Near-(3 titanium alloys such as Ti-5Al-5Mo-5V-3Cr (Ti-5553) are widely applied in aerospace and automotive industries due to their high strength and fracture toughness. While additive manufacturing (AM) via Laser Engineered Net Shaping (LENS) provides design flexibility for such alloys, their mechanical properties are directly dependent on extensive post-processing. This study demonstrates that the introduction of a 26-second interlayer dwell time during LENS fabrication enables in-situ microstructural tailoring, resulting in a distinctive alpha/(3 structure with Widmanstatten features and thus, eliminating the need for further heat treatment. The asbuilt Ti-5553 alloy achieved a superior combination of yield strength (1198 MPa) and ductility (16 %), outperforming both heat-treated and conventionally processed counterparts. Comparative annealing at 300 degrees C, 700 degrees C, and 750 degrees C led to moderate changes in strength or ductility thus proving that the as-built condition is characterized by the most balanced performance. These findings highlights, that the proper interlayer dwell time selection enable achieving application-ready mechanical properties in (3-Ti alloys directly from the AM process.

In this paper, the influences of two post-heat treatments on the structural, mechanical and corrosion resistance properties of additively manufactured Ti6Al4V alloys were discussed in detail. The materials were produced using the laser engineering net shaping (LENS) technique, and they were subjected to annealing without pressure and hot isostatic pressing (HIP) under a pressure of 300 MPa for 30 min at temperatures of 950 °C and 1050 °C. Annealing without pressure led to the formation of a thin plate structure, which was accompanied by decreasing mechanical properties and increasing elongation and corrosion resistance values. For the HIP process, the formation of a thick plate structure could be observed, resulting in the material exhibiting optimal mechanical properties and unusually high elongation. The best mechanical and corrosion resistance properties were obtained for the material subjected to HIP at 950 °C.

Fe40Al alloys produced by casting and sintering were anodized to form nanostructured oxide layers. Microstructural characterization revealed a lower grain size for the sintered alloy compared to the cast alloy. Anodizing was performed in four electrolytes with a constant etidronic acid concentration (0.3 M) and different ethylene glycol-water ratios. Different voltages (5-400 V) and treatment times (1-4 hours) were evaluated for cast and sintered Fe40Al alloys. Among the studied anodization regimes, only four anodic films formed on sintered Fe40Al were homogeneous. These films were annealed at 900 degrees C and analyzed by conventional characterization techniques (SEM/EDS and XRD). Results indicated a non-self-ordered morphology and different content of P, Fe, and Al species as a function of the electrolyte composition. Annealing post-treatment led to the formation of Fe/Al oxides and spinels in selected anodic films. An additional peak of FePO4 was detected only in the anodic film formed in pure ethylene glycol. The band gap values (UV-Vis reflectance spectroscopy) of the anodic film formed in ethylene glycol decreased from 2.87 eV to 2.45 eV after annealing. This band gap decrease was associated with the preferential formation of conductive phases (Fe2O3 and FeAlO3) over insulating phases (gamma-Al2O3 and FeAl2O4) after annealing.

The aim of this work was to manufacture tungsten composites from different initial powder mixtures by mechanical alloying followed by sintering. Two initial powder mixtures, W + 5 wt% of Y2O3 and W + 10 wt% of Y2O3, and pure W for comparison were mechanically alloyed for 50 h in a Fritsch Pulverisette P5 planetary ball mill under an argon atmosphere. The final products were consolidated by pulse plasma sintering at 1640 degrees C under a pressure of 20 MPa. The powders and consolidated pellets were examined by the XRD method. The obtained results show that during milling, the tungsten based solid solution formed. After consolidation, the XRD examination revealed that in addition to the tungsten-based solid solution and yttria, new carbide phases (Fe3C, WC, W2C and Fe3W3C) appeared. The graphite present in the carbides originated from the die used in the sintering process. SEM observations of the surfaces of the sinters revealed that the microstructure is not homogeneous and consists of areas rich in one or two elements, such as W, C, Fe or the Y2O3 phase. The microhardness of the pellets increases with the increasing content of the Y2O3 strengthening phase, whereas the values of the relative density decrease. (c) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

The Laser Engineered Net Shaping additive manufacturing method was used to prepare NiTi samples. In the process spherical gas atomized powder with particle size in the range of 45 – 115 μm containing 50.08 at.% Ni was used. DSC studies showed additional peak after ageing due to R → B19’ phase formation during cooling and reverse transformation B19’ → R during heating. The martensitic transformation temperatures and the reverse transformation both increase with the ageing time. This was associated with the formation of Ni4Ti3 precipitates during the aging, as identified for the alloy aged for 2h. As-deposited sample showed diffused DSC peaks corresponding to martensitic transformation and a good superelastic properties at RT, however after 4% strain a residual strain of 0.7% was observed. In the case of aged sample strained at room temperature a deformation of martensite occured, whereas the super elastic properties were observed at 53oC. Samples prepared for the in-situ tensile experiment using LENS method showed a strong <001> texture parallel to the build direction. In-situ tensile deformation of LENS deposited sample caused nucleation of martensitic plates first at the surface of samples; then plates nucleate preferentially at grain boundaries and propagate across grains. From the PFs measurements a following crystallographic relationship was most frequently observed: (001)B19’ || (01 )B2 and [100] B19’ || [100]B2, however other variants were also observed. Existence of martensite twins was on (110) and (10 ) planes was observed. In-situ tensile deformation of samples aged 2h/500oC causes a decrease of plate thickness from 1.15 μm to 0.9 μm, what suggests participation of strain field near Ni4Ti3 precipitates in more frequent nucleation of martensitic plates. Furthermore, more variety of crystallographic orientation relationships between cubic austenite phases like [010]B2 || [100]B19’ [001] TiNiB2|| [1 3]B19’ , [001]B2 || [011]B19’ , [100]B2 || [011]B19’ and others were observed. Some twin orientations were identified in martensite based on SEM microstructure and PF analysis, particularly at higher deformation of 8%.

The effect of Nb content on microstructure, mechanical properties and superelasticity was investigated for a series of Ti-xNb alloys, fabricated by the laser engineered net shaping method, using elemental Ti and Nb powders. The microstructure of as-deposited materials consisted of columnar β-phase grains, elongated in the built direction. However, due to the presence of undissolved Nb particles during the deposition process, an additional heat treatment was necessary. The observed changes in mechanical properties were explained in relation to the phase constituents and deformation mechanisms. Due to the elevated oxygen content in the investigated materials (2 at.%), the specific deformation mechanisms were observed at lower Nb content in comparison to the conventionally fabricated materials. This made it possible to conclude that oxygen increases the stability of the β phase in β–Ti alloys. For the first time, superelasticity was observed in Ti–Nb-based alloys fabricated by the additive manufacturing method. The highest recoverable strain of 3% was observed in Ti–19Nb alloy as a result of high elasticity and reverse martensitic transformation stress-induced during the loading.

Two different methods of rapid manufacturing—electron beam additive manufacturing (EBAM) and laser-engineered net shaping (LENS)—were used in order to fabricate NiTi elements. Microstructure and martensitic transformation temperatures of initial materials in the form of wire or spherical powder were established. The samples fabricated using LENS technique showed martensitic transformation temperature (MTT) at − 26 °C (represented by maximum martensite peak maximum in DSC) which was lower in comparison with raw powder. In the case of samples fabricated using EBAM, the MMT reached − 19 °C. The peaks of martensite and reverse transformations were diffuse due to differences in grain size and composition across the sample. Aging at 500 °C for 2 h caused not only separation of R-phase during cooling of both samples, but also formation of sharper and higher transformation peaks as well as shift of MTT to higher temperatures. Microstructural investigation showed columnar grains, near the interface of deposited element and base plate, growing perpendicular to the plate surface. The grains showed axial fiber texture <001> along the growth direction. STEM micrographs revealed the presence of elongated particles enriched in Ti. Formation of Ti-rich particles during the process led to the depletion of Ti in the matrix and contributed to increase in MTT in comparison with initial NiTi powder. LENS-deposited sample additionally contained higher dislocation density in the austenite. Compression stress/strain curves of EBAM-deposited sample revealed deformation of martensite only, while the LENS-deposited one showed almost complete superelastic effect in compression mode up to 3%.

Laser Engineered Net Shaping (LENSTM) is currently a promising and developing technique. It allows for shortening the time between the design stage and the manufacturing process. LENS is an alternative to classic metal manufacturing methods, such as casting and plastic working. Moreover, it enables the production of finished spatial structures using different types of metallic powders as starting materials. Using this technology, thin-walled honeycomb structures with four different cell sizes were obtained. The technological parameters of the manufacturing process were selected experimentally, and the initial powder was a spherical Ti6Al4V powder with a particle size of 45–105 µm. The dimensions of the specimens were approximately 40 × 40 × 10 mm, and the wall thickness was approximately 0.7 mm. The geometrical quality and the surface roughness of the manufactured structures were investigated. Due to the high cooling rates occurring during the LENS process, the microstructure for this alloy consists only of the martensitic α’ phase. In order to increase the mechanical parameters, it was necessary to apply post processing heat treatment leading to the creation of a two-phase α + β structure. The main aim of this investigation was to study the energy absorption of additively manufactured regular cellular structures with a honeycomb topology under static and dynamic loading conditions.

This paper presents a characterization study of specimens manufactured from Ti-6Al-4V powder with the use of laser engineered net shaping technology (LENS). Two different orientations of the specimens were considered to analyze the loading direction influence on the material mechanical properties. Moreover, two sets of specimens, as-built (without heat treatment) and after heat treatment, were used. An optical measurement system was also adopted for determining deformation of the specimen, areas of minimum and the maximum principal strain, and an effective plastic strain value at failure. The loading direction dependence on the material properties was observed with a significant influence of the orientation on the stress and strain level. Microstructure characterization was examined with the use of optical and scanning electron microscopes (SEM); in addition, the electron backscatter diffraction (EBSD) was also used. The fracture mechanism was discussed based on the fractography analysis. The presented comprehensive methodology proved to be effective and it could be implemented for different materials in additive technologies. The material data was used to obtain parameters for the selected constitutive model to simulate the energy absorbing structures manufactured with LENS technology. Therefore, a brief discussion related to numerical modelling of the LENS Ti-6Al-4V alloy was also included in the paper. The numerical modelling confirmed the correctness of the acquired material data resulting in a reasonable reproduction of the material behavior during the cellular structure deformation process.

The paper presents a methodology investigation of honeycomb cellular structures deformation process in quasi-static compression tests. Two honeycomb topologies with different elementary cells were designed and manufactured from Ti-6Al-4 V alloy powder with the use of Laser Engineered Net Shaping (LENS) system and compressed using a universal strength machine. To simulate the deformation process with LS-Dyna software, the mechanical properties of the material were assessed and correlated. An elasto-visco-plastic material model (Mat_Plasticity_With_Damage) was used for predicting the material behavior. The results of experimental tests and numerical simulations were compared. A reasonable agreement between deformation, failure and force histories was obtained. Additionally, both the topologies were compared for their energy absorption capabilities. The validated numerical modelling with the adopted constitutive model will be used in the further studies to analyze different cellular structures topologies subjected to dynamic loading.

REGULAR CELLULAR STRUCTURES MANUFACTURED ADDITIVELY OF Ti6Al4V Paweł Płatek 1 , Jacek Janiszewski 1 , Paweł Baranowski 2 , Jerzy Małachowski 2 , Tomasz Czujko 3 , Anna Antolak-Dudka 3 , Tomasz Durejko 3 , Faculty of Mechatronics and Aviation, Military University of Technology, Warsaw, 2 Faculty of Mechanical Engineering, Military University of Technology, Warsaw, Faculty of Advanced Technologies and Chemistry, Military University of Technology, Warsaw, e-mail: pawel.platek@wat.edu.pl

The water-atomized ATOMET 28, 1001, 4701, and 4801 powders, manufactured by Rio Tinto Metal Powders, were used for additive manufacturing by a laser engineered net shaping (LENS) technique. Their overall morphology was globular and rounded with a size distribution from about 20 to 200 µm. Only the ATOMET 28 powder was characterized by a strong inhomogeneity of particle size and irregular polyhedral shape of powder particles with sharp edges. The powders were pre-sieved to a size distribution from 40 to 150 µm before LENS processing. One particular sample—LENS-fabricated from the ATOMET 28 powder—was characterized by the largest cross-sectional (2D) porosity of 4.2% and bulk porosity of 3.9%, the latter determined by microtomography measurements. In contrast, the cross-sectional porosities of bulk, solid, nearly cubic LENS-fabricated samples from the other ATOMET powders exhibited very low porosities within the range 0.03–0.1%. Unexpectedly, the solid sample—LENS-fabricated from the reference, a purely spherical Fe 99.8 powder—exhibited a porosity of 1.1%, the second largest after that of the pre-sieved, nonspherical ATOMET 28 powder. Vibrations incorporated mechanically into the LENS powder feeding system substantially improved the flow rate vs. feeding rate dependence, making it completely linear with an excellent coefficient of fit, R2 = 0.99. In comparison, the reference powder Fe 99.8 always exhibited a linear dependence of the powder flow rate vs. feeding rate, regardless of vibrations.

The aim of this work was to apply mechanical alloying technique for synthesis of high entropy multicomponent equimolar WMoNbZrV alloy and to investigate the phase composition after milling and after heat treatment, as well as to characterize the observed changes of crystallite size, lattice strain and lattice parameter of solid solution formed. It was found that nanocrystalline bcc solid solution was characterized by crystallite size of 10 nm, lattice strain of 0.58% and lattice parameter of 3.1687 angstrom. Heating the sample up to 700 degrees C resulted in decrease of lattice strain down to 0.20%, while the crystallite size remained not changed, testifying good thermal stability of nanocrystalline bcc solid solution obtained. (C) 2018 Elsevier B.V. All rights reserved.

Bulk nanocrystalline Ni3Al-based alloys were produced by ball milling of powdered aluminium scrap alloys (two silumines with chemical compositions: Al87.5Si7.8Cu2.1Fe0.7Zn1.4Mn0.4Mg0.1 (R1 scrap) and Al88.4Si5,7Cu3,9Fe0,9Zn0,6Mn0.5 (R2 scrap)) with addition of Ni powder and subsequent hot-pressing consolidation. The final products of mechanical alloying were consolidated at 1000 degrees C for 180 s under the pressure of 7.7 GPa. The powders and the compacted samples were examined by XRD method. The results obtained show that during the milling supersaturated solid solutions Ni(Al, Si ... ) are formed and during the consolidation the disordered solid solutions transform into ordered nanocrystalline Ni3Al intermetallic based phases with a mean crystallite size of similar to 30 nm. The microhardness of the produced Ni3Al-based alloys is 955 for R1 process and 928 HV0.1 for R2 process respectively. The density of the pellets is nearly 100% of theoretical value for the Ni3Al intermetallic phase and the open porosity of the compacts is negligibly small. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

(BiFeO3)1-x-(BaTiO3)x solid solutions with x = 0.1–0.4 and 0.7 were investigated. The ceramics were prepared by mechanical activation technology and subsequent heat treatment. As was proved by X-ray diffraction, increase of BaTiO3 concentration causes a change in the crystalline structure from the rhombohedral structure characteristic of BiFeO3 to a cubic one. 57Fe Mössbauer spectroscopy allowed observation of a gradual transformation from an ordered spin structure of Fe3+ ions to the paramagnetic state with an increase of x.

X-ray diffraction and Fe-57 Mossbauer spectroscopy were applied as complementary methods in order to investigate the structure and hyperfine interactions of (BiFeO3)(i-x)-(BaTiO3)(x) solid solutions prepared by mechanical activation and subsequent heat treatment.

In the present work bulk nanocrystalline Ni3Al alloys were produced by mechanical alloying of powdered Al3Ni or Al4Ni96 alloys mixed with Ni or Al respectively, followed by a hot-pressing consolidation. In the case of both mixtures a Ni(AI) solid solution was a product of ball milling. The powders of Ni(AI) were consolidated at 1000 degrees C for 180 s under the pressure of 7.7 GPa. The XRD investigations have revealed that during consolidation the disordered solid solution transforms into the ordered nanocrystalline Ni3Al intermetallic compound with an average mean crystallite size of similar to 30 nm. The microhardness of the produced samples is 1033 and 1093 HV0.1 and is relatively high in comparison to literature data. The density of the obtained samples is close to the theoretical value of the Ni3Al intermetallic phase and the open porosity of the compacts is negligibly small. (C) 2013 Elsevier Ltd. All rights reserved.

An Al80Fe14B6 powder mixture was subjected to mechanical alloying. Presence of an amorphous structure in the milling product was revealed by XRD investigations. The calorimetric study showed that the amorphous phase crystallised above 370 degrees C. The milled Al80Fe14B6 powder was consolidated under a pressure of 7.7 GPa in different conditions: at 350 degrees C and at 1000 degrees C. Besides, the mechanically alloyed amorphous Al85Fe15 powder was consolidated at 360 degrees C. The amorphous structure was retained after consolidation applied at 350 degrees C and 360 degrees C. Compaction at 1000 degrees C caused crystallisation of the amorphous phase and appearance of metastable nanocrystalline phases. Structural investigations revealed that both bulk Al80Fe14B6 samples are composites with boron particles embedded in amorphous or nanocrystalline matrix. The hardness of the nanocrystalline-matrix composite and of the amorphous-matrix one is equal to 707 HV1 and 641 HV1 respectively, whereas that of bulk amorphous Al85Fe15 alloy is 504 HV1. The specific yield strength of amorphous-matrix and nanocrystalline-matrix composites, estimated using the Tabor relationship, is 625 and 650 kNm/kg respectively, while that of amorphous Al85Fe15 alloy is 492 kNm/kg. We also suppose that application of high pressure affected crystallisation of amorphous phase, influencing the phase composition of the products of this process. (C) 2011 Elsevier Ltd. All rights reserved.

In this work, preparation of nanocrystalline Ni(3)Al-based alloys by mechanical alloying process followed by hot-pressing consolidation is reported. Ni(75)Al(20)Co(5) and Ni(70)Al(25)Co(5) elemental powder mixtures were subjected to ball milling. Subsequently, the milling products were sintered at 1000 degrees C under a pressure of 7.7 GPa. The powders and the consolidated pellets were investigated by X-ray diffraction. The results obtained show that the milling products were in both cases supersaturated solid solutions Ni(Al,Co) and that during the hot-pressing consolidation they had transformed into nanocrystalline Ni(3)Al-based intermetallic compounds. The microhardness of the produced Ni(3)Al-based alloys is 918 HV0.1 in the case of Ni(75)Al(20)Co(5) composition and 1033 HV0.1 in the second case. The density of compacted materials is close to the theoretical value and their open porosity is negligible. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim