The Influence of Iron in Minimizing the Microstructural Anisotropy of Ti-6Al-4V Produced by Laser Powder-Bed Fusion

There remains a significant challenge in adapting alloys for metal based Additive Manufacturing (AM). Adjusting alloy composition to suit the process, particularly under regimes close to industrial practice, is therefore a potential solution. With the aim of designing new Ti-based alloys of superior mechanical properties for use in laser powder-bed fusion, this research investigates the influence of Fe on the microstructural development of Ti-6Al-4V. The operating mechanisms that govern the relationship between the alloy composition (and Fe in particular) and the grain size are explored using EBSD, TEM and in-situ high-energy synchrotron X-ray diffraction. It was found that Fe additions up to 3 wt% lead to a progressive refinement of the microstructure. By exploiting the cooling rates of AM and suitable amount of Fe additions, it was possible to obtain microstructures that can be optimized by heat treatment without obvious precipitation of detrimental brittle phases. The resulting microstructure consists of a desirable and well studied fully laminar α+ β structure in refined prior-β grains

Genomic Characterization of Interspecific Hybrids and an Admixture Population Derived from Panicum amarum × \u3cem\u3eP. virgatum\u3c/em\u3e

Switchgrass (Panicum virgatum L.) and its relatives are regarded as top bioenergy crop candidates; however, one critical barrier is the introduction of useful genetic diversity and the development of new cultivars and hybrids. Combining genomes from related cultivars and species provides an opportunity to introduce new traits. In switchgrass, a breeding advantage would be achieved by combining the genomes of intervarietal ecotypes or interspecific hybrids. The recovery of wide crosses, however, is often tedious and may involve complicated embryo rescue and numerous backcrosses. Here, we demonstrate a straightforward approach to wide crosses involving the use of a selectable transgene for recovery of interspecific [P. virgatum cv. Alamo × Panicum amarum Ell. var amarulum or Atlantic Coastal Panicgrass (ACP)] F1 hybrids followed by backcrossing to generate a nontransgenic admixture population. A nontransgenic herbicide-sensitive (HbS) admixture population of 83 F1BC1 progeny was analyzed by genotyping-by-sequencing (GBS) to characterize local ancestry, parental contribution, and patterns of recombination. These results demonstrate a widely applicable breeding strategy that makes use of transgenic selectable resistance to identify and recover true hybrids

Domain-specific risk assessment using integrated simulation: A case study of an onshore wind project

Although many quantitative risk assessment models have been proposed in literature, their use in construction practice remain limited due to a lack of domain-specific models, tools, and application examples. This is especially true in wind farm construction, where the state-of-the-art integrated Monte Carlo simulation and critical path method (MCS-CPM) risk assessment approach has yet to be demonstrated. The present case study is the first reported application of the MCS-CPM method for risk assessment in wind farm construction and is the first case study to consider correlations between cost and schedule impacts of risk factors using copulas. MCS-CPM provided reasonable risk assessment results for a wind farm project, and its use in practice is recommended. Aimed at facilitating the practical application of quantitative risk assessment methods, this case study provides a much-needed analytical generalization of MCS-CPM, offering application examples, discussion of expected results, and recommendations to wind farm construction practitioners

The influence of iron in minimizing the microstructural anisotropy of Ti-6Al-4V produced by laser powder-bed fusion

There remains a significant challenge in adapting alloys for metal-based additive manufacturing (AM). Adjusting alloy composition to suit the process, particularly under regimes close to industrial practice, is therefore a potential solution. With the aim of designing new Ti-based alloys of superior mechanical properties for use in laser powder-bed fusion, this research investigates the influence of Fe on the microstructural development of Ti-6Al-4V. The operating mechanisms that govern the relationship between the alloy composition (and Fe in particular) and the grain size are explored using EBSD, TEM, and in situ high-energy synchrotron X-ray diffraction. It was found that Fe additions up to 3 wt pct lead to a progressive refinement of the microstructure. By exploiting the cooling rates of AM and suitable amount of Fe additions, it was possible to obtain microstructures that can be optimized by heat treatment without obvious precipitation of detrimental brittle phases. The resulting microstructure consists of a desirable and well-studied fully laminar α + β structure in refined prior-β grains

Generation of graded porous structures by control of process parameters in the selective laser melting of a fixed ratio salt-metal feedstock

The demonstration of salt dissolution incorporated within laser powder-bed fusion fabrication processes has allowed the creation of complex porous structures without the need for sophisticated design algorithms. This serves to simplify the process, for porous structure creation in powder-bed fabrication techniques, creating a new opportunity for the realisation of optimised structures. A new methodology is presented here in which modulation of the energy density while using a single feedstock material enables three-dimensional control of porosity, ranging from 20% to 49%. Through structured experimentation, the response of the material to varying the process parameters in selective laser melting is evaluated and nested structures of distinct densities and morphologies are created. Correlation of the process parameters with modulus and ultimate compressive stress are established. A simple-assembly algorithm was used to generate complex parts consisting of locally assigned porosities having characteristic properties

A comparison of Ti-6Al-4V in-situ alloying in Selective Laser Melting using simply-mixed and satellited powder blend feedstocks

In-situ alloying within laser powder-bed fusion, specifically Selective Laser Melting (SLM), has been investigated for the formulation of novel alloys from elemental powders to extend the benefits offered by these technologies. Inadequate preparation of the powder feedstock prior to in-situ alloying can yield inhomogeneous microstructures, often deteriorating the mechanical performance of the deposited parts. The present work was designed to assess the use of the ‘satelliting’ method to create powder feedstocks for in-situ laser powder-bed fusion. The research was carried out on Ti-6Al-4V. Ti-6Al-4V feedstocks obtained by mixing or satelliting elemental powders were investigated and compared to a reference pre-alloyed material. The processability of the different feedstocks was assessed by comparing the microstructure of the deposits originating from the different powder blends. Results show that the powder percolation and particle size distribution of the feedstocks translate in deposited microstructures exhibiting different porosity, elemental segregation, and average grain size, revealing the impact of the powder blend characteristics on the laser energy absorbance and solidification of the alloy. This study provides fundamental insights of how to formulate powder feedstock and aims to support future research activities on the design and development of new alloys for use in powder-based additive manufacturing

Stable large area drop-on-demand deposition of a conductive polymer ink for 3D-printed electronics, enabled by bio-renewable co-solvents

Development of conductive polymer ink formulations with reliable jetting stability and physical properties could offer sustainable routes for scaling-up the 3D-printing of electronics. We report a new poly(3,4-ethylenedioxythiophene) polystyrene sulphonate (PEDOT:PSS) ink formulation, InkCG, using bio-renewable solvents dihydrolevoglucosenone (cyrene) and glycerol carbonate (GC) as an alternative to commonly used dimethyl sulfoxide (DMSO). These green organic co-solvents enhance jetting reliability and long-term stability of the ink and improve electrical properties of the deposited PEDOT:PSS layers, compared to the commonly used DMSO-containing ink formulations. We achieve large-area and high-fidelity electronic devices (array of 140 devices) with reproducible electrical performance through inkjet-based 3D printing. Enhanced performance stability is observed under cyclic bending, thermal annealing, UV or IR exposure, offering exciting opportunities for sustainable deposition of PEDOT:PSS for large-area 3D printing and its exploitation in heterostructures and flexible electronics

Impact of newborn screening for SCID on the management of congenital athymia

BACKGROUND: Newborn screening (NBS) programmes for severe combined immunodeficiency (SCID) facilitate early SCID diagnosis and promote early treatment with haematopoietic stem cell transplantation, resulting in improved clinical outcomes. Infants with congenital athymia are also identified through NBS due to severe T-cell lymphopaenia. With the expanding introduction of NBS programmes, referrals of athymic patients for treatment with thymus transplantation have recently increased at Great Ormond Street Hospital (GOSH), London, United Kingdom. OBJECTIVE: We studied the impact of NBS on timely diagnosis and treatment of athymic infants with thymus transplantation at GOSH. METHODS: We compared the age at referral and complications between athymic infants diagnosed after clinical presentation (N=25) and patients identified through NBS (N=19), referred for thymus transplantation at GOSH between 10/2019 and 02/2023. We assessed whether age at time of treatment influences thymic output at 6 and 12 months after transplantation. RESULTS: Infants referred after NBS identification were significantly younger and had less complications, in particular less infections. All deaths occurred in the non-NBS group, including six patients before and two after thymus transplantation because of pre-existing infections. In the absence of significant co-morbidities or diagnostic uncertainties, timely treatment was more frequently achieved after NBS. Treatment at <4 months of age was associated with higher thymic output at 6- and 12-months post-transplantation. CONCLUSION: NBS contributes to earlier recognition of congenital athymia, promoting referral of athymic patients for thymus transplantation prior to acquiring infections or other complications, and facilitating treatment at younger age, thus playing an important role in improving their outcomes

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy