High Temperature Tensile Strength Research Articles

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.

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.

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.

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.

Experimental analysis and response surface optimization of the influence of Zn/Al mass ratio on the creep resistance and tensile properties of As-cast Mg-Zn-Al alloy

Mg-Zn-Al (ZA) alloys are intended to exhibit creep resistance and high temperature mechanical capabilities due to appropriate Zn/Al mass ratio control. The effect of altering Al concentration (1, 2, 3, 4, 5, 6) on the tensile and creep resistance properties of Mg-9Zn-xAl alloy was determined experimentally and quantitatively optimized using response surface method (RSM). It was observed that 2 wt% Al improves both room and elevated temperature tensile strength, and ductility of the considered ZA alloy. The creep rate sharply increased when the mass fraction of aluminum rose above 4 wt%. For the purpose of forecasting the tensile and creep properties of the ZA alloy at any given aluminum mass percentage, quartic models were generated, with all model terms significant. Strong room and high-temperature tensile strength, %elongation, and creep resistance were all reached in the low Al-containing ZA alloys, with 1.597 wt% anticipated ideal Al mass concentration, according to RSM optimization.

High-temperature tensile properties of an aluminum quasicrystal-forming alloy manufactured by laser powder bed fusion

Normalized tensile samples of Al–4Fe–3Cr–2Ti (wt.%) alloy were successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing. The alloy's tensile properties and microstructure were investigated at room and high-temperature (up to 500 °C). This Al–Fe–Cr–Ti alloy exhibits exceptional thermal stability and outstanding mechanical performance at temperatures of up to 500 °C. A particularly interesting feature is the alloy's yield strength values, which reach ∼300 MPa at 300 °C and ∼180 MPa at 400 °C. The outstanding mechanical behavior of this alloy at high temperatures is attributed to the in situ precipitation of ultrafine icosahedral quasicrystalline (i-QC) particles endowed with high thermal stability. These values are notably higher than those achieved for A319, 6061-T6 and Al-8%wt.Cu–Mg–Ag cast alloys – three of the most common heat-resistant Al alloys, and higher than commercially available Al-based alloys for LPBF. Based on hardness measurements and the bimodal composite microstructure, we propose a model to predict this alloy's yield strength. This model shows a good agreement with the experimental results and can be used to maximize the alloy's tensile strength. This work describes a lightweight aluminum alloy with outstanding high temperature tensile strength within a wide range of temperatures, in addition to being additively processable and affordable.

Ti–48Al–2Cr–2Nb alloys prepared by electron beam selective melting additive manufacturing: Microstructural and tensile properties

Here, an electron beam selective melting (EBM) technique was employed to shape Ti–48Al–2Cr–2Nb alloy to combat its intrinsic brittleness and insufficient hot workability. Through process optimization, high-density samples (4.2327 g/cm3) were produced. First, the mechanism of interaction between phase transformation and microstructural evolution of EBM-formed Ti–48Al–2Cr–2Nb alloy was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscattering diffraction (EBSD). And then, the mechanism of interaction between tensile properties and microstructural evolution of EBM-formed Ti–48Al–2Cr–2Nb alloy was discussed. Based on the results, the microstructure consists of coarse equiaxed grains and fine lamellar grains, which gradually coarsen from upper to bottom. As the thickness of the layer increases from upper to bottom, the content of the B2 phase increases continuously, with a predominant component of TiAl and a small amount of Ti3Al and B2 phases. The majority of the γ-TiAl phase does not exhibit significant texture, while the α2-Ti3Al phase shows a texture of (0001) with 19.32 times the random intensity, and its c-axis is parallel to the deposition direction. Benefiting from its unique structure features, the maximum room temperature tensile strength of as-deposited Ti–48Al–2Nb–2Cr alloy reaches 854.6 MPa with an elongation of over 2%. And the maximum high-temperature tensile strength of EBM-formed Ti–48Al–2Nb–2Cr alloy reaches 707 MPa at 650 °C with an elongation over 3.5%. According to these results, the mechanical properties of our EBM Ti–48Al–2Cr–2Nb alloy are superior to those previously reported.

Influence of carbon fiber failure mode caused by TiO2 coating on the high temperature tensile strength of carbon fiber reinforced 7075 Al alloy composites

To enhance the mechanical properties of carbon fiber (CF) reinforced 7075 Al alloy material at high temperature conditions, TiO2 coating was prepared on the surface of CF by chemical vapor deposition. The composites were prepared by hot pressing sintering and hot extrusion methods. The evolution of the compositional components of the composite interface was investigated. The density, hardness, and tensile strength of the samples were measured, and the strength/density ratio of the samples was calculated at 150 °C. The results indicate that the tensile strength of coated CF reinforced composite (535 MPa) was increased by 21.3% and 5.7% compared to the tensile strength of 7075 Al alloy (441 MPa) and uncoated CF reinforced composite (506 MPa), respectively. Furthermore, the strength/density ratio of the composite also increased with the addition of TiO2 coating. The enhancement of coating on CF on tensile strength is attributed to the transformation of CF failure mode.

Microstructural Evolution and Mechanical Behavior of TA15 Titanium Alloy Fabricated by Selective Laser Melting: Influence of Solution Treatment and Aging

In this study, TA15 titanium alloys were successfully prepared using selective laser melting (SLM). The results show that the microstructure of each TA15 specimen is composed of a large number of acicular α’ martensite crystals accompanied by a lot of dislocations and twin structures in the martensite due to non-equilibrium heating and cooling via SLM. After solution treatment and aging treatment, the martensite structure is successfully transformed into a typical duplex structure and an equiaxial structure. When there is an increase in the solution temperature, the size of the equiaxed primary α phase and the elongation of the specimen gradually increases, while the thickness of the layered secondary α phase and the tensile strength of the specimen decreases accordingly. After solution treatment at 1000 °C, the specimens show the best comprehensive mechanical properties, i.e., a high-temperature tensile strength of 715 MPa and a corresponding elongation of 24.5%. Subsequently, an appropriate solution–aging treatment is proposed to improve the high-temperature mechanical properties of SLMed TA15 titanium alloys in aerospace.

A L12 precipitation strengthened Co-free medium-entropy alloy with superior high-temperature performance

In present work, the superior high-temperature properties in a novel (Ni, Cr, Fe)3(Al, Ti, Cr)-γʹ (L12) type precipitation-strengthened Co-free medium-entropy alloy (MEA) was systematically evaluated. Experimental results indicate that this γʹ-strengthened alloy demonstrates excellent structure thermal stability and no other brittle intermetallic phases formed at grain boundaries or grain interior during long-term thermal exposures. The γʹ phase in this Co-free MEA exhibits an extraordinary sluggish coarsening rate, which is much lower than most conventional superalloys and recently developing γʹ-strengthened high/medium-entropy alloys (HEAs/MEAs). This γʹ-strengthened alloy also exhibits a good combination of high γʹ-solvus temperature (1068 °C) and low mass density (7.79 g/cm3). More significantly, this γʹ-strengthened MEA shows excellent high-temperature tensile strength, especially outstanding specific strength, which is superior to most Ni/Co-based superalloys. Our present work provides a useful illustration for designing advanced high-temperature alloys based on γʹ(L12)-strengthened HEAs/MEAs, rather than Ni-based/Co-based superalloys.

Precipitates evolution during isothermal aging and its effect on tensile properties for an AFA alloy containing W and B elements

A 20Cr-25Ni-2.5Al alumina-forming austenitic alloy containing W and B elements was aged at 923 K for 5000 h, and the microstructure and tensile properties with different aging time were investigated. NiAl, σ and Laves were observed at grain boundaries (GBs) successively. The matrix was covered by NiAl and Laves with the extension of aging. The evolution of precipitates during aging contributed to the variation of tensile properties. Precipitation of nanosized NbC carbides within grains and σ phase at GBs led to a rapid increase in strength and a decrease in elongation for 500 h aging sample. In the later stage of aging, the coarsening of NiAl and Laves phases, as well as the reduction in dislocation density caused a decline in strength. The coarsening of precipitates upon aging time follows the Ostwald ripening theory. Due to its lower diffusion rate in austenite compared to Mo, W may accelerate the growth of Laves at GBs. Boron was mainly enriched in Laves instead of NiAl, NbC and σ phases after high temperature aging. The addition of W and B improved the precipitation strengthening of Laves, increasing the high temperature tensile strength after long term thermal aging. The difference in tensile properties between room temperature and 923 K is due to the ductile–brittle transition of NiAl. No σ phase was observed within grains even after 5000 h aging and elemental chromium particles occurred around Laves due to boron hindering the growth of σ.

Effect of Mo and V additions on the coarsening kinetics and high-temperature strength in γ′ precipitation-strengthened high-entropy alloys

High-entropy alloys (HEAs) containing well-stabilized nano-precipitates have a huge advantage in elevated temperature applications. This study investigated the effects of Mo and V additions on the morphological evolution, the coarsening kinetics of multi-component γ′ precipitates, and the high-temperature tensile strength of HEAs. HEAs with the additions of Mo and V have significantly lower lattice misfit values and exhibit a smaller coarsening rate of γ′ nanoparticles compared to Ni and Co-based superalloys. Moreover, the precipitate morphology related to the lattice misfit exhibits completely different effects attributed to Mo and V addition. Remarkably, Mo2.5V2.5 HEA has a yield strength of 496 MPa at 800 °C, which shows great potential for high-temperature applications.