Journal of Materials Engineering and Performance最新文献

This study explores the grindability and sustainability, focusing on tribological and lubrication capabilities of water-soluble hybrid nanofluid under minimum quantity lubrication (MQL) conditions during grinding of Nimonic-90. Nanofluids were prepared by adding 0.25, 0.75, and 1.25% volumetric concentrations of Al₂O₃ and GnP nanoparticles into deionized (DI) water. The thermal conductivity, contact angle, and dynamic viscosity of the nanofluids were characterized. Specific tangential forces, specific normal forces, coefficient of friction, and surface roughness were reduced by approximately 37, 25, 17, and 11%, respectively, compared to pure Al₂O₃-based nanofluid and by 29, 17, 14, and 12%, respectively, relative to pure GnP-based nanofluid. Consequently, a 0.75% concentration of water-based hybrid nanofluid emerged as the most promising cutting fluid and hence proposed as an environment-friendly and benign lubrication solution to enhance the grindability of Nimonic-90. Furthermore, it advocates the sustainable enhancement of hybrid nanofluid with 0.75% volumetric concentrations over other alternatives.

The Zr-1%Nb alloy is widely used as a structural material for nuclear fuel assemblies of light water reactors. One of its key properties is the behavior upon a possible loss-of-coolant accident (LOCA) that can be changed by the surface modification procedures. This paper presents the research results on the effects of both high-intense pulsed ion beam (HIPIB) irradiation and high-current pulsed electron beam (HCPEB) processing on the kinetics of its oxidation at 1200 °C in air and steam, similar to the LOCA conditions. HIPIB irradiation led to more uniform reliefs on the sample surfaces but did not change their phase composition. However, both a and c lattice parameters decreased slightly with a simultaneous increase in microstrains. After HCPEB processing, the general patterns of changes in the modified surface layers were similar, but microcracks were found in some areas. In all studied cases, weight gains were greater after oxidation in air than those in steam. Nevertheless, diffusion of oxygen and the formation of scales occurred more slowly in the modified surface layers due to their distorted crystal lattices. The main reason for the variations was different physical processes that had occurred when the surfaces had been modified with charged ions and electrons.

In the present work, the effects of combined Ca and Sr additions on the microstructure, texture and mechanical properties of hot-extruded AZ91 alloy were investigated. Moreover, a detailed characterization of the recrystallization mechanisms governing the formation of new grains and final texture in extruded base AZ91 alloy and extruded AZ91-1Ca-xSr alloys was conducted. The evolution of Al-Ca and Al-Sr precipitates and their thermal stability at 400 °C extrusion temperature is predicted by thermodynamic calculations using Thermo-Calc software. The extruded microstructure of the base AZ91 alloy reveals the presence of discontinuous dynamic recrystallized grains alongside deformed grains. In contrast, extruded AZ91-1Ca-xSr alloys exhibit fully recrystallized microstructure consisting of intermetallic Al-Ca and Al-Sr stringers elongated in the extrusion direction, forming a neckless structure of stringers. In AZ91-1Ca-xSr extrusions, Al₂Ca and Al₄Sr precipitate effectively function as sites for particle-stimulated nucleation (PSN), thereby introducing localized strain energy variations. PSN leads to the formation of nuclei with random orientations, consequently reducing the overall sharpness of the texture. Ultimately, combined addition of Ca and Sr leads to improvements in both tensile and compressive strengths, with a reduction in tension–compression yield asymmetry. The enhancement of strength of extruded AZ91-1Ca-xSr alloys is primarily attributed to precipitation strengthening and grain size reduction resulting from the addition of Ca and Sr. Compared to the existing literature on the individual addition of Ca and Sr to extruded AZ91, the combined addition of both elements demonstrates superior tensile and compressive properties.

Endodontic cements play a crucial role in root canal treatment by sealing the canal and preventing reinfection. However, existing materials have limitations, including suboptimal bioactivity, handling properties, setting times, and antimicrobial efficacy. This study aimed to develop endodontic cements incorporating bismuth oxide, lanthanum oxide, and samarium oxide, and evaluate their physicochemical and biological properties according to the ISO 6876:2012(12) standard, FTIR, and SEM analyses confirmed the formation of a calcium phosphate apatite layer, indicating the bioactive potential of the cements for tissue regeneration. Rheological testing showed that cements containing glycerin (S1, S2) had improved flowability due to the viscosity-reducing properties of glycerin. Varying the water-to-powder ratios revealed that lower ratios resulted in reduced porosity and enhanced mechanical properties, with bismuth oxide being the most effective additive. Cements containing carboxymethyl cellulose (S3-S5) exhibited optimal flow values due to the dispersion-stabilizing effect of CMC. Antimicrobial evaluation demonstrated that the S2 group, with bismuth oxide, had the highest antibacterial activity (26.51 mm), followed by samarium oxide (24.19 mm) and lanthanum oxide (20.10 mm). Similar trends were observed for the S3 and S4 groups, with bismuth oxide exhibiting the greatest efficacy. Radiopacity analysis showed that all additives significantly increased the values, with bismuth oxide reaching the highest at 7.70 mm Al. Lanthanum oxide and samarium oxide also increased radiopacity to 6.21 mm Al and 7.53 mm Al, respectively. Biocompatibility assessment using human dental pulp stem cells revealed cell viability ranging from 73 to 105% after 1 day, exceeding the 70% biomedical threshold. The developed cements meet the requirements of current legislation and are considered suitable for endodontic applications.

Hydraulic turbine steels experience severe wear and tear due to cavitation erosion (CE), impacting their efficiency and lifespan. This study investigates the microstructure and cavitation erosion performance of cold-sprayed tungsten carbide (WC) coatings on hydraulic turbine steel (CA6NM). Two coatings, namely WC-12Co and WC-17Co, were cold sprayed on turbine steel (CA6NM) by using a cold spray process. Then the microstructure analysis of the deposited coatings was done using SEM and XRD. Further, the cavitation erosion performance was examined using an ultrasonic vibration tester. The results indicate that WC decarburization did not occur. The microstructured WC-Co coating exhibits the lowest porosity and dense microstructure. Additionally, it was shown that the WC-Co coating has the greatest cavitation erosion resistance and it reduces the cavitation erosion rate by about one-third when compared to bare steel. In addition, higher jet velocity, normal impingement angle, and moderate stand-off distance were determined to be the dominant cavitation erosion variables that produced the maximum cavitation erosion. Among both coatings, WC-17Co coatings possessed higher hardness and microcrack resistance compared to WC-12Co. This may be due to their higher hardness and denser microstructure of WC-17Co coating than WC-12Co coating. Thus, this study demonstrates the potential of cold-sprayed WC-based coatings for protecting hydraulic turbine steels against cavitation erosion.

Demand for nickel-based superalloys has increased significantly in the automotive industry because of their great potential to reduce the weight of components and improve efficiency. The objective is to improve the tribological performance and tool lifespan of the GH4169 alloy through machining, focusing specifically on the potential benefits of using cryogenic cooling. Hence, the experiments are conducted under liquid nitrogen (LN₂), carbon dioxide (CO₂), and minimum quantity lubrication (MQL) conditions. The test results proved that cryogenic cooling with the inclusion of MQL helps improve tool life with better tribological characteristics. The maximum power dissipation efficiency is identified as 44%. Stable regimes such as DRX are observed at 360 °C for GH4169. The tool flank wear was reduced by 15.8%, 36.8%, and 52.6% for CO₂, MQL, and LN₂ compared to the dry alloy. Therefore, applying MQL to the GH4169 alloy significantly impacts hot deformation and wear behavior. The formation of DRX structures in the processing map is crucial to improving the mechanical properties of these cast components.

Under severe work conditions, mechanical parts made of beryllium-copper alloy may undergo fatigue failure, which seriously affects the overall service life of the equipment. Therefore, improving the fatigue resistance of such kind of alloys is of great significance for their engineering application. In this research, C17200 beryllium-copper alloy was surface strengthened by means of a self-designed surface mechanical rolling treatment (SMRT) device. The fatigue behavior before and after SMRT was investigated using a ball-on-rod rolling contact fatigue (RCF) machine, and surface failure mechanisms were analyzed. It was found that the RCF resistance of the untreated C17200 alloy was weakened with the increase in the maximum Hertzian contact stress (σ_max). After surface treatment, C17200 alloy exhibited superior RCF resistance subjected to SMRT with a static rolling force of 200 N. But among the specimens treated by SMRT, the RCF resistance of beryllium-copper alloys was weakened with the increase in the SMRT static rolling force. The RCF life of specimens treated by SMRT with a force of 400 N is similar to that of untreated specimens, while the RCF lives of specimens treated by SMRT with a force of 735 and 980 N are even lower than that of untreated specimens. Thus, applying the appropriate static rolling force during SMRT can improve the surface quality and compressive residual stress, as well as enhance the fatigue resistance of C17200 alloys.

A new α-titanium alloy Ti-6.0Al-3.0Zr-0.5Sn-1.0Mo-1.5Nb-1.0 V (Ti603) with high strength was investigated. The ingot was initially hot rolled into sheet. Then the sheet was annealed at 740 °C for 1 h; meanwhile, it was subjected to solution treatment at 900 °C for 0.5 h, followed by aging treatment at 580 °C for 3 h. The microstructure and texture of the alloy were characterized by electron backscatter diffraction (EBSD). The results show that the microstructure of the alloy evolved from lamellar to equiaxed after annealing and solid solution aging treatment. In addition, the grain size of the solid solution aging treated sample was larger compared to the annealed sample. After annealing, low-angle grain boundaries (LAGBs) are transformed into high-angle grain boundaries (HAGBs) due to the occurrence of dynamic recrystallization (DRX). This weakened the dislocations accumulation and entanglement at the grain boundaries, resulting in change in grain orientation, thereby reducing the texture strength of the sample. After solution and aging treatment, the stress concentration at the grain boundary increases, and the preferred orientation of the grains changes, resulting in a slight increase in the texture strength of the sample.

The effects of pre-deformation and peak aging on the mechanical and damping properties of (CNTs + AlN)/AZ91 composites were investigated. The results show that the solid solution treatment, 15% pre-deformation and 15% pre-deformation followed by aging treatment are all favorable to improve the room mechanical properties of (CNTs + AlN)/AZ91 composites. And that the peak aging time is also decreased due to the pre-deformation. However, only the solid solution treatment and 15% pre-deformation can significantly enhance the room damping capacity; while, 15% pre-deformation followed by aging treatment reduces the room damping capacity due to the strong pinning of denser precipitates induced by the peak aging treatment. With temperature increasing, high-temperature background damping activation energy of (CNTs + AlN)/AZ91 composites is decreased after 15%pre-deformation followed by peak aging, which indicates that the high-temperature damping not only is more easily activated, but also the activation temperature is lower and the damping value is higher, and then the better damping efficiency can be realized.

Abstract

The effects of different heat treatments, including direct aging (DA), solid solution (T4) and solid solution + aging (T6), on the microstructure, mechanical and tribological properties of Ti-6Al-4V alloy prepared by laser powder bed fusion were studied. The As-built and DA-treated samples had refined acicular α^′ martensite phase and β phase. The T4-treated sample had lamellar α phase and globular α phase, whereas the T6-treated sample had lamellar α phase and basketweave microstructure. The dislocation density was decreased after heat treatments. The samples exhibited lower strength but higher plasticity after heat treatments, which was a comprehensive reflection of the decomposition of α^′ phase, the increase in β phase content, the coarsening of grains and the reduction of dislocation density. The wear resistance of the samples increased in the order of DA-treated sample < As-built sample < T6-treated sample < T4-treated sample, which was mainly related to the morphology and content of the α/α^′ phases on their surfaces. A favorable comprehensive performance was found for the T4-treated sample: It possessed the highest microhardness (447.51 ± 18.6 HV), the moderate yield strength (791.68 ± 15.8 MPa) and ultimate tensile strength (887.25 ± 13.25 MPa), the largest elongation (15.24 ± 0.57%), the lowest wear rate (0.76 ± 0.03 × 10⁻³ mm³/(N m)).

Graphical Abstract