Currently, kinematic field measurements for studying the mechanical behavior of materials and structures use common optical methods, such as mark tracking techniques, grid methods and correlation ...techniques. These techniques are employed over a region of interest ranging from micro to millimeter scale. However, when studies need to be conducted on even smaller scales such as sub-micrometric scale, the use of more complex means of observation is required. In this case, the work can be achieved using the scanning electron microscope (SEM), and the Focused-Ion-Beam (FIB) as marking technique. An adaptation of Digital Image Correlation (DIC) method Heaviside-based Digital Image Correlation (H-DIC) is chosen to investigate the mechanical behavior and taking into account local fractures. As the studied problem is to extract strains from a fractured material using a displacement field measurement method, derivative computation for strain determination is not well adapted. The proposed approach consists in extracting the residual strains from local first gradients of H-DIC, which are less perturbed by the fractures. Various tests were performed to evaluate the validity of this new proposed approach. An application to study the mechanical behavior of a metallic composite (Al/ω-Al-Cu-Fe) is proposed. A particular exploitation of all field lies in the good separation of the strain fields and the cracked part. A discussion that focus on the comparison between a conventional DIC analysis and its extension was presented on the zones without or with fractures.
Compression test on a two-phase material Al/ω-Al-Cu-Fe, Maps after second loading/unloading cycle, and for tow zones (Z1, Z4). (a, d) SEM image, (b, e) equivalent strain H-DIC εeq∂U∂X and (c, f) norme of displacement jump vector ║U′║. Display omitted
•Coupling Scanning Electron Microscope, Focused-Ion-Beam, and Digital Image Correlation in a metrological process•Separation of strains and fracture properties using an extended DIC•Extracting residual strains from a fractured material for an ex-situ compression test•Application to study the microstructure and the mechanical behavior of a composite metallic material
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Al-matrix material composites were produced from pure Al and 40 vol% Ti3AlC2 powders using hot isostatic pressing. The nanocrystallised-Ti3AlC2 agglomerates were uniformly distributed in the Al ...matrix and formed a hard continuous skeleton. The mechanical properties of the composites were evaluated over the temperature range 20-500 C by performing compression tests at a constant strain rate. The monotonic temperature dependence of the proof stress at 0.2% plastic strain suggests that the same thermally activated mechanism controlled the composite plastic deformation over the entire temperature range. The yield stress of the composite was about twice as high as that of the Al matrix in the investigated temperature range. This proves that Ti3AlC2 particles constitute efficient reinforcement particles for the Al matrix. SEM observations showed that plastic deformation of 40Ti3AlC2/60Al composite takes place in the Al matrix while Ti3AlC2 particle agglomerates undergo substantial fracture.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Comprehensive experimental results of fully oxidized (up to YBa2Cu3O6,9-7) melt-textured YBaCuO materials with different microstructures are presented. These microstructures are built respectively: ...(1) with a high dislocations density but almost without twins (after high temperature treatment at 2 GPa) and (2) with a high twin density, but practically free from dislocations and stacking faults (after high temperature oxygenation at 10-16 MPa). It is shown that for attaining high critical current densities and fields of irreversibility (jc(H||c, 0 T)=9·104 A/cm2, Hirr=9.7 T at 77 K), a high twin density in YBa2Cu3O6.9-7 matrix of MT-YBCO is required. The density of twins in fully oxidized materials depends on the distances between Y2BaCuO5 inclusions, larger twin densities are related to shorter distances between inclusions. The influence of phase composition of the initial powder mixtures on the distances between Y2BaCuO5 inclusions have been characterized and discussed.
The mechanical properties of the ω-Al7Cu2Fe crystalline phase have been investigated over a large temperature range (650–1000 K). Despite of its antinomic structure with the icosahedral Al–Cu–Fe ...quasicrystalline phase, i.e. periodic vs non-periodic, its mechanical properties are very similar to those of the quasicrystalline phase, which strongly suggest similar deformation mechanisms. Consequently, as for the quasicrystalline structure, we propose that dislocation climb might control the plastic deformation of the ω-phase. However, in the present case, the specificities of the quasicrystalline structure cannot be invoked to justify the predominance of dislocation climb, which questions the role of quasiperiodicity on dislocation mobility. We suggest that this deformation mode certainly results from specific non-planar extensions of the dislocation core.
•Mechanical property analogies of quasicrystalline Al–Cu–Fe and ω-Al7Cu2Fe phases.•Quasiperiodicity is not essential for modelling QC-Al–Cu–Fe phase plasticity.•Plasticity is controlled by dislocation climb.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this study, we produced four composite materials with Al-based matrix reinforced by Al–Cu–Fe particles initially of the quasicrystalline (QC) phase. The processing route was a gas-pressure ...infiltration of QC particle preforms by molten commercial Al and Al alloys. The resulting composites were investigated by scanning electron microscopy (SEM) working in the energy dispersive spectroscopy (EDS) mode and by X-ray diffraction (XRD). It is shown that such a synthesis technique leads to the formation of various phases resulting from specific diffusion processes. Compression tests were performed at constant strain rate in the temperature range 290–770
K. The stress–strain curves look similar to those of Al–Cu–Fe poly-quasicrystals and show the yield point, the origin of which is however of very different nature. Composite deformation is recognised to occur through the rupture of a hard phase skeleton and localised plastic deformation in the matrix.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Starting from a mixture of Al–Cu–Fe quasicrystalline (QC) particles and Al powder, a fully dense and almost Al–Cu–Fe ω single-phase alloy was produced by spark plasma sintering. This technique allows ...synthesising large samples with sizes suitable for mechanical spectroscopy experiments. Mechanical spectroscopy was selected because it is a relevant tool for detecting the presence of structural defects at both nano and microscopic scales. Young’s moduli were measured in the 15 kHz range as a function of temperature by the resonant frequency method. Young’s moduli behave similarly for typical metals and exhibit values that are comparable to those of the Al–Cu–Fe QC phase. The damping coefficient
Q
−1
was determined at various temperatures between room temperature and 840 K over a large frequency range, i.e. between 10
−3
and 10 Hz. The results suggest that solid friction effects do occur. In addition, a relaxation peak is observed in the intermediate temperature range.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Al-matrix material composites were produced using hot isostatic pressing technique, starting with pure Al and icosahedral (i) Al-Cu-Fe powders. Depending on the processing temperature, the final ...reinforcement particles are either still of the initial i-phase or transformed into the tetragonal ω-Al00.70Cu0.20Fe0.10 crystalline phase. Compression tests performed in the temperature range 293K − 823K on the two types of composite, i.e. Al/i and Al/ω, indicate that the flow stress of both composites is strongly temperature dependent and exhibit distinct regimes with increasing temperature. Differences exist between the two composites, in particul ar in yield stress values. In the low temperatureregime (T ≤ 570K), the yield stress of the Al/ω composite is nearly 75% higher than that of the Al/i composite, while for T > 570K both composites exhibit similar yield stress values. The results are interpreted in terms of load transfer contribution between the matrix and the reinforcement particles and elementary dislocation mechanisms in the Al matrix.
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