Aging Behaviour of a 12.2Cr-10Ni-1Mo-1Ti-0.6Al Precipitation-Hardening Stainless Steel Manufactured via Laser Powder Bed Fusion

The combination of precipitation-hardening stainless steels (PH-SS) and laser powder bed fusion (LPBF) enables the manufacturing of tools for plastic injection moulding with optimised geometry and conformal cooling channels, with potential benefits in terms of productivity, part quality, and tool duration. Moreover, the suitability of LPBF-manufactured PH-SS in the as-built (AB) condition to be age-hardened through a direct aging (DA) treatment enables a great heat treatment simplification with respect to the traditional solution annealing and aging treatment (SA). However, plastic injection moulding tools experience severe thermal cycles during their service, which can lead to over-aging of PH-SS and thus shorten tool life. Therefore, proper thermal stability is required to ensure adequate tool life and reliability. The aim of the present work is to investigate the aging and over-aging behaviour of a commercially available PH-SS (AMPO M789) manufactured by LPBF in the AB condition and after a solution-annealing treatment in order to evaluate the effect of the heat treatment condition on the microstructure and the aging and over-aging response, aiming at assessing its feasibility for plastic injection moulding applications. The AB microstructure features melt pool borders, oriented martensite grains, and a cellular solidification sub-structure, and was retained during aging and over-aging. On the other hand, a homogeneous and isotropic martensite structure was present after solution annealing and quenching, with no melt pool borders, cellular structure, or oriented grains. The results indicate no significant difference between AB and solution-annealed and quenched specimens in terms of aging and over-aging behaviour and peak hardness (in the range 580–600 HV), despite the considerably different microstructures. Over-aging was attributed to both the coarsening of strengthening precipitates and martensite-to-austenite reversion (up to ~11 vol.%) upon prolonged exposure to high temperature. Based on the results, guidelines to aid the selection of the most suitable heat treatment procedure are proposed

Tensile behaviour of a hot work tool steel manufactured via Laser Powder Bed Fusion: effect of an innovative high pressure heat treatment

The combination of outstanding mechanical strength of tool steels and design freedom ensured by Additive Manufacturing (AM) processes is of a great interest for automotive applications. However, AM techniques produce peculiar defects, which affect the resulting mechanical behavior. For this reason, safety critical AM components are often subjected to hot isostatic pressing (HIP) to heal process defects. At the same time, tool steels require a proper quenching and tempering (QT) heat treatment to achieve high hardness and strength. In the present work, the effect of an innovative high pressure heat treatment (HPHT) on the tensile properties of a hot work tool steel produced via Laser Powder Bed Fusion (LPBF) was investigated. LPBF samples were subjected to two post-process heat treatments: a conventional quenching and tempering heat treatment performed in vacuum (CHT), and an innovative HPHT combining HIP e QT in a single step, to heal LPBF defects and obtain high mechanical properties. HPHT featured the same quenching and tempering cycle of CHT but it was performed under high pressure in a HIP furnace and with longer austenitizing time to promote defect closure. Tensile tests indicated no significant effect on proof and tensile strength for HPHT compared to CHT, but a significant reduction of elongation after fracture. Fractographic analyses and fracture mechanics calculations indicated that both CHT and HPHT specimens failed via crack propagation from large LPBF defects when the stress intensity factor reached the material fracture toughness. Fractographic analyses indicated an incomplete defect closure during HPHT due to the presence of an oxide film on the inner surface of defects, thus justifying the same failure mechanism and strength of CHT samples. Instead, it was proposed that the reduced elongation could arise from coarsened grains due to the longer austenitizing

Room- and High-Temperature Fatigue Strength of the T5 and Rapid T6 Heat-Treated AlSi10Mg Alloy Produced by Laser-Based Powder Bed Fusion

The AlSi10Mg alloy produced by laser-based powder bed fusion (L-PBF) is widely used to produce high-value-added structural parts subjected to cyclic mechanical loads at high temperatures. The paper aims to widen the knowledge of the room- and high-temperature (200 ◦C) fatigue behavior of the L-PBF AlSi10Mg alloy by analyzing the fully reversed rotating bending test results on mechanically polished specimens. Two heat-treated conditions are analyzed: T5 (direct artificial aging: 4 h at 160 ◦C) and novel T6R (rapid solution: 10 min at 510 ◦C, artificial aging: 6 h at 160 ◦C). The study highlights that (i) the T6R alloy is characterized by higher fatigue strength at room (108 MPa) and high temperatures (92 MPa) than the T5 alloy (92 and 78 MPa, respectively); (ii) thermal exposure at 200 ◦C up to 17 h does not introduce macroscopical microstructural variation; (iii) fracture surfaces of the room- and high-temperature-tested specimens show comparable crack initiation, mostly from sub-superficial gas and keyhole pores, and failure propagation mechanisms. In conclusion, the L-PBF AlSi10Mg alloy offers good cyclic mechanical performances under various operating conditions, especially for the T6R alloy, and could be considered for structural components operating at temperatures up to 200 °

The Energy Improvement of School Buildings: Analysis and Proposals for Action

The objective of this research is to identify a tool of analysis applicable to school buildings that, through simple input information, can make immediate assessment reduction of energy consumption for heating and associated reduction of CO2emission, as a result of improvements.The definition of a methodology of analysis allows to evaluate preliminarily the energy performance of the whole school building identifying the most problematic buildings and dividing into groups based on the construction and geometry. In the first phase all buildings have been filed through information obtained from survey and documentation of archives, then two analyses were performed to compare the energy performance of the whole sample.For the initial analysis it was applied a methodology proposed by ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic development) and designed specifically for school buildings; in the second analysis it was calculated the energy performance index for winter heating and compared with the appropriate limit value.Subsequently a sample of buildings was well selectedafter splitting the school building into homogeneous groups. The buildings have been translated into a mathematical model of the building system calibrated on actual energy consumption and dynamic conditions were simulated in order to accurately quantify the impact of the various proposed actions.The results of all combinations of intervention, obtained from the latter analysis, have been used to develop a tool that identified the type of building and construction technology in order to estimate the immediate reduction of consumption and the CO2emitted.The methodology was applied to the school building of the municipality of Castelfranco Veneto, simulating two scenarios: the first plan to interventions under the PAES (Action Plan for Sustainable Energy) for public buildings while the second considers the possibility of performing all the improvements recommended by the instrument in relation to the entire academic heritage of the city

Direct artificial aging of the PBF-LB AlSi10Mg alloy designed to enhance the trade-off between strength and residual stress relief

The AlSi10Mg alloy is one of the most studied alloys processed by the Powder Bed Fusion-Laser Beam (PBF-LB). Many already published works focus on post-process heat treatments to reduce residual stress or improve me- chanical strength. Instead, the present study aims to identify direct artificial aging (AA) heat treatment able to optimize both aspects, thus enhancing the trade-off between strengthening and residual stress relief for the PBF- LB AlSi10Mg alloy produced using a no-heated platform. Higher temperatures (190–240 ◦C) than those typically used in AA heat treatment were selected based on thermal analysis to benefit both residual stress relief and precipitation of reinforcing phases from the supersaturated solid solution of the metastable as-built alloy. The effects of AA heat treatment on mechanical properties (i.e. hardness) and residual stress were evaluated by plotting aging curves and by XRD and Raman analyses and demonstrated that different trade-offs between strengthening and stress relief can be achieved by tuning heat treatment parameters (temperature and time). In particular, the exposure at the lowest temperature (190 ◦C) induced a partial decrease in residual stress and a slight increase in hardness. By increasing heat treatment temperature and soaking time, the relief was more significant, whilst the decrease in hardness was rather limited. The results are supported by the microstructural changes observed on the samples due to the different heat treatment conditions applied and show the feasibility of designing an AA heat treatment for the PBF-LB AlSi10Mg alloy capable of satisfying the mechanical response required by the final application

Relationship between microstructure, mechanical and magnetic properties of pure iron produced by laser powder bed fusion (L-PBF) in the as-built and stress relieved conditions

In the present work, the mechanical and magnetic properties of pure iron manufactured by laser-powder bed fusion (L-PBF) were investigated both in the as-built (AB) and stress relieved (HT) conditions, with the aim of elucidating their relationship with the microstructure and evaluating whether and to what extent it can be suitable for industrial applications. The L-PBF process was optimized to obtain high density, crack-free components. Specimens for microstructural analyses, tensile and magnetic tests were manufactured under the optimized conditions and tested both in the as-built and annealed (850 degrees C for 1 h, to relieve the residual stresses) conditions. Tensile tests showed high tensile strength in both AB and HT conditions (larger than those of conventionally produced pure iron), with higher ductility and lower strength after stress relieving. The magnetic study indicated a not optimal magnetic softness although the heat treatment enhanced the permeability and reduced the coercivity with respect to the as-built condition. The high mechanical strength and low magnetic softness came from the very fine grain size (about 5 mu m) of L-PBF pure iron. Instead, the improvement of magnetic softness and ductility after heat treatment was attributed to the possible reduction of dislocation density and consequent stress relief. The results indicated the possibility to achieve a considerably high mechanical strength, in pure iron manufactured by L-PBF, although the fine grain size limits its magnetic softness

Heterozygous missense variants of SPTBN2 are a frequent cause of congenital cerebellar ataxia

Heterozygous missense variants in the SPTBN2 gene, encoding the non-erythrocytic beta spectrin 2 subunit (beta-III spectrin), have been identified in autosomal dominant spinocerebellar ataxia type 5 (SCA5), a rare adult-onset neurodegenerative disorder characterized by progressive cerebellar ataxia, whereas homozygous loss of function variants in SPTBN2 have been associated with early onset cerebellar ataxia and global developmental delay (SCAR14). Recently, heterozygous SPTBN2 missense variants have been identified in a few patients with an early-onset ataxic phenotype. We report five patients with non-progressive congenital ataxia and psychomotor delay, 4/5 harboring novel heterozygous missense variants in SPTBN2 and one patient with compound heterozygous SPTBN2 variants. With an overall prevalence of 5% in our cohort of unrelated patients screened by targeted next generation sequencing (NGS) for congenital or early-onset cerebellar ataxia, this study indicates that both dominant and recessive mutations of SPTBN2 together with CACNA1A and ITPR1, are a frequent cause of early-onset/congenital non-progressive ataxia and that their screening should be implemented in this subgroup of disorders

Estudo de fibra a partir de dejetos da cana de açúcar para desenvolvimento de novo material compósito sustentável / Study of fiber from sugar cane waste for development of new sustainable composite material

Uma grande evolução tecnológica ao longo dos anos permitiu que o homem utilizasse de conhecimentos técnicos e empíricos a seu favor, com o intuito de moldar o meio a sua volta, melhorando sua vivência, conforto, comodidade e praticidade. No âmbito dos materiais, vem sendo recorrente a maior exigência de evolução, tendo em vista atender maiores necessidades, especificações e exigências a serem cumpridas. Define-se por um material ideal aquele que atenda às necessidades do usuário, no que diz respeito a aplicabilidade e custo benéfico e do meio ambiente, no que tange a poluição, e recursos naturais. De acordo com a SIAMIG (Associação das Indústrias Sucroenergéticas de Minas Gerais), em 2021 a produção de cana-de-açúcar chegou a 70.565.766 toneladas. Diante de todo este montante produzido parte do insumo final é descartado de forma incorreta. O presente trabalho tem por objetivo apresentar uma nova metodologia de uso e aplicabilidade ao dejeto da cana a partir do desenvolvimento de um novo material compósito cuja base é o bagaço. Com o bagaço da cana-de-açúcar devidamente seco, foram selecionadas duas diferentes granulações da fibra e elaborados os materiais compósitos com resina epóxi, os quais foram submetidos a testes de compressão para análise de propriedades mecânicas

Clinico-Genetic, Imaging and Molecular Delineation of COQ8A-Ataxia: A Multicenter Study of 59 Patients.

OBJECTIVE: To foster trial-readiness of coenzyme Q8A (COQ8A)-ataxia, we map the clinicogenetic, molecular, and neuroimaging spectrum of COQ8A-ataxia in a large worldwide cohort, and provide first progression data, including treatment response to coenzyme Q10 (CoQ10). METHODS: Cross-modal analysis of a multicenter cohort of 59 COQ8A patients, including genotype-phenotype correlations, 3D-protein modeling, in vitro mutation analyses, magnetic resonance imaging (MRI) markers, disease progression, and CoQ10 response data. RESULTS: Fifty-nine patients (39 novel) with 44 pathogenic COQ8A variants (18 novel) were identified. Missense variants demonstrated a pleiotropic range of detrimental effects upon protein modeling and in vitro analysis of purified variants. COQ8A-ataxia presented as variable multisystemic, early-onset cerebellar ataxia, with complicating features ranging from epilepsy (32%) and cognitive impairment (49%) to exercise intolerance (25%) and hyperkinetic movement disorders (41%), including dystonia and myoclonus as presenting symptoms. Multisystemic involvement was more prevalent in missense than biallelic loss-of-function variants (82-93% vs 53%; p = 0.029). Cerebellar atrophy was universal on MRI (100%), with cerebral atrophy or dentate and pontine T2 hyperintensities observed in 28%. Cross-sectional (n = 34) and longitudinal (n = 7) assessments consistently indicated mild-to-moderate progression of ataxia (SARA: 0.45/year). CoQ10 treatment led to improvement by clinical report in 14 of 30 patients, and by quantitative longitudinal assessments in 8 of 11 patients (SARA: -0.81/year). Explorative sample size calculations indicate that ≥48 patients per arm may suffice to demonstrate efficacy for interventions that reduce progression by 50%. INTERPRETATION: This study provides a deeper understanding of the disease, and paves the way toward large-scale natural history studies and treatment trials in COQ8A-ataxia. ANN NEUROL 2020;88:251-263