Alloy Rods Research Articles

Experimental investigation of the effects of cooling with liquid nitrogen and air on the microstructure and mechanical properties of Zr50Cu34Al8Ag8 amorphous alloy

In the present study, Zr50Cu34Al8Ag8 amorphous alloy rods were prepared by copper mold suction casting method. The effects of cooling with liquid nitrogen (LN2) and air on the microstructure and mechanical properties of the amorphous alloy were investigated experimentally. The obtained results show that LN2 cooling led to a significant increase in the mechanical properties of the amorphous alloy that was heated to 465 °C. More specifically, the fracture strength and ultimate strain reached 1877.9 MPa and 2.96%, respectively. The improvement of mechanical properties of the amorphous alloy may be attributed to the increase of free volume content in the alloy structure. In contrast, air cooling of the samples heated to 465 °C led to the decrease in their mechanical properties.

Mechanical Failure After Total En Bloc Spondylectomy and Salvage Surgery.

ObjectiveTotal en bloc spondylectomy (TES) is a curative surgical method for spinal tumors. After resecting the 3 spinal columns, reconstruction is of paramount importance. We present cases of mechanical failure and suggest strategies for salvage surgery. MethodsThe medical records of 19 patients who underwent TES (9 for primary tumors and 10 for metastatic tumors) were retrospectively reviewed. Previously reported surgical techniques were used, and the surgical extent was 1 level in 16 patients and 2 levels in 3 patients. A titanium-based mesh-type interbody spacer filled with autologous and cadaveric bone was used for anterior support, and a pedicle screw/rod system was used for posterior support. Radiotherapy was performed in 11 patients (pre-TES, 5; post-TES, 6). They were followed up for 59 ± 38 months (range, 11–133 months). ResultsDuring follow-up, 8 of 9 primary tumor patients (89%) and 5 of 10 metastatic tumor patients (50%) survived (mean survival time, 124 ± 8 months vs. 51 ± 13 months; p=0.11). Mechanical failure occurred in 3 patients (33%) with primary tumors and 2 patients (20%) with metastatic tumors (p=0.63). The mechanical failure-free time was 94.4 ± 14 months (primary tumors, 95 ± 18 months; metastatic tumors, 68 ± 16 months; p=0.90). Revision surgery was performed in 4 of 5 patients, and bilateral broken rods were replaced with dual cobalt-chromium alloy rods. Repeated rod fractures occurred in 1 of 4 patients 2 years later, and the third operation (with multiple cobalt-chromium alloy rods) was successful for over 6 years. ConclusionConsidering the difficulty of reoperation and patients’ suffering, preemptive use of a multiple-rod system may be advisable.

Electron Backscatter Diffraction (EBSD) Analysis of Machinable Lead-Free Brass Alloys: Connecting Texture with Fracture

The current paper is related to the study of the microstructure and texture of two machinable lead-free brass alloys, namely CuZn42 (CW510L) and CuZn38As (CW511L), which were evaluated in the as-drawn and post heat treated condition. Electron backscatter diffraction (EBSD) was employed for the examination of the brass rods’ crystallographic properties in order to correlate the effect of post processing heat treatment on the evolution of phase structure and texture towards the interpretation of dynamic (impact) fracture properties. It is shown that α- and β-phase volume fractions, mean grain size, and grain boundary misorientation are the most influential factors altering the fracture resistance of single- and dual-phase brass alloy rods. The role of grain boundary engineering, through the formation of coincidence site lattice (CSL) boundaries and their evolution during thermomechanical processing, is of major importance for the design of the mechanical behaviour of new eco-friendly machinable brass alloys.

Multicomponent Fe-Based Bulk Metallic Glasses with Excellent Corrosion and Wear Resistances

In this study, new multicomponent Fe54M5Cr15Mo6Si2B4P10C4 (M = Fe, Co, and Ni, denoted as Fe59, Fe54Co5, and Fe54Ni5, respectively) bulk metallic glasses (BMGs) with excellent corrosion and wear resistances were synthesized using the J-quenching technique and fluxing treatment. The synthesized Fe-based BMGs possessed a large glass-forming ability, and the maximum diameters of the Fe59, Fe54Co5, and Fe54Ni5 glassy alloy rods reached 5.5, 4.5, and 4.0 mm, respectively. The Fe59 BMG had a wide supercooled liquid region of 65 K. Potentiodynamic tests in 3.5 wt.% NaCl solution showed that the corrosion resistances of the synthesized Fe-based BMGs were relatively better than that of the 316L stainless steel. The Fe59 BMG had the highest corrosion resistance, with the lowest self-corrosion current density in the order of 10−8 A·cm−2. Wear tests showed that the synthesized Fe-based BMGs exhibited excellent wear resistances, and the wear rate of the Fe59 BMG was as low as approximately 1.73 × 10−15 m3·N−1·m−1. The rare-earth-element-free Fe-based BMGs, especially the Fe59 BMG, have a low cost, large glass-forming ability, and excellent wear and corrosion resistance, which make them good candidates for wear-and corrosion-resistant coating materials.

Kinematics analysis and trajectory planning of a continuum manipulator

Continuum manipulators with flexibility and compliant characteristics have attracted the attention of more and more researchers due to its wide application prospect. This paper introduces the design of a continuum manipulator made with super-elastic material NiTi alloy that can increase the motion posture and obtain wide workspace of a continuum manipulator. The design adopts a novel co-radial configuration and uses NiTi alloy rods as the segmented skeleton of the manipulator, which is driven by the stepper motors installed on the base of the manipulator. Under the assumption of piecewise constant curvature bending, the homogenous transformation matrix is proposed for analyzing forward kinematics and an efficient closed-form solution based on the displacement compensation method is proposed to investigate the inverse kinematics. The end position of each segment of the manipulator is obtained through numerical simulations, and the results reveal the reachable workspace of the designed manipulator. In addition, the circular trajectory planning of the manipulator is analyzed and discussed based on its inverse kinematics. Finally, a series of experiments are conducted using the manipulator to verify the effectiveness of the proposed model. The experimental results for the space posture and the trajectory planning are consistent with the simulation results, which demonstrates that the designed continuum manipulator has good motion performance.

Tribological properties of Mn–TiN films and formation of graphite-like layers in physiological solution

TiN film and Mn–TiN films containing 2.2, 5.6, and 10.6 at% Mn were deposited on appropriate substrates using a four-target unbalanced magnetron sputtering system. The Mn contents of films were adjusted by controlling the number of Ti–Mn alloy rods embedded in the titanium target. The effects of Mn doping on the microstructure, mechanical properties, and wear properties of TiN films were systematically investigated. A relatively loose columnar structure is observed in the TiN film, which is refined and densified by the incorporation of Mn. Mn doping improves the hardness, toughness, and adhesion performance of TiN films. The Mn–TiN films containing 2.2 and 5.6 at% Mn, in particular, exhibit superior mechanical properties. Moreover, the presence of Mn has a promoting effect on the wear of TiN films in both phosphate buffer (PB) and bovine serum albumin (BSA) solutions. The Mn ions released from Mn–TiN films during friction in a BSA solution promote the formation of protein deposits. The structures of protein molecules in these deposits denature under the frictional shear force of SiC balls during sliding tests, forming graphite-like layers on the friction interfaces. These layers act as a solid lubricant and improve the wear resistance of films.

Formation ability, thermal stability, and mechanical properties of the Zr50Cu34Al8Ag8 amorphous alloys prepared by different mold materials

In the present study, Zr50Cu34Al8Ag8 amorphous alloy rods with a diameter of 3 mm were prepared and the influence of the cooling capacity on the properties of cast samples was analyzed. To this end, three mold materials, including heat-resistant steel, copper, and high purity graphite were utilized. Then the amorphous structure, glass-forming ability, and thermal stability of the cast alloy were investigated using an X-ray diffractometer and differential scanning calorimeter. A universal testing machine was applied to investigate the mechanical properties of amorphous alloys with different mold materials. The fracture characteristics of the amorphous alloy were analyzed by scanning electron microscope, and the microstructures were analyzed using a high-resolution transmission electron microscope. The experimental results showed that among the studied cases, the highest glass-forming ability was achieved from the copper mold. Moreover, the glass transition and crystallization activation energies of the amorphous alloy obtained by suction casting of high-purity graphite mold were the largest, which were 525.8 kJ/mol and 334.0 kJ/mol, respectively, reflecting good thermal stability. Meanwhile, the performed analyses revealed that the fracture strength of the amorphous alloy and the corresponding strain were 1888.2 MPa and 3.55%, respectively, indicating that the cast sample has good mechanical properties. With the decrease of the cooling rate, the content of free volume in the amorphous alloy of high-purity graphite mold suction casting decreased, and the ordered structure was generated, which was the main reason for its high thermal stability and plastic deformation ability.

Enhanced bioactivity and interfacial bonding strength of Ti3Zr2Sn3Mo25Nb alloy through graded porosity and surface bioactivation

• A coating with pores of several microns in diameter is created through micro arc oxidation (MAO) on the surface of the gradient porous Ti 3 Zr 2 Sn 3 Mo 25 Nb alloy with larger pores of hundreds microns fabricated from powder sintering on the solid alloyed core. • The MAO treatment in an electrolyte containing Ca and P enables the secondary microporous coating contained hydroxyapatite (HA), and the bone morphogenetic protein-2 (BMP-2) was further loaded on to the coating (HA+BMP). • Both HA and BMP-2 on the surface and inside pores significantly activate the bioactive of the alloy by promoting the formation of new bone tissue on the surface and stimulating new bone tissue to growth into the gradient porous Ti 3Zr2Sn3Mo25Nb alloy. • The interfacial shear strength of the coatings with HA or HA+BMP is higher than that of the coating without both HA or BMP-2 at all time after implantation, the strength in the HA+BMP coating is highest in the three coatings and is about three times of the strength of the CPT sample in all the testing implantation intervals. The gradient porous Ti3Zr2Sn3Mo25Nb (TLM) alloy rods were fabricated through sintering the alloyed powder to a solid core. The porous sample was then modified by a Micro Arc Oxidation (MAO) treatment in an electrolyte containing calcium and phosphate, a hydrothermal treatment enabled secondary microporous hydroxyapatite (HA) coating, and a further bone morphogenetic protein-2 (BMP-2) loading treatment through immersion and freeze-drying. The treatment led to an orderly secondary microporous coating containing HA nano-particles and evenly distributed BMP-2 in the porous coatings. As a result, osteoblasts could adhere and grow well on the coatings with a high cell adhesion rate and cell functional activity. The in-situ shear testing indicated that the interfacial strength had been enhanced significantly. Improvement of the bond formation and osseointegration with the titanium implant is attributed to increased surface area for the cell to attach, creating voids for the cell to grow in, and activating titanium surface by introducing bioactive ingredients such as HA and BMP-2.

Strengthening mechanism and effect of Al2O3 particle on high-temperature tensile properties and microstructure evolution of W–Al2O3 alloys

The W–Al2O3 alloy rods were successfully fabricated by the powder metallurgy process and hot swaging. Subsequently, the high-temperature tensile tests were conducted to characterize the mechanical properties of the W–Al2O3 alloy. At 800 °C, the ultimate tensile strength of W-0.25 wt% Al2O3 alloy is 611.1 MPa, which is 18% higher than that of pure W. After tension, the microstructure evolution was evaluated using metallographic microscope and transmission electron microscopy. For the pure W undergoing deformation at 1000 °C, dynamic recrystallization occurs, leading to the sharp decrease of the strength. However, the microstructure of the W-0.25 wt% Al2O3 alloy contains a large number of sub-grain and low-angle grain boundaries, which does not significantly change in the temperature range of 800–1200 oC, and the work hardening plays a leading role during the high-temperature deformation process. Due to high hardness, the dispersed Al2O3 particles effectively prevent the dislocation movement, displaying a significant strengthening effect.

Prediction of the Deformation of Aluminum Alloy Drill Pipes in Thermal Assembly Based on a BP Neural Network

The connection between the steel joint and aluminum alloy pipe is the weak part of the aluminum alloy drill pipe. Practically, the interference connection between the aluminum alloy rod and the steel joint is usually realized by thermal assembly. In this paper, the relationship between the cooling water flow rate, initial heating temperature and the thermal deformation of the steel joint in interference thermal assembly was studied and predicted. Firstly, the temperature data of each measuring point of the steel joint were obtained by a thermal assembly experiment. Based on the theory of thermoelasticity, the analytical solution of the thermal deformation of the steel joint was studied. The temperature function was fitted by the least square method, and the calculated value of radial thermal deformation of the section was finally obtained. Based on the BP neural network algorithm, the thermal deformation of steel joint section was predicted. Besides, a prediction model was established, which was about the relationship between cooling water flow rate, initial heating temperature and interference. The magnitude of interference fit of steel joint was predicted. The magnitude of the interference fit of the steel joint was predicted. A polynomial model, exponential model and Gaussian model were adopted to predict the sectional deformation so as to compare and analyze the predictive performance of a BP neural network, among which the polynomial model was used to predict the magnitude of the interference fit. Through a comparative analysis of the fitting residual (RE) and sum of squares of the error (SSE), it can be known that a BP neural network has good prediction accuracy. The predicted results showed that the error of the prediction model increases with the increase of the heating temperature in the prediction model of the steel node interference and related factors. When the cooling water velocity hit 0.038 m/s, the prediction accuracy was the highest. The prediction error increases with the increase or decrease of the velocity. Especially when the velocity increases, the trend of error increasing became more obvious. The analysis shows that this method has better prediction accuracy.

Relationship Between Work Hardening Capacity and Compressive Creep Behavior in a Hot-Extruded Mg–6Al–1Zn Alloy Rod

Relationship Between Work Hardening Capacity and Compressive Creep Behavior in a Hot-Extruded Mg–6Al–1Zn Alloy Rod

Effect of Rotational Speed on Static and Fatigue Properties of Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium Alloy Joints

In this work, rotary friction welding processes of dissimilar AA7075/AA5083 aluminium alloy rods with the diameter of 15 mm were performed at varying rotational speeds, typically 370 to 2500 rpm. The aim of this research is to improve mechanical properties, in particular, strength and fatigue performance of the weld joints. Several experiments including macro and microstructural examinations, Vickers microhardness measurements, tensile tests, fatigue tests and residual stress measurements were carried out. Results showed that at higher rotational speeds, typically 540 rpm or above, the dissimilar AA7075/AA5083 rotary friction weld joints revealed a static fracture in the AA5083 base metal side, indicating that the joint efficiency is more than 100%. It seemed that the best weld joint was achieved at the rotational speed of 1200 rpm, in which the friction heat was sufficient to form metallurgical bonding without causing excessive flash and burn-off. In such a condition, the fatigue strength of the weld joint was slightly higher than AA5083 base metal, but it was lower than AA7075 base metal. It was confirmed that the crack origin is observed at the interface followed by fatigue crack growth towards AA5083 side, and the growth of crack seemed to be controlled by microstructure and residual stress.

Structures and macrosegregation of a 2024 aluminum alloy fabricated by direct chill casting with double cooling field

Central region coarse grains and centerline segregation are common defects in aluminum ingots fabricated by direct chill (DC) casting. A double cooling field was introduced into the DC casting process to reduce these defects, whereby the external cooling was supplied by the mold and water jets, and intercooling was achieved by inserting a rod of the same alloy into the molten pool along the central axis of the ingot. Rather than forming a good metallurgical interface during solid-liquid compound casting, in the present work, the purpose of inserting the rod is to enforce internal cooling and consequently decrease the sump depth. Moreover, the insertion provides more nucleation sites with the unmolten á-Al particles. The structure and the macrosegregation of 2024 Al alloy ingots prepared by DC casting with and without the inserts were investigated. Results show that when the inserting position is 50 mm above the upper edge of the graphite ring, significant grain refinement in the central region of the ingot and a reduced centerline segregation are achieved.

Analysis of friction and wear processes in an innovative spine stabilization system. Part 1. A study of static and kinetic friction of a metal rod-polymer cord friction joint

Purpose: This analysis is the first part of research that aims to develop a model of the tribological wear of PE-UHMW cord – biometal rod combination. This type of sliding joint is applied in spine stabilization systems that enable the treatment of early-onset idiopathic scoliosis. Methods: The friction tests included force measurements, followed by the determination of static and kinetic friction coefficients as a function of the number of the performed movement cycles, and static friction coefficient with regards to the string tension force FN in the range of 50–300 N. Additionally, the surface roughness and microscopic observations of the metal rods were made. The friction measurements were carried out at a stabilized temperature T = 38 °C in the presence of distilled water and acidic sodium lactate. Results: The measurements confirmed the impact of both the number of completed movement cycles and the value of the force loaded on the cord on the static friction coefficient. Similar values of kinetic friction force occur for the pairs with the titanium alloys rods, as well as for the pairs with the steel and CoCr rod. The type of lubricant affected the obtained measurement results unevenly: (Ti6Al4V and Ti6Al7Nb – slight impact, steel 316L and CoCrMo – large impact). During microscopic observations, numerous wear products, were visible, including harder than the base material large conglomerates. Conclusions: Susceptibility of polymer fibres results in its increased resistance to wear, but it can be also combined with an increase in wear of the surface of the metal rod.

Four-Dimensional Anatomical Spinal Reconstruction in Thoracic Adolescent Idiopathic Scoliosis.

Background:Recent surgical techniques involve 3-dimensional (3D) deformity correction of adolescent idiopathic scoliosis (AIS)1-4. However, next-generation surgical strategies should ensure that the final corrected spine is not only “non-scoliotic,” but has an anatomically correct shape. We developed a 4D anatomical spinal reconstruction technique that involves the use of spatiotemporal deformity prediction to preoperatively calculate the postoperative apex of thoracic kyphosis in order to achieve an anatomically correct spinal curvature5-7.Description:During the technique, facetectomies are performed at all levels except the lowest instrumented level in order to avoid pseudarthrosis at that site. Two rods are identically bent according to the desired postoperative anatomical thoracic kyphosis, with the apex often anticipated to be between T6 and T85-7. Two different categories of spinal rod shapes have been created to cover all presenting anatomies. The single-curve rod is utilized when the lowest instrumented vertebra is L1 or above and the thoracolumbar region remains straight. The double-curve rod is utilized when the lowest instrumented vertebra is L2 or L3. With both rod types, the cranial apex is created. There are 11 shapes of pre-bent, notch-free, cobalt-chromium alloy rods available in Japan7-9. Once the 2 spinal rods are connected to all polyaxial screw heads, the rods are simultaneously rotated1,2,5,7.Alternatives:Typical thoracic AIS exhibits thoracic hypokyphosis. Therefore, correction of the thoracic kyphosis and adjustment of the main thoracic curve are the 2 most important surgical goals for achieving an anatomically correct spine. Furthermore, hypokyphosis of the thoracic spine secondary to pedicle screw instrumentations can be reduced or prevented by utilizing the posterior-approach surgical strategies that we have previously described1-4.Rationale:In a healthy human population, the apex of the thoracic kyphosis is normally located at T6 to T8 as viewed on viewing standing sagittal radiographs10. However, for some patients with AIS, the postoperative apex of the thoracic kyphosis is almost identical to the apex of the preoperative thoracic scoliosis5, which is not anatomically correct. This insufficient correction is often a result of the spinal rods being bent to match the curvature of the scoliosis5. In addition, about 70% of cases of thoracic AIS do not have identical preoperative apices of the main thoracic scoliosis and thoracic kyphosis, and about 33% of cases have the apex of the scoliosis at the lower thoracic spine (i.e., T10 and T11)5. Performing sufficient multilevel facetectomies and utilizing the proper spinal rod curvature have been reported to greatly improve postoperative sagittal curve correction11-13. This proposed technique could be especially helpful in cases in which the apex of scoliosis is located in the lower thoracic spine, which is often seen in patients with Lenke 1AR scoliosis14.Expected Outcomes:When performed with proper shaping of the spinal rods and multilevel facetectomies, the present technique is expected to result in an anatomically correct thoracic spine. The use of this technique has been reported to increase the proportion of patients with a thoracic kyphosis apex at T6 to T8, from 51.3% preoperatively to 87.2% postoperatively5. Furthermore, patients who underwent this procedure with notch-free, pre-bent rods had a significantly higher postoperative thoracic kyphosis than patients who underwent the procedure with conventional, manually bent rods7.Important Tips: Mobilization of the spine by releasing the facet joints is more important than using a rigid implant.Two rods are bent identically to the desired postoperative anatomical thoracic kyphosis; the bending is not based on the preoperative scoliosis spinal curvature.This technique is applicable for Lenke 1, 1AR, and 2 through 6 curves except for Lenke 5 curves. However, the technique for producing pre-bent rods can also be utilized for Lenke 5 curves because the initial configuration leads to sagittal alignment of the spine. Acronyms & Abbreviations: TL/L = thoracolumbar/lumbarUIV = upper instrumented vertebraUEV = upper end vertebraSD = standard deviation

Significant strengthening effect in ultra-fine grained Al alloy made by fast solidification and hot extrusion processes

Grain refinement with a facile process without additional alloying is quite desired for strengthening the Al alloys. Using the melt spinning process, we obtained the ultra-fine grained foils of Al–Mg–Si–Cu alloy (AA6061), then the foils followed by hot extrusion to produce the rods for industrial applications. The yield strength of the extruded melt-spun rod is 102% higher than that of the extruded rods of the alloy by a conventional direct chill casting. The electron backscatter diffraction results reveal that the average grain diameter in the extruded melt-spun sample is only 1.35 μm, indicating that the sample is an ultra-fine grained alloy. Through the Hall–Petch relationship, the finer grains contribute to a 66.9% increase in yield strength of the extruded rod. Moreover, the <111> fiber texture occupied 68% of the volume fraction after hot extrusion, contributing to 30.5% improvement of the yield strength in the extruded melt-spun sample. This study shows that the ultra-fine grained Al–Mg–Si–Cu alloy rods have excellent mechanical properties, which provides a strong potential for industrial application.

Microstructure evolution, enhanced aging kinetics, and mechanical properties of AA7075 alloy after friction extrusion

In the present study we utilized Friction Extrusion (FE); a solid phase processing technique; to produce fully consolidated dense 5 mm rods of AA7075 alloy. The combination of large shear stresses and temperatures at the tool-billet interface during the FE process resulted in the formation of dynamically recrystallized ∼2.0 μm equiaxed grains and fine uniformly distributed stable η (MgZn2) precipitates ∼25–100 nm in size. Formation of such a microstructure resulted in lower solutionizing temperature and times (flash annealing) as compared to the conventionally extruded counterparts. We demonstrate for the first time that the solutionizing times for the T6 heat treatment of AA7075 can be reduced by three times using this FE process. In addition to being an energy efficient process, FE also serves to improve the performance of AA7075 alloys by retaining their strength while enhancing the ductility of the material. The tensile data for samples that were flash annealed and artificially aged after FE processing showed exceptional increase in ultimate tensile strength by over 19% and yield strength by over 59%, compared with an as-FE-processed sample.

The Influence of the Soaking Temperature Rotary Forging and Solution Heat Treatment on the Structural and Mechanical Behavior in Ni-Rich NiTi Alloy.

The structural and thermophysical characteristics of an Ni-rich NiTi alloy rod produced on a laboratory scale was studied. The soak temperature of the solution heat-treatment steps above 850 °C taking advantage of the precipitate dissolution to provide a matrix homogenization, but it takes many hours (24 to 48) when used without thermomechanical steps. Therefore, the suitable reheating to apply between the forging process steps is very important, because the product’s structural characteristics are dependent on the thermomechanical processing history, and the time required to expose the material to high temperatures during the processing is reduced. The structural characteristics were investigated after solution heat treatment at 900 °C and 950 °C for 120 min, and these heat treatments were compared with as-forged sample structural characteristics (one hot deformation step after 800 °C for a 30 min reheat stage). The phase-transformation temperatures were analyzed through differential scanning calorimetry (DSC), and the structural characterization was performed through synchrotron radiation-based X-ray diffraction (SR-XRD) at room temperature. It was observed that the solution heat treatment at 950 °C/120 min presents a lower martensitic reversion finish temperature (Af); the matrix was fully austenitic; and it had a hardness of about 226 HV. Thus, this condition is the most suitable for the reheating stages between the hot forging-process steps to be applied to this alloy to produce materials that can display a superelasticity effect, for applications such as crack sensors or orthodontic archwires.

Prediction of the seismic behavior of concrete beams strengthened with aluminum alloy bars and/or basalt fiber‐reinforced polymer bars

SummaryThis paper investigated the seismic performance of reinforced concrete (RC) beams strengthened with aluminum alloy (AA) rods and/or basalt fiber‐reinforced polymer (BFRP) rods using the near‐surface mounted (NSM) technique under a low‐cycle reversed loading test. A numerical calculation procedure was presented based on the strain compatibility and static equilibrium principles for estimating the moment–curvature response of these strengthened beams. The bending deflection and shear deflection were determined by the curvature distribution and shear strain distribution along the beam length, respectively. The results showed that the strengthened beams experienced three failure modes: intermediate crack‐induced debonding (ICD), critical diagonal crack (CDC) debonding, and concrete cover separation (CCS). Increasing the number of strengthening bars on each side significantly enhances the load‐carrying capacity of the beams strengthened with either AA or BFRP bars. The predictive accuracy of the proposed methodology was evaluated by comparing the predicted load‐carrying capacities and deflections to the test characteristic points. The proposed theoretical model provided good verification of the load‐carrying capacities and deflections with high accuracy.

Effects of Fe addition on the microstructures and mechanical properties of as-extruded Zn-0.2Mg alloys

Zn-0.2Mg-(0, 0.05, 0.2, 0.4 wt%)Fe alloy rods were produced by indirectly extruding the as-cast ingots at 200 ℃. The addition of minor Fe significantly improved the ductility of as extruded Zn-0.2Mg alloy without scarifying the strength. As 0.05 wt% Fe was added, the yield strength, ultimate tensile strength and elongation were increased from 216 MPa, 228 MPa and 1.85% for Zn-0.2Mg alloy to 240 MPa, 258 MPa and 42% for Zn-0.2Mg-0.05Fe. Texture variation from basal texture to non-basal texture alongside the grain refinement contributed the great improvement of ductility and slight increase of strength, respectively. As Fe content increased from 0.05 wt% to 0.4 wt%, the volume fraction and size of the second phases changed, leading to the reduction in elongation by 50% yet maintaining the yield strength and ultimate tensile strength.