Good Ductility Research Articles

Effect of Ni and Nb concentration on microstructural evolution in a 20Cr ferritic alloy strengthened by Ni16Nb6Si7-G phase

The effects of Nb and Ni contents on the precipitation of the Ni16Nb6Si7-G phase and the resulting hardening behavior in Fe–20Cr ferritic alloys were systematically investigated using micro-hardness, electron microscopy, and atom probe techniques. The results demonstrate that an optimal Nb content of ∼0.75 wt. % promotes the precipitation of the Ni16Nb6Si7-G phase, leading to a maximum micro-hardness of approximately 430 H V when aged at 560 °C for 24 h. Excess Nb content (>0.75 wt. %) introduces the Fe2Nb-Laves phase at grain boundaries and within the grains, which competes with the G-phase for precipitation. Conversely, an increase in Ni content effectively raises the dissolution temperature of the Ni16Nb6Si7-G phase to approximately 850 °C. The austenite phase begins to form when the Ni content exceeds 4 wt. %. Finally, the strengthening effect of the Ni16Nb6Si7-G phase and its underlying competition precipitation with the Fe2Nb-Laves phase as well as the possible benefit of inducing austenite phase was discussed in the context of developing 20Cr ferritic alloys with high strength and good ductility. These findings provide valuable insights into the influence of Nb and Ni contents on the microstructural evolution and mechanical properties of the newly developed 20Cr alloy, which may be helpful in guiding the design of high performance ferritic alloys by optimizing composition and heat treatment processes.

Experimental study on seismic performance of a new precast segmental assembled single column bridge pier

Prefabricated bridge technology has come into wide spread use as fabricated technology has advanced, but engineering applications of fabricated bridge technology are primarily focused on the bridge superstructure, considerably restricting the use of prefabricated bridge technology for the bridge substructure due to the uncertainty in the seismic performance and damage mechanism of segmental assembled piers. Based on this, two new segment connection methods were proposed and applied to the prefabricated piers. Four specimens with a scale of 0.4 were designed and manufactured. The seismic performance of two new types of assembled single column piers, namely cone sleeve-FRC (CSF) wet joint segmental assembled pier and main reinforcement lap-UHPC (MRLU) wet joint segmental assembled pier, is investigated and compared with integral cast-in-place pier to analyze the effects of FRC and UHPC on the seismic performance of the piers, using the proposed static test. The results show that the pier connected by cone sleeve-FRC wet joint exhibits a good energy dissipation and ductility, small deformation, the highest peak bearing capacity and the best seismic performance. Based on the tests, finite element models of the members were created, and the member CSF-1, which has the best seismic performance, was parametrically analyzed by taking three influencing factors into account: axial compression ratio, longitudinal reinforcement area and hoop reinforcement spacing. It is indicated that a significant improvement in seismic performance can be achieved by reducing the hoop spacing, increasing the longitudinal reinforcement diameter and axial compression ratio.

Achieving a superior combination of strength and ductility by adjusting heterogeneous structure in a Fe–Mn–Al–Mo–C lightweight steel

A combination of high strength and good ductility was achieved by adjusting heterogeneous structure through varying annealing temperatures ranging from 750 to 900 °C after cold rolling in a Fe–Mn–Al–Mo–C lightweight steel. The microstructure consists of heterogeneous recrystallized, unrecrystallized grains containing nanoscale Mo2C precipitates, and intergranular Mo-enriched carbides. As annealing temperature increases, the fraction of recrystallization, and the average Schmid factor increase, while the average grain sizes and the volume fraction of Mo2C decrease. Annealing at 825 °C forms a desirable heterogeneous structure characterized by a normal bimodal grain distribution and diffuse precipitation of intragranular Mo2C particles. Tensile test results indicated that higher annealing temperatures decrease strength but enhance ductility. However, the yield strength of the 825 °C annealed sample only slightly decreases compared to the 800 °C annealed sample owing to the synergistic contributions of various strengthening mechanisms, including grain boundary, solid solution, precipitation, and heterogeneous deformation-induced strengthening. Furthermore, its ductility significantly improves, approaching that of the 850 °C annealed sample, facilitated by sustained heterogeneous deformation-induced strengthening effects and significant refinement in grain structure. The high strain hardening rate of the C825 sample is attributed to dynamic slip band refinement and local stress adjustments during later deformation stages. The heterogeneous grain structure induces a strong HDI strengthening effect due to uneven deformation, which also contributes to the high strain hardening rate. These findings highlight the potential of Fe–26Mn–8Al-1.2C–3Mo lightweight steel for applications requiring a balance of strength and ductility.

THE EFFECT OF ARC STUD WELDING PARAMETERS ON MECHANICAL PROPERTIES OF DOCOL 1500M ADVANCED HIGH STRENGTH STEEL WELDING JOINTS

Arc stud welding method is a welding method that takes advantage of the arc's ability to melt metals. Stud welding is an easy and fast welding method that is generally applied to surfaces where threading is problematic and welding is difficult. Docol 1500 martensite materials are high-strength steels with high tensile strength up to 1700 MPa and good ductility. These type of materials provide high efficiency, especially in the automotive industry, in terms of both vehicle lightness and advanced crash protection. In this study, the weldability of threaded studs made of 20MnB4 grade carbon steel was investigated using the arc stud welding process on Docol 1500M plate. The arc stud welding process was carried out using a ceramic ferrule at different combination values with electric current values ranging between 300A and 500A and different welding times ranging from 0.125 seconds to 0.300 seconds, as well as variable welding parameters such as 3mm plunge value and 5.9mm lift distance. With the experimental study, the most suitable welding parameters were try to determined according to the size and properties of the materials to obtain a quality welded. At the end of welding process, the effects of arc stud welding parameters such as welding current, welding time, plunge and lifting distance on mechanical and microstructural properties were experimentally investigated.

Effect of Cu upon recrystallization and mechanical properties of TRIP-assisted high entropy alloy

The face-centered cubic (FCC) high-entropy alloys (HEAs) have been hindered in their engineering applications due to their low yield strength. Combining multiple strengthening mechanisms with phase transformation-induced plasticity (TRIP) may serve as an effective approach to overcome the strength-ductility trade-off. In this study, (Co3Cr1.6FeNi)100-xCux (x = 0,2) high entropy alloys (HEAs) were designed. A straightforward processing route, involving hot rolling followed by annealing, was utilized to produce single-phase FCC HEAs. The alloy doped with 2 at.% Cu achieved a perfect combination of strength and ductility. It was also found that the addition of Cu suppresses the recrystallization process during the hot rolling and annealing of the alloy. The increase in strength is attributed to the synergistic effects of various strengthening mechanisms dominated by dislocation strengthening and heterogeneous deformation induced strengthening, while the TRIP effect ensures continuous strain hardening capability of the alloy while maintaining high yield strength and ensuring good ductility. These results offer valuable insights into the design and development of high-performance HEAs with exceptional strength and ductility.

Effect of heat treatment on the microstructure and mechanical properties of Mg-Gd-Y-Zr alloys fabricated by wire arc additive manufacturing

ABSTRACT Wire arc additive manufacturing (WAAM) technology is expected to be used for the fabrication of large and complex magnesium alloy components. In this work, Mg-9.54Gd-1.82Y-0.44Zr (wt.%, GW92) alloy thin-walled components were fabricated by cold metal transfer (CMT) arc in CMT-Advance mode. The microstructure of the WAAMed GW92 alloy consists of fine equiaxed ɑ-Mg grains with an average size of ∼17 μm, eutectic phases, β" phase, cubic phases, and Zr particles. The short-term high-temperature solution treatment at 525 ℃ for 25 minutes significantly reduced the content of the eutectic phase, resulting in a significant increase in elongation (EL) (13.5 ± 0.3%). The peak aging time of the solution-treated GW92 alloy at 225 ℃ for 12 h. The WAAM-T6 sample showed a significant increase in strength while maintaining good ductility, with a yield strength (YS) of 235 ± 3 MPa, ultimate tensile strength (UTS) of 360 ± 7 MPa, and elongation of 10.8 ± 1.7%. The synergistic strength and ductility properties of Mg-Gd-Y-Zr alloys fabricated by the WAAM process were significantly impacted by the short-term high-temperature solution + aging treatments to preserve the fine grain and high-density.

Trimodal Grain Structured Aluminum Matrix Composites Regulated by Transitional Hetero-Domains

Aluminum matrix composites (AMCs) with hetero-grains exhibit high strength with good ductility. A trimodal grain structure composed of ultrafine grains (UFGs), fine grains (FGs) and coarse grains (CGs) prevents the pre-mature cracking of hetero-zone boundaries in conventional bimodal grain structures; thus, it is favored by AMCs. However, the design of the size and distribution of hetero-domains in trimodal AMCs is tough, with complicated multi-scale deformation mechanisms. This study tunes the distribution of FG domains elaborately via altering the volume fraction of FG from 10 vol.% to 60 vol.% and investigates the distribution effect of FG domains on strength–ductility synergy. The optimized 2024 Al matrix composites with 30 vol.% FG exhibited a tensile strength of over 700 MPa and an elongation of 7.5%, respectively, realizing a good combination of high strength and ductility. This work enlightens the heterostructure design with a balance between heterogeneous deformation induced (HDI) strain hardening and high-content soft phase induced strain homogenization.

On the microstructural evolution and mechanical property development of additively manufactured AlCoCrFeNi2.1 eutectic high-entropy alloy with aging temperature

In this study, the microstructure and mechanical properties of a laser powder bed fusion processed eutectic high-entropy alloy, AlCoCrFeNi2.1, and the influence of aging temperature have been investigated. The as-printed material consists of a hierarchical cellular eutectic microstructure with γ cells and a B2 network along the cell boundaries. The γ matrix contains homogeneously distributed Al2O3 nanoparticles and sporadically distributed L12 long-range ordered (LRO) domains. Some B2 grains contain ultrafine body-centred cubic Cr-rich precipitates. Aging at 500–700 °C leads to disruption of the B2 network and coarsening of the B2 grains at the intersections of several cells and thinning of the rest of the regions. At 800 °C, the B2 cellular network completely disappears and turns into large isolated spherical or near-spherical B2 particles with the original γ cells being fully integrated. At 600 °C, numerous ultrafine γ′ nanoparticles form from the γ matrix and turn into elongated γ′ at 700 °C but completely disappear at 800 °C due to the formation of thermally more stable B2 precipitates. The as-printed samples show a high yield strength (YS∼ 1050 MPa) and good ductility (elongation ∼ 20 %) due to the strengthening effects from the LRO domains and the less deformable B2 and Al2O3 particles. Aging at 600–700 °C leads to significant strength improvement mainly owing to the γ′ particles. Aging at 800 °C results in a considerable decrease in YS but improves the ductility due to the disappearance of γ′ precipitates and the B2 cellular network.

Microstructure, Non-Basal Texture and Strength-Ductility of Extruded Mg-6Bi-3Zn Alloy.

To investigate the influence of Zn-alloying on the microstructure and tensile mechanical properties of Mg-6Bi alloy after hot extrusion, a new ternary Mg-6Bi-3Zn alloy was prepared by extrusion at 300 °C. The microstructures, texture, dynamic precipitates and tensile mechanical behaviors of the extruded alloy were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and a material testing machine at room temperature. After extrusion, the Mg-6Bi-3Zn alloy possesses a bimodal microstructure with elongated large unrecrystallized (unDRXed) grains and fine dynamic recrystallized (DRXed) grains. In addition, non-basal <202_1>//ED, <448_3>//ED and <112_1>//ED textures are observed within DRXed grains due to the Zn addition, leading to texture weakening in the extruded Mg-6Bi-3Zn alloy. Zn addition facilitates the dynamic precipitation behavior, leading to a 12.2% area fraction of Mg3Bi2 precipitates with an average size of 39.2 nm. Furthermore, incorporation of Zn atoms in Mg3Bi2 phases and segregation of Zn at the grain boundary are found. The extruded Mg-6Bi-3Zn alloy exhibits a tensile strength of 336 ± 7.1 MPa and a yield strength of 290 ± 5.5 MPa, as well as an elongation of 11.5%. Therefore, Zn addition is beneficial to enhance strength and keep good ductility for the extruded Mg-6Bi-3Zn alloy.

Effect of unusual texture on tension-compression asymmetry for Mg-RE alloy by viscoplastic self-consistent modeling

The tension-compression asymmetry presents notable challenges for the application of magnesium alloys in many fields. In this study, the solid-solution treated Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy's tension-compression asymmetry was examined using optical microscope (OM), x-ray diffraction (XRD), viscoplastic self-consistent (VPSC) modeling, and electron backscatter diffraction (EBSD). The VPSC hardening parameters were significantly adjusted based on the Schmid factor of deformation modes in rare earth magnesium (Mg-RE) alloy, which came from the EBSD data. Excellent agreement was found between the modified VPSC model's calculation results, especially the stress-strain curves and pole figures. The alloy exhibited good strength with a negligible tension-compression asymmetry and an impressive 0.98 ratio of compressive yield strength to tensile yield strength (CYS/TYS). The main cause could be attributed to the unusual texture of (11-20) <0001> in alloy, which eliminated the imbalance in tension and compression deformation by having a negative effect on the activation of {10-12} twinning in tensile and a positive effect in compressive deformation. The activation level of {10-12} twinning was 0.37 and 0.40 calculated by VPSC model, in the plastic deformation of tension and compression, respectively; in the tensile and compression samples, the EBSD data indicated that approximately 31.9% and 31.1% (area proportion) of the grains were deformed with twins, respectively. Both tension and compression deformation showed the {10-12} twinning in the early stage of deformation, which transformed to {11-22} twinning in the later stage. The considerable activation of pyramidal <c+a> during the later stages of deformation endowed the alloy with good ductility.

Innovative demountable steel-timber composite (STC) beams: Experimental full-scale bending tests

This study introduces an innovative demountable steel-timber composite (STC) flooring system with potential for reuse. The flooring system consists of downstanding hot-rolled I-shaped steel profiles and laminated veneer lumber (LVL) slabs connected to the steel beams with novel shear connectors. This STC flooring system aimed at reducing embodied carbon and optimizing the use of resources, offer an alternative to traditional, carbon-intensive flooring systems. The novel shear connections implemented in the STC beams facilitate demountability, adaptability, reconfiguration, and relocation of structural components, aligning with circular economy principles. Moreover, this flooring system exhibits significant promise for modularization, standardization, and off-site serial production, making it ideal for prefabrication in standard sizes and modules. Two full-scale STC beams, each with a span of 10 m, an LVL slab width of 2.51 m and thickness of 144 mm connected to a steel profile IPE 400, were simply supported and tested in six-point bending to assess their flexural response. The two tested beams were identical in terms of geometry, materials, and shear connection distribution, but differed in the type of shear connection implemented. This contribution outlines the details of the innovative flooring system and the novel connections that enable demountability and reusability of the components. Specifics of the two STC beam specimens, their assembly, the test setup, the instrumentation, and the testing procedure are presented. The results of the two full-scale bending tests demonstrate their significant load-bearing and deformation capabilities as well as potential for reuse. Additionally, the results indicate the efficacy of the novel shear connections and the beams' overall structural integrity. Despite the extensive deformation of the STC beams, the shear connections remained undamaged and slip values of less than 7 mm were recorded in the last loading stages. Within the elastic range, maximum slip values of less than 1 mm were recorded, highlighting the structural components' potential for reuse. Midspan deflections exceeding l/20 demonstrate good ductility. Strain measurements on the timber slabs revealed that the slabs' width was not fully utilized, leading to the determination of an effective width of l/5.5.

Concentrated growth factor intradermal injection assisted super-thin flap expansion for repairing skin defects: A randomized, single blinded, split-site study.

The super-thin skin flap formed by skin and soft tissue expansion has large area and good ductility, so it can be used to repair skin defects. However, because the flap is thin, the blood flow in the dermis of the super-thin expanded flap is weakened, and flap rupture and necrosis after secondary flap transfer may occur. To compare the skin thickness difference between the expanded ultrathin flaps injected with concentrated growth factor (CGF) and the blank group or saline group. From June 2021 to December 2023, 10 patients (44 sites) with large-area scars or skin tumors were treated, and a single center half randomized controlled trial was conducted. The test site of expander implantation was divided into three groups: intradermal injection of CGF group, normal saline group and blank group. The same amount of expansion was performed every 1-2 weeks, and CGF or normal saline was injected into the dermis every 4 weeks, a total of three times. After 2-3 months of expansion, color Doppler ultrasound was used to measure the skin thickness of each group. Compared with the blank group, the skin thickness of CGF group was 1.75 ± 0.08 mm, and that of BLA blank group was 1.42 ± 0.07 mm, with statistically significant difference (p < 0.0001); In the other group, compared with the saline group, the skin thickness of the CGF group was 1.54 ± 0.08 mm, and the average skin thickness of the saline group was 1.40 ± 0.08 mm, with significant difference between the two groups (p = 0.0067). CGF intradermal injection can increase the skin thickness of super-thin skin flap in the process of soft tissue expansion, which is a safe and effective auxiliary method of skin expansion.

Low-cost Ti-6Al-4V containing low content nano-carbon solid solution for achieving high strength and good ductility

With the rapid advancement of the aerospace industry, in addition to higher requirements for material properties, the cost-effective of its production have also attracted more attention. In this work, titanium matrix composite with high performance and low cost was designed using ball milling, spark plasma sintering and hot rolling process, i.e. hydrogenated dehydrogenated Ti and AlV powders as the precursor of Ti-6Al-4 V matrix, and a low content (0.15 wt%) reduced graphene oxide (rGO) with high-activity was selected to reinforce the matrix alloy. The as-rolled composite shows obvious texture orientation along the rolling direction without pores and microcracks. The incorporation of rGO led to the activation of the as-rolled composites along the {0001}[112¯0] type base slip. The as-rolled composite containing only 0.15 wt% rGO exhibits superior yield strength (1308.1 MPa) and ultimate tensile strength (1444.3 MPa), which are 11% and 9.3% higher than those of the matrix alloy, respectively, and the elongation remains at ∼5.6%. The strengthening mechanisms are mainly attributed to the solid solution strengthening effect of interstitial carbon in the matrix after the incorporation of rGO. This work highlights the development potential of low-cost and high-strength titanium matrix composites

Surface modification of CNTs through the SiO2 coating to increase the intragranular reinforcement content in Al matrix composites

Surface modification of CNTs with SiO2 coating was proposed to fabricate Al matrix composite with high-content intragranular reinforcements. The deposition of SiO2 nanoparticles on the surface of CNTs improved their compatibility with the Al matrix and thus increased the penetration of CNT@SiO2 reinforcements into Al grain interiors during powder processing. The intragranular reaction during the sintering process converted the CNT@SiO2 hybrid reinforcements into Al4O4C nanoparticles, leading to a remarkable increment in reinforcement content. As a result, incorporating CNT@SiO2 reinforcements (0.5 wt% CNT coated with 2 wt% SiO2) into Al resulted in a final composite with 9 vol% nanoreinforcement, of which 85 % were located in the grain interiors. The high-content intragranular reinforcements greatly improved dislocation storage capability and strain hardening rate, resulting in a significant increase in strength while retaining good ductility. The composite's yield strength and tensile strength increased to 370 MPa and 472 MPa, respectively, which were about 66 % and 67 % higher than those of the CNT-Al composite with the same CNT content.

Understanding the tensile ductility of a novel low-activation BCC high-entropy alloy deformed at intermediate temperature

Low-activation body-centered cubic (BCC) high-entropy alloys (HEAs) often possess poor tensile ductility. Here we report a novel low-activation VCrFeMn0.33 BCC HEA that exhibits good tensile ductility at 650 °C and above. However, it shows poor tensile ductility at 500 °C and below, indicating that the ductile-to-brittle transition temperature (DBTT) of the current HEA falls between 500 °C and 650 °C. At temperatures above DBTT, the current BCC HEA deforms via dislocation glide, similar to the tensile deformation observed in conventional ductile BCC alloys, which is rarely reported for non-refractory BCC HEAs.

Improving the strength and maintaining good ductility of as-forged Ti6Al4V alloy by regulating the microstructural defects

Solution-aging treatment is a conventional method for enhancing the strength of titanium alloys contributed by the decomposition of metastable phases, like martensite. The traditional viewpoint suggests that the martensite transformation occurring after water quenching does not significantly contribute to the strengthening of titanium alloy and this perspective actually overlooks the high strength resulting from the high-density defects formed in the martensite microstructure due to rapid cooling. So, previous studies have not fully taken advantages of the excellent strengthening capability of martensite. This study adopted a technique which combined solid solution and incomplete aging treatment to control the decomposition behavior of martensite and as a result, the strength of the as-forged Ti-6Al-4V (TC4) alloy had been obviously improved and good ductility had been maintained. Furthermore, the changes of phase structure and microstructural defects in TC4 titanium alloy during solution and aging process have been detailly studied by XRD refinement, EBSD, and TEM. Specifically, the highest tensile strength increased by 28.8 % which could reach 1224 MPa, and the elongation at fracture could still remain at 13 %. The reason is as follows. The formation of martensite after water quenching led to a substantial increase in internal microstructural defects, which were partly retained during the subsequent aging process because of lower temperature and short aging time, and the remaining martensite and microstructural defects can help maintain high strength. What's more, a small part of defects disappeared during this incomplete aging process due to martensite decomposition and recovery, which was beneficial to ductility.

Experimental and numerical study on seismic performance of assembled platform canopy with mortise-tenon joints

To investigate the seismic performance of a Y-shaped single-column platform canopy assembled using mortise-tenon joints, a 1:4 scaled specimen with two roof panels was fabricated using a real assembly process. The seismic performances, including the failure mode, hysteretic behavior, bearing capacity, ductility, and energy dissipation capacity, were measured by a low cyclic loading test, and the main influencing parameters, such as the longitudinal reinforcement ratio, linear stiffness ratio of the laminated beam to the precast column, and canopy slab height, were analyzed using validated finite element models. The test results showed that the hysteretic curve presented a pinch effect, indicating shear slip characteristics. The ultimate drift angle was 1/17, and the displacement ductility coefficient was greater than 4.5, indicating that the structure has good deformation capacity and ductility. Plastic hinges appeared at the ends of the laminated beam and base of the prefabricated columns, and the failure mode was the beam-hinge mechanism. The results of the finite element analysis were in good agreement with the test results. Parameter analysis indicated that when the longitudinal reinforcement ratio increased, the seismic performance, including the initial stiffness, ultimate bearing capacity, and ductility, increased. As the linear stiffness ratio of the laminated beam to the precast column and the height of the canopy slab increased, the initial stiffness and ultimate bearing capacity improved significantly, whereas the ductility decreased.

Seismic performance analysis and control method of composite coupled shear wall with steel plate-fiber reinforced concrete coupling beams

This paper based on the study of steel plate-fiber reinforced concrete coupling beam components, designs a basic model of composite coupled shear walls with steel plate-fiber reinforced concrete coupling beams. The seismic performance of this model was numerically simulated using the ABAQUS finite element software, analyzing the stress distribution of various parts and the development pattern of plastic hinges in the structure. It also examines how factors such as axial compression ratio, coupling beam cross-sectional dimensions, single-sided wall limb aspect ratio, and total floor height affect the seismic performance of this type of coupled shear wall, providing a reasonable range for axial compression ratios and coupling ratios for composite coupled shear walls with steel plate-fiber reinforced concrete coupling beams. Based on the obtained reasonable axial compression ratio and coupling ratio, and using the analytical solution of the continuum method, a method for controlling the seismic performance of coupled shear wall structures was proposed. Results show that the composite coupled shear walls with steel plate-fiber reinforced concrete coupling beams exhibit high load-bearing capacity and lateral stiffness under inverted triangular horizontal loads, with good displacement ductility and strong energy dissipation capability, making it an excellent seismic performance coupled shear wall system. As the axial compression ratio increases, the displacement corresponding to the yield point and peak point of the structure gradually decreases, and the displacement ductility coefficient shows a trend of first increasing and then decreasing; it is recommended that when designing steel plate-fiber reinforced concrete coupling beam-coupled shear walls, the axial compression ratio should not exceed 0.3. Numerical analysis of coupling ratio-related parameters indicates that in high-intensity seismic design areas, the range of coupling ratios should be between 45% and 60%.

Experimental and numerical investigation on flexural behavior of steel-UHPC composite slabs with PBL shear connectors

A full-scale flexural test was conducted to investigate the flexural and cracking behavior of Steel-UHPC Composite Slabs (SUCS) with PBL (Perfobond rib) shear connectors, with a focus on analyzing the impact of the tensile reinforcement ratio on flexural performance. During the test, the flexural performance of SUCS was assessed through measurements of strain, mid-span deflection, relative slip, crack width, and crack morphology. A section analysis was performed to predict the flexural and cracking behaviors of SUCS, which was further verified by experimental results. The results show that the PBL shear key effectively ensures the overall force of steel plate and UHPC plate, resulting in good ductility of SUCS under negative bending moment. As tensile reinforcement ratio increased from 0.89 % to 1.69 %, the cracking load remained stable while the yield load and ultimate load demonstrated significant improvements of 54 % and 57 %, respectively. The cross-section analysis indicated that with the increment in tensile reinforcement ratio, the contribution of tensile reinforcement to flexural capacity increased, whereas the contribution of UHPC to tensile capacity notably decreased. The equivalent uniform stress reduction coefficient of the UHPC's tensile zone, determined through simplified negative flexural bearing capacity, was calculated to be 0.87. The failure mode of negative flexural resistance differs significantly from positive flexural resistance, as it involves the breaking of the tensile steel bar.

Synergistic mechanism of hetero-structured Al–Mg–Si–Cu–Zn–Fe–Mn alloys with greatly enhanced strength, ductility and formability

Al–Mg–Si alloy sheets applied in automobile industry are required to possess good formability, high strength and ductility. Herein, our results show that a heterogeneous cellular microstructure, i.e., soft domains embedded in hard domains, can be readily attained via a short-flow processing route with concomitant improvement in the strength (YS: 177–184 MPa, UTS: 317–328 MPa), elongation (25.7%–27.3 %) and formability (r‾= 0.771, Δr = 0.047) of pre-aged alloy. The distribution of recrystallization grains, texture and coupled soft/hard domains in the Al–Mg–Si–Cu–Zn–Fe–Mn alloys and the effect on mechanical properties have been investigated. Moreover, the formation and synergistic action mechanisms of coupled soft/hard domains were put forward in this work.