Journal of Materials Engineering and Performance最新文献

Fused Deposition Modeling (FDM) is a common additive manufacturing method used to produce intricate three-dimensional structures from thermoplastics. Its affordability and adaptability have contributed to its widespread use in fields such as medicine, electronics, and aerospace. This research focused on analyzing the mechanical properties of PLA (Polylactic Acid) samples produced via FDM. Since polymers display viscoelastic behavior above their glass transition temperature, this effect was disregarded due to the complexity of computations. Instead, key material properties, including Young’s modulus, thermal expansion, and conductivity, were considered temperature-dependent. To support the simulations, Differential Scanning Calorimetry (DSC) and Thermomechanical Analysis (TMA) were conducted to determine the PLA’s glass transition temperature and thermal expansion coefficients. Tensile tests were carried out at four different temperatures (25, 55, 85, and 115 °C), with results compared to finite element simulations in Abaqus. The findings showed that at 25 °C, PLA samples were rigid and glassy, but as they approached the glass transition temperature, they became softer and more rubber-like, leading to a significant reduction in tensile strength. The highest tensile strength was observed in the horizontally printed sample (H1) at 25 °C (31.66 MPa), while the lowest tensile strength was recorded in the vertically printed sample (V1) at 115 °C (3.41 MPa). All samples were fabricated using 100% infill density to ensure structural integrity and accurate comparison. The greatest elongation was measured at 55 °C. Experimental stress–strain curves closely matched simulation results, with an error margin of less than 5%. An analysis of distortion revealed that vertically printed samples deformed more due to layer accumulation, weaker interlayer adhesion, and extended cooling times. In contrast, horizontally printed samples experienced minimal distortion, benefiting from stronger platform contact and a lower number of layers.

Ballistic standards require body armor to withstand multiple projectiles without getting penetrated. The response of a ceramic/composite armor, in terms of its back face signature (BFS) when eight hardened steel cores (HSC) at 715 m/s are fired on it, is studied numerically using finite element (FE) method. The armor consists of ceramic, hard and soft ultra-high molecular weight polyethylene (UHMWPE) layers and foam. The FE model of the projectile and armor was developed in LS-Dyna and different material models were employed to constitute their behaviors. Initially, the influence of contact conditions between ceramic tiles forming the strike face of the armor panel was studied in terms of damage propagation in adjacent tiles. Further, the deformation of the various layers and penetration of ceramic tiles and hard UHMWPE along with the reduction in length of projectiles were investigated. The developed FE model was validated by comparing the average BFS and bullet length reduction values against experimental data. It was found that although significant bullet impact energy was absorbed in damaging ceramic tiles, it still influenced the displacement response of hard armor panel (HAP) layers. The delamination lengths between composite layers are also discussed. The presented modeling techniques and developed FE model may help in improving the design of bulletproof armor panels capable of withstanding multiple bullet impacts.

Maraging steel is extensively utilized in industrial applications owing to its superior mechanical properties, including high strength, toughness, and dimensional stability. This study evaluates the feasibility of gas tungsten arc welding (GTAW) for repairing maraging steel components fabricated via laser-powder bed fusion (L-PBF). Specimens (100 × 50 × 2 mm) were produced in three build orientations (0°, 45°, and 90°) using maraging steel powder, followed by solution treatment and age hardening. Autogenous GTAW was employed to join both additively manufactured (AM) and conventionally processed samples. Microstructural and mechanical properties of the weldments were analyzed through optical and scanning electron microscopy, microhardness, and tensile testing. Results indicate orientation-dependent hardness in AM samples: 45° samples exhibited 16% lower, while 90° samples showed 4% higher hardness compared to conventional counterparts. Additionally, the ultimate tensile strength of 90° AM samples was 5% higher than that of conventional weldments. The findings demonstrate the potential of GTAW as a cost-effective repair strategy for L-PBF-fabricated maraging steel (grade 300) components.

The aluminum alloy composite processed with additive manufacturing technology (laser powder bed melting—LPBM) has better microstructural and mechanical properties and is familiar with making design freedom geometry. However, the combinations of composite powder found agglomeration, porosity due to high laser energy, and micro hot cracks, leading to a reduction in the functional properties of the composite. This research intends to overcome the above challenges and enrich the microstructural and mechanical properties of aluminum alloy (Al7075) powder blended with 0.5 wt.% graphene and 2.5-7.5 wt.% of titanium carbide (TiC) nanoparticles via a high-energy ball milling process, associated with 1% polyvinyl alcohol surfactants prevents the agglomeration. With the support of the laser powder bed melting process (LPBM), the Al7075/graphene/TiC composite is prepared with a 70 µm hatching distance with 60% overlap under argon build atmosphere, which helps to reduce the oxide formation. The LPBM-developed samples are involved in the aging process to limit the residual stress, which assists in determining the hot cracks. Effects of LPBM processing and filler on microstructural, physical, and mechanical properties are studied. The transmission electron microscope (TEM) analyzed image shows homogenous particle dispersion with improved interfacial bonding strength, with a grain size from 6 to 18 µm. The LPBM processed Al7075/1 wt.% graphene/7.5 wt.% TiC sample is 0.47% of porosity, optimum tensile strength (598 MPa), reduced elongation (7.2%), optimum impact strength (15.3 J/mm²), and improved microhardness of 228HV, respectively.

The microstructure, mechanical properties and degradation behavior of the extruded Mg-2Y-1Cu (MYC, at.%) and Mg-2Y-0.5Cu-0.5Ni (MYCN, at.%) alloys were investigated in this study. The experimental results revealed that the addition of Ni effectively refined the grain size and modified the distribution and precipitation behavior of second phase in the extruded MYC alloy. The volume fraction of the long-period stacking ordered (LPSO) phases increased from 26.8% in the extruded MYC alloy to 39.9% in the extruded MYCN alloy. Tensile testing results indicated that the Ni addition enhanced the compressive strength from 332 MPa for the extruded MYC alloy to 351 MPa for the extruded MYCN alloy. Moreover, the immersion experiments and electrochemical tests indicated that the addition of Ni significantly increased the degradation rate, hydrogen evolution and weight loss rate of the extruded MYC alloy. The hydrogen evolution rate and weight loss rate of the extruded MYCN alloy were 21.985 ml/cm²·h and 23 mg/cm²·h, increased by 174% and 170% compared to those of the extruded MYC alloy, respectively. The enhanced degradation rate of the extruded MYCN alloy was mainly due to the significant galvanic corrosion between second phase and α-Mg matrix. Additionally, the high compressive strengths of the extruded MYCN alloy were mainly attributed to grain refinement and second phase strengthening resulting from LPSO phase.

In order to investigate the influence of the shape of the powder raw material on the coating properties, this paper investigates the plasma-sintered WC particles added to Fe-based powder to prepare coatings, and characterization methods such as coating microstructure, microhardness, and friction and wear are examined. The results show that with the increase of the mass fraction of added WC-17Co, the physical phases of the coatings appeared Fe₃W₃C₃ and Co₃W₃C₃, and at the same time, the microstructure of the coatings had a dense and homogeneous grain structure without obvious defects, and irregular aggregation of WC particles was clearly observed, and fine WC precipitates dispersed in the coatings were also observed. The hardness of the coating increases with the increase of WC-17Co content, and the spherical shape of the powder has a better improvement effect. With the addition of 30% WC-17Co, the hardness of the coating reaches 800HV0.2, which is 60% higher than that of the unadded coating. Spherical WC particles with 30% addition showed a more significant improvement, with a wear rate of 10-8, which was significantly better than that of non-spherical particles. Spherical particles have a smoother particle surface, which facilitates inter-particle movement and provides better spatial accumulation of powders, and at the same volume, the WC content of the spherical form of the powder is higher.

In this study, the effects of warm rolling at 520 °C on the microstructure, mechanical, tribological, corrosion, and thermal oxidation behaviors of Incoloy-925 alloy were investigated. Plastic deformation applied at rates of 30, 50, and 70% led to a significant grain size reduction from 150 to 8 µm, resulting in improved hardness (up to 339 HV) and yield strength (up to 1480 MPa). Wear tests showed that the coefficient of friction decreased from 0.653 (untreated) to 0.548 (70% deformation), and the total mass loss dropped from 7 to 1 mg. Corrosion analysis revealed that the corrosion rate declined from 6.94 to 1.02 mpy with the increase in deformation, attributing to enhanced passive film formation and a more homogeneous surface structure. TGA/DTA analyses confirmed that warm rolling improved thermal oxidation resistance. The mass loss decreased from 0.91% (untreated) to 0.49% (70% deformation). Exothermic reactions between 400 and 950 °C observed in DTA curves indicated phase transformations, which were consistent with XRD findings revealing γ, δ, and MC-type carbide phases. Overall, the results demonstrate that warm rolling significantly enhances the surface integrity, thermal stability, and corrosion and wear resistance of Incoloy-925 alloy, making it a strong candidate for demanding industrial and biomedical applications.

The current study investigated the synthesis of pure Ni, Ni-ZrO₂, and Ni-ZrO₂-CeO₂ nanocomposites using ultrasonic pulse electrodeposition. The study focused on evaluating their mechanical properties, surface characteristics, wear performance, and corrosion resistance. The findings revealed that pure Ni composites demonstrated coarse particles with an irregular structure. However, the Ni-ZrO₂-CeO₂ nanocomposites revealed the most compact, uniform, and refined microstructure among the three, with average grain sizes of 67.9 nm for Ni and 20.8 nm for ZrO₂/CeO₂ nanoparticles. The microhardness measurements revealed high values for all composites, with pure Ni, Ni-ZrO₂, and Ni-ZrO₂-CeO₂ nanocomposites respectively averaging 375.4, 430.1, and 525.9 Hv. Moreover, the Ni-ZrO₂-CeO₂ nanocomposites demonstrated improved tribological performance, maintaining a low friction coefficient of approximately 0.31. The worn mass loss comparison showed that pure Ni composites had the 34.55 mg/m² highest average mass loss, whereas Ni-ZrO₂-CeO₂ nanocomposites demonstrated the minimal average mass loss, at 14.87 mg/m². In a 3.5 wt.% solution of NaCl, the Ni-ZrO₂-CeO₂ nanocomposites revealed outstanding corrosion resistance, sustaining minimal damage and achieving the 0.06 mm/year lowest corrosion rate among the composites. The addition of ZrO₂ and CeO₂ nanoparticles in the Ni-ZrO₂-CeO₂ composite refined the grain structure and promoted a uniform, densely packed microstructure, significantly improving corrosion resistance upon comparison with pure Ni and Ni-ZrO₂ composites. These results underline the potential of UPE for fabricating high-performance nanocomposites with advanced properties for various technological applications.

A series of AlCoCr_xFeNi_2.2 (x = 0, 0.3, 0.7, 1.1, 1.5, 1.9, 2.3) high-entropy alloys were designed and prepared. The effects of the Cr content on the microstructures and mechanical properties of the AlCoCr_xFeNi_2.2 alloys were studied. All the alloys consisted of face-centered cubic (FCC) and body-centered cubic (BCC) phases. The Cr-free AlCoFeNi_2.2 alloy exhibited a fine alternating lamellar eutectic structure, which became coarser with increasing Cr content. When x = 2.3, the lamellar eutectic structure disappears. Room temperature uniaxial tensile tests revealed significant changes in the mechanical properties with increasing Cr content. For 0 ≤ x ≤ 1.1, with increasing Cr content, the yield strength and hardness of the alloy decrease, whereas the ductility increases. Conversely, for 1.1 ≤ x ≤ 2.3, increasing the Cr content resulted in a higher yield strength and hardness of the alloy, accompanied by a decrease in ductility. The AlCoCr_0.7FeNi_2.2 alloy exhibited superior overall mechanical properties at room temperature. The tensile yield strength, hardness, and elongation were 472.9 MPa, 294.8 HV, and 26.3%, respectively. Uniaxial tensile tests on the AlCoCr_0.7FeNi_2.2 alloy at various temperatures and strain rates revealed that the strength increased with increasing temperature and decreasing strain rate. A mathematical description of the effects of temperature and strain rate on the strength of an alloy can be given by the Arrhenius-type equation. These results demonstrate that the AlCoCr_0.7FeNi_2.2 alloy maintains excellent properties even at elevated temperatures.

This work investigates the effects of heat treatment and laser shock peening (LSP) on the nanomechanical behavior of SS316L fabricated by selective laser melting (SLM). The nanoindentation, microstructural studies, phase analysis, and microhardness testing were performed under different conditions. Microstructural analysis revealed columnar structure in the as-built sample and annealing twins in the heat-treated sample. The LSP induced a high-pressure shock wave, causing severe plastic deformation and grain refinement. Phase analysis confirmed the presence of the face-centered cubic (FCC) austenite (γ) phase with no new crystalline phases. The LSP impacts increased FWHM values due to enhanced microstrain and grain refinement in LSP samples. The surface microhardness, reduced modulus, nanohardness, plastic deformation, elastic modulus, and contact stiffness of the AB + LSP sample improved by 25.81, 7.25, 24.70, 63.63, 8.97, and 9.91% as compared to the AB sample. Similarly, the HT + LSP sample showed improvements by 18.18, 6.78, 28.46, 81.27, 8.14, and 16.06% in these properties compared to the HT sample. The indentation depth and creep of AB + LSP reduced by 49.05 and 30.76%, while for HT + LSP, they reduced by 25.27 and 26.92%, respectively. These findings confirm that LSP effectively enhances the surface strength and durability of SS316L.

Graphical Abstract