The structure profile of magnesium alloy tube is difficult to control for complex microstructural evolution under the asymmetric loading of tension and compression induced during tube bending. This study investigates the electro-assisted bending of extruded AZ61 (Mg-6Al-1Zn) magnesium alloy tubes, with particular focus on the influence of pulsed current on microstructure evolution and plastic deformation mechanisms under varying degrees of deformation. The results indicate that pulsed current increases the fraction of {101¯2} tensile twins and effectively regulates twin nucleation positions along the tangential cross-sections on both sides of the bending head. The initially disordered twin distribution is transformed into a more ordered arrangement, thereby enhancing radial microstructural uniformity during bending. The thermal and electromagnetic energy generated by the current promotes the alignment or polarization of twins and dislocations along specific directions. This phenomenon suggests that pulsed current can improve the formability of magnesium alloy tubes through distinctive microstructural modifications. These findings offer valuable insights into microstructure control and bending ability enhancement of magnesium alloy tube.

This study systematically investigates the microstructural characteristics and mechanical properties of resistance spot-welded joints in 3 mm thick non-heat-treatable die-cast AlSi7MnMg alloy, with particular focus on the influence of element segregation and secondary phase behavior on fracture mechanisms and the process window. The results indicate that the weld nugget exhibits a typical dual structure consisting of columnar and equiaxed grain zones, with a corresponding "M"-shaped microhardness profile. Significant segregation of Si, Fe, and Mn elements at the nugget boundary was observed, leading to the formation of low-melting-point eutectic regions and secondary phase bands. These features induce microporosity along segregation trajectories, serving as crack initiation sites and resulting in a notably narrowed spot welding process window. From the perspective of microstructure and solute behavior during non-equilibrium solidification, this work elucidates the intrinsic mechanisms governing joint performance and process stability in non-heat-treatable die-cast aluminum alloys, providing a theoretical basis for their engineering applications.

This study successfully achieved high-quality welding of heat-treatment-free die-casting aluminum alloys using laser oscillation technology, increasing the maximum tensile shear load and displacement of the joints by up to 84% and 206%, respectively. The effects of laser oscillation on the weld microstructure can be summarized as grain refinement and suppression of macro-segregation. Laser beam oscillation welding enlarged the equiaxial grain zone, refining the average grain size by up to 85%. Higher oscillation frequencies reduced the aggregated eutectic phase, making its distribution more uniform. Additionally, porosity within the weld was reduced by up to 74%, transforming the fracture behavior from brittle to a typical microporous ductile fracture.

In this study, laser oscillation welding was utilized to offer an effective solution for the joint welding of heat-treatment-free die-cast aluminum alloys, which expands the practical applications of automotive structural parts and heat sinks for electronic devices. The effects of oscillation amplitude on the macro-morphology, microstructure, and properties of the alloy weld were examined, and a molten pool flow model was developed to compare the behavior of the molten pool with and without oscillation. The results show that increasing the oscillation amplitude eliminates the coarse Al15(Fe,Mn)3Si2 phase, resulting in a finer and more uniform distribution of the eutectic Si and Mg2Si phases. At an oscillation amplitude of 7 mm, the maximum tensile shear load and displacement were 2761 N and 1.17 mm, respectively. Laser oscillation was found to enhance the fluidity of the molten pool, reduce porosity, improve weld quality, and effectively decrease cracks and inhomogeneous grain distribution. These findings provide a research basis for optimizing the laser oscillation welding process and for the practical welding of fabricated devices.

To facilitate the industrial application of wrought Mg alloys, this study explores the impact of the rare earth (RE) element Sm on the microstructure and mechanical properties of hot-rolled Mg-1Al-0.3Ca alloy. The results indicate that the average grain size and basal texture intensity of the hot-rolled Mg-1Al-0.7Sm-0.3Ca alloy are significantly reduced compared to the hot-rolled Mg-1Al-0.3Ca alloy. This reduction can be attributed to the pinning effect of grain boundaries and grain refinement facilitated by the presence of the fine Al2Sm phase. Additionally, the addition of Sm leads to an increase in yield strength and ultimate tensile strength, along with a decrease in elongation. This can be attributed to the combined effects of the strengthening mechanism provided by a significant number of Al2Sm particles and the stress concentration occurring at the sharp corners of these particles. Significantly, this study proposes the substitution of expensive RE elements with more cost-effective Sm in the design of Mg alloys for low-alloy systems. The excellent mechanical properties of the Mg-1Al-0.7Sm-0.3Ca alloy provide a reference for the future development of high-performance Mg alloys.

Natural materials are valued for their lightweight properties, high strength, impact resistance, and fracture toughness, often outperforming human-made materials. This paper reviews recent research on biomimetic composites, focusing on how composition, microstructure, and interfacial characteristics affect mechanical properties like strength, stiffness, and toughness. It explores biological structures such as mollusk shells, bones, and insect exoskeletons that inspire lightweight designs, including honeycomb structures for weight reduction and impact resistance. The paper also discusses the flexibility and durability of fibrous materials like arachnid proteins and evaluates traditional and modern fabrication techniques, including machine learning. The development of superior, multifunctional, and eco-friendly materials will benefit transportation, mechanical engineering, architecture, and biomedicine, promoting sustainable materials science. Statement of Significance Natural materials excel in strength, lightweight, impact resistance, and fracture toughness. This review focuses on biomimetic composites inspired by nature, examining how composition, microstructure, and interfacial characteristics affect mechanical properties like strength, stiffness, and toughness. It analyzes biological structures such as shells, bones, and exoskeletons, emphasizing honeycomb strength and lightness. The review also explores the flexibility and durability of fibrous materials like arachnid proteins and discusses fabrication techniques for biomaterials. It highlights impact-resistant materials that combine soft and hard components for enhanced strength and toughness, as well as lightweight, wear-resistant biomimetic materials that respond uniquely to cyclic stress. The article aims to advance sustainable materials science by exploring innovations in multifunctional and eco-friendly materials for various applications.

The die-casting process of ADC12 aluminum alloy right crankcase cover was simulated based on AnyCasting software, and the influence of pouring temperature, initial mold temperature and injection speed on the filling and solidification process of ADC12 right crankcase cover casting was explored by orthogonal experiment method. The optimal process parameters were obtained through optimization, and the die-casting mold was designed. The program was verified in production. The results show that the porosity and shrinkage of the right crankcase cover are mainly concentrated in the thick wall part. The sequence of process parameters that affect the residual melt modulus is pouring temperature, initial mold temperature, and injection speed; The best combination of process parameters: pouring temperature is similar to 680 degrees C, initial mold temperature is similar to 200 degrees C, injection speed is similar to 5 m/s. By analyzing the filling process and temperature field simulation results, the casting structure, mold structure and cooling system were optimized, and the process plan was improved. The production verification was carried out according to the optimized process plan. The casting quality is good and has no obvious defects, which meets the actual production needs.

The mechanical properties of as -cast metallic materials depend strongly on the size and shape of grains, which are critical microstructural parameters dictated by the interplay of nucleation and growth of crystalline solids during solidification. In our experiments, the microstructure transition from coarse columnar crystals into fine equiaxed crystals for dilute Al-Mn-Si alloys was achieved by using sub -rapid solidification with the addition of Al-5Ti-1B grain refiner. The average grain size of Al alloy was reduced from a millimeter size to 73 mu m. Through temperature gradient calculation, we found that the acquisition of fine equiaxed crystals could be attributed to the existence of a high number density of TiB2, acting as effective nucleation sites with an increase in total undercooling. Furthermore, the curvature supercooling, constitutional undercooling, thermal undercooling, and kinetic undercooling during sub -rapid solidification were quantitatively determined for given solidification rates. Our results showed that constitutional undercooling, rather than thermal undercooling, was primarily responsible for the formation of fine equiaxed grains, with the assistance of Al-5Ti-1B grain refiner. This work provides a new insight into the grain refining mechanism under sub -rapid solidification. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Laser nitriding is an effective modification technique to improve the comprehensive mechanical properties of metallic glasses (MGs). However, numerous micro-defects, such as pores and humps, usually appear on the lasernitriding-treated (LNed) MG surface, and therefore additional post-treatment is required. Herein, laser shock processing was implemented to flatten the LNed MG and as well modify its surface mechanical property. The dependence of the laser shock flattening process on the laser energy density was investigated. The results revealed that the surface micro-defects on the LNed MG were significantly reduced after laser shock flattening, and accordingly, the surface roughness ( S a) was decreased, with a maximum reduction of 61.87% (from 0.48 to 0.183 mu m) achieved at a relatively high laser energy density of 178.3 J/cm 2 . Furthermore, nanoindentation measurements indicated that although the surface hardness of the LNed MG was decreased after laser shock flattening, it was still higher than that of the as-cast MG.

Exhaust air recycling is a simple and commonly used technique to save energy when using a dryer. The fixed-bed drying test device with increased efficiency by condensation is a clean and energy-saving drying test device developed by combining exhaust air recycling and condensation dehumidification technology. In this paper, through comparisons with or without exhaust air circulation using the single factor test of drying process parameters and the response surface test of corn drying on this test device to investigate the energy-saving effect and drying characteristics resulting from the novel drying method of increased efficiency by condensation. We drew the following main conclusions: (1) increased efficiency drying by condensation resulted in an energy savings of 32–56% compared with the conventional open hot air drying; and (2) during the increased efficiency corn drying by condensation, the mean energy and exergy efficiencies were within 31.65–51.26% and 41.69–63.52%, respectively, when the air temperature was in the 30–55 °C range, and they were 24.96–65.28% and 30.40–84.90%, respectively, when the air passed through the grain layer at 0.2–0.6 m/s; both of these increased with increasing air temperature, and decreased with increasing air velocity. These conclusions may constitute an important reference for investigating the energy-saving drying process of increased efficiency by condensation and developing relevant energy-saving drying equipment.

In this work, the quasi-in-situ electron backscattered diffraction (EBSD) is employed to investigate the static recrystallization occurring at the interface of deformation twinning interactions in liquid nitrogen temperature (LNT) rolled AZ61 alloy during electric pulse treatment (EPT). It was found that recrystallization nucleation occurred at the {1012} tensile twin (TTW) interaction, after which new grains and part of the original grains consumed {1012} TTW and grow up. By contrast, recrystallization nucleation occurs not only at the {1011} {1012}double twin (DTW) interactions but also within twin boundaries during subsequent EPT. When multiple twins come into being in the exact grain, the recrystallization growth showed obvious directionality: first, recrystallization grains grow along with {1011} - {1012} DTW and {1011} CTW boundaries and consume them; then the {1012} TTWs are consumed and the growth direction of recrystallization grains shifts to along with their boundaries.

Application of HFQ® technology to 7xxx-series alloy sheet has attracted increased attention because of the rapidly growing demand for lightweight automobiles. The present research employed the AA7075-H18 cold-rolled sheet suitable for continuous HFQ® production as the investigation object for the first time. Tensile experiments were performed using a Gleeble-3800 thermo-mechanical simulator within the temperature range of 300 °C –450 °C and strain rate range (0.001 s−1–10 s−1) to characterise the plastic flow behaviour under the application of HFQ® conditions. The tensile samples were soaked at the solution temperature, after which they were quenched to the target temperature and immediately tested. Static recovery (SRV) and static recrystallization (SRX) occurred during the application of solution heat treatment (SHT) process. The modified Zerilli-Armstrong (ZA) constitutive model of AA7075 under conditions representative of HFQ® was developed based on the Gleeble test data. At elevated temperatures, the AA7075 alloy exhibited noticeable temperature and strain rate sensitivity. The plastic flow stress of the sheet decreased substantially with the increase in deformation temperature or the decrease in strain rate, and the elongation after fracture slightly increased in parallel with the deformation temperature or strain rate. Microstructural evolution and plastic flow curves confirmed that dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred at elevated temperatures. The proposed ZA equation and Yld2000-2d yield function were applied to model the HFQ® process of a cup-shaped part, and the numerical results were in good agreement with the experimental data.

Here we report a novel Mg-4.5Al-1.5Sn-0.5Ca (wt%) alloy with high mechanical properties produced via sub rapid solidification (SRS) and controlled rolling. In virtue of SRS combined with homogenization treatment, the morphology of CaMgSn phase changes from long-rod to refined spherical/quasi-spherical, which cannot be achieved via conventional solidification (CS) followed by homogenization treatment. By subsequent controlled rolling, dispersed nano-sized CaMgSn precipitates (similar to 16 nm) could form in Mg-4.5Al-1.5Sn-xCa alloys (x = 0.3 and 0.5 wt%). Compared to the rolled Mg-4.5Al-1.5Sn alloy, the rolled Mg-4.5Al-1.5Sn-0.5Ca alloy shows an impressive combination of strength (a yield strength of similar to 275 MPa and an ultimate tensile strength of similar to 338 MPa) and ductility (an elongation of similar to 20%). The increase in yield strength is mainly due to grain boundary strengthening, Orowan strengthening and texture strengthening. The high ductility is enhanced prominently as a result of dispersed nano-sized CaMgSn precipitates. The present work proposes a novel processing strategy to spheroid and refine coarse eutectic CaMgSn phase with a high melting point, which is important in achieving a good synergy of strength and ductility for Mg alloys.

In this work, static recrystallization induced by deformations twins in cryogenic rolled AZ61 alloy during electric pulse treatment is investigated by using quasi-in-situ electron backscattered diffraction. Besides of the {10 (1) over bar 2} tensile twins, {10 (1) over bar 1} compression twins, {10 (1) over bar 2}-{10 (1) over bar 1} double twins are also observed in the as-deformed AZ61 alloy. It has been found that recrystallization occurs preferentially at the early stage of electric pulse treatment, with {10 (1) over bar 2}-{10 <()over bar> 1} double twins and {10 (1) over bar 1} compression twins being effective nucleation sites for recrystallization. In contrast, lenticular {10 (1) over bar 2} tensile twins are consumed by surrounding grains that are with growth advantage. Our results suggest a feasible way to tailor the microstructure of Mg alloys through cryogenic rolling and electrical pulse accelerated recrystallization.

In this work, electrical pulse treatment and isothermal heat treatment are employed to tailor the microstructure of the hot-rolled AZ61 alloy. The influence of pulsed current on the crystal growth mechanism and precipitation phase diffusion was investigated. According to the findings, electrical pulses enhance the recrystallization and dissolution of Mg17Al12 precipitate in hot-rolled AZ61 alloy. The recrystallization fraction of EPTed samples is higher than that of the isothermal HTed counterparts. The amount of Mg17Al12 phase is considerably reduced with the increased EPT duration. In contrast, the Mg17Al12 phase fraction in isothermal HTed samples is just slightly changed. The Nernst–Einstein formula indicates that the electrical pulse effectively improves the total diffusion flux in the diffusion system via the coupling of athermal effect and thermal effect.

The microstructure and mechanical properties of a Mg-6Al-1Zn-0.9Sn alloy processed by equal channel angular pressing (ECAP) at temperatures of 250 °C and 300 °C were investigated. It was found that the refinement of the microstructure was very dependent on the processing temperature. The main reason for the difference in grain refinement was the precipitation of secondary-phase particles. Texture information obtained by electron back-scatter diffraction (EBSD) showed the gradual formation of a 45° texture during the ECAP process, while the maximum intensity was different for processing temperatures at 250 °C and 300 °C. By calculating the contribution from different strengthening mechanisms, it was found that a 45° texture had a huge influence on grain boundary strengthening and thus the yield strength.

It has been well known that electric pulse can be utilized to enhance the plasticity of metals, which is attributed to the change of dislocation dynamics, e.g., localized planar slip to homogeneous wavy slip. Here, we show another effect of pulse current, which facilitates texture weakening through room-temperature dynamic recrystallization and additionally improve the plasticity of a polycrystalline Mg-3Al-1Sn-1Zn alloy. By conducting a tensile test under electrical pulse, we found that the peak flow stress and fracture strain depend strongly on current density. As peak current densities increases, the flow stress drops and the fracture strain increases. Our Electron Backscatter Diffraction results suggest that dynamic recrystallization occurs at room temperature, which develops a weakened texture. Our work provides a new insight into electroplasticity mechanism in Mg alloys.

A high-strength Mg-4Sm-2Yb-0.6Zn-0.4Zr extruded alloy with bimodal microstructure was creep tested in compression at temperatures of 200 °C and 225 °C under applied stress in the range of 120–200 MPa. The creep curves of the alloy are dominated by a steady-state creep stage and a transient primary creep stage. An abnormal decrease of creep rate is observed in the later period of the steady-state creep stage, particularly the creep at high stress levels more significant, and the underlying reasons are proposed. Moreover, the alloy exhibits high stress exponents (n = 8.7 at 200 °C and n = 7.4 at 225 °C) and activation energies ranging from 225 kJ/mol to 310 kJ/mol. It is shown that the high stress exponents can be well rationalized by the commonly adopted threshold stress method in this work, which results in the modified stress exponents near 5, suggesting five power law, with some indicator of dislocation creep. Transmission electron microscopic observations revealed that cross-slip of dislocations is the dominant creep mechanism in recrystallized grains, while cross-slip of dislocations is operative in hot-worked grains. Besides, a fraction of γ" phase in hot-worked regions was transformed to γ′ phase during creep while not in recrystallized regions, thus coexistence of γ" and γ’ in hot-worked regions. Also, these γ-typed phases play an important role in creep of the studied alloy. Finally, the studied alloy owns better creep resistance than those of benchmark Mg alloys such as AE and AX series alloys.

Pulse current assisted treatment has gained more attention in metallic materials, which is efficient and energy-saving, as compared with traditional heat treatment. However, the microstructural evolution of magnesium alloys with varied pre-deformation under pulsed current is still unclear. In this work, AZ91 alloy is subjected to gradient rolling and pulse current treatment (∼40 s). After gradient rolling, a transition zone from the initial to deformed microstructure was obtained in the sample, and the evolution of phases and twins can be analyzed precisely and continuously. Due to the difference in the Joule heat distribution of pulse current, a large number of fine Mg17Al12 phase are precipitated and dispersed, the precipitation and dissolution process of Mg17Al12 phase occur simultaneously. The region with moderate deformation has the largest recrystallization fraction, and the {101¯1}−{101¯2} double twins and {101¯1} compression twins are the preferred nucleation sites in the early stage of pulse current treatment. The weaken of texture is due to the newly formed grains with non-basal orientations. This work provides a new insight into the microstructural control of pre-deformed magnesium alloys under pulse current assisted treatment.