High Temperature Tensile Behavior Research Articles

High Temperature Tensile and Fatigue Behaviors of Additively Manufactured IN625 and IN718

Recent advancement and research efforts in additive manufacturing (AM) have made it a promising technology to fabricate nickel-base superalloy parts in near net shapes. IN625 and IN718 are the commonly used superalloys in elevated-temperature applications in the aerospace and energy sectors. However, the fatigue performance of the additively manufactured (AM) components often depends on the defects like porosity, micro-cracks, and lack-of-fusions, etc. In addition, the presence of columnar grains and residual stresses also affects their fatigue performance. In this study, IN625 and IN718 specimens were fabricated via both laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) followed by stress-relief and standard heat treatments. Both alloys exhibited similar defect characteristics and grain morphologies. High-temperature fatigue properties of both IN625 and IN718 were tested at two strain amplitudes of 0.005 and 0.01 mm/mm and at two elevated temperatures of 427 and 625 °C. The fatigue lives of both alloys decreased with increasing testing temperatures. AM IN718 showed inferior fatigue performance at both test temperature and strain amplitudes in L-PBF conditions while in LP-DED condition both alloys have shown comparable fatigue performance.

High-Temperature Tensile and Creep Behavior in a CrMoV Steel and Weld Metal.

The 2.25Cr1Mo0.25V steel is a vanadium-modified 2.25Cr1Mo steel and is being widely used in the manufacture of heavy-wall hydrogenation reactors in petrochemical plants. However, the harsh service environment requires a thorough understanding of high-temperature tensile and creep behaviors of 2.25Cr1Mo0.25V steel and its weld for ensuring the safety and reliability of hydrogenation reactors. In this work, the high-temperature tensile and creep behaviors of base metal (BM) and weld metal (WM) in a 2.25Cr1Mo0.25V steel weldment used for a hydrogenation reactor were studied experimentally, paying special attention to its service temperature range of 350–500 °C. The uniaxial tensile tests under different temperatures show that the WM has higher strength and lower ductility than those of BM, due to the finer grain size in the WM. At the same time, the short-term creep tests at 550 °C reveal that the WM has a higher creep resistance than that of BM. Moreover, the creep damage mechanisms were clarified by observing the fracture surface and microstructures of crept specimens with the aid of scanning electron microscopy (SEM). The results showed that the creep damage mechanisms of both BM and WM are the initiation and growth of creep cavities at the second phase particles. Results from this work indicate that the mismatch in the high-temperature tensile strength, ductility, and creep deformation rate in 2.25Cr1Mo0.25V steel weldment needs to be considered for the design and integrity assessment of hydrogenation reactors.

Effects of Heat Treatment on High Temperature Mechanical Property and Corrosion Resistance of Hastelloy X Manufactured by Selective Laser Melting

In previous studies, the microstructure, mechanical properties and corrosion resistance of Hastelloy X fabricated by selective laser melting (SLM) have been investigated; however, it is hoped that heat treatment will effect on its properties. Therefore, this study is to discuss heat treatment effect on Hastelloy X fabricated by SLM. It is interestingly found that fracture strain greatly increases with heat treatment, and the yield ratio decreases, which demonstrates the material is more reliable. High temperature tensile behavior is discussed; it is worth mentioning that not only fracture strain of the HT sample increases greatly at 550∘C in comparison with SLM sample, but also ultimate tensile strength increases from 632 MPa to 639 MPa; the results show that the mechanical property can be improved at medium and high temperature by heat treatment. The corrosion resistance of HT sample deteriorates slightly, which can be explained by Cr-rich precipitates. In conclusion, the material after heat treatment is suitable for applications requiring high mechanical reliability and medium and high temperature occasions, but it is not befitting for corrosive environments.

High-temperature tensile and creep behaviour of Inconel 625 superalloy sheet and its associated deformation-failure micromechanisms

Thermal tensile and creep properties provide important information for selecting the suitable service conditions for metal materials. In this study, the effects of temperature on the tensile and creep properties, microstructure evolution, and deformation mechanisms of thermal-rolled Inconel 625 sheets were systematically investigated at 650 and 750 °C. The results showed that type B + C serrations dominated the tensile deformation at 650 °C. As the tensile temperature increased to 750 °C, type C serrations occurred in the early stages of the deformation and gradually transformed to type B serrations with the increase of the strain level. The microscopic observations through transmission electron microscopy (TEM) indicated that type B and C serrations were related to the carbon atom–moving dislocation interactions and nucleation–growth process of twin deformation, respectively. Moreover, the creep tests at 650 °C exhibited a better creep resistance than that at 750 °C. The results from the electron backscatter diffraction and TEM indicated combined grain boundary sliding and dislocation slipping as the main creep mechanisms at 650 °C. Moreover, the creep stress can accelerate the precipitation of the γ″ phases at 650 °C, which plays an important role in improving creep resistance, thereby improving the efficiency in strengthening Ni-based alloys. In addition, δ phase precipitation occurred during creep loading at 750 °C. The δ phases/matrix interfaces can act as nucleation sites to initiate dynamic recrystallization, which greatly affects the reduction of the work hardening rate and consequently, decreasing the creep resistance at 750 °C.

High temperature tensile, compression and creep behavior of recycled short carbon fibre reinforced AZ91 magnesium alloy fabricated by a high shearing dispersion technique

The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 μm) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91.

High-temperature tensile behaviors and microstructural evolutions of a directionally solidified Ti–45Al–5Nb–2Mn alloy

Investigations on the high-temperature tensile performances and deformation behaviors of the directionally solidified Ti–45Al–5Nb–2Mn alloy revealed that an increase in the tensile temperature resulted in the occurrence of brittle-ductile transition (BDT) and the BDT temperature was beyond 1173 K. The mixed mode of inter- and trans-lamellar fracture governed the brittle fracture, and except for dimples, there were split lamellae on the ductile fracture surface. The main cracks propagated along a tortuous path and multiple secondary cracks were formed adjacent to the main cracks. The dislocation mechanism controlled the high-temperature tensile deformation. The lamellar interface remained flat at 1073 K and 1173 K, but there was significant strain existing at the lamellar interface, which made the orientation relation of α2 lath and γ lath change to be (200)γ//(011‾0)α2and [001]γ//[0001]α2. At the tensile deformation of 1273 K, the lamellae coarsened irregularly by the phase degradation reaction of α2→γ and dynamic recrystallization.

Evaluation of high-temperature tensile behavior for metal foils by a novel resistance heating assisted tensile testing system using samples with optimized structures

To evaluate the tensile behavior of metal foils by resistance heating (RH) assisted tensile testing system accurately, this study proposed to embed a digital image correlation (DIC) system with laser speckles for the measurement of full-field strain distribution. Furthermore, the sample structures were optimized to achieve uniform temperature and strain distribution. An infrared camera was used to monitor the temperature distribution. Rectangular samples instead of dog-bone shaped samples were proposed. A model for calculating the temperature distribution was established to optimize the sample structure. The parameters that influence the temperature distribution and tensile behavior were studied. As results, compared to the strain measured by a non-contact extensometer, the maximum deviation of the strain measured by DIC was less than 6% when the nominal strain was larger than 0.013. It is confirmed that the proposed tensile testing system is reliable for measuring the temperature and full-field strain distributions. Sample shape influenced temperature distributions of smaller samples while it almost had no influence on the temperature distributions of larger samples. The temperature difference was not affected by the material type but by the sample size. The proposed rectangular shape was validated to be feasible for RH assisted tensile testing. The sample length was successfully optimized for a more uniform temperature distribution by the established model. Although the tensile deformation was not influenced by the sample shape, the temperature distribution resulted in a non-uniform strain distribution before achieving ultimate tensile strength. Longer effective sample length between two clamping jigs contributed to a more uniform temperature distribution and material deformation. A more accurate evaluation of high-temperature tensile behavior for metal foils can be achieved by the proposed RH assisted tensile testing system using rectangular samples with an optimized structure.

Corrigendum to “The metallurgical bonding and high temperature tensile behaviors of 9Cr-1W steel and 316L steel dissimilar joint by friction stir welding” [J. Manuf. Process. 44 (2019) 241–251

Corrigendum to “The metallurgical bonding and high temperature tensile behaviors of 9Cr-1W steel and 316L steel dissimilar joint by friction stir welding” [J. Manuf. Process. 44 (2019) 241–251

Corrigendum to “The metallurgical bonding and high temperature tensile behaviors of 9Cr-1W steel and 316L steel dissimilar joint by friction stir welding” [J. Manuf. Process. 44 (2019) 241–251

Corrigendum to “The metallurgical bonding and high temperature tensile behaviors of 9Cr-1W steel and 316L steel dissimilar joint by friction stir welding” [J. Manuf. Process. 44 (2019) 241–251

Experimental and Numerical Analysis of Microstructure and High-Temperature Tensile Behavior of a Directionally Solidified Superalloy

A comprehensive cellular automaton algorithm coupled with finite element method was developed for the simulation of temperature field, heat transfer characteristics and the anisotropic grain growth during a directional solidification (DS) process. Nucleation parameters at the interface of the alloy and the chill plate were adjusted at four levels, and the evolution of macrostructure during competitive growth of grains has been characterized. The sensitivity of grain structure to heat transfer coefficients between alloy/chill plate and alloy/ceramic mold was also evaluated at a constant nucleation condition. The results were compared with the microscopic images and measurements of the experimentally cast DS specimens. This model was then utilized for the development of another micro-mechanical finite element model of the cast bars including the realistic grain boundaries and misorientations. To complete a simulation of a whole manufacturing chain from casting process to mechanical behavior evaluation, high-temperature tensile behavior of the cast bars was then elucidated through experiment and FE analysis.

Effect of samarium on the high temperature tensile properties and fracture behaviors of Al–Zn–Mg–Cu–Zr alloy

The Al-6.7Zn-2.6Mg-2.0Cu-0.1Zr alloy is modified by Sm for the purpose of improving its mechanical properties at high temperatures. According to the results, the as-cast structure can be refined through 0.3% Sm modification treatment, and finer precipitates can be obtained after aging. In the meantime, with the addition of Sm, a new high melting point Al10Cu7Sm2 phase is formed, the initial decomposition temperature of the alloy is raised, and the thermal stability is enhanced. As indicated by the tensile test results at room temperature and high temperatures, the strength of the modified sample was improved compared with the unmodified alloy. According to fracture surface analysis, ductile fracture conforms to the fracture characteristic exhibited by the modified alloy at room temperature and high temperatures. The improvement on high temperature strength of the modified alloy is attributed largely to a combination of grain refinement, precipitation strengthening and heat resistant phase to grain boundary pinning.

Effect of annealing temperature on microstructure and high-temperature tensile behaviour of Ti-6242S alloy produced by Laser Powder Bed Fusion

This work is focussed at investigating the properties of additive manufactured Ti-6242S, a Ti alloy with excellent mechanical strength and stability up to 550 °C. Special attention is given to the ...

High-temperature tensile characteristics and constitutive models of ultrahigh strength steel

Abstract In this investigation, the isothermal tensile experiments over wide ranges of deformation parameters (strain rate and tensile temperature) are conducted for studying the high-temperature tensile behaviors of an ultrahigh strength steel. The influences of deformation parameter on high-temperature tensile behaviors, fracture characteristics and deformation mechanisms are analyzed. Moreover, Arrhenius-type phenomenological (AP) model developed by the regression method or the Nelder-Mead (NM) simplex method, and the artificial-neural-network (ANN) model developed by combining genetic algorithm (GA) and back propagation learning algorithm (BP) are proposed, respectively. The results show that the high-temperature tensile behavior of the studied steel exhibits the typical work hardening and dynamic recovery characteristics. The necking capability increases with the strain rate decreasing and tensile temperature increasing. However, the large deep dimples dramatically deteriorate the loading capability during the localized necking, leading to the poor elongation to fracture at low strain rate. Both for the modeling and verifying data, the AP model developed by the NM simplex method shows the relatively high relative coefficient (higher than 0.9963), low average absolute relative error (lower than 1.6692%) and narrow error band (controlled in ±6.8MPa), compared with the AP model developed by the regression method and the GA-BP ANN model.

High-temperature tensile and creep behavior of Cu–Nb composites: A discrete dislocation plasticity investigation

Tensile and creep responses of Cu–Nb composites are predicted at 400°C using a high-temperature discrete dislocation plasticity (DDP) framework where the multilayer composites are idealized as two-dimensional unit cells with periodic boundary conditions. Considering the fact that the interfaces in multilayer composites dominate their plastic response, bi-material interfaces are treated here so as to store lattice dislocations via formation of steps at the interfaces. While dislocations in the Nb layer are assumed to move by glide-only at 400°C, they move by a combination of glide and climb in the Cu layer at this temperature. Material parameters for the layers are obtained at 400°C by fitting the DDP predictions of the tensile response of Cu–Nb composites to the experimental data corresponding to the composites with the layer thickness in the range 65nm≤h≤2μm. Using these material parameters, the framework enables quantitative predictions of the creep responses of these composites at 400°C, which are in very good agreement with the available experimental data. Investigations of the results demonstrate that: (i) the creep response of Cu–Nb composites, in line with observations, is dependent on the laminate length scale h as well as on the stress indicating that the creep behavior is dislocation dominated; (ii) the average stresses within the layers remain almost unchanged (with some fluctuations) during the time history indicating that there is a limited load transfer between the Nb and Cu layers during the creep process; and (iii) the dislocation and step densities in the Cu layers are higher than those in the Nb layers implying that the interfaces interact with a high flux of climbing dislocations from the Cu layers. Predictions of the deformed shapes of the Cu–Nb composites including the deformed configurations of the interfaces imply that annihilation of climbing Cu dislocations at the interfaces is the dominant interaction mechanism that occurs at the interfaces. This resembles a recovery mechanism in the bi-material interfaces that facilitates dislocation generation and movement in the Cu layers and thus enhances the creep strains.

On the High-Temperature Flow Response of Friction Stir Processed Magnesium Metal Matrix Composites

AbstractIn the current work, multi-pass friction stir processing (FSP) was utilized to fabricate samples of fine-grained aluminum–zinc (AZ) magnesium alloy and its metal matrix composite (MMC). The microstructure and high-temperature tensile behavior of friction stir processed (FSPed) AZ31 and AZ31/SiC MMC at various strain rates in the range of 10−2 to 10−4 s−1 were investigated, and the fracture mechanisms of each condition were analyzed. The results verified that MMC samples exhibited a remarkable enhancement in microhardness. The evolution of inclined basal texture was observed after processing for both FSPed and MMC samples. The ambient temperature stress–strain response revealed that the formability of AZ31 has improved after friction stir processing, whereas high-temperature flow curves were discernibly sensitive to strain rate. Equiaxed deep dimples were detected on the fracture surfaces of FSPed samples, but decreased strain rate led to an increase in the number of dimples as attributed to the recrystallization of new grains.

High-temperature tensile behavior of 3D SiC/SiC composites

The high-temperature tensile properties and stress-strain behavior of a 3D SiC/SiC composites prepared by the PIP method were investigated. Based on the FESEM analysis of the fracture morphology, the tensile failure mechanism of the composite at elevated temperature was discussed. The results show that the tensile strength of SiC/SiC composites showed a significant decline for specimens from a room temperature value of 482.5 MPa, to 167 MPa and 138 MPa at 1100 °C and 1300 °C, respectively. The toughening mechanism of composites at 1100 °C, including interface debonding, long pull-out fibers, and fracture mirror characteristics, is consistent with the pseudo-plastic fracture behavior implicated in the stress-strain curve. As a result of more significant oxidation, the fracture morphology of the specimen tested at 1300 °C was characterized by the signs including fiber-to-fiber bonding, larger size glassy phase, and shorter fiber pull-out length.

Influence of copper content on the high temperature tensile and low cycle fatigue behavior of cast Al-Cu-Mn-Zr alloys

The relationship between low cycle fatigue (LCF) and monotonic tensile fracture strain was investigated for cast Al-Cu-Mn-Zr alloys containing 6 and 9 wt% Cu at 250 °C. The 9% Cu alloy consisted of larger size and volume fraction of brittle intermetallic grain boundary particles that fractured during tensile tests to reduce the fracture strain by 50% compared to the 6% Cu alloy. LCF life was similar between the two alloys and weakly influenced by the particles. LCF life and fracture strain were poorly correlated due to the dominant influence of particles on monotonic tensile crack but not on fatigue crack.

High-temperature Tensile Behavior in Coarse-grained and Fine-grained Nb-containing 25Cr–20Ni Austenitic Stainless Steel

In this study, tensile behavior of Nb-containing 25Cr–20Ni austenitic stainless steels composed of coarse or fine grains has been investigated at temperatures ranging from room temperature to 900 °C. Results show that the tensile strength of fine-grained specimens decreases faster than that of coarse-grained specimens, as the test temperature increases from 600 °C to 800 °C. The rapidly decreasing tensile strength is attributed to the enhanced dynamic recovery and recrystallization, because additional slip systems are activated, and cross-slipping is accelerated during deformation in fine-grained specimens. After tensile testing at 700–900 °C, sigma phases are formed concurrently with dynamic recrystallization in fine-grained specimens. The precipitation of sigma phases is induced by simultaneous recrystallization as the diffusion of alloying elements is accelerated during the recrystallization process. Additionally, the minimum ductility is observed in coarse-grained specimens at 800 °C, which is caused by the formation of M23C6 precipitates at the grain boundaries.

High temperature tensile properties, deformation, and fracture behavior of a hybrid-reinforced titanium alloy composite

In present work, a hybrid-reinforced titanium alloy has been β forged and heat treated successively. The microstructure evolution, deformation mechanism and fracture behavior were investigated to evaluate the contribution of HT on strength. The fine zone was formed after HT at the prior β grain boundary, and the (TiB + TiC + Y2O3) reinforcement could significantly enlarged the area of fine zone and homogenized the microstructure. Silicide precipitation was also observed in intra lamellar and α/β boundary after HT, thereby increasing the strength via Orowan strengthening mechanism. In addition, the deformation mechanism analysis indicated that the grain boundary slip contributed a great effort to the high temperature deformation during tensile testing. Due to the formation of fine zone and silicide precipitation, the grain boundary strength and intragranular strengths both improved. However, the equal-strength temperature improved more thus leaded to a high yield strength in (TiB + TiC + Y2O3)/α-Ti composite after HT. This result also had a substantial influence on fracture morphology, which achieved considerable strength in the matrix and composite at elevated temperature.

Constitutive Equation and Hot Processing Map for Tensile Test of Mg-13Gd-4Y-2Zn-0.5Zr Alloy at Elevated Temperature

The high temperature tensile behavior of Mg-13Gd-4Y-2Zn-0.5Zr alloy was investigated at deformation temperature of 400-520 °C and strain rate of 0.001-0.5 s-1, and the stress-strain curves were obtained by using INSTRON 3382. The high temperature tensile constitutive model and hot processing map of the alloy were established, and the reliability of the hot processing map was further verified by analyzing the microstructure of the deformed alloy. The results showed that the dynamic recrystallization (DRX) occurred of Mg-13Gd-4Y-2Zn-0.5Zr alloy during the tensile tests under high temperature conditions, and its peak stress decreased with the increase of deformation temperature or strain rate. The Arrhenius equation can be used to fit the rheological behavior of the alloy. The thermal deformation activation energy Q was 259.13kJ/mol, and the maximum error between the model and the experimental data was less than 9%. It can be concluded that the optimum deformation parameters of the alloy were temperature of 500-520 °C and strain rate of 0.01-0.001 s-1 based on the dynamic material model and hot processing map.