The paper presents an experimental program carried out to check the load bearing capacity of a steel fibre reinforced concrete (SFRC) floor in northern Italy. The extensive mechanical ...characterization focused on the suitability of 3 non-standardized test methods for quality control and tensile constitutive curve assessment was performed, this consisting of: uniaxial tensile test (UTT), double edge wedge splitting test (DEWST) and double punching test (DPT) to characterize the post-cracking mechanical properties of the material. The joint experimental programme, carried out at the Politecnico di Milano and at the Universitat Politècnica de Catalunya, included the flexural characterization of four shallow beams (1.5 × 0.5 × 0.25 m
3
) and six standard notched beams (0.55 × 0.15 × 0.15 m
3
). All the samples were produced from the same batch and with the same SFRC mix which was applied for the floor. After that, 192 cores were drilled from the shallow beams and subjected to either UTTs, DEWSTs or DPTs. The stress level, the scatter and the constitutive curves derived from the non-standardized tests were identified and analysed. The calculated constitutive curves were used to predict the behaviour of the shallow beams.
The hydrogen effect on a X65 carbon steel was investigated by tensile tests under both ex-situ and in-situ hydrogen charging conditions. The fractured samples were characterized and compared using a ...combination of scanning electron microscopy, electron backscattering diffraction, and energy-dispersive spectroscopy. The work highlights that the in-situ hydrogen charging is a necessity for investigation of hydrogen detrimental effects on the studied material, where a pronounced reduction in fracture elongation, the evolution of secondary cracks on gauge surface, and the corresponding brittle fractography were thoroughly characterized after in-situ testing. The reason resides in the rapid hydrogen outgassing effect, which was proved by Fick's law-based diffusion models. Then the interrupted tensile tests were performed to track the crack initiation and propagation behavior. The results show that the majority of cracks initiated at the interfaces of MnS and Al2O3 inclusions or between inclusions and matrix, which attributes to the elevated stress concentration around the inclusions. Moreover, the cracks were found to propagate along the {110} slip planes.
•Ex-situ and in-situ H charging method was compared on a X65 carbon steel.•In-situ H charging is more suitable for investigation of hydrogen embrittlement.•H-induced cracks initiate at non-metallic inclusions due to stress concentration.•H-induced cracks propagate in transgranular manner along the {110} planes.
Tensile deformation and damage evolution of a metastable β titanium alloy (Ti–5Cr–4Al–4Zr–3Mo–2W–0.8Fe) with lamellar microstructure are studied by in-situ tensile test under scanning electron ...microscopy. In the tensile process, the main deformation modes include the dislocation slip, phase interface shear and grain boundary shear, and the geometrical orientation of α lamellae determines the activation of different slip systems and whether the interface shear is involved in deformation. The α lamellae may kink and even fragment under severe deformation. Slip transfer is prone to occur between α lamella and β interlayer that satisfy the Burgers orientation relationship, and the slip lines will deflect and bifurcate as more slip systems are activated and grains rotate. Due to the localized stress concentration and inhomogeneous deformation, the grain boundaries, phase interfaces, tips of β interlayers, junctions of colonies composed of α lamellae and shear bands are all the positions where are easy to generate microvoids. The crack propagates along a zigzag path on account of the synergistic reaction mechanism of critical resolved shear stress, activated slip system, shear band and grain boundary shear, resulting in an intergranular and transgranular mixed fracture mode.
Due to environmental problems by the use of synthetic fibers in composite materials, researchers are more concerned with searching for eco-friendly materials. Consequently, the use of reinforcing ...fibers of natural origin is the best option that promotes the obtaining of materials that do not harm the environment. This paper presents characterization of Cortaderia selloana grass (Pampas) fibers by physical-chemical analysis, FTIR, XRD, thermogravimetric analysis, single fiber tensile test and SEM analysis. Diameter (372.6 µm), density (1261 kg/m
3
), cellulose content (53.7 wt.%), crystallinity index (22%), tensile strength (20 ± 1.0 MPa), Young's modulus (8.88 GPa), and thermal stability (320°C) properties were identified in the Cortaderia selloana grass (Pampas) fibers. Overall properties of these fibers showed that it could be an alternative source as reinforcement material for the manufacture of composite materials.
AlCoCrFeNi2.1 eutectic high-entropy alloy (HEA) was fabricated in as-cast and additively manufactured (AM) states. The hydrogen embrittlement susceptibility of both materials was investigated through ...in-situ uniaxial tensile test. Combining several advanced high-resolution scanning electron microscopy (SEM)-based techniques, the deformation and hydrogen embrittlement behavior have been intensively discussed. Interfacial cracking along both phase boundaries and grain boundaries are found to be responsible for the hydrogen-assisted fracture of this material. The cracking susceptibility has a dependence on the manufactured phase morphology. The orientation relationship between the phases and the misorientation between grains also have a significant impact on the hydrogen-induced cracks.
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•Eutectic HEA AlCoCrFeNi2.1 is fabricated by casting and additive manufacturing (AM).•AM specimen has higher H content than as-cast one after same cathodic charging.•Surface cracks are induced by H upon loading.•Angle between phase boundary and load axis influences interfacial crack possibility.•High-angle grain boundaries embrittle more than low-angle and phase boundaries.
A comparative analysis between the microstructure and the tensile properties of eutectic Sn–Bi, (Sn–Bi)–0.5In, and (Sn–Bi)–0.5Ni solder alloys was conducted, and the shear strengths of the alloys as ...Cu/solder/Cu joints were evaluated. Tensile tests were performed on bulk solder alloys, followed by post-test fracture surface analysis. The cross-sectional microstructure and shear strength of the Cu/solder/Cu joints were investigated, and the fracture surface of the joints was examined after shear tests. The results of the tensile tests indicated that the In-bearing solder alloys had the highest elongation property and the lowest ultimate tensile strength among all the solder alloys tested in this study. The shear-test results also indicated the advantage of In addition for the suppression of both the excessive growth of solder/substrate interfacial intermetallic compounds and Bi coarsening within the solder bulk, which resulted in superior shear strength in both as-reflowed and thermally aged solder joints. In addition, the dimple-like structure on the fracture surfaces of the tensile- and shear-tested In-bearing solder alloys and joints indicated the ductile property of the alloys.
Due to their high levels of formability and crashworthiness, the new quenching and partitioning (QP) steels are increasingly being used in car‐body structures. Using a unique experimental technique ...for tensile testing in a large strain‐rate range of 10−4–1000 s−1, an anomalous work‐hardening behavior is found in a QP1180 steel that may affect its formability and crashworthiness. At the lowest strain rate of 10−4 s−1, the work‐hardening rate θ decreases linearly with increasing flow stress. With an increasing strain rate, however, an increasingly severe nonlinearity in the work‐hardening rate is evident, as has been observed in metastable austenitic steels when the deformation‐induced martensitic transformation occurs at lower temperatures. This work‐hardening‐rate peak reaches its maximum at 10 s−1. Above this value, the peak decreases again, and at more than 500 s−1, it behaves like the quasi‐static test. The corresponding material characteristics, such as elongation and strength, change similarly.
By tensile testing a quenching and partitioning steel (QP1180) in a wide strain rate range of 10−4–1000 s−1, an abnormal work‐hardening behavior is observed. The material properties such as uniform and fracture elongation or area reduction at fracture change correspondingly. This work‐hardening anomaly may have a contradictory influence on sheet‐metal formability and the crashworthiness of the stamped parts.
In-situ tensile test accompanied by electron backscatter diffraction (EBSD) analyses were performed on polygonal ferrite (PF) and bainite dual-phase steel, selected regions of interest were analyzed ...following plastic deformation of the steel. Deformation-induced crystal orientation evolution, localized strain concentration, slip transfer, and geometrically necessary dislocation (GND) density were tracked. Results revealed that heterogeneity deformation facilitated formation subregions with crystal orientation deviation in grain and fragmented the grain by the new low angle grain boundaries (LAGBs) or medium angle grain boundaries (MAGBs). The PF grains with ND// preferred crystal orientation exhibited high orientation stability, and almost all load axes of the selected PF grains moved to the 101 pole, resulting in enhancing {111} orientation component at high strain levels. With the lattice rotation during deformation, the high angle grain boundaries (HAGBs) can change to MAGBs, which was beneficial to maintain coordination deformation among grains. Localized strain concentration can be decreased by the slip transfer across the PF grain boundaries or bainite/PF phase boundaries, which reduced the risk of micro-void formation. Additionally, the variation of α12 GND tensor average value (Ave. α12) revealed that the ferrite was continuous plastic deformation, while the bainite occurred stage hardening. The required strain for the coordination deformation was controlled by strain hardening behavior.
•The deformation behavior of ferrite and bainite dual phase was studied by in situ EBSD.•Orientation evolution revealed the grains heterogeneous deformation and texture evolution behavior.•The factors of affecting slip transfer were proposed.•α12 GND tensor average value was used to describe the coordinated deformation.
This study reported a strategy of three-stage heat treatment to simultaneously improve yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of laser melting deposited (LMDed) ...Ti-6Al-4V titanium alloy. After the three-stage heat treatment, the basketweave microstructure consisting of acicular α laths in the as-built sample was transformed to a multiscale-α microstructure consisting of the coarse-plate α, fine-plate α and ultrafine α in the heat-treated sample. The effect of microstructure on the tensile properties was revealed via in-situ tensile test combined with the analysis of the deformation and fracture mechanism. Although the coarse-plate α in heat-treated sample is larger than the acicular α in as-built sample, the combination of multiscale α grains with a certain relative content aroused an increment of the YS from 879 ± 28 MPa in as-built sample to 973 ± 9 MPa in heat-treated sample. The good deformation compatibility among the multiscale α grains impeded the crack propagation effectively, which resulted in the improvement of the EL from 14 ± 2% to 16 ± 1%. Furthermore, the improvement of the EL enhanced the dislocation multiplication and strain hardening in the multiscale α microstructure to induce the increment of the UTS from 945 ± 40 MPa to 1092 ± 20 MPa. The results could provide a guidance for tailoring microstructure and improving the strength and ductility of additive manufacturing titanium alloy.
In this study, the recycled Al-Mg-Mn-Fe alloys having different Fe levels (0.1%, 0.5%, and 0.8%) were successfully developed by applying squeeze casting without heat treatment. Optical and scanning ...electron microscopy, synchrotron X-ray tomography and radiography, X-ray diffraction, and tensile tests combined with thermodynamic calculations were used to study the correlation between the microstructural evolution and mechanical properties. The results showed that for the alloys with an applied pressure of 75 MPa, as the Fe increase from 0.1% to 0.8%, the yield strength (YS), and ultimate tensile strength (UTS) increased from 122 MPa and 244–146 MPa and 289 MPa, and elongation decreased from 34% to 12%. Even though Fe additions increased the volume fraction of Fe-rich intermetallic phases, it significantly increased the UTS and YS. The synchrotron X-ray tomography and deep-etched results both show that the 3D morphology changed from individual Chinese-script to interconnected plate-like. The 3D morphology of 0.8Fe alloy clearly demonstrate that the hole partially or whole penetrated the entire rectangle-shaped Al6(FeMn) phases, which is due to the close-packed plane growth. In-situ synchrotron X-ray radiography results showed the facet growth behaviour of Al6(FeMn) in 0.8Fe alloys during solidification with a long needle-like shape. The size of primary Al6(FeMn) phases decreases, whereas their number increases with increasing cooling rate. Moreover, the applied pressure was beneficial in refining the size of α-Al grains and Fe-rich phases and reducing the volume fraction of pores, thus contributing to the improvement of strength and elongation. The in-situ tensile test results indicated that the crack initiated in the Fe-rich phases and pores, and the slip lines were blocked by the Fe-rich phases resulting in the strengthening of the secondary phases.
•Fe addition increases the ultimate tensile and yield strength of Al-Mg-Mn alloys.•The 3D morphology of Fe-rich phases is reconstructed by synchrotron X-ray tomography.•The formation mechanism of hollow structure of primary Al6(FeMn) phases is revealed.•Fe-rich phases block the movement of slip lines and improves the strength.
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