High Temperature Tensile Strength Research Articles

Exploring the multi-scale evolution mechanism of the ultra-high-temperature mechanical behaviour of carbon/carbon composites

The microstructure and mechanical properties of Carbon/Carbon (C/C) composites were investigated after ultra-high-temperature heat treatment (HTT) in the range of 30 – 2950 °C. The evolutionary mechanisms of the mechanical behaviour were explained at three scales: graphene sheets, carbon fibre (CF) monofilaments and the C/C composites. The results displayed that the tensile strength of CF monofilaments decreases monotonically as the HTT increases, while C/C composites present a tendency to decrease and then increase, demonstrating that CF/matrix interfacial properties play a decisive role in the tensile properties. Obvious microstructure change of C/C composites after HTT at 2700 °C was observed, meanwhile the high temperature tensile strength (measured at 2000 °C and 2500 °C) for the composites treated at temperature beyond 2600 °C was higher than that of room temperature. The high-temperature mechanical properties of C/C composites were regulated by the competing mechanisms of the graphite crystallite structure and the skin-core structure of CF monofilament, the CF/matrix interfacial strength and the porosity of C/C composites.

Microstructural characteristics and mechanical properties of laser-welded Ta10W/GH3030 joints with beam offset

Influences of the laser beam offset (LBO) on the microstructures as well as room-temperature and high-temperature mechanical properties of Ta10W/GH3030 dissimilar-material joints were investigated. In laser-welded Ta10W/GH3030 joints prepared under three conditions with LBOs of −0.2 mm (offset toward Ta10W), 0 mm, and + 0.2 mm (offset toward GH3030): the fusion zones (FZ) all contained expulsed substances Ni3Ta, NiTa, and Cr2Ta and their microhardness was certainly higher than the base metal (BM); a transition layer containing high contents of Ni3Ta, NiTa, and Cr2Ta phases was observed at the Ta10W/FZ interface. With the increase of the LBO, the contents of Ni3Ta, NiTa, and Cr2Ta in the FZ gradually declined, the average grain size in the FZ increased slightly, the microhardness of the FZ dropped rapidly, and the thickness of the transition layer at the Ta10W/FZ interface reduced obviously. Either in the room-temperature or high-temperature (750 °C) tensile tests, Ta10W/GH3030 joints were always fractured at the Ta10W/FZ interface, showing the typical brittle fracture mode, and the tensile strength of joints was enhanced with the increasing LBO. Under LBOs of −0.2, 0, and + 0.2 mm, the room-temperature tensile strengths of Ta10W/GH3030 dissimilar-material joints were 266.4, 308.6, and 341.2 MPa, while the high-temperature (750 °C) tensile strengths were 97.6, 191.5, and 202.7 MPa, respectively.

Enhanced high-temperature mechanical properties and strengthening mechanisms of chemically prepared nano-TiC reinforced IN738LC via laser powder bed fusion

Fabrication of high-strength nickel-based composites to meet the demanding service requirements in aerospace environments is a significant challenge. This paper introduces the wet chemical method to prepare the nano-TiC reinforced IN738LC. In contrast to the conventional ball milling approach, this method attains superior attachment of nanoparticles. By employing a full-factorial experimental design, the correlation between Laser-powder bed fusion (L-PBF) processing parameters and the porosity, micro-hardness, and high-temperature tensile strength of as-built samples was examined. The results indicate that the optimal processing parameters are a laser power of 225 W, scanning speed of 750 mm/s, and hatch space of 0.09 mm, with a Volumetric energy density (VED) of 111.1 J/mm3. Compared to IN738LC, the chemically prepared TiC-IN738LC exhibits a 45 % increase in room temperature tensile strength (400 MPa) and a 65 % increase in high-temperature tensile strength (120 MPa). Compared with ball-milled TiC-IN738LC, the chemically prepared samples present superior microstructure with more equiaxed grains. The morphological analysis of the tensile samples reveals that the presence of dimples are crucial in enhancing the ductility properties. Furthermore, this study identifies the Orowan strengthening mechanism and the grain refinement strengthening mechanism as the principal mechanisms of reinforcement by nano-ceramics.

Enhanced high temperature mechanical and oxidation behavior of direct energy deposited TiC/Inconel 718 gradient coatings

While Inconel 718 is commonly employed in high-temperature settings, its performance at elevated temperatures is notably diminished in comparison to its performance under ambient conditions. In this study, Inconel 718 (IN718), Inconel 718 with 5 layer of Inconel 718–5 wt% TiC gradient coatings (CG-5), and Inconel 718 with 5 layer of Inconel 718–10 wt% TiC gradient coatings (CG-10) were fabricated using direct energy deposition (DED) to investigate the influence of TiC content on the mechanical and oxidation properties at elevated temperatures through the regulation of microstructural changes. Following the incorporation of TiC, the microstructures underwent a transformation into refined equiaxed crystals, carbides, and columnar crystals, replacing the coarsened columnar crystals and Laves phase present in IN718. Compared to IN718, the high-temperature tensile strength of CG-5 and CG-10 has increased by 80% and 180% at 900 ℃. Meanwhile, the mass gain due to oxidation per unit area of CG-5 and CG-10 has decreased by 23% and 11%, respectively. The results indicate that CG-10 exhibits a combination of highest high-temperature tensile strength and the enhanced resistance to high-temperature oxidation when compared to IN718 and CG-5.

Mechanical and Metallurgical behavior of Manual Metal Arc Welded P91 Ferritic Martensitic Steel Joints

In the nuclear power plant industry, Cr-Mo ferritic steels are indispensable due to their high-temperature tensile strength, creep strength, and resistance to stress corrosion cracking. This study evaluated and analyzed the mechanical properties and metallurgical behavior of indigenously developed filler (over matched with base metal) manual metal arc welded Cr-Mo ferritic steel (hereafter referred as P91 steel). The analysis revealed that the ultimate tensile properties of the weld joint exceed those of the unwelded metal, being 6% higher than the base metal. Consequently, the joint efficiency for the weld joint is 106%. However, the impact toughness of the weld pad is significantly lower compared to the unwelded metal, nearly 2.5 times less than the base metal. The weld metal region’s microstructure is characterized by untempered lath martensite pinned with dense dislocations, which is attributed to rapid cooling from the liquidus range. Furthermore, a distinct Heat-Affected Zone (HAZ) was identified adjacent to the weld metal region, which results from the elevated temperature experienced in this area.

Evolution of NbC during laser welding and its impacts on the performance of molybdenum alloy joint

Influences of addition of niobium carbide (NbC) in the fusion zone (FZ) on room-temperature and high-temperature mechanical properties of laser-welded joints of molybdenum (Mo) alloys were studied. Results show that after adding NbC powder, the average Vickers microhardness in the upper part of the FZ increases from 183.0 HV to 712.3 HV; the room-temperature tensile strength grows from 33.9 MPa to 323.1 MPa, reaching 45.4 % that of base metal (BM). In addition, the fracture mode of joints turns from intergranular fractures into transgranular fracture; at 1100 °C, the high-temperature tensile strength of joints added with NbC is 141.6 MPa, which is 65.9 % that of BM. Energy dispersive spectrometer (EDS) and electron backscattered diffraction (EBSD) results show that after adding NbC powder, the average grain size in the FZ diminishes from 40.3 μm to 32.9 μm, where the number of low-angle grain boundaries (LAGBs) increases; the FZ not only contains NbC phase but also a large quantity of Nb2O5 and Mo2C phases dispersed on grain boundaries (GBs), and the number of MoO2 phase on GBs decreases apparently. Therefore, physical mechanisms underlying significant improvement of room-temperature and high-temperature tensile strengths of laser-welded joints of Mo alloys added with NbC in the FZ mainly include fine-grain strengthening, GB purification, and GB strengthening.

Achieving optimal comprehensive properties in heat resistant Cu-based alloys by regulating complex elemental interaction

Coherent γ′-phase precipitation strengthened heat-resistant Cu-based alloys exhibit promising application in the field of high-temperature. In the work, to further improve the comprehensive performance of the alloys, the elements Cr, Zr, Zn and Ti are introduced into the model alloy (Cu83.33Ni12.50Al4.17 at.%). The existence state of the adding elements and their influence on comprehensive properties, including the in-situ high-temperature hardness, tensile properties and stability, etc., was unveiled. Furthermore, the Cu83.33Ni11.11Al2.78Cr1.04Ti1.04Zr0.35Zn0.35 alloy with excellent comprehensive properties was designed and prepared, exhibiting a high-temperature tensile strength of 370 MPa and an elongation of 3.7 % and high temperature stability of up to 400 h at 873 K. The reasons for the improvement of comprehensive properties can be attributed to the following aspects: (1) The adding elements not only inhibit discontinuous precipitation but also refined the size of the γ' phase and improved its thermal stability; (2) Cr and Zr inhibit the precipitation of deleterious D024-Ni3Ti phase caused by Ti; (3) The BCC-Cr (precipitation strengthening phase) and Ni5Zr phases (grain boundary strengthening phase) are introduced. This study successfully demonstrates the advantages of addition of multiple-elements through regulating their interaction, thereby establishing a robust foundation for designing heat-resistant Cu-based alloys in future investigations.

A transfer learning strategy for tensile strength prediction in austenitic stainless steel across temperatures

Austenitic stainless steel plays a pivotal role in the nuclear industry with exceptional mechanical properties and corrosion resistance, wherein high-temperature tensile strength (∼290 °C) is a critical factor in ensuring its performance and reliability. This study focuses on the predictive modeling of tensile strength in cast austenitic stainless steel at room and elevated temperatures by developing a transfer learning strategy. The application of a gradient-boosting decision tree algorithm, enhanced by key features derived from room-temperature analyses and augmented with partial high-temperature data, results in significantly increased accuracy. The effective selection of features underscores the stability of critical variables across different temperatures, affirming the efficacy of the proposed transfer learning strategy. The work sheds light on material selection and design for high-temperature applications, and lays the groundwork for future exploration into predictive modeling of material properties in extreme conditions.

Enhancing high-temperature performance of Inconel 718 LDED samples through hybrid laser polishing post-treatment

ABSTRACT A hybrid laser polishing post-treatment was introduced to enhance the surface quality and high-temperature performance of laser directed energy deposition (LDED) Inconel 718 samples. The surface morphology and microstructure were analysed before and after laser polishing, and the result showed that the surface roughness was reduced by 97.4% and the grains of the recrystallized layer were refined through this post-treatment. Furthermore, the wear resistance, corrosion behaviour, and tensile strength of the laser polishing LDED Inconel 718 samples at the high-temperature of 650°C were investigated detailed. The result showed that the high-temperature tensile strength saw an increase of 14.97%, while both the high-temperature wear resistance and corrosion performance of Inconel 718 exhibited improvements compared to the as-fabricated samples.

Microstructure and mechanical properties of a dissimilar metal welded joint of Inconel 617 and P92 steel with Inconel 82 buttering layer for AUSC boiler application

The application of the novel dissimilar metal welded (DMW) joint, utilizing Inconel 617 and P92 steel, was showcased in the advanced ultra-supercritical (AUSC) boiler. The work has been performed to investigate the effect of Inconel 82 (ERNiCr-3) buttering layer on microstructure and mechanical properties (high-temperature tensile strength, impact strength and microhardness) of gas tungsten arc welded (GTAW) dissimilar joint between Inconel 617 and P92 steel fabricated using the Inconel 617 (ERNiCrCoMo-1) filler. For optical microscopy and scanning electron microscopy (SEM), samples were machined along a transverse direction which comprised the butter layer, weld metal, and heat-affected zone of both sides. The energy-dispersive X-ray spectroscopy (EDS) was used to map the interface of the buttering layer and weld metal and butter layer and P92 steel. The high-temperature tensile testing and Charpy impact testing at room temperature were conducted for the integrity assessment of the welded joint. The examination of microstructure and hardness revealed that the buttering layer of Inconel 82 filler successfully mitigated a significant portion of the brittle martensitic microstructure from the coarse-grained heat-affected zone (CGHAZ), along with hardness peaks on the side of P92 steel. The conventional method of DMW joint fabrication, without the use of a buttering layer, has been demonstrated to be less favourable compared to the new fabrication method, which incorporates a buttering layer. The TiC/NbC carbides were identified in the Inconel 82 buttering layer, whereas M23C6 and Mo6C carbides were found in the Inconel 617 filler weld. Near the interface of the Inconel 82 buttering layer and P92 steel, the formation of peninsula and island structures, as well as Type I and Type II boundaries, were confirmed. Additionally, element diffusion of Ni, Cr, and Fe was observed. The tensile test results indicated an ultimate tensile strength of 620 ± 4 MPa and % elongation of 19 ± 4 % at room temperature, with fracture occurring in the buttering layer near the interface of the buttering layer and P92 steel. At temperatures of 550 °C and 650 °C, the ultimate tensile strength decreased to 448 MPa and 326 MPa, respectively, with fractures occurring in the P92 steel, irrespective of temperature. The hardness of the Inconel 82 buttering layer and Inconel 617 filler weld were 219 ± 10 HV and 248 ± 11 HV, respectively. The Charpy impact toughness of the Inconel 82 buttering layer and Inconel 617 filler weld were 138 ± 6 J and 115 ± 4 J, respectively. The study comprehensively investigates and discussed the correlations between microstructure and mechanical properties.

Enhancing the High Temperature Tensile Strength of Fe36Ni36Cr10Mo1Al17 Alloy by Substituting Al with Si

Enhancing the High Temperature Tensile Strength of Fe36Ni36Cr10Mo1Al17 Alloy by Substituting Al with Si

Impact of intermetallic phases on the localised pitting corrosion and high-temperature tensile strength of Al–Si[sbnd]Mg[sbnd]Cu[sbnd]Ni alloys

The influence of Ni-rich intermetallic particles (IMPs) on the microstructure, high-temperature mechanical properties, and corrosion behaviour of Al–Si–Mg–Cu–Ni alloys was investigated. The presence of coarse block-like γ-Al7Cu4Ni and thin needle-like δ-Al3NiCu IMPs contributed to low-temperature alloy strengthening during tensile tests. However, void nucleation and coalescence within the IMPs facilitated ductile fracture and alloy rupture, resulting in a lower tensile strength at high temperatures. Although both IMP phases had a cathodic electrochemical nature, resulting in strong galvanic corrosion, the γ-Al7Cu4Ni phase acted as the primary cathode, amplifying localised pitting while reducing the overall alloy corrosion resistance.

High-temperature tensile strength of alumina-spinel refractory by Brazilian test at 1200°C coupled with DIC in-situ monitoring

This study investigated for the first time the corrosion effect of Al2O3-MgAl2O4 refractory by steel ladle slag using a DIC-coupled Brazilian test at 1200 °C. Three types of alumina-spinel materials were used in the test, namely, original non-infiltrated refractory, slag-infiltrated at 1450 °C as well as postmortem refractory after 69 cycles of work in the sidewalls of steel ladle. Lab infiltration was conducted at 1450 °C using CaO-Al2O3-SiO2-based ladle slag and its analog enriched with manganese (10% MnO). The tensile strength of postmortem material at 1200 °C was the highest at 10.7 MPa, and it was 52% and 70% higher than for reference and MnO-enriched slag, respectively, and 80% higher than for original refractory. The significantly raised tensile strength of slag-infiltrated materials vs. original non-infiltrated brick was directly related to the densification of microstructure by corrosion products (mainly CA6, CA2, Fe) which caused the infiltrated materials to be stiffer and with a more brittle nature to fracture.

Laser Powder Bed Fusion of GH4099 Superalloy: Parameter Optimization and Effect of Heat Treatment on Microstructure and Mechanical Properties

Ni-Cr-Co-W superalloy (GH4099) can be used to manufacture high-temperature structural components of aero-engine combustion chambers for long-term service below 900 °C. This study provides a comprehensive evaluation of the GH4099 superalloy fabricated using the laser powder bed fusion (LPBF) technique, focusing on the optimization of processing parameters and a systematic investigation of the microstructural evolution and mechanical properties of the as-deposited and heat-treated samples. An optimal parameter combination was established using the response surface method (RSM) design and the variance method. The as-deposited GH4099 alloy is primarily composed of columnar crystals grown epitaxially and M23C6 carbides without the generation of the γ′-phase. After solution treatment, recrystallization and grain growth occurred, with the alloy remaining as large, irregularly shaped polygonal columnar crystals. The aging process precipitated substantial γ′-phase, which internally existed as a mixture of equiaxed and columnar crystals. LPBF-GH4099 superalloy exhibited a maximum room-temperature tensile strength of 1137.80 MPa and a high-temperature tensile strength of 780 MPa at 800 ℃. Various strengthening mechanisms were observed in the as-deposited and heat-treated samples. The most significant grain boundary strengthening effect was observed in the deposit state, while solution strengthening was primarily due to the segregation of elements, such as Mo, W, and Cr, in the γ matrix. Precipitation strengthening, predominantly due to the γ′-phase, emerged as the main strengthening mechanism for the GH4099 superalloy post-aging treatment. This study presents significant insights into the LPBF-GH4099 alloy and provides a solid foundation for future studies and practical applications in this field.

High-temperature tensile strength of C/SiC composite under laser-induced high heating flux in an aerobic environment

Based on the advantages of laser high brightness, a high-temperature mechanical property measuring device has been developed, which can measure the high-temperature strength of C/SiC composites under the condition of short-term high-temperature rise rate and solve the problem of over-oxidation of materials in conventional high-temperature mechanical properties experiments. The experimental results show that the maximum temperature rise rate is 260 ℃/s at the initial heating stage, and the test time is controlled within 35 s. The tensile strength of the prepared C/SiC composites decreased first and then increased at high temperatures and laser-induced high temperatures. The experimental results are similar to those in the literature under the inert atmosphere. Oxidation has less of an effect on the mechanical characteristics of materials under conditions of rapid temperature rise. The system can be used to test the mechanical properties of composite materials at high temperatures and as a simulation platform for the thermal response of specific thermal protection systems subjected to a constant heat flux. This study can provide a new idea for testing ultra-high temperature mechanical properties of C/SiC materials and provide key technical support for the engineering application and high-temperature testing of C/SiC materials in high-temperature environments.

Effect of Mn/Ag Ratio on Microstructure and Mechanical Properties of Heat-Resistant Al-Cu Alloys.

This paper mainly investigated the effect of the Mn/Ag ratio on the microstructure and room temperature and high-temperature (350 °C) tensile mechanical properties of the as-cast and heat-treated Al-6Cu-xMn-yAg (x + y = 0.8, wt.%) alloys. The as-cast alloy has α-Al, Al2Cu, and a small amount of Al7Cu2 (Fe, Mn) and Al20Cu2 (Mn, Fe)3 phases. After T6 heat treatment, a massive dispersive and fine θ'-Al2Cu phase (100~400 nm) is precipitated from the matrix. The Mn/Ag ratio influences the quantity and size of the precipitates; when the Mn/Ag ratio is 1:1, the θ'-Al2Cu precipitation quantity reaches the highest and smallest. Compared with the as-cast alloy, the tensile strength of the heat-treated alloy at room temperature and high temperature is greatly improved. The strengthening effect of the alloy is mainly attributed to the nanoparticles precipitated from the matrix. The Mn/Ag ratio also affects the high-temperature tensile mechanical properties of the alloy. The high-temperature tensile strength of the alloy with a 1:1 Mn/Ag ratio is the highest, reaching 135.89 MPa, 42.95% higher than that of the as-cast alloy. The analysis shows that a synergistic effect between Mn and Ag elements can promote the precipitation and refinement of the θ'-Al2Cu phase, and there is an optimal ratio (1:1) that obtains the lowest interfacial energy for co-segregation of Mn and Ag at the θ'/Al interface that makes θ'-Al2Cu have the best resistance to coarsening.

Improving mechanical performance of heat-resistant eutectic Al-Fe-Ni alloy by in-situ TiB2 particles

The mechanical performance and strengthening mechanism of in-situ TiB2 ceramic particles reinforced eutectic Al-Fe-Ni alloy were researched. The smaller-sized TiB2 particles are uniformly distributed inside the grain and larger-sized particles tend to gather at the eutectic grain boundary. The hardness and room temperature tensile tests show that TiB2 particles improve the comprehensive mechanical properties of the eutectic alloy. Meanwhile, the high temperature tensile strength of eutectic alloys is also enhanced by particles. The pinning effect of TiB2 particles on dislocation and eutectic boundary are the main strengthening mechanisms. The study on the microstructures and properties of TiB2 particles reinforced eutectic alloys provides guidance for enhancing the mechanical performance of eutectic Al alloys.

Microstructure evolution and mechanical properties of Al-12Si-xCu-yNi-1Mg alloy with different Ni/Cu ratios

High-temperature properties are the key factor affecting the industrial application of cast Al-Si alloy. In this paper, four kinds of Al-12Si-xCu-yNi-1Mg (y = 7.5-x, x:4.84, 5.17, 5.55, 6.00.) alloys were prepared by changing the Ni/Cu ratio and regulating the type and proportion of the heat-resistant phase, and then systematically analyzed the changing of microstructure and mechanical properties and clarified the heat resistance mechanism of the alloy. The experimental results show that with the increase of the Ni/Cu ratio, the eutectic Si phase of the as-cast alloys was refined, the blocky Al2Cu phase and the strip Al7Cu4Ni phase disappeared, and the reticular Al3CuNi heat-resistant phase increased, and the size of Al3CuNi phase decreases first and then increases. After T6 heat treatment, the eutectic silicon spheroidized, and the nickel-rich phase did not change significantly. As the Ni/Cu ratio increases, the tensile strength of the alloy at room temperature increases first and then decreases, and its tensile strength at high temperature increases continuously. When the Ni/Cu ratio is 0.45, and the maximum value of tensile strength at room temperature is 355 MPa. When the Ni/Cu ratio is 0.55, the content of the Al3CuNi phase with high thermal stability is most, and the Al2Cu phase with poor stability is less, so the high-temperature tensile strength is the highest, and the value of tensile strength at 275 °C, 325 °C and 375 °C is 192 MPa, 172 MPa, and 89 MPa, respectively.

The Important Role Played by High-Temperature Tensile Testing in the Representation of Minimum Creep Rates Using S-Shaped Curve Models

It is important to characterize the creep life of materials used in power plants and aeroengines. This paper illustrates the important role played by a material’s tensile strength in enabling accurate creep property representations to be made. It also shows that published high-temperature tensile strength values are not always suitable for use in certain creep models due to its strain rate dependency. To deal with the absence of such suitable date on tensile strength, this paper estimates such values directly from minimum creep rate data. When this technique is applied to models that represent the relationship between minimum creep rates and normalized (with respect to tensile strength) stress using S-shaped curves, an improvement in the fit to data on 2.25Cr–1Mo steel was observed. The findings suggest an important need for future research into the most appropriate strain rates to be used in high-temperature tensile testing when the purpose is to use the resulting tensile strength values for use in creep modeling.

Modeling temperature dependence of tensile fracture strength for rocks considering phase transition and the direct effect of thermal damage

Accurately and conveniently acquiring the tensile fracture strength of rocks at different temperatures is vital no matter for the security or economical design of deep underground engineering projects. Extensive testing in the laboratory, assisted with fitting approaches, is the main method to obtain the high-temperature tensile fracture strength in the available literature. However, the high-temperature destruction test is difficult to conduct and requires numerous time and resources. In this work, considering the main physical mechanisms such as phase transition and thermal damage that affect the tensile fracture strength of rocks at high temperatures, theoretical models for predicting their temperature-dependent tensile fracture strength (TDTFS) are established based on the Force-Heat Equivalence Energy Density Principle. The presented models achieve great prediction on the different variation trends of tensile strength below and above the phase transition temperature, as well as the corresponding sudden change of strength. For rocks without phase transition, the presented model only needs some physical parameters tested at room temperature can get a good prediction capacity on the TDTFS. Moreover, a new theoretical characterization model of the equivalent thermal damage parameter was presented and take a comparison with the previous model. Finally, the potential applications and limitations of the TDTFS model are further discussed. The application threshold of the presented TDTFS models is relatively low, and they may therefore be suitable as a method for providing a rapid and preliminary evaluation of strength at a large temperature range for rock engineering.