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Development of a high strength Al–Zn–Si–Mg–Cu alloy for selective laser melting
摘要： Despite additive manufacturing processes are already widely used in several industrial applications, there are few materials that are specifically designed and optimized for these technologies. Currently, only few Al alloys are available on the market and employed for 3D printing of structural parts. In particular, SieMg bearing alloys are the most common Al alloys for additive manufacturing, featuring high processability but moderate mechanical properties. By this work, we studied the effect of Si addition on the hot cracking susceptibility of a high strength AleZneMgeCu alloy. A preliminary activity has been carried out by blending AleZneMgeCu and AleSieMg powders and analysing their microstructure and properties achieved after selective laser melting. Eventually a new AleZneSieMgeCu alloy has been designed, produced as powder alloy by gas atomization and tested. The microstructure and phase transformations of the new alloy has been investigated by synchrotron X-ray diffraction, differential scanning calorimetry and microscope analysis. The AleZneSieMgeCu alloy processed by selective laser melting featured a relative density of 99.8%, no hot cracks were noticed within the investigated microstructures. The ability of the new alloy to respond to aging starting from both as built and solution annealed conditions has been also evaluated. A good response to direct aging (directly from as built condition) was demonstrated, featuring yield strength and ultimate tensile strength of 402 and 449 MPa, respectively, and hardness of 174 HV after optimized aging at 165 (cid:1)C for 2 h.
关键词： Differential scanning calorimetry,Metal additive manufacturing,Mechanical properties,Synchrotron X-ray diffraction,High strength Al alloy
更新于2025-11-21 11:18:25
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Interfacial structure of SrZr <sub/><i>x</i> </sub> Ti <sub/>1?</sub><sub/><i>x</i> </sub> O <sub/>3</sub> films on Ge
摘要： The interfacial structure of SrZrxTi1?xO3 films grown on semiconducting Ge substrates is investigated by synchrotron X-ray diffraction and first-principles density functional theory. By systematically tuning the Zr content x, the effects of bonding at the interface and epitaxial strain on the physical structure of the film can be distinguished. The interfacial perovskite layers are found to be polarized as a result of cation-anion ionic displacements perpendicular to the perovskite/semiconductor interface. We find a correlation between the observed buckling and valence band offsets at the SrZrxTi1?xO3/Ge interface. The trends in the theoretical valence band offsets as a function of Zr content for the polar structures are in agreement with reported X-ray photoelectron spectroscopy measurements. These results have important implications for the integration of functional oxide materials with established semiconductor based technologies.
关键词： synchrotron X-ray diffraction,density functional theory,valence band offsets,SrZrxTi1?xO3 films,Ge substrates,interfacial structure
更新于2025-09-23 15:21:01
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Persistence of the R3m Phase in Powder GeTe at High Pressure and High Temperature
摘要： As a phase-change material, rhombohedral GeTe (space group R3m) was believed to transform to the cubic rock-salt phase (B1) at 3–4 GPa, associated with the disappearance of a Peierls distortion. However, using a combination of synchrotron X-ray diffraction and theoretical calculations, we found that the R3m phase persists from ambient pressure up to pressures of about 15.8 GPa, in contrast to previous reports. Neither was the B1 phase observed in a heating X-ray powder diffraction experiment. The spurious transformation from R3m to B1 is caused by changes to the compression ratio of lattice parameters in the R3m phase under high pressure/temperature. These findings provide insight into transitions of phase-change materials, relevant to other materials undergoing displacive transitions under high pressure/temperature.
关键词： structural phase transitions,density-functional theory,high pressure,phase-change materials,high temperature,GeTe,synchrotron X-ray diffraction
更新于2025-09-23 15:21:01
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Diffusion of Oxygen and Nitrogen into Titanium under Laser Irradiation in Air
摘要： This paper examines the dynamic interactions between pure titanium and ambient air under transient laser processing conditions. The microstructures and composition distributions of the reaction products on and within the titanium samples are reported, which lead to the estimation of high-temperature diffusion coefficients for nitrogen and oxygen into the titanium substrate. In-situ synchrotron X-ray diffraction testing is conducted to reveal the high temperature reaction steps between titanium and air. The formation mechanisms of both titanium nitrides and titanium oxides are discussed.
关键词： titanium oxidation,titanium nitridation,synchrotron X-ray diffraction.,in-situ phase transformation,laser irradiation
更新于2025-09-12 10:27:22
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Exploring the Correlation between Subsurface Residual Stresses and Manufacturing Parameters in Laser Powder Bed Fused Ti-6Al-4V
摘要： Subsurface residual stresses (RS) were investigated in Ti-6Al-4V cuboid samples by means of X-ray synchrotron diffraction. The samples were manufactured by laser powder bed fusion (LPBF) applying different processing parameters, not commonly considered in open literature, in order to assess their influence on RS state. While investigating the effect of process parameters used for the calculation of volumetric energy density (such as laser velocity, laser power and hatch distance), we observed that an increase of energy density led to a decrease of RS, although not to the same extent for every parameter variation. Additionally, the effect of support structure, sample roughness and LPBF machine effects potentially coming from Ar flow were studied. We observed no influence of support structure on subsurface RS while the orientation with respect to Ar flow showed to have an impact on RS. We conclude recommending monitoring such parameters to improve part reliability and reproducibility.
关键词： additive manufacturing,Ti-6Al-4V,residual stress,synchrotron X-ray diffraction
更新于2025-09-11 14:15:04
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Titanium and nitrogen interactions under laser additive manufacturing conditions
摘要： To understand how to make bulk titanium parts or coatings with desired levels of titanium nitrides, this paper investigates the dynamic interactions between titanium and nitrogen under representative laser-based additive manufacturing (AM) conditions. Under a set of gas environments containing different concentrations of nitrogen, the titanium and nitrogen reaction products—formed under typical Selective Laser Melting (SLM) and Laser Engineered Net Shaping (LENS) AM scanning conditions—are examined for compositions, phases, and microstructures. In-situ synchrotron X-ray diffraction (SXRD) test is performed to reveal the high temperature reaction steps between titanium and nitrogen.
关键词： Synchrotron X-ray diffraction,in-situ phase transformation,Titanium nitridation,Laser melting
更新于2025-09-11 14:15:04
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Raman scattering of impact diamonds
摘要： We report the results of a study of the polycrystalline powder of the diamond-lonsdaleite from the Popigai crater (Siberia) using UV micro-Raman spectroscopy and high-resolution synchrotron X-ray diffraction. By subtracting two experimental Raman spectra of diamond-lonsdaleite samples with close amounts of diamond and lonsdaleite, we were able to identify the polytypic composition of impact diamonds in contrast to the method of X-ray diffraction. We have managed to get for the first time the spectrum of "pure" lonsdaleite. Its deconvolution has allowed us to identify all the three Raman - active vibrational modes E2g, A1g, and E1g whose positions agree well with the results of ab initio calculations.
关键词： Raman scattering,polytypic composition,impact diamonds,synchrotron X-ray diffraction,lonsdaleite,UV micro-Raman spectroscopy
更新于2025-09-10 09:29:36
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-II
摘要： The basic and the charge density wave (CDW) structures of the monoclinic NbS3-II polymorph were studied by synchrotron x-ray diffraction, ab initio calculations, simulation of electron diffraction patterns, and by atomic-resolution transmission electron and low-temperature scanning tunneling microscopies. It is con?rmed that the basic structure belongs to the space group P 21/m and is described with a unit cell, formed of four pairs of symmetry-related trigonal prismatic (TP) columns [a0 = 0.96509(8) nm, b0 = 0.33459(2) nm, c0 = 1.9850(1) nm, and β0 = 110.695(4)?]. The incommensurate components of the two CDWs, (cid:3)q1 = (0, 0.298, 0) and (cid:3)q2 = (0, 0.352, 0), are related as q1b + 2q2b ≈ 1. Both CDWs form their own modulation patterns with unit cells (am = 2a0, bm = b0/qjb, cm = c0, βm = β0) and are ordered along adjacent isosceles TP columns either pairwise or with both columns modulated by either the (cid:3)q1 or (cid:3)q2 CDW only. The CDWs are ordered according to one of the two possible modulation pattern space groups, Cm or C2/m. If considered as long-period commensurate, the entire modulated structure with both CDWs included is described within experimental error with an enlarged unit cell (a = 2a0, b = 37b0, c = c0, and β = β0) and with all atoms displaced from their average positions in accord with the speci?ed modulation pattern.
关键词： synchrotron x-ray diffraction,ab initio calculations,charge density wave,scanning tunneling microscopy,transmission electron microscopy,NbS3-II
更新于2025-09-09 09:28:46