High Temperature Mechanical Properties Research Articles

Anodic Dissolution Characteristics of GH4169 Alloy in NaNO3 Solutions by Roll-Print Mask Electrochemical Machining Using the Linear Cathode.

GH4169 alloy/Inconel 718 is extensively utilized in aerospace manufacturing due to its excellent high temperature mechanical properties. Micro-structuring on the workpiece surface can enhance its properties further. Through-mask electrochemical micromachining (TMEMM) is a promising and potential processing method for nickel-based superalloys. It can effectively solve the problem that traditional processing methods are difficult to achieve large-scale, high-precision and efficiency processing of surface micro-structure. This study explores the feasibility of electrochemical machining (ECM) for GH4169 using roll-print mask electrochemical machining with a linear cathode. Electrochemical dissolution characteristics of GH4169 alloy were analyzed in various electrolyte solutions and concentrations. Key parameters including cathode sizes, applied voltage and corrosion time were studied in the roll-print mask electrochemical machining. A qualitative model for micro-pit formation on GH4169 was established. Optimal parameters were determined through experiments: 300 μm mask hole and cathode size, 10 wt% NaNO3 electrolyte, 12 V voltage, 6 s corrosion time. The results demonstrate that the micro-pits with a diameter of 402.3 μm, depth of 92.8 μm and etch factor (EF) of 1.81 show an excellent profile and localization.

Effect of strain rate and temperature on dynamic compressive behavior of HfBeTiZrCuNi high entropy bulk metallic glass

This study investigated the high-temperature dynamic mechanical properties of Hf-based high entropy bulk metallic glass (HE-BMG). Uniaxial dynamic compressive tests of Hf-based HE-BMG were conducted at elevated temperatures (from 298 to 800 K) under a high strain rate (from 1000 to 5000 s−1) by a split Hopkinson pressure bar (SHPB) device with a high-temperature system, and the failed specimens were analyzed in terms of microstructures and fracture modes. The dynamic test results show that the maximum compressive stress and the total strain decrease with increasing strain rate and temperature, exhibiting significant strain rate and temperature sensitivity. Three different fracture modes were observed with increasing strain rates, while heating the temperature could promote the transition process of the fracture modes. When the adiabatic or heating temperature reaches above the crystallization temperature, the embrittlement caused by metallic glass crystallization makes the fracture mode change. The mechanical behavior of Hf-based HE-BMG at high temperatures and high strain rates could be attributed to the combination of adiabatic heating and embrittlement.

A novel high-Cr CoNi-based superalloy with superior high-temperature microstructural stability, oxidation resistance and mechanical properties

A novel high-Cr CoNi-based superalloy with superior high-temperature microstructural stability, oxidation resistance and mechanical properties

Microstructure, high temperature mechanical properties and sliding wear behavior of (NiCrW)1-x(Al2O3)x

(NiCrW)1-x(Al2O3)x composites with different nano-Al2O3 ratios (x = 0, 1, 2.5, 5 wt %) were prepared using powder metallurgy techniques. The influence of the Al2O3 content on the microstructure, phase composition, high-temperature mechanical properties, and wide-temperature-range friction and wear performance of the composites was investigated. The corresponding high-temperature strengthening and wear-resistance mechanisms were also investigated. The results indicated that as the alumina content increased, the tensile and compressive strengths of the composites decreased at room temperature (RT). However, at high temperatures (800 °C), the opposite trend was observed. Notably, the composite with 5 wt % Al2O3 exhibits the highest tensile strength (189.20 MPa) and compressive strength (446.61 MPa) at 800 °C. The addition of alumina had a relatively minor impact on the friction coefficient of the composites but significantly affected the wear rate. Specifically, the composite with 5 wt % Al2O3 demonstrates optimal friction and wear performance at high temperatures. This enhancement was primarily attributed to the reinforcement of the mechanical properties of the matrix material owing to the addition of alumina. Additionally, the formation of a friction glaze layer rich in Cr2O3 and NiO oxides on the worn surface contributed to improved wear resistance. This study is important for understanding the performance and applications of metallic materials.

Insights into hardening and strengthening in ultrafine Ti(C, N)-based cermets

Ultrafine Ti(C, N)-based cermets are vacuum-sintered by refining the particle size of raw materials and tailoring the WC/TaC ratio to achieve the improvements in comprehensive mechanical properties and cutting performance. The hardness, flexural strength and tool lifespan of ultrafine Ti(C, N)-based cermets are substantially higher than those of submicron Ti(C, N)-based cermets with the same composition because of the refined grains and the improved distributions of both metal phases and residual stress. The hardness attenuation behavior and strengthening mechanism in Ti(C, N)-based cermets at different test temperatures have been proposed. At 400 ℃, the hardness attenuation of Ti(C, N)-based cermets depends mainly upon the softening of metal phases. However, at 800 ℃, the hardness attenuation of Ti(C, N)-based cermets is mainly related to the reduced bearing capacity of hard ceramic phases and interfacial sliding. The addition of refractory TaC is beneficial for the improvement of high-temperature mechanical properties and the tool lifespan, attributed to the strengthening of the ceramic framework by tantalum atoms.

Study of high temperature mechanical properties and damage behavior of Ni-YSZ anode/SrO–MgO–SiO2 glass-ceramic sealant/430 s.s. interconnect system in solid oxide fuel cells (SOFC)

In the sealing system of Ni-YSZ anode/SrO–MgO–SiO2 glass-ceramic sealant/430 s s. interconnect, the phase transformation and mechanical properties of interfaces are studied after operating 0 h, 100 h, and 1800 h at 750 °C. The results show that the interface fracture appears in the glass/anode and glass/interconnect interfaces after operating at 1800 h. The interface mechanical parameters within different operation times are collected to investigate the effects of crystallization, penetration, and high temperature mechanical properties on the interlayer stress and structure damage. The Sr2MgSi2O7 crystal phase increases the glass modulus from 104.5 GPa to 129.8 GPa with a runtime from 0 h to 1800 h. The modulus of the Ni-YSZ interface also increases from 82.4 GPa to 128.3 GPa with the glass penetration process. The 430 s s. modulus is reduced by 13 % at 750 °C after 1800 h to reach 191.1 GPa. The established anode/glass/interconnect interlayer stress model accurately calculates the compressive stress at the glass/anode side interface and glass/interconnect side interface, with values reaching −755.2 MPa and −587.1 MPa, respectively. The crystallization zone of the SrO–MgO–SiO2 glass-side interface near Ni-YSZ and 430 s s. become the stress damage sensitive zones and break under interlayer stress.

A novel L12-strengthened single crystal high entropy alloy with excellent high-temperature mechanical properties

In this work, a novel and low-cost L12-strengthened single crystal high entropy alloy (HEA) was prepared through the seeding method of directional solidification. The microstructures, tensile properties and deformation mechanisms of the single crystal HEA were systematically investigated. The volume fraction of L12 precipitates after heat treatment was almost 80%, which was higher than that of conventional single crystal superalloys. The maximum yield strength, ultimate tensile strength and elongation, which were separately as 897 MPa, 1038 MPa and 37%, were obtained at the intermediate temperature of 800 °C. Moreover, at higher temperature (900 °C and 1000 °C), the HEA was able to maintain excellent performance, which was comparable to the commercial René N5 second-generation Ni-based single crystal superalloy. Finally, the high performance was examined by the model of strengthening contribution, which proved that the high-volume fraction of L12 precipitates in single crystal HEA was the primary reason for their significant precipitation and solid solution strengthening. Additionally, the formation of Lomer-Cottrell locks and stacking faults could enhance the high-temperature properties of the single crystal HEA.

Secondary degradation of bio-oil degraded crumb rubber and preparation of stable degraded crumb rubber modified asphalt

Using bio-oil to desulfurize and degrade crumb rubber (CR) significantly enhances the compatibility between CR and asphalt, improving the workability of CR-modified asphalt and providing environmental and economic benefits. However, the secondary degradation of bio-oil degraded crumb rubber (ODR) in asphalt hinders the stability of ODR-modified asphalt. To optimize the mechanical performance of ODR-modified asphalt, the secondary degradation behaviors of ODR were investigated. The degree of CR degradation was determined by solubility testing, while the rheological properties and chemical structures of ODR-modified asphalt were characterized through rotational viscometer, dynamic shear rheometer, bending beam rheometer, and Fourier transform infrared spectrometer. The processes for preparing stable ODR modifier and ODR-modified asphalt were proposed to mitigate the damage caused by bio-oil and degraded CR to the high temperature mechanical properties of asphalt. The results show that at lower processing temperatures for ODR-modified asphalt, the volatilization of light components is predominant, while higher processing temperatures prompt secondary degradation of ODR. By stirring at 280°C for 2 hours to acquire moderately degraded CR, and then concentrating it at 220°C for 2 hours, a stable ODR less susceptible to secondary degradation can be obtained. The workability, temperature sensitivity, and low temperature cracking resistance of stable ODR-modified asphalt improve significantly. The reduction of ester group and increase in aromaticity restore the high temperature deformation resistance of ODR-modified asphalt. Further, the inclusion of composite SBS extends the range of rheological properties in ODR-modified asphalt, bolstering the application potential of ODR in asphalt pavement.

Improving High-Temperature Mechanical Properties of Additively Manufactured Inconel 718 Through Heat Treatment

Improving High-Temperature Mechanical Properties of Additively Manufactured Inconel 718 Through Heat Treatment

One-pot synthesis of copolyamide PA MXDT-MXD6 towards oxygen-barrier and high-temperature transparent applications

Semi-aromatic polyamides have long been recognized for their exceptional comprehensive properties in numerous demanding applications. Among them, poly(m-xylylene adipamide) (MXD6) was commonly used in oxygen-barrier packaging but suffered diminished transparency due to thermal crystallization. Herein, we introduced terephthalic acid (PTA) as rigid monomer units into the chain of MXD6 to prepare amorphous copolyamides PA MXDT-MXD6 via one-pot polycondensation, guided by thermal analysis. The chemical structure of copolyamides was confirmed using 1H NMR and FTIR spectra. Thermal analysis revealed that the copolyamides exhibited high thermal stability, amorphous characteristics, and improved glass transition temperatures (110.9–136.5 °C). Pyrolysis kinetics further demonstrated that copolyamides have enhanced thermal stability and lifetime. Furthermore, copolymerization resulted in numerous amide bonds conjugated with benzene rings, leading to superior high-temperature transparency, oxygen-barrier, and mechanical properties compared to MXD6 and other reference polyamides. These characteristics indicate the potential suitability of copolyamides as transparent and heat-resistant barrier materials.

High-temperature flexural mechanical properties of SiC/SiC composites

To assess the flexural behavior of SiC/SiC composites in high-temperature atmospheric environments, three critical influencing factors were identified: selection of fixtures, loading and supporting roller dimensions, and span-to-thickness ratio. Subsequently, through experimental methods and finite element model simulations, the impact of these factors was investigated. The study identified the most suitable fixture materials and configuration dimensions for SiC/SiC materials. It was found that as the span-to-thickness ratio increases, the flexural strength of the material continues to rise, reaching a turning point at 543 MPa, after which it decreases. The maximum interlaminar shear stress consistently decreases with an increasing span-to-thickness ratio. Combined with the failure mode analysis of the samples, it was observed that for a span-to-thickness ratio equal to or greater than 16, the sample failure modes are all valid. Additionally, regarding the observed non-linearity in the stress-strain curve when testing with a larger span-to-thickness ratio, it is recommended to apply a large deflection correction to the flexural stress.

Study on Thermodynamic Coupling Performance of Multi-Level Lattice Structures

With the development of hypersonic vehicle, the design of heat-resistant and load-bearing surface of hypersonic vehicle has gradually become a key technology affecting its combat effectiveness. As a new type of lightweight and high-strength structure, lattice structure has excellent mechanical properties such as ultra-light, high specific strength and high specific stiffness, and special properties such as vibration reduction, heat dissipation and sound absorption. Among them, the multi-level lattice structure can increase the bearing efficiency of the structure at low relative density, and increase the heat transfer area at the same time, so as to improve the heat protection and bearing capacity of the structure. This study includes three aspects of high temperature out-of-plane compression test, high temperature numerical simulation comparison, and structural optimization for the designed multi-level pyramid lattice, in order to obtain the bearing capacity of the multi-level pyramid lattice at 350°C, and further improve the bearing performance by optimizing the core structure. Through experiments and verification, the multi-level pyramid lattice designed and optimized in this study can further meet the requirements of thermal protection and load-bearing performance of aircraft compared with the single-level pyramid lattice, and can provide a reference for the study of high temperature mechanical properties of lattice structures, the design of new multi-level lattice structures and the engineering application of lattice structures.

High-temperature mechanical properties of additively manufactured 420 stainless steel

Martensitic stainless steels are indispensable alloys in various high stress and temperature applications such as plastic injection molds and components in steam generators. Subtractive manufacturing methods used to fabricate these parts, however, limits its functionality and performance due to design constraint of cooling channels. This limitation can be resolved by means of additive manufacturing while ensuring that acceptable high-temperature properties can be achieved. In this work, the mechanical behavior of additively manufactured 420 stainless steel (AM420SS) is explored through material constitutive modeling to determine the mathematical model that best describes its flow stress in extreme conditions. This is accomplished by subjecting the samples to hot compression under the strain rates of 0.1–1.0 s−1, and temperatures between 973–1423 K (700 °C–1150 °C) via Gleeble thermomechanical test. The experimental data were used to generate the predictive flow stress curves of constitutive models which includes Johnson-Cook, Zerilli-Armstrong, Zener-Hollomon, and Hensel-Spittel equations. Results showed that Zener-Hollomon and Hensel-Spittel models are the most accurate material constitutive equations with relatively high R values of 0.986 and 0.976, and low average absolute relative error values of 6.96% and 7.69%, respectively. The material constants derived from these models can be applied in finite element analysis simulations to assess the performance of using AM420SS parts at high temperature and strain conditions.

Effect of fan-shaped structure on high temperature tensile properties of nickel-based deformed superalloys

GH4742 alloy is a kind of precipitation-hardened superalloy, which is widely used in turbine disc, compressor disc, bearing ring and other parts due to its excellent high temperature mechanical properties. In this paper, high-temperature tensile comparison experiments were carried out at four temperatures, 1050 °C, 1080 °C, 1110 °C and 1140 °C, between alloy A containing a fan-shaped structure and alloy B without a fan-shaped structure. The results show that the tensile strength and plasticity of alloy A at 1050 °C are superior to those of alloy B. With the increase of temperature, the difference of tensile strength and plasticity between alloy A and B decreases gradually. By analyzing the fracture, both alloy A and B were found to have a large number of tough dimples, which showed ductile fracture characteristics. But alloy B was found to have some icing-like fracture at 1050 °C, which showed some brittle fracture characteristics. After 1110 °C, the difference in tensile strength and plasticity between alloy A and B almost disappears because γ′ phase is completely dissolved in the matrix. TEM results show that dislocations gather around the large-size γ′ phase, and for the small-size γ′ phase, dislocations tend to cut into γ′ phase directly. The results show that the existence of fan-shaped structure is beneficial to the high temperature tensile properties of GH4742 alloy, which has a certain reference effect on the production of GH4742 alloy in the future.

Mechanical properties and microstructure of high-strength and high-ductility steel at elevated temperature

This paper aims to investigate the mechanical behavior and microstructure of a novel high-strength and high-ductility (HSHD) steel at different temperatures ranging from 25 to 600 °C. The testing machine conducted uniaxial tensile tests with seven different temperatures. The true plastic stress-strain curves of HSHD steel were fitted using the Ludwigson model based on the experimental results, and the microstructure of HSHD steel was analyzed using Electron Backscatter Diffraction (EBSD). The experimental results revealed an obvious temperature-mechanical response relationship in HSHD steel, showing a gradual decrease in tensile strength and yield strength with increasing temperature, while the uniform and post-necking elongation exhibit a trend of decreasing and then increasing. Compared to other steels, HSHD steel exhibited significant advantages of strength-ductility balance over a wide range of temperatures. A Ludwigson model coupled with temperature parameters was established, which provided a good fitting effect to the true plastic stress-strain curves of HSHD steel. Microstructure analysis shows significant Brass and Copper textures near the fracture surface of HSHD steel at all temperatures. Additionally, a large number of deformation twinning was observed within the grain of HSHD steel. The excellent high-temperature mechanical properties of HSHD steel can be attributed to the strong thermal stability of deformation twins.

Microstructure evolution and mechanical properties for oxygen-rich ZrTiAlV alloy during in-situ semi-solid processing

Oxygen-rich ZrTiAlV alloy reinforced by spherulite ZrO phase was prepared by in-situ semi-solid processing. The results of high temperature (500°C) mechanical properties test confirmed that alloy elongation after semi-solid processing at 1500°C was close to that for the as-forged material, whereas yield and tensile strength were increased by 66.4% and 30.8%, respectively. SEM and EBSD results confirm that morphology selection of non-equilibrium growth is mainly controlled by the initial core shape, with dendrites always growing along the <110> direction following the Twin-Plane-Reentrant-Edge mechanism. Improved alloy strength is attributed to fine grain strengthening and precipitation strengthening caused by the ZrO phase, and α phase spheroidization ensures alloy plasticity. We also propose a crack deflection toughening mechanism for the alloy.

Influence of Zr Microalloying on the Microstructure and Room-/High-Temperature Mechanical Properties of an Al-Cu-Mn-Fe Alloy.

Here, 0.3 wt.%Zr was introduced in an Al-4 wt.%Cu-0.5 wt.%Mn-0.1 wt.%Fe alloy to investigate its influence on the microstructure and mechanical properties of the alloy. The microstructures of both as-cast and T6-treated Al-Cu-Mn-Fe (ACMF) and Al-Cu-Mn-Fe-Zr (ACMFZ) alloys were analyzed. The intermetallic compounds formed through the casting procedure include Al2Cu and Al7Cu2Fe, and the Al2Cu phase dissolves into the matrix and re-precipitates as θ' phase during the T6 process. The introduction of Zr results in the precipitation of L12-Al3Zr nanometric precipitates after T6, while the θ' precipitates in ACMFZ alloy are much finer than those in ACMF alloy. The L12-Al3Zr precipitates were found coherently located with θ', which was assumed beneficial for stabilizing the θ' precipitates during the high-temperature tensile process. The tensile properties of ACMF and ACMFZ alloys at room temperature and elevated temperatures (200, 300, and 400 °C) were tested. Especially, the yield strength of ACMFZ alloys can reach 128 MPa and 65 MPa at 300 °C and 400 °C, respectively, which are 31% and 33% higher than those of ACMF alloys. The strengthening mechanisms of grain size, L12-Al3Zr, and θ' precipitates on the tensile properties were discussed. This work may be referred to for designing Al-Cu alloys for application in high-temperature fields.

A novel cast Co68Al18.2Fe6.5V4.75Cr2.55 dual-phase medium entropy alloy with superior high-temperature performance

A newly-designed Co68Al18.2Fe6.5V4.75Cr2.55 medium entropy alloy (MEA) with FCC + B2 structure exhibits not only an excellent strength-ductility combination at room temperature, but also an outstanding high-temperature mechanical properties in particular. The phase formation, microstructure and deformation mechanism of this designed dual-phase MEA at room and high temperatures were investigated and discussed in detail. Based on experimental results (XRD, SEM and TEM) and theoretical analysis (calculated diagram and empirical thermodynamic parameters), it is demonstrated that this newly-designed MEA consists of a dual-phase structure of a face-centered-cubic (FCC) phase (70.3 vol %) plus chemically ordered body-centered cubic phase (B2) (29.7 vol %). Meanwhile, the FCC phase is enriched with Co, Fe and Cr elements, while the B2 phase is enriched with Al and Co elements. Furthermore, compared with some HEAs/MEAs and commercial alloys, this newly-designed dual-phase MEA exhibits excellent strength-ductility combination with a high compressive yield strength of ∼1254 MPa, a fracture strength of ∼2657 MPa and a large compressive plasticity of ∼34.6 % at room temperature. In particular, the studied MEA also shows an outstanding high-temperature performance with an ultrahigh yield strength of ∼1213 MPa at 600 °C and ∼626 MPa at 800 °C, respectively. The excellent comprehensive mechanical properties of this designed dual-phase MEA at both room and temperatures mainly originate from synergy effect of alternate FCC + B2 structure and strengthening contributions of B2 phase. These important findings not only reveal the deformation and strengthening mechanisms of the newly-designed dual-phase MEA, but also provides an effective alloy design strategy for developing advanced structural materials serving as a wide range of temperature.

Rapid estimation of γ' solvus temperature for composition design of Ni-based superalloy via physics-informed generative artificial intelligence

The exceptional high-temperature mechanical properties of Ni-based superalloys are mainly stemmed from the L12 γ' phase, therefore it is crucial to discover Ni-based superalloys with high γ' solvus temperatures. Utilizing generative artificial intelligence, we have developed a framework to swiftly evaluate the γ' solvus temperature and tailor Ni-based superalloys, accelerating the process of discovering Ni-based superalloys. Physics-informed artificial neural network emerged as the optimal choice for reverse engineering, outperforming other models with an R2 score of 0.917 and a mean absolute error of 15 K. In the reverse design process, 20,000 virtual alloy samples were generated based on divide-and-conquer variational autoencoder which divides the dataset into distinct clusters by K-means algorithm provides a structured representation of the alloy composition space, thereby facilitating a more nuanced understanding of its inherent complexities. In a specific alloy design example, 563 samples were identified through screening based on criteria like γ' solvus temperature, composition deviation index, price, and density. Thermodynamic calculations were used to further screen Ni-based superalloys with exceptional high-temperature properties. The showcase of BA alloy discovery through generative artificial intelligence demonstrates the potential of our research to steer the creation of novel compositions for Ni-based superalloys with outstanding high-temperature properties.

Effects of various proportions TiB2p-TiCp reinforced Al–Cu–Mg composites in high-temperature mechanical properties and sliding wear behaviors

Synergistic reinforcement of dual-phase particles with different sizes was always considered superior to single-phase reinforcement in composites, but there were few studies to investigate the role of each part in enhancing properties. In this work, 40 vol% (TiB2p-TiCp)/Al–Cu–Mg composites with different proportions of TiB2p and TiCp (3:1, 2:1, 1:1, 1:2 and 1:3), were fabricated by the combustion synthesis to contrast the strengthening effect of dual-phase particles from the interface stability and the characteristics of dual-phase particles. Calculated by the first principle, TiB2 (3.12 J/m2) presented better interfacial stability with Al matrix than TiC (1.61 J/m2). Under the circumstance of the same volume fraction, the composites with a higher proportion of TiB2p usually show higher yield and maximum compressive strength and effectively prevent the crack growth of composites. However, excess submicron sized TiB2p tends to produce cracks at the hexagon edge when the loads were applied and formed crack loops delaminating materials. When the TiB2p/TiCp proportion was 1:1, the plasticity and strength were beneficially balanced at the elevated temperature. Otherwise, the composite with TiB2: TiC = 3:1 possessed the best wear resistance (coefficient of friction: 0.22) at a sliding velocity of 0.32 mm/s, 30 N load) among other composites (AR12, AR11, AR21, and AR31) at 473 K, which reduced 45%, 64%, 73% and 86%, respectively. The main wear mechanism was abrasive wear when the TiB2 proportion was dominant. Submicron sized TiB2p with better interface bonding can keep the rigidity of the composites to resist the plastic flow, while TiC nanoparticles are easier to be extracted during the wear process.