The Johnson-Mehl-Avrami Model Applied to Martensitic Kinetics in Ausformed Cooper Based Shape Memory Alloy

CuAlNi shape memory alloys which are used as sensors and actuators have also been investigated recently as materials for medicine devices. This study shows the influence of the thermo – mechanical treatments in CuAl13Ni4 shape memory alloy on martensitic transformation kinetics and microstructures. While maintaining a constant 20% degree of deformation, deformation temperature was varied between 800 oC and 1000 oC. The alloy was investigated by differential scanning Calorimetry (DSC) and optical microscopy. The validity of JMA model to the kinetics analysis was checked. The changes in the microstructure and kinetic transformations have been linked to the evolution of the rolling temperature that introduced high density dislocations in initial phase and changes fraction and interaction between the β1’ (18R) and γ1’ (2H) martensite coexisting in this shape memory alloy

Structural characteristics of multilayered ni-ti nanocomposite fabricated by high speed high pressure torsion (Hshpt)

47PCCDI/2018 MANUNET 3 PN3-P3-302 grant number 99-2019It is generally accepted that severe plastic deformation (SPD) has the ability to produce ultrafinegrained (UFG) and nanocrystalline materials in bulk. Recent developments in high pressure torsion (HPT) processes have led to the production of bimetallic composites using copper, aluminum or magnesium alloys. This article outlines a new approach to fabricate multilayered Ni-Ti nanocomposites by a patented SPD technique, namely, high speed high pressure torsion (HSHPT). The multilayered composite discs consist of Ni-Ti alloys of different composition: a shape memory alloy (SMA) Ti-rich, whose Mf > RT, and an SMA Ni-rich, whose Af < RT. The composites were designed to have 2 to 32 layers of both alloys. The layers were arranged in different sequences to improve the shape recovery on both heating and cooling of nickel-titanium alloys. The manufacturing process of Ni-Ti multilayers is explained in this work. The evolution of the microstructure was traced using optical, scanning electron and transmission electron microscopes. The effectiveness of the bonding of the multilayered composites was investigated. The shape memory characteristics and the martensitic transition of the nickel-titanium nanocomposites were studied by differential scanning calorimetry (DSC). This method opens up new possibilities for designing various layered metal-matrix composites achieving the best combination of shape memory, deformability and tensile strength.publishersversionpublishe

Smelting and recycling evidences from the Late Bronze Age habitat site of Baiões (Viseu, Portugal)

Many aspects of bronze production during Late Bronze Age in Western Europe are so far unknown. In the present study selected artefact fragments and metallurgical debris, which include a slag fragment, from the emblematic Late Bronze Age habitat site of Castro da Senhora da Guia de Baio˜es (Viseu, Portugal) have been studied by optical microscopy, micro-EDXRF, SEM–EDS and XRD. Evidences were found for bronze production involving smelting and recycling. Compositional analysis showed that the artefacts are made of a bronze with 133 wt.% Sn (average and one standard deviation) and a low impurity pattern, namely <0.1 wt.% Pb, being comparable with the composition of other bronzes from the same region (the Central Portuguese Beiras). This alloy is generally different from elsewhere Atlantic and Mediterranean bronzes, which show frequently slightly lower Sn contents and higher impurity patterns,namely Pb which is often present as an alloying element. The present study gives further support to early proposals suggesting the exploration of the Western Iberian tin resources during Late Bronze Age, and besides that, it indicates that metalworking and smelting could have been a commonplace activity requiring no specific facilities, being bronze produced at a domestic scale in this Western extreme of Europe

Embedded fiber sensors to monitor temperature and strain of polymeric parts fabricated by additive manufacturing and reinforced with NiTi wires

POCI-01-0145-FEDER-016414 (FIBR3D) BI/UI96/6642/2018 BI/UI96/6643/2018 PD/BD/128265/2016 UID/CTM/50025/2019 UIDB/00667/2020 FCT-SFRH/BD/146885/2019 UIDB/50025/2020 UIDP/50025/2020This paper focuses on three main issues regarding Material Extrusion (MEX) Additive Manufacturing (AM) of thermoplastic composites reinforced by pre-functionalized continuous Nickel–Titanium (NiTi) wires: (i) Evaluation of the effect of the MEX process on the properties of the pre-functionalized NiTi, (ii) evaluation of the mechanical and thermal behavior of the composite material during usage, (iii) the inspection of the parts by Non-Destructive Testing (NDT). For this purpose, an optical fiber sensing network, based on fiber Bragg grating and a cascaded optical fiber sensor, was successfully embedded during the 3D printing of a polylactic acid (PLA) matrix reinforced by NiTi wires. Thermal and mechanical perturbations were successfully registered as a consequence of thermal and mechanical stimuli. During a heating/cooling cycle, a maximum contraction of ≈100 µm was detected by the cascaded sensor in the PLA material at the end of the heating step (induced by Joule effect) of NiTi wires and a thermal perturbation associated with the structural transformation of austenite to R-phase was observed during the natural cooling step, near 33.0◦ C. Regarding tensile cycling tests, higher increases in temperature arose when the applied force ranged between 0.7 and 1.1 kN, reaching a maximum temperature variation of 9.5 ± 0.1◦ C. During the unload step, a slope change in the temperature behavior was detected, which is associated with the material transformation of the NiTi wire (martensite to austenite). The embedded optical sensing methodology presented here proved to be an effective and precise tool to identify structural transformations regarding the specific application as a Non-Destructive Testing for AM.publishersversionpublishe

Experimental analysis of niti alloy during strain-controlled low-cycle fatigue

PTDC/CTM-CTM/29101/2017- POCI-01-0145-FEDER-029101 UIDB/EMS/00285/2020 UIDB/50025/2020-2023The interaction between the stress-induced martensitic transformation and resistivity behavior of superelastic NiTi shape memory alloy (SMA) was studied. Strain-controlled low-cycle fatigue up to 6% was monitored by in situ electrical resistivity measurements. The experimental results show that a great motion of martensite fronts results in a significant accumulation of defects, as evidenced by transmission electron microscopy (TEM), before and after the tensile cycles. This gives rise to an overall increase of the resistivity values up to the maximum deformation. Therefore, the research suggests that shape memory alloy wire has great potential as a stress sensor inside bulk materials.publishersversionpublishe

Design, metallurgical characteristics, and mechanical performance

Funding Information: FMBF acknowledges the funding of CENIMAT/i3N by national funds through the FCT‐Fundação para a Ciência e a Tecnologia, I.P., within the scope of Multiannual Financing of R&D Units, reference UIDB/50025/2020‐2023. The authors ackowledge Fernanda Carvalho for running the differential scanning calorimetry tests on the endodontic files. Publisher Copyright: © 2023 The Authors. International Endodontic Journal published by John Wiley & Sons Ltd on behalf of British Endodontic Society.Aim: To compare two flat-side single-file rotary instruments with three single-file reciprocating systems through a multimethod assessment. Methodology: A total of 290 new NiTi single-file rotary (AF F One Blue 25/0.06 and Platinum V.EU 25/0.06) and reciprocating (One Files Blue R25, Reciproc Blue R25, Reciproc R25) instruments were selected, carefully examined for any major deformations, and evaluated regarding their macroscopic and microscopic design, nickel and titanium elements ratio, phase transformation temperatures, and mechanical performance (time/rotation to fracture, maximum torque, angle of rotation, microhardness, maximum bending, and buckling strengths). One-way anova post hoc Tukey, T-test, and nonparametric Mood's median tests were used for statistical comparisons (α = 5%). Results: Tested instruments had identical blade counts and near-identical helical angles of approximately 24° (rotary instruments) and 151° (reciprocating instruments). The flat-side analysis revealed a few inconsistencies, such as discontinuity segments, different orientations, and gaps in the homogeneity of the bluish colour. Microscopically, flat-side instruments exhibited blade discontinuity and an incomplete S-shaped cross-section. The surface finish was smoother for One Files Blue and more irregular for both rotary instruments. There were distinct phase transformation temperatures amongst all instruments. All heat-treated instruments were in R-phase arrangement, and Reciproc was in R-phase plus austenite at test temperature (20°C). Compared with the reciprocating instruments, both flat-side instruments exhibited lower results in the cyclic fatigue tests using two different clockwise kinematics, maximum torque, angle of rotation, and maximum buckling strength (p <.05). The rotary systems also exhibited low flexibility (p <.05). AF F One Blue had the lowest microhardness, whilst Reciproc had the highest value. Conclusion: This multimethod investigation revealed that the flat-side rotary instruments underperformed the reciprocating instruments regarding cyclic fatigue (with two different clockwise kinematics), maximum torque, angle of rotation, maximum buckling strength, and flexibility. Manufacturing inconsistencies were also observed in some of the flat-side instruments, including discontinuity segments, different orientations, and in the homogeneity of their bluish colour given by the heat treatment.publishersversionpublishe

Continuous Flux Thermal Treatments for Improving the Resistance at Alternate Bending of Medium to High Strength Steel Strips

The research was focused on obtaining medium to high strength steel strips for strapping heavy products by applying continuous flux thermal treatments on common grades, cheap carbon steels. For steel strapping the behavior at alternate bending is an important issue, thus an objective of the research was to make sure that the treated products withstand a critical number of alternate bending cycles and further more an improvement of the resistance at alternate bending by applying thermal treatments in continuous flux was pursued. The paper presents the results of the alternate bending test, SEM fractographs, optical analysis of the fracture surface and surface of the strip in the vicinity of the fracture surface after breaking by alternate bending using a stereo-microscope and optical analysis on etched and un-etched samples in transversal section along the rolling direction in the vicinity of the fracture surface using a metallographic optical microscope; for the following samples: the raw material in strain-ardened state, samples subjected to continuous flux quenching from 900 °C and tempering by passing through the furnace maintained at 600 °C, and samples subjected to quenching from 900 °C and tempering by passing through the furnace maintained at 700 °C

Multimethod Assessment of Design, Metallurgical, and Mechanical Characteristics of Original and Counterfeit ProGlider Instruments

Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.A multimethod study was conducted to assess the differences between original (PG-OR) and counterfeit (PG-CF) ProGlider instruments regarding design, metallurgical features, and mechanical performance. Seventy PG-OR and PG-CF instruments (n = 35 per group) were evaluated regarding the number of spirals, helical angles, and measuring line position by stereomicroscopy, while blade symmetry, cross-section geometry, tip design, and surface were assessed by scanning electron microscopy. Energy-dispersive X-ray spectroscopy and differential scanning calorimetry were used to identify element ratio and phase transformation temperatures, while cyclic fatigue, torsional, and bending testing were employed to assess their mechanical performance. An unpaired t-test and nonparametric Mann–Whitney U test were used to compare instruments at a significance level of 5%. Similarities were observed in the number of spirals, helical angles, blade symmetry, cross-sectional geometries, and nickel–titanium ratios. Measuring lines were more reliable in the original instrument, while differences were noted in the geometry of the tips (sharper tip for the original and rounded for the counterfeit) and surface finishing with PG-CF presenting more surface irregularities. PG-OR showed significantly more time to fracture (118 s), a higher angle of rotation (440°), and a lower maximum bending load (146.3 gf) (p 0.05). Although the tested instruments had a similar design, the original ProGlider showed superior mechanical behavior. The results of counterfeit ProGlider instruments were unreliable and can be considered unsafe for glide path procedures.publishersversionpublishe

PAISAGEM E TURISMO: QUALIDADE VISUAL DA PRAIA DO CUMBUCO - CAUCAIA/CE

Este artigo objetiva analisar a qualidade visual da paisagem da praia do Cumbuco, no município de Caucaia/CE, Região Metropolitana de Fortaleza. Como suporte teórico utilizou-se teóricos da geoecologia das paisagens. Os principais resultados foram: variedade de elementos naturais, diversidade e naturalidade média às paisagens, presença de médios e grandes indicadores detratores, como: casas de veraneio, barracas, restaurantes, hotéis e condomínios. Como constatação inferiu-se que a qualidade visual é média, principalmente na área de maior concentração de turistas significando que a paisagem, motivadora dos fluxos turísticos, transformou-se perdendo características próprias e adquirindo novas feições