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Amauri Garcia - One of the best experts on this subject based on the ideXlab platform.
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transition from High Cooling Rate cells to dendrites in directionally solidified al sn pb alloys
Materials today communications, 2020Co-Authors: Ricardo Oliveira, Thiago A Costa, Marcelino Dias, Camila Konno, Noe Cheung, Amauri GarciaAbstract:Abstract The preprogramming of the solidification Cooling Rate during casting of some Al-based bearing materials, has been used to achieve microstructural patterns conducive to better wear responses. For Al-Sn castings, improvements in the wear resistance were reported to occur when Higher amounts of Sn remained segregated in the spacings of the dendritic Al-rich matrix. In this sense, a cellular microstructure could be more adequate since the segregated Sn would be contained along the cells boundaries and not spread through the interstices of multiple dendritic arms. This study investigates a range of Al-xSn alloys compositions (x = 1, 2.6, 7.5, 9, 10 wt.%) and an Al-(9 wt.%)Sn–(1 wt.%Pb), with a view to determining the ranges of Sn concentrations and solidification Cooling Rates ( T ˙ ) for which High Cooling Rate cells are stable, as well as the reverse cellular/dendritic transition. For T ˙ from 1 to 40 K/s, it is shown that for Al-Sn alloys having Sn 10 wt.% it is completely dendritic. The reverse transition from High Cooling Rate cells to dendrites is shown to occur for the Al-9 wt.%Sn alloy, with T ˙ T ˙ > 6 K/s in a fully cellular Al-rich matrix. The Al-9 wt.%Sn-1 wt.%Pb ternary alloy casting also exhibits a reverse cellular/dendritic transition, with dendrites occurring also for T ˙ T ˙ > 8 K/s.
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High Cooling Rate regular and plate like cells in sn ni solder alloys
Advanced Engineering Materials, 2018Co-Authors: Marcella G C Xavier, Bismarck Luiz Silva, Amauri Garcia, Jose E SpinelliAbstract:Broad ranges of Cooling Rates (urn:x-wiley:14381656:media:adem201701179:adem201701179-math-0001) 0.8–30.5 and 0.4–5.0 K s−1 are attained during directional solidification of eutectic Sn–0.2 wt% Ni and hypereutectic Sn–0.5 wt% Ni alloys, respectively. A reverse High Cooling Rate cell‐to‐dendrite transition occurs for the eutectic composition and a transition from High Cooling Rate cells to plate like cells for the hypereutectic alloy. High Cooling Rate β‐Sn cells are associated with Cooling Rates >5.5 and >2.7 K s−1 for eutectic and hypereutectic compositions, respectively. A processing diagram, relating the ‘urn:x-wiley:14381656:media:adem201701179:adem201701179-math-0002–Ni content’ space with the microstructural morphology, is proposed. A combination of plate like cells and plate NiSn4 eutectic phase results in Higher ductility
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High Cooling Rate cells, dendrites, microstructural spacings and microhardness in a directionally solidified Al–Mg–Si alloy
Journal of Alloys and Compounds, 2015Co-Authors: Crystopher Brito, Noe Cheung, Guillaume Reinhart, Henri Nguyen-thi, Nathalie Mangelinck-noel, José Spinelli, Amauri GarciaAbstract:Transient unidirectional solidification experiments have been carried out with an Al–3 wt%Mg–1 wt%Si alloy under Cooling Rates (T_ ) in the range 0.2–45 K/s. A reverse cells > dendrites transition is shown to occur with the High-Cooling Rate cellular region associated with T_ > 2 K/s and the dendritic region with T. < 0.8 K/s. Experimental growth laws correlating the cellular and dendritic spacings with the Cooling Rate are proposed. It is shown that the microhardness is directly influenced by both morphologies of the Al-rich matrix and by the relative fractions of Mg2Si and Fe bearing intermetallics that vary differently with the Cooling Rate.
Christoph Schick - One of the best experts on this subject based on the ideXlab platform.
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scanning nanocalorimetry at High Cooling Rate of isotactic polypropylene
Macromolecules, 2006Co-Authors: Felice De Santis, S Adamovsky, Giuseppe Titomanlio, Christoph SchickAbstract:A wide set of Cooling scans and subsequent melting behavior of isotactic polypropylene (i-PP) were investigated using differential scanning calorimetry and nanocalorimetry at very High Cooling Rate. The latter technique offers, indeed, the distinctive possibility to perform heat capacity measurements at Rates of more than 1000 K/s, both in Cooling and in heating, to characterize the crystallization. When the i-PP sample was solidified with Cooling Rate larger than 160 K/s, a novel enthalpic process was observed that was related to the mesomorphic phase formation. Furthermore, at Cooling Rates Higher than 1000 K/s, the i-PP sample did not crystallize neither in the α nor in the mesomorphic form. The subsequent heating scan starting from −15 °C showed an exothermic event, between 0 and 30 °C, ascribed to the mesophase cold crystallization.
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scanning microcalorimetry at High Cooling Rate
Thermochimica Acta, 2003Co-Authors: S Adamovsky, A A Minakov, Christoph SchickAbstract:Abstract Heat capacity measurements at fast Cooling and heating were realized for linear polyethylene NBS SRM (standard reference material) 1484 sample, ca. 120 ng, in the melting-crystallization region. A commercial vacuum sensor, thermal conductivity gauge TCG-3880, Xensor Integrations, was utilized as a cell for a micro-calorimeter suitable for such measurements. The cell consists of a thin-film Si 3 N x membrane with a film-thermopile and a film-heater, which are formed at the membrane center. The current at the heater as well as the signal from the thermopile were monitored in real time during fast scanning of temperature of the central part of the membrane. The measurements were performed in an ambient gas, so that controlled Cooling and heating Rates up to 5×10 3 K/s were achieved. As conditions were not adiabatic, the heat leakage from the sample was calibRated and was taken into account for heat capacity measurements. A simple calibration algorithm was developed for such measurements. Thus, a step towards ultra fast Cooling scanning calorimetry was made.
Michel Coret - One of the best experts on this subject based on the ideXlab platform.
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hot tearing sensitivity of al mg si alloys evaluated by x ray microtomography after constrained solidification at High Cooling Rate
2011Co-Authors: Eliane Giraud, M Suery, Jerome Adrien, Eric Maire, Michel CoretAbstract:The mechanical behavior of alloys resulting from a mixture of a AA6061 base alloy with different alloys from the Al-Si and Al-Mg series used as filler alloys during welding has been investigated under conditions close to welding. The specimens have been subjected to constrained solidification carried out at a High Cooling Rate of 80 K/s. In the test developed in this study, the central part of the specimen is initially melted. During solidification, this zone suffers strains only geneRated by thermal contraction and solidification shrinkage, which can possibly lead to the formation of hot cracks. The hot cracking sensitivity of the various alloys has been determined thanks to X-ray microtomography observations which have allowed imaging the zone solidified under constrained conditions and measuring the volume fraction and the number of open cracks as a function of Si and Mg contents. The variation of stress induced by deformation of the solid during constrained solidification has been also measured as a function of solid fraction. The results show that: (1) stress developed within the solidifying alloy exhibits the same variation whatever the Si and Mg contents. Stress starts increasing at the coherency of the solid skeleton and increases much more sharply when coalescence occurs. (2) the alloys with Si and Mg contents exceeding 3 and 2 wt% respectively are less sensitive to hot tearing in comparison with the base alloy; (3)Al-Mg filler alloys seem to be the best solution to reduce hot cracking in 6061 welded joints.
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experimental study of the phase transformation plasticity of 16mnd5 low carbon steel under multiaxial loading
International Journal of Plasticity, 2002Co-Authors: Michel Coret, Sylvain Calloch, Alain CombescureAbstract:Abstract This paper is concerned with the experimental behaviour of a 16MND5 steel (french vessel steel) under complex loading. A particular attention is paid to plasticity induced by phase transformation. We present an experimental set-up to apply thermo-mechanical loads under tension-torsion. This apparatus enables us to reach temperature of 1200 °C at a maximum heating Rate of 60 °C s−1 and a High Cooling Rate of −30 °C s−1. A series of tests is performed in order to show the rule of loading on transformation plasticity.
Cheng Jiang Huang - One of the best experts on this subject based on the ideXlab platform.
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a phase field simulation of austenite to ferrite transformation kinetics in low carbon steels
Acta Materialia, 2006Co-Authors: Cheng Jiang Huang, David J Browne, Shaun McfaddenAbstract:Abstract A new phase field model has been developed which can simulate the austenite to ferrite (γ → α) transformation in low carbon steels at large space and time scales and involving multiple ferrite grain growth. The two-dimensional phase-field simulation shows that interface composition does not obey the local equilibrium assumption, while grain growth obeys a parabolic law for most of the transformation. The kinetics of continuous Cooling transformation are successfully modelled. Results suggest that nucleation occurs both along austenite grain boundaries and within grains for High Cooling Rate transformations. Grain coarsening behind the transformation front is predicted. Two interesting phenomena, namely, interface acceleration, and solute enrichment behind the impingement fronts, are disclosed via this phase-field simulation.
Wei Liu - One of the best experts on this subject based on the ideXlab platform.
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comparison of solidification cracking susceptibility between al mg and al cu alloys during welding a phase field study
Scripta Materialia, 2018Co-Authors: Shaoning Geng, Ping Jiang, Xinyu Shao, Chunming Wang, Chu Han, Rong Chen, Wei LiuAbstract:Abstract Based on two-dimensional phase-field simulations, we demonstRated the possible reasons why Al-Mg alloys can have better resistance to solidification cracking than Al-Cu alloys despite their wide freezing temperature range. Using Al-4.0 wt% Cu and Al-4.0 wt% Mg alloy as examples, we found that back-diffusion is negligible due to the relatively High Cooling Rate, and extensive coalescence occurs at earlier solidification stage in Al-4.0 wt% Mg alloy compared with Al-4.0 wt% Cu alloy. With considering coalescence predicted by phase-field simulations, the calculated solidification cracking index of Al-Mg alloy is reasonably lower than Al-Cu alloy.