91 steel

Additive manufacturing (AM) rapidly produces complex shapes crucial for energy technologies and engineering designs. In this work, the microstructure and mechanical properties of additive manufactured Grade 91 (modified 9Cr–1Mo) ferritic/martensitic (FM) steel were investigated. Computational thermodynamics, synchrotron X-ray diffraction, scanning electron microscopy, and microhardness testing were utilized to quantify microstructure (crystallographic phases, microstrain), lattice parameters, and mechanical properties as functions of the build directions and post-build heat-treatment. The as-built microstructures were found to contain a large fraction of microstrain due to two-dimensional defects, and a low-carbon martensite phase (maximum value 38.4 vol%), as quantified from the X-ray diffraction analysis. It was shown that a post-build heat-treatment can effectively remove this martensitic phase and promote the formation of desired microstructures with dispersed M23C6 carbides which was consistent with Thermo-Calc predictions. From the X-ray diffraction analysis, an ∼82.5% reduction in microstrain, a 61.5% increase in the coherent grain size and complete elimination of body-centered tetragonal (BCT) phase demonstrated that an appropriate heat-treatment of AM built FM steel yields microstructures and hardness comparable to conventionally processed steel. However, based on lattice parameter and hardness map statistics, heat-treatment on the as-manufactured steel did not eliminate anisotropy.

The impact of energy policy on traditional buildings: Towards a holistic decision-making framework for retrofitting: Part 2

The Energy Performance of Buildings Directive (EPBD) is the European Union’s main policy instrument for reducing the built environment’s contribution to climate change. Energy Performance Certificates (EPC) are a tool of this policy, providing buildings with a performance rating. In the UK these have become the benchmark by which the Minimum Energy Efficiency Standards (MEES) are judged, rendering residences lower than an E illegal to rent out. This has pushed property owners to undertake energy retrofitting interventions to ensure compliance. In traditional buildings this is potentially problematic. Buildings of this type rely on permeability to control moisture dynamics; the insertion of less permeable barriers can interrupt their internal hygrometry leading to condensation, damp and decay. As a result, subsequent damage to the building fabric can bring energy policy into conflict with heritage conservation. Existing frameworks that attempt to mitigate the tension within these agendas often fall short in explicitly considering the the problem holistically. This research first asks if pressure from policy is leading to incompatible retrofits. Secondly, it aims to develop a holistic framework that unites heritage and energy agendas with current policy. An inductive, pragmatic approach was undertaken. Using a historic estate’s residential portfolio as a case study, condition surveys were carried out to assess whether properties retrofitted with secondary glazing were experiencing problems with condensation. The results of this were significant, supporting the argument that energy policy is driving incompatible retrofitting interventions. Exploratory data analysis was carried out on an existing EPC dataset to highlight inconsistencies with the EPC methodology. Finally, these findings were combined with questionnaire survey results, targeted at both professionals and occupants, to inform a decision-making framework that incorporated energy efficiency, heritage values, life cycle cost analysis (LCC), building assessment, occupant behaviour, with a feedback loop promoting a bottom-up approach to policy. This issue contains Part 2 which will deal with the methodology and results. Part 1 in the previous issue set the scene.

Highly-efficient additive manufacturing of Inconel 625 thin wall using hot-wire laser metal deposition: Process optimization, microstructure, and mechanical properties

Hot-wire-based laser metal deposition (HW-LMD) technique was used for additive manufacturing of Inconel 625 thin-walled parts. The desired process window was obtained through the Taguchi experiment design, and the defect-free Inconel 625 thin-walled structures were efficiently manufactured with a wire deposition rate of 1.72 kg/h. The microstructure, phase composition, microhardness, and tensile properties of the Inconel 625 thin walls were studied in detail. The results showed that the microstructure of the Inconel 625 thin wall was mainly composed of a large number of columnar dendrites with an average grains size of 12.5 μm, and the growth direction of the columnar dendrites was perpendicular to the substrate surface. γ-Ni was the base phase of the as-deposited Inconel 625 thin walls and irregularly shaped Laves precipitates were observed in the inter-dendritic region. The microhardness of the Inconel 625 thin wall over the build direction was homogenous and the average microhardness was 258 HV1, which was 35.7 % higher than that of the wrought alloy. The tensile strength of the as-deposited Inconel 625 thin walls exhibited anisotropy according to the relationships between stress loading direction and microstructural texture. The maximum tensile strength and elongation of the as-deposited Inconel 625 thin wall were respectively 825.91 MPa and 55.62 %, which were close to the wrought alloy 625. Meanwhile, through comparative analysis, it was found that the tensile properties of the Inconel 625 samples fabricated in this study were superior to samples produced using conventional arc additive manufacturing methods.

Effects of beam shaping on copper-steel interfaces in multi-material laser beam powder bed fusion

Multi-material laser beam powder bed fusion (PBF-LB) is a promising approach to meet industrial demands for multifunctional components, due to its enhanced freedom of design. Copper and stainless steel are interesting materials to be combined due to the high electrical and thermal conductivity of copper and the mechanical strength and wear resistance of steel. However, this system suffers from copper contamination cracking (CCC), a phenomenon which leads to intergranular cracking of the steel due to penetration of liquid copper. The more these materials intermix, the greater the amount of copper that can penetrate and damage the steel. Mixing is more intense when steel is below copper during printing, a situation that cannot always be avoided due to design constraints. In this sense, this research tackles the worst scenario of printing CuCrZr onto 316L and analyses the effect of beam shaping on interface quality. For the first time, a ring-mode laser was applied to multi-material PBF-LB with the goal to reduce intermixing. It was observed that using a ring-mode laser source instead of a Gaussian beam decreases mixing of the two alloys and reduces interface defects, albeit being unable to completely suppress cracking. Grain size and texture were also affected by the beam shape, with the Gaussian beam leading to formation of small equiaxed grains along 20 layers of CuCrZr, resulting in random texture. The ring-mode laser source, on the other hand, yields columnar grains and <100> texture along the build direction. Both beam shapes were observed to induce supercooling below the liquid miscibility gap in the Cu–Fe system. Besides the expected γ-Fe and ε-Cu phases, iron was also found to crystallize in a body-centered cubic (BCC) lattice structure, which is believed to happen due to Ni depletion of the steel in Cu-rich compositions, coupled to insufficient copper within the Fe-rich liquid during solidification. BCC fractions are higher for the Gaussian beam. These differences in microstructure and BCC fraction are attributed to the high intermixing of CuCrZr and 316L when applying Gaussian beams, which is around 10 times higher than with the ring-mode laser.

Fatigue Resistance Assessment of WAAM Carbon Steel

This study presents a comprehensive exploration of the fatigue resistance of wire arc additive manufacturing (WAAM) carbon steel for lattice structures. Microstructural analysis unveils substantial grain dimensions characterized by a distinctive crystallographic configuration. These grains exhibit equiaxed characteristics, demonstrating uniform dimensions in all directions. The prevailing microstructure is dominated by ferrite grains. In tandem with the microstructural insights, hardness evaluations were conducted in correspondence with the part's deposition direction. The analysis of these measurements unveiled a consistent base material hardness of approximately 159 HV. The uniform distribution of hardness profiles supports the deduction that WAAM carbon steel uniformly embodies strength attributes. This congruence aligns harmoniously with the uniform microstructure evident in microscopic analyses. The yield strength of the WAAM carbon steel exhibits higher values in the build direction, peaking at 392 MPa. The bending fatigue tests revealed a fatigue limit approximating 180 MPa for WAAM carbon steel, evident in both the build and deposition directions. Fatigue strength of WAAM carbon steel mirrors that observed for reference material S355MC steel sheet.

Special interlayer pause strategy for controlling grain morphology and tensile property anisotropy of TC11 alloys fabricated by directed energy deposition technology

Directed energy deposition (DED)-built titanium alloys have long suffered from the anisotropic mechanical properties induced by the long columnar prior β grains growing along the building direction, which restricts their applications. In this work, a special interlayer pause (SIP) strategy is designed to reduce the tensile property anisotropy by adjusting the grain morphology. The grain morphologies, microstructure, crystallographic texture, tensile properties and their anisotropy of DEDed TC11 titanium alloys were systematically investigated. The results show that the SIP strategy promotes the columnar-to-equiaxed transition of grain morphology, reduces grain sizes, and weakens the crystallographic textures. The microstructure of SIP samples consists of superfine basketweave and lamellar α laths and residual β phases. The average length of α laths increases with the SIP layer number. In addition, the maintained superfine α phases contribute to an ultrahigh yield strength of ∼1200 MPa of the SIP samples. The yield strength of the horizontal direction gradually decreases and that of the vertical direction increases with increasing the SIP layer number, resulting in a lowered strength anisotropy of less than 2%. When adopting an optimal SIP strategy, the as-deposited TC11 alloy exhibits a relatively small ductility anisotropy.

Modelling and researching the evolution of stress during arc-directed energy deposition (ADED) hybrid inter-layer hammering

ABSTRACT Hybrid manufacturing of arc-directed energy deposition (ADED) and inter-layer hammering can build components with low detrimental residual stress (RS) and warping. Inter-layer hammering with lower load demand has proved to be a promising technology to improve the microstructure and mechanical properties. In this paper, a finite element model of the ADED hybrid inter-layer hammering was constructed for the first time. The accuracy of the model is evaluated by comparing thermal history, RS, and warping. The results show that the maximum compressive RS -25Mpa appears at 3 mm from the top of the wall after a single inter-layer hammering. The RS of the inspection position is reduced by 74.6% after six layers of hammering compared with the wall manufactured by ADED alone, and low-stress distribution with a value of -30Mpa appears in the range of 7 mm to 15 mm from the substrate surface. The warping of the wall in the building direction was completely suppressed (from 0.21 mm to 0 mm). In addition, the plastic strain introduced by the hammering at the wall top exacerbates the “misfit” between the regions of the wall top, resulting in tensile stress at the wall top.

Ranking building design and operation parameters for residential heating demand forecasting with machine learning

The European Union's Energy Performance in Buildings Directive has made significant strides in enhancing building energy efficiency since its inception in 2002. However, approximately 75% of EU buildings still fall short of energy-efficient standards. Furthermore, there is a growing momentum to extend the concept of nearly zero-energy buildings to entire districts, thereby fostering Net-Zero Energy Districts. This underscores the necessity for large-scale urban building energy modelling to identify and improve underperforming buildings and energy transition planning. Given the increasing interest in black box models for building energy performance, this study aims to identify common input variables in buildings energy demand literature, analyse their influence, and develop a heating demand prediction model using different algorithms: Random Forest, XGBoost, and Extra Trees. Four large datasets generated from white-box simulation in three Spanish cities were used for training and testing the models. Four features consistently stand out as the most important for prediction: shape factor, infiltration rate, south equivalent surface, and internal gains, regardless of the training algorithm or the climatic zone. The multi-location XGBoost algorithm with an optimizer emerged as the best-performing model, with an average Mean Absolute Percentage Error value hovering around 40%. Analysis employing SHapley Additive exPlanation (SHAP) values showcases the model's ability to identify factors that drive higher heating energy demand, alongside its strong predictive performance. This suggests potential integration of the model into programmes to identify key variables to be addressed during building renovation. Additionally, results show the potential of XGBoost-based software's potential for identifying building renovation targets.

Determination of the anisotropy in mechanical properties of laser powder bed fusion Inconel 718 by ultrasonic testing

ABSTRACT This study aims to investigate the effects of build direction on the as-fabricated microstructure and mechanical properties of Inconel 718 specimens manufactured via the Laser Powder Bed Fusion (L-PBF) technique. The microstructures and mechanical properties of the specimens were characterized via SEM, EBSD,ultrasonic wave velocity measurements, hardness and tensile tests. For the as-fabricated condition, the highest tensile strength (1114 MPa) was obtained with the horizontally built specimens while the vertically built ones have the highest 40% elongation. The computational analysis produced results that closely aligned with the measured yield strength values of L-PBFed samples. Additionally, a strong correlation was observed between the hardness values and longitudinal ultrasound velocity of L-PBF Inconel 718 specimens. Consequently, the non-destructive ultrasonic evaluation provided valuable insights into the anisotropy of mechanical properties, complementing information obtained from conventional tensile tests.

Dual wire arc additive manufacturing of compositionally graded Alx-Co-Cr-Fe-Ni high-entropy alloy

Graded materials are promising alloys due to their improved strength and ductility. In this study, a functionally graded Alx-Co-Cr-Fe-Ni high entropy alloy with a variation of Al concentration along the building direction was produced in-situ by dual wire arc additive manufacturing for the first time, and the microstructure and mechanical properties of the deposited alloy were investigated. The results showed that the FCC + BCC dual-phase gradually transformed to a single BCC phase with increasing Al content, the precipitation temperature of the ordered B2 phase became high, and the precipitation temperature range of the disordered BCC phase became wider, which promoted the formation of the disordered BCC phase. With the change in phase ratio, the hardness gradually increased from 342 HV to 397 HV, and the bottom deposited alloy had an optimal combination with a compressive strength of 827.4 MPa and elongation of 42.3%. Compared to the bottom region, the top region shows much higher sliding wear resistance. The high-density dislocations and grain refinement result in better toughness and strength in the bottom region, while the segregation of Cr elements at the grain boundaries changes the properties of the grain boundaries and makes them more brittle in the top region. This investigation realizes a novel method to fabricate GHEAs, which can produce a more convenient and cost-effective gradient material with a complex composition.

Advanced Ti-Nb-Ta Alloys for Bone Implants with Improved Functionality.

The additive manufacturing of titanium-niobium-tantalum alloys with nominal chemical compositions Ti-xNb-6Ta (x = 20, 27, 35) by means of laser beam powder bed fusion is reported, and their potential as implant materials is elaborated by mechanical and biological characterization. The properties of dense specimens manufactured in different build orientations and of open porous Ti-20Nb-6Ta specimens are evaluated. Compression tests indicate that strength and elasticity are influenced by the chemical composition and build orientation. The minimum elasticity is always observed in the 90° orientation. It is lowest for Ti-20Nb-6Ta (43.2 ± 2.7 GPa) and can be further reduced to 8.1 ± 1.0 GPa for open porous specimens (p < 0.001). Furthermore, human osteoblasts are cultivated for 7 and 14 days on as-printed specimens and their biological response is compared to that of Ti-6Al-4V. Build orientation and cultivation time significantly affect the gene expression profile of osteogenic differentiation markers. Incomplete cell spreading is observed in specimens manufactured in 0° build orientation, whereas widely stretched cells are observed in 90° build orientation, i.e., parallel to the build direction. Compared to Ti-6Al-4V, Ti-Nb-Ta specimens promote improved osteogenesis and reduce the induction of inflammation. Accordingly, Ti-xNb-6Ta alloys have favorable mechanical and biological properties with great potential for application in orthopedic implants.

Study on properties of 304 wire arc additive manufacturing stainless steel TIG welded joints

In this study, 304 stainless steel thin-wall component were obtained by wire arc additive manufacturing (WAAM) as one of the methods of additive manufacturing. In view of the limits that the WAAM technology can not produce large and complex components at one time, TIG welding was chosen during secondary processing to achieve the effectively connection. Weldability, microstructure, texture strength and mechanical properties were particularly investigated when welding along the traveling and building direction. The results show that welding along the traveling direction gained better performance weld joints than building direction including higher tensile and yield strength, greater elongation and lower texture strength. Besides, the grain orientation changed from [001] before welding to [111] after welding in both traveling and building direction.