Good Ductility Research Articles

Seismic Performance of Cross-Shaped Partially Encased Steel–Concrete Composite Columns: Experimental and Numerical Investigations

Special-shaped partially encased steel–concrete composite (PEC) columns could not only improve the aesthetic effect and room space use efficiency, but also exhibit good mechanical performance under static load when used in multi-story residential and office buildings. However, research on the seismic performance of special-shaped PEC columns is insufficient and urgently needed. To investigate the seismic performance of cross-shaped partially encased steel–concrete composite (CPEC) columns, three CPEC columns were designed and tested under combined constant axial load and lateral cyclic load. The test results show that the CPEC columns had good load capacity and ductility, and that the columns failed because of concrete crushing and steel flange buckling after the yielding of the steel flange. The plump hysteresis loops indicated that the CPEC column also had good energy dissipation capacity. Due to the constraint of hydraulic jacks, increasing the load ratio would decrease the effective length, thereby increasing the load capacity of the CPEC column and decreasing the ductility. A finite element model was also established to simulate the response of the CPEC columns, and the simulated results agree well with the experimental results. Thereafter, an extensive parametric analysis was performed to study the influences of different parameters on the seismic performance of CPEC columns. For the CPEC column with an ideal hinged boundary condition at the top, its lateral load capacity gradually decreases with the growth of the load ratio and link spacing and increases with the rise of the steel yield strength, concrete compressive strength, flange and web thickness, and sectional aspect ratio. This research could provide a basis for future theoretical analyses and engineering application.

Ductile Ag2S0.7Te0.3 compounds fabricated by using mechanical alloying method

Recently, Ag2S-based compounds have aroused intensive research interest due to their metal-like ductility, high shape-conformability, and decent thermoelectric (TE) performance at room temperature. The melting–annealing method is commonly adopted to prepare Ag2S-based compounds. Compared with the melting–annealing method, the mechanical alloying (MA) method has the advantages of short period and low cost, but it has not been adopted to prepare ductile Ag2S-based compounds. Herein, we successfully prepare the ductile Ag2[Formula: see text][Formula: see text] compound by using the MA method. The as-prepared Ag2[Formula: see text][Formula: see text] products are small spheres with a diameter of several millimeters rather than the powders. These spheres are phase pure with homogeneous element distribution and good deformability. After the consolidation process at 773 K, the Ag2[Formula: see text][Formula: see text] prepared by using the MA method shows good ductility like that prepared by the melting-annealing method. Finally, a maximum bending strain of above 15%, a maximum compressive strain of above 40%, and a maximum figure-of-merit (zT) of 0.5 are obtained, indicating the feasibility of MA in the preparation of ductile TE compounds.

Crack Behavior of Eccentrically Braced Frame Type-V with Ground Granulated Blast Furnace Slag

To make the structure stronger and stiffer, which is more susceptible to earthquake forces, a special mechanism is required to improve the structure's lateral stability. EBF-V with a horizontal link beam is a brace that can enhance structural performance by providing good stiffness and ductility. On the other hand, GGBFS, as a partial OPC replacement material, was applied to contribute to using more environmentally friendly materials. Besides offering a smaller carbon footprint, GGBFS also positively improves the mechanical properties of concrete. Thus, this study focuses on investigating the crack propagation pattern of reinforced concrete braced frames combined with 20% GGBFS in EBF-V with three variations of link beam element lengths of 0 cm (CBF), 15 cm (EBF-V-) and 25 cm (EBF-V-25). As a result, the CBF specimen showed the best seismic performance. In EBF specimens, there is an increase in the collapse mechanism to be more ductile. The link beam plays a role in making the crack pattern more focused. EBF-V-15 performs well under seismic loading with large lateral capacity and ductility. The cracks in the frame are evenly distributed, dominated by fine cracks, and symmetrical on both sides. This validates that GGBFS plays a good role in improving the frame performance with its pore-filling effect and pozzolanic reaction.

Ultrastrong and ductile FeNi-based alloys through Pd-containing multicomponent L12-type precipitates

Precipitation strengthening stands as a paramount strategy for enhancing the mechanical properties of FeNi-based alloys. Conventional precipitates used for strengthening typically contain only two major constituent elements selected from Ni, Al, and Ti. However, knowledge about the intrinsic properties and strengthening mechanisms of multicomponent precipitates remains limited. Here, we propose introducing novel multicomponent L12-type precipitates containing palladium (Pd) to strengthen FeNi-based alloys. The strengthened FeNi alloy achieves an eightfold increase in strength compared to the FeNi matrix while maintaining good ductility. Using meticulous micro-characterization and energy-dispersive X-ray spectroscopy (EDS) techniques, in conjunction with first-principles calculations, this study investigated the effects of Pd addition on the thermodynamic stability, morphology, coherency, and strengthening mechanisms of the precipitates. Results indicate that the addition of Pd induces the nucleation of L12-type precipitates, increases their ductility, and eliminates anisotropy in the shear modulus of the precipitates. Excessive Pd content can alter the shape of precipitates from spherical to acicular due to increased interfacial mismatch between the precipitates and the FeNi matrix. These insights shed light on the impact of Pd addition on the intrinsic properties of L12-type precipitates, offering a promising pathway for the design of advanced FeNi-based alloys with optimized mechanical performance.

Multi-scale annealing twins generate superior ductility in an additively manufactured high-strength medium entropy alloy

Coherent twin boundaries (CTBs) are internal planar defects that offer a promising pathway for designing advanced metallic materials with superior strength-ductility synergy. However, incorporating nanoscale CTBs into additive manufacturing (AM) microstructures is highly challenging without severe plastic deformation. Here, by utilizing the intrinsic cellular structures in AM alloys, we for the first time achieved a high density of multi-scale annealing twins in a laser powder bed fusion (LPBF) Ni35Co35Cr25Ti3Al2 medium-entropy alloy. These multi-scale annealing twins, together with nanoprecipitates and dislocations, resulted in gigapascal strength (∼1.4 GPa) and substantial tensile ductility (∼25 %). We reveal that the AM-induced cellular structures, decorated with entangled dislocations and Ti segregation at the cellular boundaries, facilitate the abundant nucleation of multi-scale annealing twins through interactions with migrating recrystallization boundaries. Additionally, the cellular precipitation networks enhance the thermal stability of nanoscale annealing twins. Frequent dislocation-TB interactions during deformation contribute to superior strain hardenability and thus good ductility. Synergized multiple strengthening mechanisms, i.e., boundary strengthening, precipitation strengthening, and dislocation strengthening, are responsible for the excellent strength. Our present findings advance the design of AM microstructures by harnessing the beneficial effects of cellular structures and provide valuable guidance for developing alloys with exceptional mechanical properties.

EFFECTS OF PROCESSING AL-MG ALLOY BY SEVERE PLASTIC DEFORMATION: TENSILE PROPERTIES AT HIGH TEMPERATURES

Aluminum and wrought non age-hardenable such as Al-Mg alloys became interesting alternatives for various structural applications in spite of generally moderate strength, but relatively good formability and good corrosion resistance. Increasing overall strength while preserving or even improving ductility in special conditions without any any change in chemical composition that oppositely could alter other features of the material - such as weldability, becomes an objective worthy of research. A suitable way to increase the potential of Al-Mg alloys is the raising up the mechanical properties by structural refinement. Ultrafine grain size provides enhanced mechanical and/or physical properties such as strength and very good ductility – close to superplasticity at slightly higher strain rate and relatively lower temperatures – and better corrosion resistance. Well-known as one of the most encouraging and efficacious structure refining method amid other severe plastic deformation (SPD) techniques, equal channel angular pressing (ECAP) has been deeply investigated thanks to dramatic improvements in structure and therefore properties of bulk ultrafine grained/nanostructured materials. The aim of this study is to evaluate by tensile testing at higher temperatures the mechanical properties of an Al-3.4%Mg alloy previously processed by ECAP up to 8 passes, as a candidate for replacing AA5154 which contains different amounts of chromium. The tensile tests conducted at different temperatures using a computer-controlled testing machine with different strain rates showed in terms of engineering stress vs. engineering strain evolution that the ECAPed Al-3.4%Mg alloy have the potential to be used in technological processes at high temperatures, opening opportunities for industrial applications requiring high ductility.

Regulating the mechanical anisotropy of Mo2AC MAX phases through interlayer control

The structural editing protocol for layered carbides (MAX phases) has been proven to be an effective means of expanding the MAX family. Therefore, this study employs first-principles calculations to manipulate the mechanical anisotropy of Mo2AC MAX phase by regulating the interlayer (A = Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se). By manipulating the A layer, the anisotropy of Young's modulus can alternate among spindle, funnel, and shuttle shapes, while the shear modulus can similarly transition among these forms. This method can adjust anisotropy indices AU from 0.13 to as high as 3.4 and Ashear from 1.15 % to 25.37 %. Besides, electronic calculations indicate that the interlayers of Mo2AC (A = metal) possess a large number of free electrons along the XY plane, while the electrons in Mo2AsC and Mo2SeC are distributed along the Z-axis. Consequently, Mo2AsC and Mo2SeC exhibit good ductility and are suitable for mechanical processing. This work lays a solid foundation for the manipulation of mechanical anisotropy in practical engineering applications through the regulation of the interlayer in the Mo2AC MAX phase.

Tensile behaviors of rolled and annealed 90W7Ni3Fe alloy

Tungsten heavy alloys (WHAs) with two-phase composite structures display unique mechanical properties. Here, we explore the effects of rolling strain and annealing temperature on tensile behaviors of 90W7Ni3Fe WHAs. Cold rolling followed by low-temperature annealing (<1000 °C) induces an increase in yield strength at the expense of ductility. The ductility of WHAs can only be restored by raising the annealing temperature to 1000 °C. Keep the annealing at 1000 °C while gradually increasing the rolling strain not only improves the strength of WHAs but also maintain a good ductility. Once exceeding a critical rolling strain of 60 %, the yield strength of WHAs increases to 1480 MPa, while result in a substantial decrease in ductility. The evolutions of two-phase composite structures with rolling and annealing induces the alterations of the tensile properties of WHAs. These results provide a reference for designing thermal-mechanical processing recipes for WHAs.

Electronic, optical, elastic, and thermal properties of the half-Heusler-derived Ti2FeNiSb2: A DFT study

The electronic, optical, elastic, and thermal transport properties of half-Heusler-derived (HHD) Ti2FeNiSb2 are comprehensively characterized via density functional theory. The stability of HHD Ti2FeNiSb2 is evaluated by the phonon dispersion, formation energy, and phase separation, and its elastic constants meet the mechanically stable conditions. HHD Ti2FeNiSb2 is predicted to be an indirect nonmagnetic semiconductor with a bandgap of 0.94 (PBE) eV and 1.75 (HSE06) eV. To further understand the electronic structures, the atomic orbital projection of the electronic band structure is systematically studied and discussed. The band structures and bandgap can be sensitively tuned by the strain. The calculated elastic and optical properties indicate that Ti2FeNiSb2 has good ductility and hardness, and the optical property calculations reveal its excellent potential for harvesting solar energy. Using the elastic properties, the minimum lattice thermal conductivity is evaluated by the Slack, Clarke, and Cahill models. Based on the Slack model, the lattice thermal conductivity is 5.93 W/mK at 300 K; this value is consistent with the experimental value.

Injection Micropile Bar Fatigue Resistance at Loads Lower and Greater than the Yield Strength of Steel

One of the techniques commonly applied today for deep foundation construction is based on self-drilling injection micropiles. Micropiles are structural elements intended primarily for reinforcing foundations and buildings, particularly under difficult terrain conditions. The goal of the tests presented herein is to inspect the fatigue resistance, strength and ductility of injection micropiles formed from 28Mn6 steel at loads significantly exceeding the values defined for the fatigue test in the requirements of the relevant European Assessment Document (EAD). The test results and the micropile bar strain model εM presented in this paper are primarily of interest to designers for the purposes of determining the fatigue resistance of steel micropiles, which find particular application in land degraded by mining activity that is characterised by frequent terrain vibration and mining-induced tremors. None of the R25N injection micropile bars failed during the fatigue resistance testing at 2·106 cycles at a load Fu = 0.7·FRe0.2 (under the yield strength of the 28Mn6 steel) as well as at Fu = 1.0·FRe0.2 and Fu = 1.2·FRe0.2, where the bars operated at the limit of and significantly above the load FRe0.2 which results in stress at the yield point of the 28Mn6 steel. Furthermore, the bar tests conducted at static and cyclic loading demonstrated the high strength and good ductility of the 28Mn6 steel.

A novel reduced thermal conductivity ductility cement-based composite material with containing aerogels: Towards multi-function in buildings

Fully exploring and expanding the performance of building materials has become an important direction for the sustainable development of building materials. In this study, low-density silica aerogel (LSA) with a density of 74.3 kg/m³ and conventional silica aerogel (CSA) with a density of 141.6 kg/m³ were used as partial aggregates to prepare a reduced thermal conductivity ductility cement-based composite material (RTCDCC). Based on this, the effects of LSA and CSA at different contents on the compressive strength, four-point bending performance, water absorption, thermal conductivity, and density of RTCDCC were compared and studied. The results showed that when the aerogel content was the same, the influence of LSA on the mechanical and physical properties of the mixture was more significant compared to CSA. Furthermore, the mixture exhibits good ductility when the content of aerogel was less than 30 %. Additionally, the impact of different density aerogels on the internal pore distribution of the mixture was investigated through low-field nuclear magnetic resonance (NMR) tests, providing further insights into the reasons for the variations in performance between LSA and CSA mixtures. Notably, the RTCDCC prepared in this study not only has good compressive strength but also maintains a lower thermal conductivity, and an average comprehensive performance index (Icp) of 0.63, which promotes the application of aerogel in the realm of multi-function building materials.

Sc/Zr microalloying on strength-corrosion performance synergy of wire-arc directed energy deposited Al-Mg

ABSTRACT WADED Al-Mg and Al-Mg-Sc-Zr aluminium alloy thin-wall components were produced. Heat treatment (350°C aging for 4 h) was further conducted. The effects of Sc/Zr addition on porosity, microstructure, mechanical properties and corrosion behaviour were investigated. With Sc/Zr adding, pore area fraction decreased from 0.208 to 0.005% and grain size decreased from 84.34 to 19.54 μm. In WADED Al-Mg-Sc-Zr component, microstructure showed refined equiaxed grains. Mechanical properties were improved with 360 MPa ultimate tensile strength (UTS), 185 MPa yield strength, and 23.31% elongation. After heat treatment, UTS increased to 388 MPa with good ductility (22.53%) maintained. The grain refinement and Al3(Sc, Zr) particles were the key factors for mechanical property improvement. The corrosion behaviour was improved with introduced Sc/Zr and further optimised after heat treatment. The corrosion exhibited layered characteristics due to the distribution of primary Al3(Sc, Zr) while minor-size secondary Al3(Sc, Zr) along grain boundaries improved the corrosion behaviour.

Seismic performance of an assembled monolithic concrete column

A prefabricated concrete column-to-column structure connected by high-strength bolts is proposed. To explore the seismic performance and failure form of the structure, the finite element analysis software is used to simulate the low-cycle repeated load test. The hysteretic curve and skeleton curve of the structure are obtained, and the stiffness degradation law, ductility and energy dissipation capacity of the structure are quantitatively analyzed to evaluate the seismic performance of the structure. The results show that the ductility coefficient of the structure is basically between 2.19 and 4.97, and the ductility coefficient of most specimens is greater than 3.0, indicating that the structure has good ductility and deformation capacity. The equivalent viscous damping coefficients of the specimens are in the range of 0.21–0.29, indicating that the structure has good energy dissipation capacity. In a certain range, increasing the thickness of the end plate has no significant impact on the energy consumption capacity of the structure. The compressive strength of the concrete in the core area is greatly improved under the constraint of the end plate bolts, and end plate bolt connection can well realize the transmission of force and give full play to the performance of materials.

Analysis of microstructure and compressive properties of full coral concrete under fiber reinforcement

Based on the compressive tests of 120 cubes in 10 groups, the effects of different chopped fibers (polypropylene fiber PPF, glass fiber GF, basalt fiber BF) and their content on the compressive properties of coral aggregate seawater concrete (CASC) were studied. The microstructure of CASC was analyzed by scanning electron microscopy (SEM), and the relationship between microstructure and macroscopic properties was established. The results show that the growth rate of compressive strength of fiber CASC is fast in the early stage and slow in the late stage. When 1 kg/m3, 2 kg/m3 and 3 kg/m3 of PPF were added to the CASC, the compressive strength increased by 6.2 %, 17.4 % and 9.9 %, respectively. SEM images show that PPF forms a dense, chaotic three-dimensional mesh structure in the matrix, which can effectively inhibit crack extension within a certain doping range. Compared with BF and GF, PPF has a more significant effect on improving the mechanical properties of CASC, and the optimal PPF content is 2 kg/m3. Adding PPF could improve the brittleness of concrete and make it show good ductility when it is destroyed.

Testing and finite element analysis of internal mechanical properties of compressed concrete

In order to conduct intensive research on the inside stress-strain curve relationship of compressed concrete, a novel relevant testing device was developed and embedded inside concrete specimens and we conducted conventional uniaxial compression loading tests on concrete specimens. Based on experimental data, combined with several typical constitutive equations of concrete, simulation is conducted on the experiment. The results show that the core area inside the concrete has good ductility compared to the other parts, and the measured constitutive curve inside the concrete is reasonable and accurate, which is in good agreement with the finite element simulation results based on Chinese standards. It proves that the relevant measurement methods have fine accuracy and applicability, and can be further promoted and used.

Dislocation cells tailored precipitation enhancing mechanical properties of a high Gd content Mg alloy

High Gd content Mg alloys are expected to overcome the poor heat resistance of magnesium (Mg) alloys. However, the low ductility limits their applications. Nano-precipitates is a viable method to enhance the strength without seriously plummeting ductility. In this study, ultrafine and densely arranged dislocation cells, with an average size of 27 nm, were obtained in Mg-11.5Gd-2Y-0.5Zr-0.5Ag-0.5Nd alloy after hot rolling. During the aging process, the dislocation cells facilitated the precipitation of fine and high-density β'. In the peak-aged (225 °C, 15 h) alloy, the volume fraction of β′ could reach 20.3 %, and the average length and thickness of β′ are 10 and 5.9 nm, respectively. The alloy with such a microstructure exhibited a yield strength (YS) of 403 MPa, and an EL of 8.3 % at room temperature. YS of the alloy was still 357 MPa, 310 MPa, and 206 MPa at 200 °C, 250 °C, and 300 °C, respectively. The high YS is attributed to grain boundary, dislocation, solid solution, and precipitation strengthening, among which precipitation strengthening is dominant. Moreover, the nano-β′ could be sheared, thereby coordinating the plastic deformation. Therefore, the present alloy achieved high YS while maintaining good ductility.

Welding of Steel - Its Mechanism and Applications in Multiple Sectors

Among different metals steel can be easily welded and welded steel has required strength, good ductility and sufficient resistance to general corrosion media. Since steel welding is being used in all types of fabrication industries, the mechanism of steel welding has been explored for different types of steel along with its multiple applications.

AlxCoCrCuFeNi (X = 0, 0.8) high entropy alloys fabricated by laser powder bed fusion

ABSTRACT The AlxCoCrCuFeNi (x = 0, 0.8) high entropy alloys (HEAs) were prepared by laser powder bed fusion (LPBF), and the effects of volumetric energy density (VED) and heat treatment on microstructures and mechanical properties of HEAs were investigated. The results show that the CoCrCuFeNi HEA has a single FCC phase structure and exhibits good ductility. Its yield strength is relatively low, being 520 MPa. After the alloy composition was adjusted from CoCrCuFeNi to Al0.8CoCrCuFeNi, the HEA changed from FCC single-phase to FCC + BCC dual-phase structure and the hardness and compressive properties were significantly improved. Among them, the Al0.8CoCrCuFeNi HEA prepared with the VED of 167 J/mm3 has the best mechanical properties, with a compressive yield strength of 652 MPa and good plasticity. After annealing at 600°C and 900°C for 1 h, the mechanical properties of HEAs are significantly improved. In particular, the microhardness and compressive yield strength of the Al0.8CoCrCuFeNi HEA annealed at 600°C for 1 h are 378 HV and 810 MPa, respectively. The coordinated deformation between FCC and BCC domains, back stress strengthening, solid solution strengthening and precipitation strengthening after heat treatment make the Al0.8CoCrCuFeNi HEA achieve a balance of high strength and good ductility.

Study on evaluation method of circular small shadow profusion in chest CT reconstruction images of pneumoconiosis

Objective: To select chest CT image patterns for the diagnosis of pneumoconiosis and establish a method for determining the profusion of circular small shadows in chest CT. Methods: In April 2021, 66 cases of occupational pneumoconiosis patients with digital radiography (DR) chest radiographs and chest CT imaging data with circular small shadow as the main manifestations were selected as the study objects. 1.5 mm and 5 mm chest CT axial images, 1 mm and 5 mm chest CT coronal multi-plane recombination (MPR) images, and 5 mm chest CT coronal maximum intensity projection (MIP) images were used to observe the different characteristics of pneumoconiosis patients, and were compared and analyzed with DR chest radiographs to establish the experimental chest CT standards. The consistency of the profusion results between the experimental chest CT standards and GBZ 70-2015 Diagnosis of Occupational Pneumoconiosis was verified. Results: All the 66 objects were male, including 33 cases of stage Ⅰ pneumoconiosis, 17 cases of stage Ⅱ pneumoconiosis and 16 cases of stage Ⅲ pneumoconiosis. By observing five chest CT images of 66 objects, we found that chest CT images of different modes could clearly display and identify abnormal images such as small circular shadow, large shadow, small shadow aggregation, honeycomb glass shadow, flake glass shadow, uniform low-profusion glass shadow, mesh glass shadow, cable shadow, linear shadow, subpleural spinous shadow, subpleural nodules, various kinds of emphysema and lung texture distortion and fracture. Small shadow aggregation was usually accompanied by the appearance of large shadow. The vascular shadows in 5 mm CT images had good ductility, and small nodules were easy to distinguish. The coronal MIP image of 5 mm chest CT used edge enhancement technology, which was prone to small shadow fusion and fibrotic shadow fusion. The coronal MPR image of 5 mm chest CT was highly consistent with the DR chest radiographs in terms of the integrity of film reading. GBZ 70-2015 standard was used to compare the profusion of DR chest radiographs and 5 mm chest CT coronal MPR images of 66 objects, and the consistency test Kappa=0.64. GBZ 70-2015 standard and experimental chest CT standard were used to compare the profusion results of DR chest radiographs and 5 mm chest CT coronal MPR images of 66 objects, respectively, and the consistency test Kappa=0.80, with high consistency. Conclusion: 5 mm coronal MPR image is suitable for chest CT imaging in the diagnosis of pneumoconiosis. Following the selection path and method of GBZ 70-2015 profusion criterion, the established experimental chest CT standard in determining the profusion of small circular shadows in 5 mm coronal MPR images of chest CT with pneumoconiosis has a high consistency with GBZ 70-2015 standard.

Tensile Properties of a Non-Equiatomic Ni–Co–V Medium Entropy Alloy at Cryogenic Temperature

The development of strong and ductile alloys for application in cryogenic temperatures has long been sought after. In this work, we have developed a face-centered cubic Ni10Co56.5V33.5 multi-principal element alloy (MPEA) that exhibits a balanced combination of high strength and good ductility at 77 K, based on the considerations of large local lattice distortion (LLD) and low stacking fault energy. The small-grained Ni10Co56.5V33.5 MPEA exhibits a yield strength of 1400 MPa and an ultimate tensile strength of 1890 MPa, while preserving a good ductility of 23%. Moreover, precession electron diffraction and transmission electron microscopy revealed multiple deformation mechanisms, including wavy dislocations, atypically severely twisted dislocation bands, hierarchical stacking faults, and deformation twins, which are implicated in the alloy’s outstanding mechanical performance. These insights offer a strategic guide for the design of strong and ductile alloys, particularly for utilization in extreme environments.