High Temperature Tensile Behavior Research Articles

Effect of solution and cooling methods on the high-temperature mechanical behavior of Ti60 alloy

The influence of solution treatment temperature and cooling rate on the mechanical behavior of Ti60 alloy at 600℃ was investigated. Five different solution treatment temperatures and five different cooling methods were used for the Ti60 alloy. The study revealed that, at the same solution treatment temperature the ultimate tensile strength (UTS) and elongation (Z%) of the water-quenched (WQ) microstructure were 32 % and 61 % higher, respectively, compared to the furnace-cooled (FC) microstructure. The WQ microstructure exhibited significantly superior strength and ductility. This phenomenon was primarily attributed to the differences in microstructural morphology caused by varying cooling methods. The effects of different cooling methods on high-temperature tensile behavior were discussed in terms of fracture morphology, high-angle grain boundaries, and void distribution. On the other hand, the UTS of the air-cooled (AC) microstructure initially increased and then decreased with decreasing solution treatment temperature, while the UTS of the FC microstructure decreased with decreasing solution treatment temperature. This phenomenon was mainly due to the competing effects of effective slip length (colony size) and elemental distribution. The correlation between solution treatment temperature and cooling rate parameters and high-temperature mechanical properties was established using the response surface methodology (RSM). The optimized solution cooling scheme was determined to be at 1012℃ with a cooling rate of 4238℃/min.

High-temperature mechanical behavior and microstructural destabilization evolution of the lightweight refractory high-entropy alloy prepared by laser additive manufacturing

Lightweight refractory high-entropy alloy (LRHEA) has lower density and higher specific strength, which makes it very promising for future applications in rocket engine components. Their high-temperature resistance to softening and high microstructure stability in a wide temperature range are also essential to sustaining their performance due to being used in harsh, high-temperature situations. In this work, the high-temperature tensile behavior of Al0.3NbTi3VZr1.5 LRHEA fabricated by laser additive manufacturing has been systematically investigated from 400 °C to 800 °C, and the relationship between the deformed microstructure and the mechanical behavior was revealed, and analyzing the reasons for the thermodynamic instability of the solid solution in LRHEA are discussed in detail. It is found that the weakening of the high entropy effect at intermediate temperatures reduces the stability of the solid solution, and the accelerated diffusion between elements further promotes the solid solution destabilization, mainly manifested as the Laves phase and the local chemical fluctuation (LCFs). The high dislocation density introduced by the additive manufacturing technology leads to the irregular connection of the Laves phases within the grains, and it can be improved by grain growth. The high negative mixing enthalpy competes with the high-entropy effect, and temperature is the decisive factor. In this situation, the atomic clusters were promoted and induced spinodal decomposition for generating LCFs. The formation of LCFs exhibits solute competition with the emergence of the C14 Laves phase, and the phase proportions fluctuate at different temperatures. This work provides new thinking and attention for developing lightweight, heat-resistant materials.

High-Temperature Tensile Behavior of Structural Steel Grades with Varying Manganese Contents

Abstract Three low-carbon (∼0.1 wt.% carbon) grades of structural steel with varying manganese content (0.75–1.5 wt.%) with ferrite-pearlite microstructure were used for the study. The 1.5 % manganese steel is a microalloyed steel with vanadium, niobium, and titanium content, which is strengthened by interphase precipitates. The steels were tensile tested at room temperature and in the temperature range between 200°C–700°C, at 100°C intervals. The elevated temperature flow strengths of the steels studied show higher strength values for the higher manganese steel. It was found that the manganese enhanced the strength at all ranges of test temperatures. The retention factor of the conventional structural steels was less than or equal to 0.50 against 0.66 for a fire-resistant steel grade. The study shows that the addition of elements such as chromium, molybdenum is required to achieve a higher retention factor to fulfill the requirement of fire resistance characteristics.

High-temperature tensile behaviors of an ultra-strong aluminum alloy fabricated by additive manufacturing

Additively manufactured (AM) Al alloys have widespread applications. Their high-temperature mechanical behaviors are also of significant interest. In this study, we investigated the microstructure and mechanical behavior of Al-2Ti-2Fe-2Co-2Ni (at%) alloy processed by laser powder bed fusion. The as-printed alloy contains a distinctive heterogeneous microstructure characterized by nanoscale intermetallic lamellae arranged in rosette patterns in the Al matrix. Notably, this alloy exhibits high tensile strength and thermal stability up to 500 °C as revealed by in-situ tension studies in a scanning electron microscope. The enhanced high temperature performance can be attributed to a substantial volume fraction of well-dispersed, nanoscale stable intermetallic particles.

High temperature tensile properties and deformation behavior of CoCrFeNiW0.2 high entropy alloy

High entropy alloys (HEAs) have been a new-type of structural materials, which show good performance in various extreme conditions. In the present study, we systematically investigated the high temperature deformation behavior of as-cast CoCrFeNiW0.2 HEA under different temperatures from 298 to 1173 K and various strain rate of 1 × 10−4 s−1 to 5 × 10−3 s−1. An obvious temperature dependence of yield strength can be found with a remarkable decrease from 362 MPa at 298 K to 119 MPa at 1173 K. The normal Portevin–Le Chatelier (PLC) effect was presented in the intermediate temperature range of 673 K to 1073 K, the serrated flow transformed in the sequence of A → A + B → A + C → B + C → C with the increasing temperature, which is caused by dynamic strain aging (DSA). W atoms played an important role in the interaction between solute atoms and dislocations. Fractography analysis suggests the failure mode transition from transgranular fracture to intergranular fracture. Electron backscatter diffraction (EBSD) demonstrates that the high temperature deformation mechanism of the HEA is dominated by dynamic recovery (DRV). Additionally, transmission electron microscopy (TEM) was performed to observe the dislocation configurations and the interaction between dislocations and μ phase precipitates at various temperatures, and these results further identify the high temperature deformation mechanism. To summarize, this study indicates the proposed HEA has excellent high temperature mechanical properties and a wide range of potential applications in many fields.

High-temperature tensile behavior and constitutive model in Co-free Fe40Mn20Cr20Ni20 high-entropy alloy

High-entropy alloys (HEAs) have attracted widespread attention from scholars as a new type of material employed in extreme environments. However, as a main kind of HEAs, many face-centered cubic single-phase HEAs are restricted in industrial applications due to their lower yield strength and high cost when containing expensive elements such as Co. In this study, dispersion strengthening by heat treatment was introduced in low-cost Co-free Fe40Mn20Cr20Ni20 HEA to improve its strength, and its high-temperature tensile behavior and constitutive model were studied to explore its potential application at high temperatures. It is found that when subjected to quasi-static room-temperature stretching, the heat-treated sample exhibits a yield strength of 534 MPa and a tensile plasticity of 26.8%. In addition, the tensile behavior of samples after heat treatment was investigated at high temperature (573–873 K) and low strain rate (10−3–10−1 s−1). The results suggest that the yield strength decreases with increasing temperature and decreasing strain rate. Moreover, at 873 K and 10−3 s−1, the electron backscatter diffraction system and x-ray diffraction results of the deformed sample indicate that the softening curve is driven from the recovery of materials. Finally, the flow stress was predicted using the Arrhenius equation and Artificial Neural Network model (ANN), and the two models were assessed using the average absolute relative error and coefficient of correlation (R). The results showed that the ANN had higher accuracy.

High-temperature tensile properties and deformation behavior of a multi-phase FeNiCrAlTi alloy

Single-phase multi-principal elements alloys (MPEAs) within the elevated temperature experience particularly severe strength loss, and even a distinct ductile-to-brittle transition. Herein, we report on a non-equiatomic, multi-phase FeNiCrAlTi MPEA which possesses remarkable combinations of mechanical properties across a wide range of temperatures from 400 °C to 800 °C, especially its specific yield strength possesses nearly 100 MPa/g∙cm−3 at 600 °C. The excellent mechanical behavior benefits from the synergistic effect of the special phase structure and precipitation strengthening by the ordered Ni (Al, Ti) B2 nanoparticles. The transformation of deformation mode at 600 °C should be considered the dominant of the resistance to intermediate or high-temperature embrittlement. This work provides a new methodology for regulating mechanical properties of superior alloys that involve high-temperature conditions.

Constructing high-density dislocations by primary (Nb,Ti)(C,N) to induce massive secondary precipitations in austenitic heat-resistant cast steel

The microstructural evolution and the high-temperature tensile properties of a novel Nb-Ti-N alloyed austenitic heat-resistant cast steel were investigated during the isothermal aging at 900 °C for up to 1000 h. The mechanisms of enhancing strength-ductility synergy and the high-temperature tensile fracture behaviors after the aging process were analyzed in detail through tensile tests at 900 °C. Obtained results show that the high-density dislocation regions and the Cr segregation, formed around the intragranular primary (Nb,Ti)(C,N), provided numerous nucleation sites for submicron-sized secondary M23C6 precipitates. The density of secondary M23C6 significantly increased, while the coarsening rate was notably reduced during the aging process. Simultaneously, the uniform dispersed precipitation of nano-sized secondary (Nb,Ti)C was promoted by massive dislocations, which exhibited high resistance to coarsening during long-term aging. The improvement of high-temperature strength was attributed to the precipitation strengthening effects induced by the submicron-sized M23C6 and nano-sized (Nb,Ti)C particles. Additionally, the enhancement of ductility during aging was mainly due to the more effective stress transmission and the ameliorated interface relationship between primary (Nb,Ti)(C,N) and austenitic matrix, which was facilitated by the abundant precipitation of secondary phases. The current findings indicate that high-density dislocations constructed by the intragranular primary (Nb,Ti)(C,N) induce the extensive dispersion of secondary strengthening phases, which enhanced both ultimate tensile strength of 158 MPa and elongation of 45.3% at 900 °C after isothermal aging for 1000 h.

High-temperature tensile behavior of AlSi7Mg parts built by LPBF under high-productivity conditions

High-temperature tensile behavior of AlSi7Mg parts built by LPBF under high-productivity conditions

In-situ X-ray computed tomography of high-temperature tensile behavior for laser powder bed fused Invar 36 alloy

The laser powder bed fusion (PBF-LB) process provides great potential for additive manufacturing of Invar 36 alloy, which possesses a unique low coefficient of thermal expansion. However, the high-temperature tensile behavior of PBF-LB processed Invar 36 alloy has not been explored, severely restricting its applications. Hence, herein, in-situ X-ray computed tomography (XCT) tensile tests were conducted at 200 °C and 600 °C for PBF-LB processed Invar 36 alloy, and the microstructure after heat treatment, fracture morphology, post-mortem microstructure, and nano-precipitates were observed. The in-situ XCT analysis of damage evolution reveals that the tensile behavior at elevated temperatures is sensitive to numerous closely spaced lack-of-fusion (LOF) pores with relatively large equivalent diameters, distributed in the adjacent melt pools or deposited layers. These LOF pores promote the stress concentration and facilitate rapid crack propagation, resulting in a significantly diminished strength and ductility. In contrast, the small number of metallurgical and keyhole pores, possessing large spacing and relatively high sphericity, have negligible influence on the tensile behavior. Therefore, Invar 36 alloy with only metallurgical and keyhole pores can be considered defect-free, displaying an excellent yield strength of 360.0 MPa and a considerable elongation of 65.0% at 200 °C. However, as the temperature increases to 600 °C, both the yield strength and elongation show a marked decrease to 150.0 MPa and 5.4%, respectively. This weakening is accompanied by the observation of a brittle fracture and the formation of secondary cracks. The degradation in mechanical properties can be attributed to the decomposition of Cr-containing SiP2O7, which leads to the formation of numerous small-sized SiO2 and P2O5 precipitates at 600 °C. These precipitates induce embrittlement of the grain boundaries and contribute to the formation of secondary cracks. The anomalous brittle fracture observed is attributed to the intergranular fracture mode, which results from the low grain boundary energy as well as the decomposition of nanoprecipitates. Additionally, the perpendicular orientation of flatter columnar grain boundaries to the loading direction plays a role in the formation of secondary cracks. This high-temperature mechanical performance of strength, elongation, failure mode, and corresponding microcosmic mechanism advances the understanding and widespread application of PBF-LB processed Invar 36 alloy.

Analysis of Hot Tensile Fracture and Flow Behaviors of Inconel 625 Superalloy.

In this work, Inconel 625 alloy is explored regarding high-temperature tensile deformation and fracture behaviors at a strain rate of 0.005-0.01 s-1 under a deformation temperature ranging from 700-800 °C. The subsequent analysis focuses on the impact of deformation parameters on flow and fracture characteristics. The fractured surface reveals that ductile fracture is dominated by the nucleation, growth, and coalescence of microvoids as the primary failure mechanisms. The elevated deformation temperature and reduced strain rate stimulate the level of dynamically recrystallized (DRX) structures, resulting in intergranular fractures. The Arrhenius model and the particle swarm optimization-artificial neural network (PSO-ANN) model are developed to predict the hot tensile behavior of the superalloy. It indicates that the PSO-ANN model exhibits a correlation coefficient (R) as high as 0.9967, surpassing the corresponding coefficient of 0.9344 for the Arrhenius model. Furthermore, the relative absolute error of 9.13% (Arrhenius) and 1.85% (PSO-ANN model) are recorded. The developed PSO-ANN model accurately characterizes the flow features of the Inconel 625 superalloy with high precision and reliability.

High-temperature tensile behaviors of a bimodal-grained Mg-Mn-Ce alloy

In this work, the high-temperature tensile behaviors of an extruded Mg-0.9Mn-0.5Ce (wt%) alloy with bimodal-grained microstructure were investigated, and the tensile tests were conducted at 423 K ∼ 523 K with the strain rate ranging from 6.0 × 10−3 s−1 to 1.5 × 10−1 s−1. It was found that the alloy exhibited a maximum fracture elongation of ∼156% and a highest strain-rate sensitivity exponent of 0.36 when deformed at 473 K. The softening effects generated by continuous dynamic recrystallization, the activation of < c + a > slipping on the pyramidal planes and grain boundaries migration collaboratively contributed to the high fracture elongation. As temperature increases to 523 K, microstructure stability was rapidly decreased and the deformation ability was severely restricted owing to the growth of grains, resulting in the adequate fracture elongation and low strain-rate sensitivity exponent.

Development of Fe–Cr–Si deposited layer manufactured by laser directed energy deposition process

In this study, the mechanical and corrosion characteristics of a corrosion-resistant layer made of stainless steel (STS) 316 L and Fe–Cr–Si alloy powder were investigated using laser-directed energy deposition (DED). In the STS 316 L deposited specimen, both the substrate and deposited layer were face-centred cubic (FCC). The deposited Fe–Cr–Si layer was clearly separated from the substrate because it was composed of body-centred cubic (BCC). Despite the phase differences, the surface of the Fe–Cr–Si-deposited layer showed a lower corrosion rate than that of the STS 316 L. All the deposited specimens exhibited typical high-temperature tensile behavior. However, the Fe–Cr–Si deposited layer at 600 °C showed a notable reduction in strength and increased elongation compared to the room temperature (RT) and 300 °C test results owing to the carbide concentration and phase transformation in the deposited layer. Because nuclear facilities mainly operate at temperatures below 600 °C, Fe–Cr–Si materials can also be used as nuclear piping coating materials. This study provides a mechanism for the high-temperature properties and corrosion resistance of the Fe–Cr–Si deposited layer and makes it competitive for application in fourth generation nuclear power systems.

Investigation of microstructures and high-temperature tensile behavior of heat treated GTD222 nickel-based superalloy prepared by selective laser melting

In this study, various heat treatment methods including direct aging and solution aging were performed on the selective laser melted (SLMed) GTD222 nickel-based superalloy, and the microstructures and high-temperature tensile behavior of the superalloys were systematically investigated. The results indicate that, in comparison to the as-deposited superalloy, both direct aging and solution aging lead to a significant enhancement in high-temperature strength and ductility. The directly aged superalloy exhibits a higher yield strength, while the solution-aged ones displays superior elongation. Specifically, at a tensile temperature of 760 °C, the superalloy subjected to a solution treatment at 1240 °C demonstrates the most favorable tensile properties, boasting a tensile strength of 835 MPa, an elongation rate of 6.5 %, and a reduction in area of 13 %. This study also provides a detailed discussion of the high temperature tensile behavior of the SLMed GTD222 superalloy after heat treatment.

Tensile creep mechanisms of Al-Mn-Sc alloy fabricated by additive manufacturing

The incorporation of Sc/Zr elements into aluminum (Al) alloys provides great opportunities for high temperature applications, due to the high coherency with the Al matrix, the high thermal stability and the high strengthening potentials of the generated Al3(Sc,Zr) precipitates. In this study, the microstructure, thermal stability, high temperature tensile and creep behaviors of additively manufactured Al-Mn-Sc alloy were systematically evaluated. The Al-Mn-Sc alloy demonstrated sound high temperature yield strength as compared with other reported Al alloys made by additive manufacturing. However, the formed large area fraction (approximately 60%) of fine grain boundaries significantly promoted the dislocation annihilation and reduced the creep threshold stress, though the inherent thermally stable solutes and/or precipitates contributed to its high creep activation energy. On the other hand, the primary Alx(Mn,Fe) and Aly(Sc,Zr) particles and the fine grain boundaries severed as the potential cavity nucleation sites, enhancing the cavity kinetics during creep loading. The cavity nucleation and coalescence process, which basically dominated the tertiary stage of the creep lifetime and led to the final fracture, were further revealed through a cavity evolution model. Future creep-resistant Al alloy design outlook, especially for the inoculates modified Al alloys with fine grain structures, were proposed based on the present findings.

Significant enhancement in high temperature performance of TiAl matrix composites by a novel configuration design

Ti5Si3/TiAl composites were successfully prepared by pressure infiltration and subsequent reactive annealing. Final microstructure of Ti5Si3/TiAl composites was dependent on the reactive annealing temperature, which varied from 1350 °C to 1420 °C, two typical microstructures could be achieved: (i) An unique core-shell structure (Core: fully lamellar α2-Ti3Al/γ-TiAl with in-situ synthesized Ti5Si3 particles predominantly distributed at the interfaces of α2/γ lamellar colonies; Shell: equiaxed γ-TiAl with Ti5Si3 particles distributed in γ grain boundaries); And (ii) A novel quasi-network structure composed of fully lamellar α2/γ and a majority of Ti5Si3 particles with a quasi-network distribution. The formation of the two microstructures could be attributed to the chemical composition heterogeneity which was caused by the difference in interdiffusion rate of Ti and Al elements in different annealing temperatures. The comparative investigations on high temperature tensile properties and creep behavior showed that the core-shell Ti5Si3/TiAl composites exhibited a better specific strength (165 MPa⋅g−1⋅cm3) and higher ultimate tensile strength (633 MPa) at 800 °C, which was 12 % higher than that of the quasi-network Ti5Si3/TiAl composites. While the creep behavior analysis showed that in compassion with equiaxed γ phase, the slip distance of dislocations in fully lamellar α2/γ phase was shorter, impeding the motion of dislocations more effectively. And core-shell Ti5Si3/TiAl composites possessed a large number of grain boundaries concentrating in the shell which became weaker in the high temperature, facilitating the formation of creep pores in the shell and the final premature fracture. Hence, the quasi-network Ti5Si3/TiAl composites containing a higher content of fully lamellar α2/γ exhibited a better creep resistance than that of core-shell Ti5Si3/TiAl composites. More importantly, the steady state creep rate at 750 °C under the fixed stress of 250 MPa of quasi-network Ti5Si3/TiAl composites was relatively low, only 3.305 × 10−8 s−1, comparable to that of third-generation TiAl alloys.

Microstructural evolution, high temperature tensile deformation behavior, and deformation mechanism in an Mg–Zn–Y–Ca–Zr alloy processed by multidirectional forging and hot rolling

To explore high temperature ductility, a new Mg-2.70Zn-1.34Y-0.37Ca-0.02Zr (wt.%) alloy has been fabricated by novel multidirectional forging (MDF) and hot rolling. The microstructure and mechanical properties were investigated. The average grain size of MDF + hot rolled alloy is 10.89 ± 0.90 μm refined from the as-cast average grain size of 60.03 ± 0.72 μm. The ultimate tensile strength of 260.51 ± 1.03 MPa, yield strength of 192.29 ± 1.21 MPa, and elongation of 17.83 ± 0.72 % were obtained at room temperature. For high temperature tensile behavior, microstructural examination revealed that continuous dynamic recrystallization and discontinuous dynamic recrystallization are the main softening mechanism in the temperature range of 573–673 K, while dynamic grain growth with bimodal grains and twins is discovered at 723 K in this alloy. X-ray diffraction and scanning electron microscopy –energy dispersive spectroscopy examinations revealed that the constituent phases are composed of α-Mg solid solution and intermetallic compounds of Ca2Mg6Zn3, Mg3YZn6 (I-phase), and Mg3Zn3Y2 (W-phase). The microstructural evolution, such as dynamic recrystallization and dynamic grain growth at desired tensile temperatures, is related to the thermal stability of constituent phases. The elongation to failure of 215.4 % was demonstrated at 673 K and 1.67 × 10−2 s−1, exhibiting high strain rate quasi-superplasticity. A power-law constitutive equation was established. The deformation activation energy of 177.948 kJ/mol and stress exponent of 4.494 revealed that the dominant deformation mechanism of this alloy at elevated temperatures of 573–723 K is dislocation climb controlled by lattice diffusion.

Tensile properties of Ti6.5Al2Zr1Mo1V titanium alloy fabricated via electron beam selective melting at high temperature

Here, near α titanium alloy TA15 (Ti-6.5Al–2Zr–1Mo–1V) samples were fabricated by electron beam selective melting (EBSM) and their high-temperature tensile deformation behaviors were studied at 773K–1023K. The results show that the tensile strength decreases gradually with the deformation temperature while the yield ratio increases as temperature increases from 773K to 923K, and then decreases gradually with further increasing the temperature. The deformation mechanism of EBSM-built TA15 samples at elevated temperatures can be ascribed to work hardening caused by the increase of dislocation density, and softening caused by the recovery and recrystallization. The studied TA15 alloy exhibits obvious work hardening behaviors at both 773K and 823K, dynamic recovery occurs during tensile deformation at 873K, and dynamic recrystallization plays a dominant role at 923K–1023K. The EBSM-built TA15 samples have excellent mechanical properties at medium temperatures, and the present results are helpful for the industrial applications of EBSM-built titanium alloy components in the aerospace fields.

High-Temperature Tensile Behaviour of GTAW Joints of P92 Steel and Alloy 617 for Two Different Fillers.

This study explores the high-temperature (HT) tensile rupture characteristics of a dissimilar gas-tungsten-arc-welded (GTAW) joint between P92 steel and Alloy 617, fabricated using ER62S-B9 and ERNiCrCoMo-1 fillers. The high-temperature tensile tests were performed at elevated temperatures of 550 °C and 650 °C. An optical microscope (OM) and a field emission scanning electron microscope (FESEM) were utilized to characterize the joint. The high-temperature test results indicated that the specimen failed at the P92 base metal/intercritical heat-affected zone (ICHAZ) rather than the weld metal for the ERNiCrCoMo-1(IN617) filler. This finding confirmed the suitability of the joint for use in the Indian advanced ultra-supercritical (A-USC) program. The fracture surface morphology and presence of precipitates were analysed using an SEM equipped with energy dispersive spectroscopy (EDS). The appearance of the dimples and voids confirmed that both welded fillers underwent ductile-dominant fracture. EDS analysis revealed the presence of Cr-rich M23C6 phases, which was confirmed on the fracture surface of the ER62S-B9 weld (P92-weld). The hardness plot was analysed both in the as-welded condition and after the fracture.

Ambient and high temperature tensile behaviour of DLD-manufactured inconel 625/42C steel joint

In recent years, much attention has been directed towards multi-material systems produced using additive manufacturing technologies. Especially directed energy deposition-based systems provide a powerful tool for relatively simple production of components with controlled chemical composition in certain directions and locations. In this contribution, the potential of bimetallic material manufacturing based on the combination of nickel alloy Inconel 625 and 42C steel using direct laser deposition process was investigated. The monolithic single material blocks as well as graded blocks with alternate material deposition order were produced and investigated via light and scanning electron microscope. In addition, the miniaturized tensile tests at ambient and high temperatures were performed. It was observed that the character of two-material joint changed with the order of deposited materials. Based on the maps of chemical composition, it was shown that joint Inconel 625 to 42C was rather gradual, while 42C to Inconel 625 had sharp distribution of the main elements around the fusion line. The tensile test results demonstrated that the location of preferential failure was the joint itself in the case of gradual interface regardless of the test temperature. On the other hand, the sharp joint failed within Inconel 625 material at room temperature, while at elevated temperature the failure was observed in 42C steel region.