Development and characterisation of Al-based alloys processed by PBF-LB/M

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Ongoing Challenges of Laser-Based Powder Bed Fusion Processing of Al Alloys and Potential Solutions from the Literature—A Review

Their high strength-to-weight ratio, good corrosion resistance and excellent thermal and electrical conductivity have exponentially increased the interest in aluminium alloys in the context of laser-based powder bed fusion (PBF-LB/M) production. Although Al-based alloys are the third most investigated category of alloys in the literature and the second most used in industry, their processing by PBF-LB/M is often hampered by their considerable solidification shrinkage, tendency to oxidation, high laser reflectivity and poor powder flowability. For these reasons, high-strength Al-based alloys traditionally processed by conventional procedures have often proved to be unprintable with additive technology, so the design and development of new tailored Al-based alloys for PBF-LB/M production is necessary. The aim of the present work is to explore all the challenges encountered before, during and after the PBF-LB/M processing of Al-based alloys, in order to critically analyse the solutions proposed in the literature and suggest new approaches for addressing unsolved problems. The analysis covers the critical aspects in the literature as well as industrial needs, industrial patents published to date and possible future developments in the additive market

Effect of Cu Content on the PBF-LB/M Processing of the Promising Al-Si-Cu-Mg Composition

Over the past few years, several studies have been conducted on the development of Al-Si-Cu-Mg alloys for PBF-LB/M processing. The attention gained by these systems can be attributed to their light weight and strength provided by a solid solution in the as-built state and by precipitation after heat treatment. However, published studies have kept the copper content below its solubility limit in the Al-Cu binary system under equilibrium conditions (5.65 wt%). The present study aims to explore Al-Si-Cu-Mg systems with high copper content, starting with the well-known AlSi10Cu4Mg system, moving towards AlSi10Cu8Mg, and arriving at AlCu20Si10Mg, a system never before processed with PBF-LB/M. Through the SST approach, the production of bulk samples, advanced microstructural characterization by SEM and FESEM analysis, phase identification by XRD analysis, and preliminary investigation of the mechanical properties through Vickers micro indentations, the effects of copper quantities on the processability, microstructural properties, and mechanical behavior of these compositions were investigated. The obtained results demonstrated the benefits of the supersaturated solid solution and the fine precipitation resulting from the addition of high Cu contents. In particular, the AlCu20Si10Mg system showed a very distinctive microstructure and unprecedented microhardness values

The Influence of Processing Parameters on the Al-Mn Enriched Nano-Precipitates Formation in a Novel Al-Mn-Cr-Zr Alloy Tailored for Power Bed Fusion-Laser Beam Process

Among the recently developed compositions tailored for the power bed fusion-laser beam process (PBF-LB), the novel Al-Mn-Cr-Zr alloy stands out. This composition exploits high solid solution strengthening, achieving a high hardness value in the as-built condition. The produced samples are inherently crack-free and have a good level of densification (similar to 99.5%). The goal of this study is to investigate how this quaternary system is affected by the laser power while retaining a similar volumetric energy density. A comparison between the microstructural features and the mechanical performance was performed on a set of samples processed with power values ranging from 100 to 170 W. Microstructural features were investigated through optical microscopy, Electron Back Scattered Diffraction (EBSD) investigation and feature analysis using advanced microscopy to examine the amount, distribution, and shape of precipitates in the different process conditions. Although the quantitative feature analysis permitted analysis of more than 60 k precipitates for each power condition, all samples demonstrated a low level of precipitation (below 0.3%) with nanometric size (around 75 nm). The mechanical performances of this quaternary system as a function of the laser power value were evaluated with a microhardness test, recording very similar values for the different process conditions with a mean value of approximately 104 HV. The results suggested a very stable system over the tested range of process parameters. In addition, considering the low level of precipitation of nanometric phases enriched in Al-Mn, a supersaturated state could be established in each process condition

Low-Power Laser Powder Bed Fusion Processing of Scalmalloy®

Among recently developed high-strength and lightweight alloys, the high-performance Scalmalloy(®) certainly stands out for laser powder bed fusion (LPBF) production. The primary goal of this study was to optimize the Scalmalloy(®) LPBF process parameters by setting power values suitable for the use of lab-scale machines. Despite that these LPBF machines are commonly characterized by considerably lower maximum power values (around 100 W) compared to industrial-scale machines (up to 480 W), they are widely used when quick setup and short processing time are needed and a limited amount of powder is available. In order to obtain the optimal process parameters, the influence of volumetric energy density (VED) on the sample porosity, microstructure and mechanical properties was accurately studied. The obtained results reveal the stability of the microstructural and mechanical behaviour of the alloy for VEDs higher than 175 Jmm(−3). In this way, an energy-and-time-saving choice at low VEDs can be taken for the LPBF production of Scalmalloy(®). After identifying the low-power optimized process parameters, the effects of the heat treatment on the microstructural and mechanical properties were investigated. The results prove that low-VED heat-treated samples produced with an LPBF lab-scale machine can achieve outstanding mechanical performance compared with the results of energy-intensive industrial production

Palliative care in the emergency department as seen by providers and users: a qualitative study

Background Much effort has been made to explore how patients with advanced chronic illness and their families experience care when they attend the Emergency Department, and many studies have investigated how healthcare professionals perceive Palliative Care provision in the Emergency Department. Various models exist, but nonetheless incorporating palliative care into the Emergency Department remains challenging. Considering both healthcare professionals\u2019 and users\u2019 perspective on problems encountered in delivering and receiving appropriate palliative care within this context may provide important insight into meaningful targets for improvements in quality of care. Accordingly, this study aims at exploring issues in delivering palliative care in the Emergency Department from the perspective of both providers and users, as part of a larger project on the development and implementation of a quality improvement program in Italian Emergency Departments. Methods A qualitative study involving focus group interviews with Emergency Department professionals and semi-structured interviews with patients with palliative care needs in the Emergency Department and their relatives was conducted. Both datasets were analyzed using Thematic Analysis. Results Twenty-one healthcare professionals, 6 patients and 5 relatives participated in this study. Five themes were identified: 1) shared priorities in Emergency Department among healthcare professionals and patients, 2) the information provided by healthcare professionals and that desired by relatives, 3) perception of environment and time, 4) limitations and barriers to the continuity of care, and 5) the contrasting interpretations of giving and receiving palliative care. Conclusions This study provides insights into targets for changes in Italian Emergency Departments. Room for improvement relates to training for healthcare professionals on palliative care, the development of a shared care pathway for patients with palliative care needs, and the optimization of Emergency Department environment. These targets will be the basis for the development of a quality improvement program in Italian Emergency Departments

Covid-19 and the role of smoking: the protocol of the multicentric prospective study COSMO-IT (COvid19 and SMOking in ITaly).

The emergency caused by Covid-19 pandemic raised interest in studying lifestyles and comorbidities as important determinants of poor Covid-19 prognosis. Data on tobacco smoking, alcohol consumption and obesity are still limited, while no data are available on the role of e-cigarettes and heated tobacco products (HTP). To clarify the role of tobacco smoking and other lifestyle habits on COVID-19 severity and progression, we designed a longitudinal observational study titled COvid19 and SMOking in ITaly (COSMO-IT). About 30 Italian hospitals in North, Centre and South of Italy joined the study. Its main aims are: 1) to quantify the role of tobacco smoking and smoking cessation on the severity and progression of COVID-19 in hospitalized patients; 2) to compare smoking prevalence and severity of the disease in relation to smoking in hospitalized COVID-19 patients versus patients treated at home; 3) to quantify the association between other lifestyle factors, such as e-cigarette and HTP use, alcohol and obesity and the risk of unfavourable COVID-19 outcomes. Socio-demographic, lifestyle and medical history information will be gathered for around 3000 hospitalized and 700-1000 home-isolated, laboratory-confirmed, COVID-19 patients. Given the current absence of a vaccine against SARS-COV-2 and the lack of a specific treatment for -COVID-19, prevention strategies are of extreme importance. This project, designed to highly contribute to the international scientific debate on the role of avoidable lifestyle habits on COVID-19 severity, will provide valuable epidemiological data in order to support important recommendations to prevent COVID-19 incidence, progression and mortality

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men