Journal of Materials Engineering and Performance最新文献

This work investigated the application of the LSV-KOH test to quantify deleterious phases in a UNS S32707 hyper duplex stainless steel (HDSS). HDSS is a metal alloy with excellent corrosion resistance, but it can form deleterious phases (DP) when exposed to high temperatures. These phases can reduce the corrosion resistance and mechanical properties of HDSS by creating chromium-depleted zones in the microstructure. The LSV-KOH test was applied to a UNS S32707 HDSS aged at different temperatures ranging from 700 to 950 °C. The total amount of DP was quantified by quantitative metallography using a scanning electron microscope (SEM). The effect of KOH concentration on the test results was studied and optimized. The optimal KOH concentration found was 6.0 mol L⁻¹. A R² of 0.99 was reached when LSV-KOH response was plotted versus DP%. The LSV-KOH was compared with the DL-EPR test, the results demonstrated that the LSV-KOH test was more sensitive and accurate than the DL-EPR test in detecting and quantifying DP. Further investigation of the specimens’ surfaces after each test demonstrated that LSV-KOH acts directly on deleterious phases, while DL-EPR acts in DP contours. The study demonstrates that the LSV-KOH test has several advantages over the DL-EPR test for evaluating the microstructural transformations of HDSS caused by thermal ageing.

A Ni-Cr alloy powder, designated MB40, with an average size of 30.5 µm, was used as a grain boundary modifier in a recycled neodymium-iron-boron (Nd-Fe-B) matrix to improve the corrosion resistance, coercivity and other properties of the rare-earth sintered magnet. Nd-Fe-B powder with an average grain size of 95.1 µm was obtained by milling. The effects of doping with different amounts of MB40 (0, 0.5 and 1 wt.%) on the properties of the recycled magnet compared with an initial magnet were investigated. X-Ray Diffraction analysis revealed the formation of the Fe₁Nd₁Ni₄ and NiCrFe phases, after sintering, as well as the tetragonal phase Nd₂Fe₁₄B matrix phase in the magnet doped with 1 wt.% of MB40. Scanning Electron Microscopy images coupled with energy-dispersive x-ray spectroscopy demonstrated that in the sample doped with 1 wt.% MB40, Cr-Ni diffuses into the grain boundaries, thus improving the microstructure of the magnet. Electrochemical Impedance Spectroscopy and potentiodynamic polarization were employed for corrosion characterization. The magnet doped with 1wt.% MB40 exhibited the highest corrosion potential (E_corr = − 696 mV), polarization resistance (R_P = 1151.2 Ω·cm²) and a low corrosion rate (V_corr) of 4.34 µm·year^-1 compared to the starting (initial) sample. The optimum characteristics of recycled NdFeB were obtained by blending milled NdFeB powder with 1 wt.% MB40, achieving the best values for product energy (BH_max), coercivity (H_C) and hardness, respectively 48.03 MGOe, 10.8 KOe and 587 HV.

In this paper, the microstructural evolution and tribological behavior of an FeCoNiCr alloy containing Sm fabricated by the Laser Metal Deposition technique were investigated. The study employs x-ray diffraction analysis, energy-dispersive spectroscopy, and friction coefficient measurements to comprehensively investigate the impact of Samarium (Sm) addition on the microstructural evolution and frictional behavior of high-entropy alloys (HEAs). Results reveal that the inclusion of 0.4-0.8 wt.% Sm effectively inhibits the formation of coarse phases at the interface between HEAs and 45 steel substrates, enhancing their bonding strength while inducing the precipitation of secondary phases within the HEA matrix. During frictional processes, distinct characteristics in friction coefficients in the friction pair between HEAs against 304 stainless steel beads and SiC beads are observed. Sm-added HEAs demonstrate relatively stable friction coefficients and different friction behaviors with various Sm content, which can be attributed to changes in friction mechanisms caused by formation of oxide particles as lubricant on the contact surface.

In this article, the influence of CO₃²⁻/HCO₃⁻ on the corrosion behavior of B30 Cu-Ni alloy in 3.5 wt.% NaCl solution was systematically studied utilizing a series of tests. The results demonstrate that the surface film is the primary factor causing different corrosion resistance of B30 alloy in various solutions. The average corrosion rate of B30 alloy immersed in the solution of 3.5% NaCl + 0.05 M NaHCO₃ is 0.123 mm/a, while the alloy in 3.5% NaCl solution containing 0.05 M Na₂CO₃ exhibits the lowest corrosion rate of 0.027 mm/a. The addition of CO₃²⁻ induces a transition from surface activation state to the passivation state, resulting in the formation of a passive film on the alloy surface. Furthermore, B30 alloy exhibits obvious activated characteristic in NaCl solution containing HCO₃⁻, which is attributed to the fact that H⁺ ionized by HCO₃⁻ seriously damages the stable structure of passive film, causing the generation of a corrosion product film with lower protective ability. This indicates that the inhibiting effect of H⁺ on passivation is greater than the promoting impact of CO₃²⁻. Moreover, the substrate of B30 alloy primarily experiences selected dissolution of Cu element.

The paper systematically studied the effect of AC density on corrosion resistance of FeCoNi HEA in simulated Golmud soil solution. The results imply that the applied i_AC seriously decreases the anticorrosion property of the HEA. In particular, under high AC density, the active state is presented and the corrosion characteristic changes from slightly local pitting to uneven overall corrosion with massive large-sized corrosion pits. Moreover, after imposed AC of 100 A/m², the honeycomb holes are produced within passive film, which suggests that AC severely damages the film integrity, and reduces the protection and stability of the film. This phenomenon is due to the reason that as i_AC rises, more generated hydrogen ions/atoms and Cl⁻ are absorbed on the defect regions of passive film, significantly promoting the film dissolution, and facilitating the pitting initiation and development.

Surface microtexturing of the flank faces of tools is a promising way to improve the quality of machined workpiece surfaces. However, microtextures are often clogged in the process of machining because of the derivative cutting. The impact of derivative cutting on machined surface is frequently ignored. In this study, a microtexture was developed on the flank face of an Al₂O₃ ceramic tool, which paralleled to the cutting edge. The influence of derivative cutting on machined surfaces required to be systematically investigated according to surface roughness, surface topography, work hardening, and microstructural analysis. Results showed that derivative cutting occurred at cutting velocities ranging from 90 to 270 m/min, leading to an enhancement in the surface quality. Derivative cutting had an obvious impact on surface roughness, with the cutting velocity increased from 90 to 270 m/min. Furthermore, the bottom edge of the texture as a “cutting edge” can timely replace the main cutting edge of sudden failure, leading to the tool lives extension and surface quality improvement.

An accurate flow stress model is crucial in precisely describing material flow behavior and enhancing the precision of hot deformation simulations. Here, the flow stress data of 40Cr10Si2Mo steel were obtained from isothermal compression tests at temperatures of 1173-1398 K and strain rates of 0.01-10 s⁻¹. The flow stress curves were corrected by considering the effect of interfacial friction and deformation heating. These corrected curves were then used to establish the Arrhenius model, back-propagation artificial neural network (BP-ANN) model, and back-propagation artificial neural network optimized by the Harris hawks optimization algorithm (HHO-BP) model. Each flow stress model’s prediction accuracy was assessed using the correlation coefficient (R), average absolute relative error (AARE), and mean square error (MSE). Comparative analysis reveals that the HHO-BP model exhibits the highest precision, as evidenced by its R, MSE, and AARE values of 0.99923, 10.4669, and 1.282%, respectively. Following this, the HHO-BP model was employed to expand the stress–strain data of 40Cr10Si2Mo steel at temperatures of 1210 K, 1285 K, and 1360 K. These expanded data were then used in thermal compression simulations, and high load-stroke simulation accuracy was achieved.

In this study, the method of depositing alumina thin films through magnetron sputtering has been explored using a molecular dynamics approach. The impact of particle incidence energy and substrate temperature on the crystallization behavior of these films was examined. It was found that the crystallization ratio of the films is influenced by the coordination number of atoms. As the incident energy increases, the crystallinity of the deposited films gradually approaches an optimal level. However, surpassing this optimal incident energy leads to irreversible radiation damage, resulting in progressive amorphization. Additionally, it was observed that the optimal energy for ion contribution to the film diminishes with increased substrate temperature. At a substrate temperature of 300 K, the ideal energy for ion transfer to the growing film is found to be 50 eV, which decreases to 40 eV at a temperature of 700 K. The type of film crystallization is primarily in the γ-phase, with the proportion of α-phase diminishing as the incident energy increases. Furthermore, the rate of decrease in α-phase content slows with an increase in temperature. These results were used to analyze the transformation of amorphous to crystalline alumina and to determine the window for the transformation to γ-Al₂O₃. Moreover, the mechanisms of the crystallization process and the transformation of the crystalline morphology were analyzed.

Heat-treated materials have improved mechanical qualities that can be used in demanding engineering applications. Production costs are the primary driving force behind the adoption of optimization techniques and new technologies in the production industry. Minimum quantity lubrication (MQL) is a subject of research as a possible substitute for flood cooling, which is notorious for having harmful effects on the atmosphere and operator wellbeing. This research is distinctive in that it examines the impact of MQL with hexagonal boron nitride (hBN) nanolubricants on maximizing the machinability during hard turning of AISI/SAE 1060 steel. The present paper provides a comprehensive investigation into the impact of dry, pure MQL, and hybrid MQL (0.5 and 1 vol.% hBN) cooling conditions on the turning performance of AISI/SAE 1060 steel using TiN-coated carbide inserts. Furthermore, by reducing energy consumption and waste generation, our research aims to support the advancement of sustainable and environmentally friendly machining methods. Hybrid MQL (1 vol.% hBN) cooling condition, 40 m/min cutting speed, and 0.1 mm/min feed rate are the optimum values for yielding maximum tool life and minimum of both surface roughness and tool–chip interface temperature.

In the domain of electronic packaging, the application of Sn-Zn-based solders is recognized for its low melting point and satisfactory wettability. However, the reliability of solder alloy is compromised by the presence of the Zn-rich phase. This study focuses on the effect of Bi doping on the microstructure evolution of Zn-rich phase, thermal properties, wettability, oxidation resistance, and corrosion resistance of Sn-6.5Zn solder alloy. Compared to Sn-6.5Zn solder alloy without Bi, the introduction of Bi led to the trend where the size of the Zn-rich phase initially decreased and then increased, with the minimum size reaching 2.4 µm at the Bi concentration of 3.0 wt.%. Beyond the Bi addition of 3.0 wt.%, the small white dot-like Bi particles precipitating from the β-Sn matrix were observed. These particulate Bi phases tended to cluster around the Zn-rich phase, eventually forming lamellar structures. The incorporation of Bi served to lower the eutectic temperature, yet it widened the melting range. This phenomenon is attributed to the inherent low melting point of Bi; its presence extended the eutectic reaction temperature range and broadened the melting region. At the Bi content of 3.0 wt.%, the alloy demonstrated superior wettability and corrosion resistance, with corrosion products being small spherical ZnO, which is mainly attributed to the presence of finer Zn-rich phase in the alloy. When the Bi content was limited to 1.0 wt.%, the alloy showed the preferable oxidation resistance, possibly due to the Bi being dissolved in the Sn matrix after addition, leading to smaller Zn-rich phase size and finer β-Sn phase. These results indicate that the addition of an appropriate amount of Bi has a certain improvement on the physical and chemical properties of Sn-6.5Zn solder alloy, further enhancing the theoretical research of Sn-Zn-based solders, which may have an important impact on their electronic applications.