Journal of Materials Engineering and Performance最新文献

The effect of the post-weld heat treatment (as-weld, 615 °C/16 h, and 615 °C/48 h) on the mechanical properties at the high-temperature of ENiCrFe-7 weld overlay cladding materials has been investigated by the microstructure observation combined with the tensile test. The results show that the precipitates increase not only in the grain boundaries (Nb₅Si₃ and Cr₂₃C₆), but also in the interdendrites (NbC) with increasing the heat treatment time, and the residual stresses first decrease which result from their being relieved by the heat treatment, and those of precipitates increase which result in the residual stresses slightly increased. For the heat treatment alloy ENiCrFe-7 after 615 °C/16 h, it has the worst tensile strength. However, for that of alloy ENiCrFe-7 after 615 °C/48 h, owing to having the most intergranular and interdendritic precipitates, it has the best tensile strength. On the other hand, the elongation gradually increases with increasing the heat treatment time which results from the precipitations of the NbC particles.

Due to its lightweight and high-strength-to-weight ratio, the demand for aluminum alloy AA6061 in automotive and aerospace industries necessitates robust joining with similar and dissimilar materials. Electromagnetic crimping (EMC) is a high-speed and contactless material joining process. This study investigates the effect of target rod surface geometry on the crimping of AA6061 tubes onto AA6061 rods. Experiments were performed at a discharge energy of 6.34 kJ by changing the target rod surface geometry to threading, knurling, grooving, and a plain finish. Samples were crimped with a multi-turn Archimedean spiral coil and a double taper field shaper for steady and concentrated magnetic pressure. Threaded rods showed higher load-bearing strength than knurled, grooved, plain finish samples under pullout, and compressive shear loading. Further, cross-sectional analysis was performed to get insights about material flow and deformation mechanisms. A microhardness test was conducted to understand the flyer and target material deformation behavior under high strain rate conditions. This study demonstrates that threaded surface geometry on the target rod significantly enhances EMC joint strength. In contrast, target rods with knurled surface geometry demonstrate higher hardness near the crimp interface due to more impact points and local strain-hardening effects.

The objective of this research is to address the issue of excessive degradation in magnesium alloys and to achieve controlled degradation of such alloys. To fulfill this objective, montmorillonite/polypyrrole-polycaprolactone (MMT/PPy-PCL) composite coatings were fabricated on the surface of AZ31B magnesium alloy through a two-step method. The outcomes of the study revealed that the PCL-PPy composite coating, developed on the foundation of MMT pre-coating, exhibited a protection efficiency of over 95% for the magnesium alloy substrate, significantly enhancing its corrosion resistance. The incorporation of PPy particles in the composite coating facilitated cell adhesion and proliferation, thereby improving the material’s biocompatibility. Furthermore, the introduction of PPy augmented the number of surface pores in the initially dense PCL composite coating by 0.9-2.5%. Adjusting the PPy particle content in the composite coating proved beneficial in regulating the coating’s porosity, thereby aiding in controlling the degradation rate of the magnesium alloy matrix. Additionally, the cell viability of the MMT/PPy-PCL composite coating consistently exceeded 90%, indicating its favorable impact on the biocompatibility of the magnesium alloy. AZ31B magnesium samples coated with the MMT/PPy-PCL composite coating demonstrated exceptional performance in terms of corrosion resistance, mechanical properties, and biocompatibility. This suggests that it holds great promise as a versatile medical implant material, offering an optimal combination of characteristics for various biomedical applications.

High-frequency induction heating (HFIH) is emerging as a clean and environmentally friendly candidate for rapidly melting the metallic wire to develop a directed energy deposition (DED) process. However, the development of a novel high-frequency induction heating-based directed energy deposition (HFIH-DED) process is in the early stage, where the limiting size of the wire is the main concern over a narrow domain of process parameters. This study discloses the critical size for melting titanium wire at 375 A coil current, 298 kHz frequency and 250 mm/min wire feed rate (WFR) to develop the process. A 2D axisymmetric finite element (FE) model is developed, integrating wire feed velocity to investigate the time required to reach the melting temperature of the Ti-6Al-4 V wire. The power transfer efficiency of the HFIH-DED process reaches to a maximum point with an increase in the wire diameter. Here, the critical diameter for melting the wire is 4 mm. An experimental setup is developed for an HFIH-DED process to deposit a single bead using investigated wire critical size with an optimized multi-loop and multi-turn induction coil. The metal transfer rate is enhanced by 50% when the coil current increases from 375 to 400 A and WFR from 250 to 325 mm/min. The high-speed camera image shows the mode of metal transfer is globular with a transfer frequency of 1 Hz. High-magnification SEM micrographs confirm a lamellar α + β structure growing along heat dissipation. XRD analysis verifies the β phase in the HFIH-DED sample with [110] and [200] peaks. The current study endeavors a process window where the HFIH-DED can deposit a high-melting-point material.

Tuning the interfacial interaction between the filler and the matrix is essential to fabricate high-performance polymer nanocomposites. Epoxy resin-based composites face inherent matrix limitations in tribological applications. Nanosilica (nano-SiO₂) shows promise as a nano-filler for enhancing the mechanical properties of epoxy resin, but its poor dispersibility, agglomeration tendency, and limited compatibility with epoxy present challenges. A multifaceted approach is needed to improve anti-wear and friction reduction properties while enhancing mechanical attributes. This study investigates the integration of silane-modified nano-SiO₂ and basalt flakes (BFs) as fillers in epoxy resin (EP) formulations. Various filler ratios were used to create nano-SiO₂/BFs/EP composite coatings. When basalt flakes were added at 30% and nanosilica at 5%, the resulting composite exhibited optimal friction reduction and anti-wear properties, with the coefficient of friction and wear rate decreasing by 64.3% and 56.2%, respectively, compared to pure epoxy coatings. Scanning electron microscopy (SEM) analysis revealed enhanced interfacial adhesion among nano-SiO₂, basalt flakes, and epoxy, along with improved fracture toughness. This improvement is attributed to the participation of amine-functionalized nano-SiO₂ in the curing process of epoxy, which, when mixed with basalt flakes, reduces adhesion between the flakes, promotes better dispersion, and enhances the overall performance of the epoxy matrix. During friction and wear, the lamellar structure of the basalt flakes and the "ball effect" of nano-SiO₂ facilitate rolling friction, while the layered structure of wear debris provides excellent lubrication properties.

Graphical Abstract

This study aims to model and explore the effect of major variables of the laser cladding process including laser power (P), laser scanning speed (S), and powder feed rate (F) on the single-track geometry of Stellite 6 cobalt-based alloy applied on Steel AISI 5046. For this purpose, substrates of GM locomotive crankshaft alloy were covered with Stellite 6 cobalt-based powder through a laser cladding process. To evaluate the geometric, microstructural, elemental, and phase characteristics, optical microscope, field emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction were used, respectively. Statistical models revealed that single-track dimensions are determined by the interplay of laser power, scanning speed, and feed rate, specifically through complex variable combinations. The results indicated that the height, width, penetration depth, dilution, and wettability angle of the single-track layers are controlled as P^4/5S^−5/4F^1/2, P^6/10S^−2/10_, P⁴S^−3/7F^−6/7, P⁴F^−6/5, and P^4/5S^−5/4F^1/2, respectively. Based on these experimental relations, the map of process variables was obtained for predicting the single-track geometry and as a guide for selecting suitable parameter levels in the laser cladding process of Stellite 6 on locomotive crankshaft alloy. Based on the geometric properties of the laser clad of interest, this map can be used for selecting the process variables. The microstructural and phase characterizations indicated that the clad layer is the form of cobalt γ solid solution with planar and cellular crystallization structures close to the interface, columnar dendritic structure in the central region, and coaxial dendritic structure across the clad surface.

Mono-tungsten carbide (WC) synthesis via a cost-effective self-propagating high-temperature synthesis (SHS) process has attracted considerable research and development interest in recent years. The WO₃-Mg-C system is widely used in SHS owing to its intensive exothermic characteristics, making it ideal for this process. Excess carbon is required to increase carburization efficiency without the use of additives. However, excessive free carbon negatively affects synthesis quality. This study investigated the effects of excess carbon on a WO₃-Mg-C system and its effective control. To verify the hypothesized carbon-loss reaction induced by the carbothermal reduction of MgO, we decreased the combustion temperature (T_C) by adding diluents with different properties, such as NaCl and excess Mg. The decreased T_C and increased NaCl and MgO contents promoted particle refinement by suppressing particle growth during synthesis.

This study thoroughly investigates the effect of Ultrasonic Impact Treatment (UIT) on the impact toughness of S355J2 steel welded joints prepared using gas tungsten arc welding (GTAW). The study systematically analyzes the mechanisms by which UIT affects impact toughness through Charpy impact tests, optical microscopy, scanning electron microscopy (SEM) analysis, and microhardness measurements. The experimental results indicate that the average impact toughness of the welded joints significantly increased to 66.02 J/cm² after UIT, representing a 45.39% improvement. Regular UIT significantly improved the surface quality of the samples, reducing surface roughness, enhancing surface uniformity, and effectively minimizing stress concentration, thereby inhibiting crack propagation. Additionally, by refining the surface grain size, UIT enhanced the surface hardness of the material. Observations from SEM revealed the mechanisms by which UIT strengthens and toughens the impact toughness of the welded joints, showing significant plastic deformation in the impact fracture zone, enlarged void areas, and a transformation in the fracture characteristics of the radiative zone. These changes suggest that UIT enhances the material’s resistance to crack propagation, increases energy consumption during crack growth, raises fracture stress, effectively slows down material degradation, and even achieves crack suppression.

The primary objective of this study is to evaluate the biodegradability of polylactic acid-based scaffolds in phosphate buffer solution. Applying 3D printing technology via fused deposition modeling, 27 porous scaffolds were fabricated. The weight loss and pH values of the 27 scaffolds immersed in phosphate buffer solution remained neutral throughout the incubation period until the sixth week, when they began to fall significantly. The maximum swelling of 7.04% was observed in the scaffold with a layer thickness of 0.20 mm, a scanning speed of 30 mm/sec, and 60% of infill. Furthermore, surface modification of scaffolds was done by virtue of gold-palladium sputter coating, which was an attemptable approach for the development of gold-palladium coated polylactic acid scaffolds for the first time. The electrochemical analysis allowed us to observe that the coated scaffolds followed pseudo-passivation owing to their physical gold-palladium coating characteristics (electropositive nature), prompting an improvement in the formation of the gold-palladium adsorbed and electrolytic solution absorbed (adsorption–absorption)-based layer on scaffolds.