Journal of Materials Engineering and Performance最新文献

Thin surface conversion layers formed by precipitation from slightly acidic iron phosphating solutions with different additives were examined by scanning electron microscopy (SEM) energy-dispersive x ray (EDS) and glow discharge optical emission spectroscopic (GD OES) surface analytical techniques revealing important details on their in depth elementary composition on the nanoscale. Some stoichiometric mineralogical analogies were also sought and explored based on the detected components of the coprecipitated nanolayers. During the spray phosphating process the molybdate additive formed codeposits through the whole insoluble iron phosphate-oxide-hydroxide type surface film that could incorporate traces of alkali and alkaline earth cations like Na, K, Ca, and Mg as well. Magnesium as an additive was then also added to the iron phosphating solution as its nitrate salt in different concentrations and its advantageous properties were evaluated after checking the corrosion resistance of the then e-coated (KTL epoxy painted) phosphate steel plates (Q-panels) by the standard salt spray test (ISO 9227), showing acceptable data up to 720 h exposure in 5 wt.% NaCl solution at 35 °C.

In this study, copper matrix composites reinforced with varying silicon carbide (SiC) contents (0.25, 0.5, 0.75, and 1 wt.%) were fabricated using spark plasma sintering (SPS). The effects of SiC reinforcement on the microstructure, hardness, porosity, electrical conductivity, and tribological performance were systematically investigated. Brinell hardness values increased with higher SiC content, reaching up to 76 HB for the 1 wt.% SiC composite. This improvement was accompanied by a gradual increase in porosity from 0.6 to 2.1%. Electrical conductivity decreased from 93% IACS to 66% IACS with increasing SiC content. Tribological tests revealed that the specific wear rate was significantly reduced, reaching as low as 1.1 × 10⁻⁴ mm³/N m at 15 N due to the formation of a protective tribolayer. These results demonstrate that incorporating small amounts of SiC can substantially improve hardness and wear resistance, while maintaining acceptable electrical performance, making Cu-SiC composites promising candidates for durable electrical contact applications.

The waterborne polyurethane (WPU) has been applied in many fields due to environmental friendliness; however, most of the single-component WPU still has the problems of poor water resistance and low stability. Thus, this work developed an interpenetrating network (IPN) waterborne polyurethane/polyacrylate composite emulsion (WPUA) and then used organofluorine as hydrophobic modifier. The stability, morphology, and film-forming performances of as-prepared organofluorine modified WPUA (FWPUA) were investigated. These results showed that the storage stability of as-prepared FWPUA exceeded 6 months and the water contact angle of FWPUA film reached 93.38° and the water absorption rate reduced to 9% exhibiting good hydrophobic performance. The surface of FWPUA film was rougher and the degree of “wrinkling” in the cross-section was significantly deeper with the increasing of the organofluorine content. In addition, the tensile strength of optimized FWPUA film was 8.83 MPa and the average light transmittance in the range of 390-780 nm was 92%. Therefore, as-prepared FWPUA in this work can replace WPUA and has potential in hydrophobic coating and film.

The properties of TC1 / 1060 / 6061 Ti/Al explosive composite tungsten argon arc welding dissimilar welded joints were analyzed by means of SEM, EBSD, XRD and EDS. The results show that the microstructure of the weld changes from coarse β grains to lamellar martensitic α' phases. There is an appropriate amount of mutual diffusion of titanium/aluminum atoms at the welding, indicating that there is a strong interatomic bonding force in the weld. There are no titanium and aluminum intermetallic compounds produced in welds, but exists Al/Fe and Al/Mg compounds, indicating that the bonding quality of the weld is lower than untreated. The weld may become a point of stress concentration in the joint which affects the bearing capacity of joint. The composite welding specimens have strong tensile properties and poor shear properties.

In this study, the changes in precipitation behavior and mechanical properties of Fe−17Mn-0.88C high-manganese steel under different aging times are studied using SEM, EPMA, and TEM, combined with complementary micromechanical characterization techniques such as nanoindentation. There is no significant change in micron-sized precipitates, but the amount of nano-sized V₂C precipitates increases obviously and the distribution is more uniform as the aging time (AT) increases. The improvement of mechanical properties of the tested steel can be ascribed to precipitation strengthening. The variation of yield strength (from 484 to 548 MPa) with AT (from 1 to 24 h) is mainly attributed to the increase of volume fraction and homogeneous distribution of the nano-sized V₂C precipitates. The optimum AT is considered as 24 h, it obtains the maximum hardness (250 HWB) and better impact toughness (81 J). Moreover, the yield strength increment caused by precipitation strengthening and peak work-hardening rate of AT24 steel are up to 27.8 MPa and 65 GPa, respectively. The entire mechanical properties are characterized by NanoBlitz three-dimensional (3D) maps, and the values of nano-hardness and Young's modulus of AT24 steel are greater than 16.86 GPa and 370 GPa.

Laser deposition repair technology is a process that utilizes light and heat to locally melt the material on the surface of an alloy, enabling the repair of the material. The alloy produced by this method exhibits significant differences compared to those obtained through conventional forging techniques. Consequently, selecting the appropriate heat treatment process is critical for optimizing the mechanical properties of the repaired alloy. This study investigates the grain morphology, microstructure, and mechanical properties of TA15 titanium alloy repaired via laser deposition, under various annealing conditions, both at room temperature and elevated temperatures. The results indicate that specimens annealed below the β-phase transition temperature exhibit a bimodal microstructure in the base material region. The heat-affected zone (HAZ) is characterized by a mixture of “sawtooth” α-phase, lamellar α-phase, and β-phase, while the repaired region exhibits a net-basket-like microstructure. For the specimen annealed at 1000 °C for 2 h, the α-phase in the base material region is completely eliminated, whereas in the HAZ, the α-phase predominantly exists in the form of cluster bundles. Polygonal grains are observed in the repaired zone. The HTR900-annealed specimen demonstrates a favorable balance between strength and ductility at room temperature, exhibiting a tensile strength of 971.86 MPa, a yield strength of 791.68 MPa, and an elongation of 13.23%. At 500 °C, the HTH900-annealed specimen maintains a satisfactory combination of strength and plasticity. Under elevated temperature conditions (500 °C), the mechanical properties of both HTH900 and HTH950 annealed specimens outperform those of the HTH1000 annealed specimens.

Material Extrusion (MEX) technology, a cost-effective 3D printing method for the fabrication of complex metal parts, has received considerable interest because it allows parts to be made through multiple steps such as printing, debinding and sintering in a simpler, safer and more cost-effective way than other technologies. However, controlling and predicting surface roughness, crucial for functional parts, remains an open challenge. This is due to the layer-by-layer deposition method that generate a poor-quality surface compromising the performance and limiting the potential applications. In this context, post-treatments aim to modify the characteristics of the as-sintered parts to achieve desired functionalities in terms of mechanical strength, surface finish and functional properties. In the present work, surface mechanical treatments such as compressed air shot-blasting and sand-blasting have been applied on 316L parts realized by MEX. Post process parameters as the size and the shape of the media and the treatment pressure and treatment time were studied using the Design of Experiment approach. The roughness and surface morphology were then analysed as outputs and used as drivers to provide a better knowledge of the effects of surface post treatment process on MEX metal parts. After post treatment, the minimum roughness achieved along the lateral faces was in a range of 4.37-4.85 μm, respectively − 69.5 and − 62.4% compared to the as-sintered condition, and on the top face 2.44-3.14 μm, respectively − 55.6% and − 46.7% compared to the as-sintered condition. Furthermore, the combination of an angular shape media, a coarse size media and a high value of pressure (4 bar) changed dramatically the layer-wise surface texture of the samples due to the material removal and consequently weight loss in a range of 2.0-2.5%.

Ta/Re-laminated composite materials show promising application prospects in space engine nozzles. The physical and chemical properties of the Ta-Re solid solution at the Ta/Re interface are crucial determinants of the composite’s high-temperature performance. This study explores the stability, mechanical, and thermodynamic properties of the ReTa₃ solid solution using first-principles calculations. The formation enthalpy (ΔH) and cohesive energy (E_coh) of ReTa₃ are calculated to be − 0.171 eV/atom and − 9.805 eV/atom, respectively. These data indicate that ReTa₃ can form spontaneously and is energetically stable. The solid solution exhibits notable mechanical properties, including high toughness (Pugh’s ratio = 3.70) and hardness (H_V = 3.86 GPa), along with low anisotropy. Thermodynamically, at 0 GPa and 2000 K, the average atomic heat capacity of ReTa₃ (C_p = 27.485 J·mol⁻¹·K⁻¹) closely matches that of Re (C_p = 27.183 J·mol⁻¹·K⁻¹) and Ta (C_p = 27.576 J·mol⁻¹·K⁻¹). The coefficient of thermal expansion for ReTa₃ (α = 2.459 × 10⁻⁵·K⁻¹) lies between those of Re (α = 2.011 × 10⁻⁵·K⁻¹) and Ta (α = 2.648 × 10⁻⁵·K⁻¹) at 0 GPa and 2000 K. Such a property effectively reduces the temperature gradient within the material, thereby mitigating the risk of thermal cracking and interfacial debonding. These behaviors are attributed to the hybridization of electron orbitals between Re and Ta atoms, leading to energy level splitting at the Fermi level and a reduction in the bond energy of pseudo-covalent bonds within the unit cell. This comprehensive analysis of ReTa₃ provides insights into the electron transfer mechanisms that govern its properties and offers a theoretical foundation for the composition control and performance optimization of transition layers in Ta-Re-layered composite materials.

This study investigates the effect of heat build-up, as a function of different building modes and energy input, on the microstructure and mechanical properties of Al-Si10-Mg parts processed by Selective Laser Melting (SLM). Three different volumetric energy densities (67 J/mm³, 70 J/mm³ and 86 J/mm³) were applied for building samples. The building chamber was heated at 200 °C to reduce residual stress. The samples were processed in Horizontal (H) and Vertical (V) modes. The H and V samples were investigated using an Optical Microscope (OM), a Scanning Electron Microscope (SEM), x-ray diffraction (XRD), Vickers microhardness, and tensile tests. Moreover, the electrical conductivity (EC) of the samples was investigated. The amount, size, and morphology of the defects were also analyzed by Image J software. Different building modes significantly influenced the heat build-up, microstructure, and hardness at a set energy density. Vertical samples exhibited a coarser microstructure and reduced homogeneity along the growth direction (z-axis) compared to horizontal samples. V samples also showed significant variations in microstructure and hardness along the z-axis, whereas H samples maintained greater uniformity. Furthermore, the percentage of defects increased in V samples and decreased in H samples with increasing heat input. Finally, after tensile test, a misalignment in mechanical response for H and V modes has been observed at all the energy densities except the lowest one.

Graphical Abstract

This study reports the synthesis and characterization of Ni-P-AlN nanocomposite coatings with varying concentrations of aluminium nitride (AlN) nanoparticles. The coatings were deposited on carbon steel substrates using an electroless deposition technique. Structural (XRD, SEM) and compositional analyses (EDX) confirmed the successful co-deposition of AlN nanoparticles into the Ni–P matrix. A comparative analysis of the developed coatings indicates that Ni-P-AlN nanocomposite coatings exhibit their best mechanical and corrosion resistance performance with an optimum composition of AlN nanoparticles at 0.75 g/L. The improvement in microhardness of Ni-P-AlN nanocomposite coatings with increasing concentration of AlN nanoparticles can be attributed to the formation of a compact coating structure, grain refinement, and dispersion hardening effect. Similarly, an enhancement in corrosion protection efficiency of Ni-P-AlN nanocomposite by the gradual increase of AlN nanoparticles may be attributed to the reduction in the active area of the Ni-P matrix and reduced porosity due to the filling of pores by AlN nanoparticles. A decline in mechanical and corrosion-resistant properties beyond the optimal concentration (0.75 g/L) is observed, likely due to excessive agglomeration of AlN nanoparticles caused by their high surface area. These findings demonstrate that Ni-P-AlN nanocomposite coatings are suitable for many industries.