Characterisation of abrasive water-jet process for drilling titanium and carbon fibre reinforced polymer stacks

Experiments were carried out in stacks composed of titanium and carbon-fibre-reinforced polymer (CFRP) with the aim to investigate the effect of water-jet process variables on drilled diameter and surface condition. A design of experiments (DoE) approach was taken, considering variables such as water pressure, traverse rate, abrasive mass flow and stack set-up. Two different set-ups were investigated: CFRP over titanium (CFRP/Ti) and vice versa (Ti/CFRP). The experimental variables were related to taper ratio, surface roughness of the hole bore, hole quality and surface condition. Statistical analysis was carried out in order to develop mathematical models which include process variables interactions and quadratic terms. This led to models with high correlation and prediction power; which allow a better understanding of the process and can form the base for further process optimisation. The models were validated with additional experiments and showed good agreement with the water-jet system. The results showed that set-up and its interaction with other process variables has a strong influence on the performance of the abrasive water-jet system for producing holes in hybrid materials

A preparative mass spectrometer to deposit intact large native protein complexes

Electrospray ion-beam deposition (ES-IBD) is a versatile tool to study the structure and reactivity of molecules from small metal clusters to large protein assemblies. It brings molecules gently into the gas phase, where they can be accurately manipulated and purified, followed by controlled deposition onto various substrates. In combination with imaging techniques, direct structural information on well-defined molecules can be obtained, which is essential to test and interpret results from indirect mass spectrometry techniques. To date, ion-beam deposition experiments are limited to a small number of custom instruments worldwide, and there are no commercial alternatives. Here we present a module that adds ion-beam deposition capabilities to a popular commercial MS platform (Thermo Scientific Q Exactive UHMR mass spectrometer). This combination significantly reduces the overhead associated with custom instruments, while benefiting from established high performance and reliability. We present current performance characteristics including beam intensity, landing-energy control, and deposition spot size for a broad range of molecules. In combination with atomic force microscopy (AFM) and transmission electron microscopy (TEM), we distinguish near-native from unfolded proteins and show retention of the native shape of protein assemblies after dehydration and deposition. Further, we use an enzymatic assay to quantify the activity of a noncovalent protein complex after deposition on a dry surface. Together, these results not only indicate a great potential of ES-IBD for applications in structural biology, but also outline the challenges that need to be solved for it to reach its full potential

A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation

The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected alpha-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design. Recent demands to design alloys in a more sustainable way have discouraged the use of critical elements that are rare. Here the authors demonstrate a segregation-based strategy to produce a sustainable steel, Fe18Mn3Ti, without critical elements while achieving ultrahigh-strength

Interface characteristics in an α+β titanium alloy

The α/β interface in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) was investigated via center of symmetry analysis, both as-grown and after 10% cold work. Semicoherent interface steps are observed at a spacing of 4.5±1.13 atoms in the as-grown condition, in good agreement with theory. Lattice accommodation is observed, with elongation along [1210]α and contraction along [1010]α. Deformed α exhibited larger, less coherent steps with slip bands lying in {110}β. This indicates dislocation pile-up at the grain boundary, a precursor to globularization during heat treatment. Atom probe tomography measurements of secondary α plates in the fully heat-treated condition showed a Zr excess at the interface, which was localized into regular structures indicative of Zr association with interface defects, such as dislocations. Such chemo-mechanical stabilization of the interface defects would both inhibit plate growth during elevated temperature service and the interaction of interface defects with gliding dislocations during deformation

New U-Pb ages for syn-orogenic magmatism in the SW sector of the Ossa Morena Zone (Portugal)

The Ossa-Morena Zone (OMZ) is a major geotectonic unit within the Iberian Massif (which constitutes an important segment of the European Variscan Belt) and one of its distinguishing features is the presence of a noteworthy compositional diversity of plutonic rocks. In the SW sector of the OMZ, the tonalitic Hospitais intrusion (located to the W of Montemor-o-Novo) is considered a typical example of syn-orogenic magmatism, taking into account that both the long axis of the plutonic body and its mesoscopic foliation are oriented parallel to the Variscan WNW-ESE orientation. Another relevant feature of the Hospitais intrusion is the occurrence of mafic microgranular enclaves within the main tonalite. In previous works (Moita et al., 2005; Moita, 2007), it was proposed that: (1) the Hospitais intrusion is part of a calc-alkaline suite, represented by a large number of intrusions in this sector of the OMZ, ranging from gabbros to granites; (2) the enclaves are co-genetic to the host tonalite in the Hospitais pluton. In this study, zircon populations from one sample of the main tonalite (MM-17) and one sample of the associated enclave (MM-17E) were analysed by ID-TIMS for U-Pb geochronology. In each sample, three fractions of nice glassy, euhedral, long prismatic and inclusion free crystals were analysed. The results from the three fractions of MM-17 yielded a 206Pb/238U age of 337.0 ± 2.0 Ma. Similarly, for the enclave MM-17E a 206Pb/238U zircon age of 336.5 ± 0.47 Ma was obtained. These identical ages, within error, are in agreement with a common parental magma for the tonalite and mafic granular enclaves. Similar U-Pb ages have been reported in previous works for plutonic and metamorphic events in this region (e.g.: Pereira et al., 2009; Antunes et al., 2011). Furthermore, also in the SW sector of the OMZ, palaeontological studies (Pereira et al., 2006; Machado & Hladil, 2010) carried out in Carboniferous sedimentary basins containing intercalated calc-alkaline volcanics (Santos et al., 1987; Chichorro, 2006) have shown that they are mainly of Visean age. Therefore, magmatism displaying features typical of continental arc setting seems to have been active in this part of the OMZ during the Lower Carboniferous times

Towards engineering the perfect defect in high-performing permanent magnets

Permanent magnets draw their properties from a complex interplay, across multiple length scales, of the composition and distribution of their constituting phases, that act as building blocks, each with their associated intrinsic properties. Gaining a fundamental understanding of these interactions is hence key to decipher the origins of their magnetic performance and facilitate the engineering of better-performing magnets, through unlocking the design of the "perfect defects" for ultimate pinning of magnetic domains. Here, we deployed advanced multiscale microscopy and microanalysis on a bulk Sm2(CoFeCuZr)17 pinning-type high-performance magnet with outstanding thermal and chemical stability. Making use of regions with different chemical compositions, we showcase how both a change in the composition and distribution of copper, along with the atomic arrangements enforce the pinning of magnetic domains, as imaged by nanoscale magnetic induction mapping. Micromagnetic simulations bridge the scales to provide an understanding of how these peculiarities of micro- and nanostructure change the hard magnetic behaviour of Sm2(CoFeCuZr)17 magnets. Unveiling the origins of the reduced coercivity allows us to propose an atomic-scale defect and chemistry manipulation strategy to define ways toward future hard magnets

Crater formation by fast ions: comparison of experiment with Molecular Dynamics simulations

An incident fast ion in the electronic stopping regime produces a track of excitations which can lead to particle ejection and cratering. Molecular Dynamics simulations of the evolution of the deposited energy were used to study the resulting crater morphology as a function of the excitation density in a cylindrical track for large angle of incidence with respect to the surface normal. Surprisingly, the overall behavior is shown to be similar to that seen in the experimental data for crater formation in polymers. However, the simulations give greater insight into the cratering process. The threshold for crater formation occurs when the excitation density approaches the cohesive energy density, and a crater rim is formed at about six times that energy density. The crater length scales roughly as the square root of the electronic stopping power, and the crater width and depth seem to saturate for the largest energy densities considered here. The number of ejected particles, the sputtering yield, is shown to be much smaller than simple estimates based on crater size unless the full crater morphology is considered. Therefore, crater size can not easily be used to estimate the sputtering yield.Comment: LaTeX, 7 pages, 5 EPS figures. For related figures/movies, see: http://dirac.ms.virginia.edu/~emb3t/craters/craters.html New version uploaded 5/16/01, with minor text changes + new figure