Journal of Materials Engineering and Performance最新文献

This study aims to investigate the influence of Cr content on the high-temperature mechanical, oxidation, and electrical properties of powder metallurgy ferritic stainless steel for solid oxide fuel cell (SOFC) interconnect. To achieve this objective, ferritic stainless steel water-atomized powders with different Cr content were first compacted and then sintered at 1380 °C for 2 h under hydrogen atmosphere. The properties were evaluated through high-temperature tensile tests at 800 °C, oxidation tests, and area-specific resistance (ASR) measurements. Microstructural characterization was conducted using x-ray diffraction (XRD), scanning electron microscope (SEM) with energy-dispersive spectroscope (EDS). The results indicated that with an increase in Cr content, the strength of the powder metallurgy ferritic stainless steel specimens increased, while the elongation decreased at 800°C. Additionally, oxidation mass gain decreased, and ASR decreased. Commercially available ZMG232 ferritic stainless steel was employed for high-temperature mechanical, oxidation, and electrical properties comparison. Compared to ZMG232, the high-temperature yield strength and tensile strength of powder metallurgy ferritic stainless steel specimens were higher with 22 wt.% and 26 wt.% Cr content. And with 17 wt.% Cr content, there was a significant difference in oxidation mass gain and ASR. However, with 22 wt.% and 26 wt.% Cr content, oxidation mass gain and ASR were relatively close, indicated that the high Cr content powder metallurgy ferritic stainless steel in this study can be an alternative to the commercially available ZMG232 ferritic stainless steel.

The laser-directed energy deposition (LDED) technique exhibits unique advantages in the production of high-entropy alloy (HEA), offering a novel approach for repairing and fabricating HEA coatings. However, the quality of deposited tracks is significantly influenced by multiple process parameters. To achieve well-formed and high-quality deposited tracks, this study employs response surface methodology (RSM) to investigate the underlying reasons and patterns governing the impacts of pivotal parameters on various assessment criteria of tracks. Based on the mathematical model of parameter-response correlation developed by RSM, the optimization was carried out by executing the second generation multi-objective optimization non-dominated sorting genetic algorithm II (NSGA-II) using Matlab code. The outcomes illustrate the Pareto frontiers of optimal coupling of multiple process parameters and multiple-objective matching of deposited tracks evaluation indicators. When employing the optimal process parameters, the microstructure gradually refines into non-directional equiaxed grains along the deposition direction, accompanied by a three-step stable increase in micro-hardness, yielding a single track with excellent morphology and microstructure. These findings provide theoretical support for the deposition of HEA with excellent morphology and performance.

Wire arc additive manufacturing (WAAM) employs an electric arc-based deposition process, but achieving the desired mechanical and metallurgical properties in WAAM is challenging. The pre-heating phase is critical for reducing residual stress and maintaining consistent heat input. This study introduces an automated induction-based pre-heating system integrated and made compatible with WAAM, evaluating its effectiveness on low carbon steel (ER 70S-6). The induction pre-heater is designed to meet application-specific needs, with dynamic power adjustments based on material composition and substrate size. It comprises a power source, cooling chiller, coil box, and pyrometer for temperature monitoring. Deposition is done using a CNC system utilizing a Cold Metal Transfer Metal Inert Gas (CMT-MIG) setup, comparing samples with and without pre-heating at maximum temperature. The study employs various techniques, including Electron Back-Scattered Diffraction analysis, x-ray diffraction, microhardness testing, and tensile tests, to assess the impact of pre-heating on dilution, grain size, residual stress, and mechanical properties. The results of this investigation illustrate that pre-heating markedly augments dilution by 15-20%, thereby fortifying interlayer bonding. Additionally, it refines the grain structure, diminishes residual stress by up to 50%, and elevates tensile strength by 10%, accompanied by an approximate 20% increase in hardness value for low carbon steel. The induction-based pre-heating system innovated in this research seamlessly integrates with Wire Arc Additive Manufacturing (WAAM), providing significant benefits in attaining the desired mechanical and metallurgical properties for additively manufactured components.

Quaternary ammonium salts have high corrosion inhibition performance, but anions have a significant impact on their corrosion inhibition performance. Based on this, the effects of I⁻ and Br⁻ on the corrosion inhibition performance in bisimidazole were investigated carefully. In this work, two imidazoline derivatives (MZB and MZI) were synthesized and their structures were verified by infrared spectrum (IR) and nuclear magnetic resonance (NMR). The corrosion inhibition performance and mechanism were evaluated comprehensively through weight loss, electrochemical experiments and theoretical calculations. The weight loss experiment showed that the corrosion inhibition rates of MZB and MZI at the concentration of 2.0 mmol/L were 94.52% and 95.52%, respectively, and followed the Langmuir isotherm adsorption. The open circuit potential and potentiodynamic polarization curve (Tafel) demonstrated that MZB and MZI were cathodic corrosion inhibitors, electrochemical impedance spectroscopy studies have shown that with the concentration of MZB and MZI increased, their corrosion inhibition ability improved gradually, at the concentration of 2.0 mmol/L, their corrosion rates were 96.82% and 97.57%, and the addition of corrosion inhibitors mainly increased the film resistance (R_f) and charge transfer resistance (R_ct) within the corrosion inhibition system, thereby improving their corrosion inhibition efficiency. XPS, EDS and IR further confirmed that MZB and MZI can adsorb on the surface of Q235 to form a stable protective film. Density functional theory and molecular dynamics simulation further confirm this theory from the molecular level.

The microstructure, hardness, and wear behavior of Al-6 Si-3.5 Cu alloy were modified by various routes including the addition of three different amounts of beryllium, T4 heat treatment, and a hybrid method of adding 0.06 wt.% Be plus T4 heat treatment. The results showed that the addition of 0.06 wt.% Be led to the absence of the β-phase, the formation of the less harmful α-phase with the best aspect ratio, and changed the coarse acicular Si to fibrous Si. The highest hardness, as well as lowest wear weight loss and wear rate, were observed in the sample modified by the hybrid method since the addition of Be caused the formation of the α-phase, prevented the formation of the β-phase, and led to the more uniform distribution of phases in the Al matrix. In addition, the modification methods resulted in a decrease in the contribution of the adhesive wear in the samples modified by 0.06 wt.% Be and the hybrid method, with the dominance of abrasive wear in the sample modified by the hybrid method as the sample with the highest wear resistance.

During the hot extrusion process of metals, billets are continuously loaded into the press and joined together under high hydrostatic pressure, forming a single extruded profile. Contamination at the billet-to-billet interface, such as oxides and dust residues, produces a welded zone (i.e. charge welds) with compromised mechanical properties, leading to the scrap of the resulting profile portion. To optimize the discharging process, the exact starting point and the extent of the billet-to-billet interaction must be precisely identified. This study aims to develop an innovative model based on phase field method to capture the interaction between immiscible fluids at high viscosity, capable of predicting the charge welds evolution within the COMSOL Multiphysics FEM code. To validate the model, two industrial case studies were experimentally investigated, involving the extrusion of AA6060 and AA6082 profiles with different process parameters and cooling conditions. The collected data were compared with simulation outcomes, revealing a good agreement with errors always below the 8% both in terms of charge welds onset and extent. This validation proved the reliability of the proposed model in accurately predicting extrusion defects.

This research provides valuable insights into the design, development, and analysis of the quasi-static energy absorption properties of dimensionally distinct 2D and 3D sandwich lattice structures. The Laser Powder Bed Fusion-based SS316L 2D Honeycomb, 3D Octet, and 3D TPMS Gyroid were designed and manufactured to study their mechanical behavior under quasi-static loading in the light of dimensional aspects. The energy absorption of the 3D TPMS Gyroid structure is found to be the highest at 51.73 MJ/m³ with a uniform collapse mode. However, the 2D structure performed better in elastic and densification regions with a superior elastic modulus and the highest densification strain of 0.68 while undergoing a unique unit cell-based deformation. The results show that while the 3D structures are the best energy absorbers; the 2D structures are preferred when stiffness is required in addition to energy absorption, providing practical implications for the design and application of these structures.

Energy transfer (ET)-based ZnGa₂O₄:Mn²⁺, Cr³⁺ phosphors with the capacity for ratiometric light conversion have been designed. The Mn²⁺ and Cr³⁺ ions in the ZnGa₂O₄:Mn²⁺, Cr³⁺ act as ET donors and receptors, respectively, by changing the doping amount of energy receptor Cr³⁺ ions, phosphor materials show different emission colors (green to deep red). The relationship between red and green phosphorescence is ratiometric and linear and, when 254 nm excitation is stopped, the phosphor shows a dark green afterglow. This ET-based ratiometric green-to-red light conversion provides a facile, sensitive and selective method for dynamic anti-counterfeiting.

In this work, rapid heat treatment followed by aging (RHTA) was proposed to improve the creep properties of Ti-5Al-5Mo-5 V-1Cr-1Fe alloy produced by sintering and hot deformation of blended elemental powder compacts. At 400 °C., the stress exponents of alloy after annealing and RHTA are 2.66 and 3.05. At the stress of 300 MPa with temperatures in the range of 400-500 °C., the activation energies of alloy after annealing and RHTA are 192.1 kJ/mol and 223.0 kJ/mol, respectively. The stress exponents and activation energies indicate that the creep in specimens after annealing and RHTA was mainly affected by dislocation climb, which has been proved by the jogged screw dislocations observed by TEM. The fine α lamellae obtained by RHTA contributed to the evidently better creep resistance than that of the alloy with equiaxed structure after hot rolling and annealing. Importantly, the results confirmed that the bimodal microstructure obtained by RHTA can achieve better creep resistance than full lamellae structure obtained by traditional heat treatment.

In this work, the surface crystallization behavior and magnetic properties of Fe_81.5+xSi₃B_10−xP_3.5C_0.2Cu_0.8Nb₁ nanocrystalline alloys were systematically investigated. It was found that the surface crystallization phenomenon occurs at the free-side surface of the as-cast ribbon, and the temperature interval between the first and second crystallization peaks increased to 159 °C with an increase in Fe content up to 83.5 at.%. It is of importance that the structure inhomogeneity caused by the surface crystallization disappears, and a fine and uniform nanocrystalline structure with average grain size of 18 nm is obtained when annealed at 530 °C for 10 min. The presence of an appropriate surface nanocrystallization layer was found to be advantageous in enhancing the soft magnetic properties of Fe_81.5+xSi₃B_10−xP_3.5C_0.2Cu_0.8Nb₁ nanocrystalline alloy, rather than causing their deterioration after annealing. As a result, Fe_83.5Si₃B₈P_3.5C_0.2Cu_0.8Nb₁ alloy ribbons in the optimal annealing state show improved soft magnetic properties, including high B_s of 1.68 T and low H_c of 6.43 A/m. These findings are helpful to understand the influencing mechanism of surface crystallization of amorphous precursor on the crystallization behavior and soft magnetic properties.