Sagging resistance of warm formed aluminum brazing sheet

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Materials Processing Technology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Materials Processing Technology, #254,2018-04-01, http://dx.doi.org/10.1016/j.jmatprotec.2017.11.041 The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jmatprotec.2017.11.041 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Interrupted tensile tests, performed between room temperature (RT) and 250°C, were used to simulate warm forming of an AA3003/AA4045 brazing sheet. Brazing performance was predicted from sagging distance measurements after a thermal cycle. The sagging distance as a function of strain for sheets strained at 150°C was similar to that of RT strained samples, while the sagging distances were larger at all levels of applied strain for sheets strained at 200°C and 250°C. Large sagging distances were correlated with the occurrence of liquid film migration during simulated brazing and a recovered substructure in the core alloy, while small sagging distances were associated with a coarse, recrystallized core alloy. The poor brazing performance of sheets formed above 150°C was attributed to a reduction in the stored strain energy during forming, resulting in recovery rather than recrystallization during brazing, leaving a microstructure which is susceptible to liquid film migration.Natural Sciences and Engineering Research Council of Canada [Grant number APCPJ 447970-13] Ontario Research Fund and Initiative for Automotive Manufacturing Innovation [File number RE-1-054

Interfacial bonding mechanism in Al/coated steel dissimilar refill friction stir spot welds

The final publication is available at Elsevier via https://doi.org/10.1016/j.jmst.2019.01.001 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Defect-free dissimilar Al/zinc coated steel and Al/AlSi coated steel welds were successfully fabricated by refill friction stir spot welding. However, Al alloy and uncoated steel could not be welded under the same welding condition. Al-Zn eutectic layer formed at the Al/zinc coated steel interface showed non-uniformity in thickness and nanoscale intermetallic (IMC) produced was discontinuous. The bonding formation between the Al-Zn layer and the surrounding materials was attributed to a liquid/solid reaction mechanism. Bonding formation at Al alloy and AlSi coated steel interface was attributed to a solid/solid reaction mechanism, as the joining process did not involve with melting of base metals or AlSi coating materials. Kissing bond formed at the weld boundary acted as a crack initiation and propagation site, and the present study showed that weld strength of Al 5754/AlSi coated steel was greatly influenced by properties of original IMC layer.Natural Science and Engineering Council of CanadaCanadian Foundation for Innovatio

New insights into martensite strength and the damage behaviour of dual phase steels

International audienc

Post heat treatment of additive manufactured AlSi10Mg: On silicon morphology, texture and small-scale properties

Post-fabrication heat treatment, including solution treatment (at 520 °C for 1 h) followed by water quenching (WQ), air cooling (AC) and furnace cooling (FC), was performed on a selective laser melted AlSi10Mg alloy. The objective is to assess the effect of various cooling rates on the microstructure (specifically eutectic-Si morphology) and small-scale mechanical properties, measured by employing a depth-sensing nanoindentation platform, of the selective laser melted AlSi10Mg alloy. Results show extensive evolutions in the microstructure and the mechanical properties of the heat-treated materials relative to the as-fabricated sample. Upon solutionizing treatment, the eutectic Si is first fragmented, then spheroidized, and finally coarsened when cooled with slow rates. The microstructural evolution directly affects the mechanical properties, where the as-fabricated and the FC are the hardest and the softest structures, respectively. This is directly attributed to the size and morphology of the eutectic-Si within the microstructure. The findings of this study could help to adjust the optimized heat-treatment process to fabricate SLM AlSi10Mg parts with desirable microstructure and mechanical properties

The role of titanium on the microstructure and mechanical properties of additively manufactured C300 maraging steels

In this study, C300 metal powders containing two different Ti contents (0.72 and 1.17 wt%) were used to additively manufacture maraging steel samples in both horizontal and vertical directions via laser powder bed fusion (LPBF) technique. The effect of Ti addition on the microstructural and mechanical properties of the additively manufactured (AM) maraging steels was investigated using scanning, transmission electron microscopies (SEM, TEM), and electron backscatter diffraction (EBSD) along with uniaxial tensile and hardness testing procedures. Besides, X-ray diffraction (XRD) technique was employed to identify various phases formed during the LPBF process. The results showed that the horizontally printed Ti-rich samples exhibited higher retained austenite (γ) phase and superior values of hardness and tensile strength, while those ones vertically prepared showed an excellent ductility that could bring benefits in high-cycle fatigue applications. The TEM observations confirmed the presence of CoNi precipitates as well as high dislocation densities in the horizontal high Ti content samples, which are associated with higher strain hardening and tensile strength

On microstructure and work hardening behavior of laser powder bed fused Al-Cu-Mg-Ag-TiB2 and AlSi10Mg alloys

In this paper, we investigate the correlation between microstructure and mechanical properties, including work hardening rates of two aluminum alloys, Al-Cu-Mg-Ag-TiB2 (A205) and AlSi10Mg, both additively manufactured using laser powder-bed fusion (LPBF) technique. Solutionizing followed by over-aging (T7) and artificial aging (T6) heat treatments were performed on as-built specimens of A205 and AlSi10Mg alloys, respectively, to investigate and compare the evolution of microstructure and tensile properties. Tensile tests based on ASTM E8/E8M standard were performed systematically on both materials in both as-built and heat-treated conditions. High-magnification microstructural characterizations including scanning electron and transmission electron microscopies and electron backscattered diffraction were performed to identify the microstructure-property correlations. The A205 alloy contains an ultrafine uniform equiaxed grain structure with no cell and/or epitaxial growth structure. However, the AlSi10Mg contains a cellular microstructure of primary α‐Al cells surrounded by a continuous cellular Si network. Tensile results on A205 (as-built) revealed discontinuous yielding, while the A205 (T7 HT) material serrated plastic flow instability. T7 heat treatment resulted in a 42.4% and 38% increase in yield stress (YS) and ultimate tensile strength (UTS), respectively, and elongation decreased from 12.5% to 9.5% consequently. However, considerable grain growth, coarsening of Si particles, and dissolution of some Mg2Si phases through solutionizing and T6 aging on AlSi10Mg resulted in increased elongation (5.49–14.20%) and decreased YS and UTS (14.5% and 19.4% respectively). The effect of distinct microstructural features of A205 and AlSi10Mg in as-built condition and their evolution in opposite directions upon aging (in terms of mechanical properties) is reflected in their work-hardening behavior. Considerably higher work hardening of AlSi10Mg alloy in both as-built and aged conditions compared to A205 is linked with the cellular structure containing hard eutectic-Si particles at the cell boundaries

Supercapacitive carbon nanotube-cobalt molybdate nanocomposites prepared via solvent-free microwave synthesis

Cobalt molybdate (CoMoO4) nanoplatelets with a crystalline-amorphous core-shell structure anchored via multi-walled carbon nanotubes were prepared by a solvent-free microwave synthesis method. The entire procedure took only 15 min. The nanocomposite shows a promising capacitance of 170 F g 12\ub9 with a potential window of 0.8 V, degrading by only 6.8% after 1000 cycles.Peer reviewed: YesNRC publication: Ye

High strain rate deformation behavior, texture and microstructural evolution, characterization of adiabatic shear bands, and constitutive models in electron beam melted Ti-6Al-4V under dynamic compression loadings

The results of an investigation on the influence of strain rate on the microstructural and texture evolution, adiabatic shear band characterization, and deformation mechanism of electron beam melted Ti-6Al-4V vertically built cylindrical rods are presented and discussed in this paper. Typical initial microstructure includes a mixture of α (aluminum-rich) and β phases (vanadium-rich) and grain boundary α along with the columnar prior β-grain boundaries. High strain rate compressive loadings were applied using a Split-Hopkinson pressure bar at the strain rates of 700 s−1 and 1650 s−1 at room temperature. By increasing the strain rate from 700 s−1 to 1650 s−1, the maximum stress and total strain in the alloy increased by 510 MPa and 141%, respectively. The higher dislocation density in the more severely deformed sample led to a more considerable amount of dislocation cells and consequent subgrains, high-angle grains, and piled-up dislocations. Intense shear strain localization leading to the adiabatic shear bands formation that occurred at higher strain rates. Texture investigations of the ASB region proposed that α→β phase transformation occurred within the ASB. Flow behavior prediction and experimental data revealed reasonable accordance, using the Gao-Zhang-Yan and the Chang-Asaro model

Electrochemical supercapacitor electrodes from sponge-like graphene nanoarchitectures with ultrahigh power density

We employed a microwave synthesis process of cobalt phthalocyanine molecules templated by acid-functionalized multiwalled carbon nanotubes to create three-dimensional sponge-like graphene nanoarchitectures suited for ionic liquid-based electrochemical capacitor electrodes that operate at very high scan rates. The sequential \u201cbottom-up\u201d molecular synthesis and subsequent carbonization process took less than 20 min to complete. The 3D nanoarchitectures are able to deliver an energy density of 7.1 W\ub7h kg\u2013\ub9 even at an extra high power density of 48\u2009000 W kg\u2013\ub9. In addition, the ionic liquid supercapacitor based on this material works very well at room temperature due to its fully opened structures, which is ideal for the high-power energy application requiring more tolerance to temperature variation. Moreover, the structures are stable in both ionic liquids and 1 M H2SO4, retaining 90 and 98% capacitance after 10\u2009000 cycles, respectively.Peer reviewed: YesNRC publication: Ye