Journal of Materials Engineering and Performance最新文献

The low-cost, cobalt-free bulk AlFeCrNi medium entropy alloy (MEA) was produced using the argon arc melting method, utilizing a cold-compacted pellet as the raw material. The microstructural analysis, phase analysis, and mechanical properties of the as-cast MEA were examined and compared with those of the homogenized AlFeCrNi MEA. Both as-cast and homogenized samples were characterized using x-ray diffraction and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy (EDS). The mechanical properties were assessed based on hardness and compressive strength. X-ray diffraction analysis reveals that in both the as-cast and homogenized AlFeCrNi MEA exhibits the ordered B2 phase and a disordered type BCC structure. Energy-dispersive spectroscopy (EDS) identified the ordered phase as NiAl intermetallics, while the disordered phase corresponds to a (Fe, Cr) solid solution. A strong agreement is observed between the criteria for forming multi-component alloys and the theoretical structure predictions. The DSC analysis confirms the absence of phase transformations in the as-cast MEA up to 1000 °C. The microhardness of the as-cast and homogenized MEA is measured at 504.9 ± 11.44 HV and 436 ± 10.78 HV, respectively, while their compressive yield strength is 1255.61 MPa and 1134.46 MPa. Both variants exhibit a strain exceeding 50%.

In this study, the Mg-5Al-1Zn-3La-1Gd alloy with grain size of 5.18 μm was fabricated using a dual deformation approach involving extrusion followed by rolling (E + R). The slip modes, dislocation characteristics, and mechanical properties were investigated. The results demonstrate that the activation of < c + a > slip is successfully achieved alongside the weakening of basal texture, both of which are linked to grain boundary segregation. Following E + R processing, the yield strength (YS) and ultimate tensile strength (UTS) increase by approximately 170 and 57 MPa, respectively. The overall strengthening arises from a combination of grain refinement, dislocation strengthening, and precipitation strengthening. Moreover, the presence of numerous short < c + a > dislocations in the E + R alloy enhances deformation capability.

Natural fiber composite materials are vital in moving toward sustainable development. The primary characteristics of natural composites are to have a comparable strength-to-weight ratio, with degradation behavior. Even though the natural fiber composite offers environmental benefits, its exposure to moisture drastically affects its performance, with fracture characteristics being vital. The primary objective of the study is to determine the stress intensity factor (SIF) under mode I (tensile opening) and mode II (shear) loading of banana-sisal (BS) composites, considering under moisture diffusion. In this work, the effect of moisture diffusion is studied by conducting accelerated moisture absorption test, via immersing the composite material in distilled water under controlled condition. In addition, the feasibility of replacing the conventional epoxy with cardanol-based bio-epoxy as matrix material is also studied, which enhances the sustainability of the composite material. The testing was carried out using Arcan fixtures for both dry and wet specimen with various crack length (a/W = 0.1 and 0.3) to determine the stress intensity factors (SIF), K_I and K_II. The SIFs for bio-epoxy composites are higher compared to epoxy composites in both dry and wet conditions, indicating the higher resistance offered by bio-epoxy composite for crack propagation. Particularly in wet condition for mode II loading, bio-epoxy has higher SIF for 0.3 a/W, with 1.14 MP.√m for bio-epoxy compared to 0.79 MPa.√m for epoxy composite specimen. In both bio-epoxy and epoxy composites, the moisture diffusion decreases the critical values of K_IC and K_IIC compared to dry ones, which is mainly due to the degradation of fiber/matrix bonding. Based on SEM analysis, the failure under mode I is predominated by fiber breakage, whereas under mode II is predominated by fiber pull out.

The development of efficient and stable transition metal-based electrocatalysts has always been an important step in the development of low-cost electrocatalysts for water splitting. High-entropy alloys (HEAs) comprising five or more elements in near-equiatomic proportions have attracted ever-increasing attention for their distinctive properties, such as exceptional strength, corrosion resistance, high hardness, and excellent ductility. Herein, FeCoCrNiAl, FeCoCrNiCu, and FeCoCrNiAlCu high-entropy alloys were prepared by vacuum arc furnace melting, and the effects of different element compositions on electrocatalytic reactions were explored. The results show that the FeCoCrNiAlCu high-entropy alloy (HEA) exhibits an excellent catalytic activity in a 0.5 M H₂SO₄ solution. Hence, the FeCoCrNiAlCu HEA exhibits an overpotential of 134 mV at 10 mA cm^-2 for the hydrogen evolution reaction (HER), which is lower than FeCoCrNiAl (189.3 mV), FeCoCrNiCu (191.3 mV) and the FeCoCrNiAlCu HEA possesses a relatively low Tafel slope (99.8 mV dec-1). Furthermore, it exhibits superior stability for i-t cycle. This work provides a useful method to design high-efficiency and low-cost high-entropy alloy catalysts for various necessary reactions.

Laser-directed energy deposition (L-DED) is a key additive manufacturing technology with extensive applications in aerospace, automotive, and biomedical industries due to its ability to fabricate complex geometries and repair high-value components. However, optimizing material strength, toughness, and process efficiency remains a critical challenge due to issues such as microstructural anisotropy, residual stress, and defect formation. This review presents a comprehensive multidimensional strategy for enhancing the performance of L-DED manufactured materials by integrating material selection, process control, structural optimization, and advanced manufacturing technologies. It evaluates the mechanical properties of commonly used materials and analyzes the influence of laser power, scanning strategies, and powder feed rate on melt pool behavior, grain morphology, and defects. Additionally, it explores novel structures and technological advancements aimed at improving microstructural uniformity and reducing porosity. The review also introduces an integrated optimization framework that combines AI-driven process control, real-time monitoring, and sustainable manufacturing techniques. By addressing these key challenges, this study contributes to the development of high-strength, defect-free, and industrially viable L-DED technologies, facilitating their broader adoption in high-performance engineering applications.

Due to the growing importance of aluminum alloys for lightweight sheet metal parts in the automotive industry, stretch flangeability of aluminum alloys is one of the critical parameters in the overall assessment of their formability. In this work, stretch flangeability of five different aluminum alloys (AA2024, AA5083, AA5754, AA6061, and AA7075) and two grades of steel (DP600 steel and extra-deep drawing steel) has been investigated by numerical simulation of the hole expansion test along with characterization of their tensile properties and anisotropy. The hole expansion tests were carried out to validate the predicted hole expansion ratio, major and minor strains, and thinning at failure. It has been found that AA5754 and AA6061 exhibited the highest hole expansion ratio among the Al alloys studied in the present work which is significantly higher than that of DP600 steel but lower than that of extra-deep drawing steel. AA2024 and AA5083 also exhibited higher stretch flangeability than DP600 steel, making these four alloys potentially suitable for lightweight sheet metal parts involving stretch flanging where very high strength is not an essential requirement.

As an essential technology in metal additive manufacturing (AM), laser powder bed fusion (LPBF) has garnered significant attention owing to its unique capability to fabricate complex structural components with high design freedom, near-perfect density and enhanced mechanical properties. Herein, the influences of processing parameters on the microstructure characteristics and mechanical properties of LPBF-built AlSi10Mg samples are experimentally investigated, and a finite element model with multi-track laser scanning is developed to explore the effect of non-equilibrium solidification on the formation of metallurgical defects and microstructure evolution during LPBF process. The experimental results demonstrate that the tensile properties of LPBF-built samples can be significantly enhanced by decreasing the porosity level, and the optimized processing parameters yield an ultimate tensile strength (UTS) of 448 ± 3 MPa and an elongation to failure of 8.3 ± 0.9%. Analysis of predicted melting pool morphologies indicates that the formation mechanism of the melting pool is conductive melting, and the lack-of-fusion defects can be eliminated through the optimization of the overlap ratio between adjacent melting pools. Simulation results confirm that the cooling rate serves as a reliable indicator of α-Al cell size in the microstructure of LPBF-built AlSi10Mg, and fine cellular structures with cell size of ~ 0.45μm are obtained when performing a high scanning speed of 1200 mm/s. Notably, the correlation between the mechanical properties and the solidification cell size also indicates that the UTS and yield strength can be highly improved with the refinement of the α-Al cells, while the elongation to failure remains highly sensitive to the microstructural defects.

The present study investigated the effect of temperature and Cr addition on the slip-twinning competition in BCC-Fe through molecular dynamics simulations. A sharp crack {113}/(langle 110rangle) with a crack plane {113} and crack tip (langle 110rangle) was created. A tensile load with a strain rate of 10⁸ s^-1 was applied along the crack plane direction. Plastic deformation through twinning was noticed at two locations in the pure BCC-Fe system at T = 10 K, one at the crack tip and the other at the hard grip and the surface intersection region (surface region). A twinning to slip transition was noticed at T = 600 K at the crack tip due to the coupling of local stresses with thermal energy. However, the same transition was observed at a much higher temperature, 1000 K, in the surface region. A strong coupling between local stress concentration and thermal energy changed the deformation mode in BCC-Fe. Further, the effect of Cr on the deformation mode in BCC-Fe was studied at a fixed temperature of 10 K. Slip-stabilized twinning (slip followed by twin) was noticed at the crack tip and the surface region at 18 at.% Cr and 50 at.% Cr additions in BCC-Fe, respectively. Twinning to slip transition was noticed at the crack tip at 70 at.% Cr addition indicated the strong coupling between local and internal stresses. Further, twinning to slip transition in the entire Fe−70 at.% Cr binary alloy system was observed at 1300 K. Strong thermal energy, internal, and local stress coupling were noticed in the present study. The slip occurred through 1/2 (langle 111rangle) type edge dislocation nucleation.

NiTi alloys with varying La₂O₃ concentrations (0, 0.05, 0.10, and 0.15%) were fabricated using selective laser melting (SLM). The effects of La₂O₃ content on the microstructure, phase transformation behavior, and friction and wear properties of SLM-NiTi alloys were investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, microhardness testing, tensile testing, and friction and wear testing. The results show that the addition of La₂O₃ enhances the fluidity of the molten pool. Specifically, when the La₂O₃ content is 0.05%, the metallurgical bonding performance is optimal, the grains in the molten pool are more refined, and the microhardness value reaches a maximum value of 395.3 HV. With the increase of La₂O₃ content, the phase transformation temperature first increases and then decreases. It is worth noting that when the La₂O₃ content exceeds 0.10%, the reverse martensitic phase transformation is promoted. When the La₂O₃ content is 0.05%, the width and depth of the wear scar are the smallest, the amount of wear debris on the wear surface is reduced, and no obvious plastic deformation is observed, which indicates that both abrasive wear and adhesive wear effects are reduced, and there is only slight oxidation wear, thus showing the best wear resistance.

The initial corrosion behavior of E690 steel in NaCl solutions with different chloride ion concentrations was studied using SEM, EBSD, electrochemical testing, and AFM. The results show that the microstructure of E690 steel is mainly composed of lath bainite. As the concentration of chloride ion increases, the corrosion potential of E690 steel becomes more negative, the corrosion current density increases significantly, and the corrosion resistance decreases. The corrosion resistance of steel is mainly controlled by the microstructure in the early stages of corrosion. The high dislocation density of bainite and the electrochemical activity of grain boundaries make it prone to corrosion. In low concentration NaCl solutions, corrosion mainly occurs at the grain boundaries of bainite laths. As the chloride ion concentration increases, the original `austenite grain boundaries exhibit obvious corrosion characteristics, which accelerates the corrosion rate.