Effect of alloying elements on the Sr modification of Al-Si cast alloys

Strontium-based modifier alloys are commonly adopted to modify the eutectic silicon in aluminum-silicon casting alloys by changing the silicon shape from an acicular to a spherical form. Usually, the modifier alloy necessary to properly change the silicon shape depends on the silicon content, but the alloying elements’ content may have an influence. The AlSr10 master alloy’s modifying effect was studied on four Al-Si alloys through the characterization of microstructural and mechanical properties (micro-hardness and impact tests). The experimental results obtained on gravity cast samples highlighted the interdependence in the modification of silicon between the Si content and the alloying elements. After modification, a higher microstructural homogeneity characterized by a reduction of up to 22.8% in the size of intermetallics was observed, with a generalized reduction in secondary dendritic arm spacing. The presence of iron-based polygonal-shaped intermetallics negatively affects Sr modification; coarser silicon particles tend to grow close to α-Fe. The presence of casting defects such as bifilm reduces Sr modification’s beneficial effects, and little increase in absorbed impact energy is observed in this work

Synthesis and Characterization of Nanostructured Oxide Layers on Ti-Nb-Zr-Ta and Ti-Nb-Zr-Fe Biomedical Alloys

Nanoporous/nanotubular complex oxide layers were developed on high-fraction β phase quaternary Ti-Nb-Zr-Ta and Ti-Nb-Zr-Fe promising biomedical alloys with a low elasticity modulus. Surface modification was achieved by electrochemical anodization aimed at the synthesis of the morphology of the nanostructures, which exhibited inner diameters of 15–100 nm. SEM, EDS, XRD, and current evolution analyses were performed for the characterization of the oxide layers. By optimizing the process parameters of electrochemical anodization, complex oxide layers with pore/tube openings of 18–92 nm on Ti-10Nb-10Zr-5Ta, 19–89 nm on Ti-20Nb-20Zr-4Ta, and 17–72 nm on Ti-29.3Nb-13.6Zr-1.9Fe alloys were synthesized using 1 M H3PO4 + 0.5 wt% HF aqueous electrolytes and 0.5 wt% NH4F + 2 wt% H20 + ethylene glycol organic electrolytes

Residual stress analysis applied to HPDC aluminium components: a case study

High-Pressure Die Casting (HPDC) is a casting process largely diffused in the aluminium foundries. By HPDC is possible to obtain aluminium castings with thin walls and high specific mechanical properties in short cycle times. Aluminium HPDC castings are commonly intended for the automotive sector: engine, covers, engine blocks and more in general the powertrain. In recent years, one of the most important focus in the automotive sector is decreasing the powertrain weight, acting on stock allowances in certain parts of the casting. This reduction can affect the dimensional features and in turn the residual stress inside the casting. Despite that, it is possible to obtain beneficial compression states into the castings by mean of post-process operations, such as shot-blasting, to reduce or remove residual stresses by mean of heat treatments. Residual stresses can be assessed by an X-Ray residual stress measurement device, a nondestructive technique that allows observing the process parameters effect into the casting. In this work, after a detailed analysis of the residual stress measurement available for aluminium castings, a powertrain component realized in aluminium alloy EN AC 46000 was analysed. These analyses involved both dimensional response and related residual stresses in the as-cast state and the shot-blasted-state on a valve cover, to understand and prevent the residual stress states into the aluminium castings

Design and manufacturing of a Nd-doped phosphate glass-based jewel

This paper reports the results of the designing, manufacturing and characterization of a jewel obtained by means of coupling the dogmas of industrial design to the analytical engineering approach. The key role in the design of the jewel was played by an in-house synthesized Neodymium (Nd)-doped phosphate glass, selected due to its easy handling and capability to change color according to the incident light wavelength. The glass core was covered by a metal alloy to mitigate its relatively high fragility and sensitivity to thermal shock and, at the same time, to highlight and preserve its beauty. The selection of the proper metal alloy, having thermo-mechanical properties compatible with those exhibited by the glass, was carried out by means of Ashby's maps, a powerful tool commonly adopted in the field of industrial design

Information-rich quality controls prediction model based on non-destructive analysis for porosity determination of AISI H13 produced by electron beam melting

The number of materials processed via additive manufacturing (AM) technologies has rapidly increased over the past decade. As of these emerging technologies, electron beam powder bed fusion (EB-PBF) process is becoming an enabling technology to manufacture complex-shaped components made of thermal-cracking sensitive materials, such as AISI H13 hot-work tool steel. In this process, a proper combination of process parameters should be employed to produce dense parts. Therefore, one of the first steps in the EB-PBF part production is to perform the process parameter optimization procedure. However, the conventional procedure that includes the image analysis of the cross-section of several as-built samples is time-consuming and costly. Hence, a new model is introduced in this work to find the best combination of EB-PBF process parameters concisely and cost-effectively. A correlation between the surface topography, the internal porosity, and the process parameters is established. The correlation between the internal porosity and the melting process parameters has been described by a high robust model (R-adj(2) = 0.91) as well as the correlation of topography parameters and melting process parameters (R-adj(2) = 0.77-0.96). Finally, a robust and information-rich prediction model for evaluating the internal porosity is proposed (R-adj(2) = 0.95) based on in situ surface topography characterization and process parameters. The information-rich prediction model allows obtaining more robust and representative model, yielding an improvement of about 4% with respect to the process parameter-based model. The model is experimentally validated showing adequate performances, with a RMSE of 2% on the predicted porosity. This result can support process and quality control designers in optimizing resource usage towards zero-defect manufacturing by reducing scraps and waste from destructive quality controls and reworks

Colata per gravità di un FGM in lega di alluminio: ottimizzazione del trattamento termico e proprietà finali

Le leghe di alluminio sono largamente utilizzate nel settore dell’autoveicolo per produrre ad esempio blocchi motore, coperchi punterie, pistoni, grazie all’ottima correlazione tra resistenza meccanica e leggerezza che le contraddistingue. In particolare, i pistoni sono soggetti a fratture per fatica vista la loro duale richiesta di resistenza alla fatica termica e di duttilità lungo l’intero volume del pezzo. I FGM (Functionally Graded Materials) sono materiali compositi avanzati ideati per garantire una graduale variazione di proprietà e composizione lungo il volume del materiale stesso. In questo lavoro, la lega per pistoni EN AC 48000 è impiegata insieme alla lega EN AC 42100 per la realizzazione di un FGM, con l’obiettivo di ottenere una variazione di proprietà lungo il volume del pezzo che garantisca le caratteristiche meccaniche ottimali per un pistone. Le proprietà finali richieste vengono ottenute per mezzo di trattamento termico T6 con solubilizzazione a 530°C ed invecchiamento artificiale a 175°C fornendo caratteristiche meccaniche apprezzabili

Gestione delle conchiglie nella colata in gravità e possibili vie per migliorarne prestazioni e durata

La colata in gravità è una tecnologia di largo impiego nelle fonderie di alluminio: seppur ben nota è ancora attuale. Nonostante molte ricerche negli ultimi anni si siano focalizzate sullo studio di processi ad elevata produttività come la pressocolata, vi è ancora una larga serie di prodotti che viene ottenuta tramite colata in gravità, grazie a cui è possibile ottenere getti con difettosità ridotta e proprietà meccaniche superiori. Nonostante la colata in gravità sia una tecnologia che non è possibile definire innovativa, l’evoluzione subita dai componenti in termini di geometria, dimensioni e volumi, ha imposto un aumento della produttività a fronte di una riduzione delle tolleranze accettabili. Questi cambiamenti hanno inficiato sulla vita delle conchiglie in acciaio, utensili che si usurano sempre più facilmente. Per ottimizzare il processo produttivo è necessario introdurre su questa tecnologia già conosciuta degli elementi innovativi. In questo studio è presentato lo stato dell’arte dei metodi per aumentare la vita delle conchiglie nella colata in gravità con particolare attenzione all’effetto della rugosità superficiale della conchiglia e del metodo di verniciatura sulla resistenza ad usura ed alla metallizzazione dell’acciaio. L’alluminio fuso infatti, durante il processo di colata, interagisce con l’acciaio di cui è costituita la conchiglia, producendo usura da erosione e metallizzazione delle superfici con cui entra in contatto. Per limitare il danneggiamento della conchiglia si utilizzano comunemente delle vernici, al fine di creare una barriera tra i due materiali. Tuttavia il processo di verniciatura spesso viene effettuato basandosi su principi qualitativi e troppo spesso semi-quantitativi. Questo studio vuole investigare in modo più approfondito le fasi da seguire per l’ottenimento di una verniciatura ottimale, andando a utilizzare differenti vernici commerciali e valutandone la loro resistenza sia dal punto di vista sia della finitura superficiale della conchiglia che della resistenza alle alte temperature, simulando le condizioni d’uso reali della conchiglia, attraverso prove di usura e prove di immersione in alluminio fuso

Detection and distribution of European stone fruit yellows (ESFY) in apricot cv. ‘Bergeron’ and epidemiological studies in the province of Trento (Italy)

The aim was to investigate the performance of ‘Bergeron’ on ‘Wavit’ in 4 experimental fields, in the province of Trento (Italy), where European stone fruit yellows (ESFY) caused by “Candidatus Phytoplasma prunorum” has been constantly spreading since 2000.This included visual inspections for typical symptoms (early bud-break during dormancy and premature leaf-roll) and a highly sensitive Real time-PCR (Rt-PCR) assay. 25 % of the propagation material was checked with this method and found to be healthy, before planting in 2005.The epidemiology of the disease was also studied by focusing on: the presence of the vector Cacopsylla pruni (Scopoli) on conifers, the detection of “Ca. P. prunorum” in psyllid eggs and the transmission efficiency at different stages. This was done by exposing apricot trees in 2 locations, during 2 periods from January to July, to the overlapping presence in the orchards of the re-immigrants and the new generation of C. pruni. The results obtained demonstrated that ‘Bergeron’ seems to be highly susceptible to ESFY: typical bud-break was rarely observed, but up to 20-30% of the plants showed premature leaf-roll, fruit deformation and dieback. C. pruni was caught only once on Picea abies during winter; “Ca. P. prunorum” was found in 4 egg samples from 2 locations and the preliminary results on the exposed trees confirmed that the re-immigrants could be the most efficient vectors at least on apricot.Keywords: Prunus armeniaca, cultivar ‘Bergeron’, Real time-PCR, “Candidatus Phytoplasma prunorum”,epidemiolog

Position paper of the Italian Association of Medical Oncology on the impact of COVID-19 on Italian oncology and the path forward: the 2021 Matera statement

The coronavirus disease 2019 (COVID-19) pandemic has severely affected cancer care and research by disrupting the prevention and treatment paths as well as the preclinical, clinical, and translational research ecosystem. In Italy, this has been particularly significant given the severity of the pandemic's impact and the intrinsic vulnerabilities of the national health system. However, whilst detrimental, disruption can also be constructive and may stimulate innovation and progress. The Italian Association of Medical Oncology (AIOM) has recognized the impact of COVID-19 on cancer care continuum and research and proposes the '2021 Matera statement' which aims at providing pragmatic guidance for policymakers and health care institutions to mitigate the impact of the global health crisis on Italian oncology and design the recovery plan for the post-pandemic scenario. The interventions are addressed both to the pillars (prevention, diagnosis, treatment, follow-up, health care professionals) and foundations of cancer care (communication and care relationship, system organization, resources, research, networking). The priorities to be implemented can be summarized in the MATERA acronym: Multidisciplinarity; Access to cancer care; Telemedicine and Territoriality; Equity, ethics, education; Research and resources; Alliance between stakeholders and patients