High Temperature Tensile Tests Research Articles

Microstructure and Mechanical Properties at Elevated Temperature of Powder Metallurgy Al-Zn-Mg-Cu Alloy Subjected to Hot Extrusion

In this work, Al-Zn-Mg-Cu powders containing 0.15 and 0.33 wt % oxygen were utilized to prepare high-strength aluminum alloys through the process of cold isostatic pressing, sintering, hot extrusion, and heat treatment. Microstructural and mechanical properties at elevated temperatures of 250, 350, and 450 °C were investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and high-temperature tensile tests. Results showed that the tensile strengths of the obtained Al-Zn-Mg-Cu alloys with 0.15 wt % oxygen were 185, 46, and 18 MPa at 250, 350, and 450 °C, respectively. When the oxygen content of Al-Zn-Mg-Cu alloy rose to 0.33 wt %, the tensile strengths at the corresponding temperature reached up to 205, 68, and 25 MPa, respectively. The excellent high-temperature performance could be attributed to double hindrance to dislocation motion and grain boundary migration by a large amount of nano γ-Al2O3 created by the in-creased oxygen, thereby resulting in fine grains even at high temperatures.

Strengthening mechanism and effect of Al2O3 particle on high-temperature tensile properties and microstructure evolution of W–Al2O3 alloys

The W–Al2O3 alloy rods were successfully fabricated by the powder metallurgy process and hot swaging. Subsequently, the high-temperature tensile tests were conducted to characterize the mechanical properties of the W–Al2O3 alloy. At 800 °C, the ultimate tensile strength of W-0.25 wt% Al2O3 alloy is 611.1 MPa, which is 18% higher than that of pure W. After tension, the microstructure evolution was evaluated using metallographic microscope and transmission electron microscopy. For the pure W undergoing deformation at 1000 °C, dynamic recrystallization occurs, leading to the sharp decrease of the strength. However, the microstructure of the W-0.25 wt% Al2O3 alloy contains a large number of sub-grain and low-angle grain boundaries, which does not significantly change in the temperature range of 800–1200 oC, and the work hardening plays a leading role during the high-temperature deformation process. Due to high hardness, the dispersed Al2O3 particles effectively prevent the dislocation movement, displaying a significant strengthening effect.

Elevated temperature tensile properties of an extruded aluminium alloy reinforced with SiCp

Abstract Elevated temperature tensile properties of AlSi7Mg (Al-7 %Si– 0.7 %Mg) and its composites with 10 and 20 vol.% SiCp in the as-extruded form were investigated. The cast ingots of the matrix alloy and the composites were produced by the permanent die casting technique and extruded at 480 °C using an extrusion ratio of 10 : 1. The high-temperature tensile tests were carried out over the temperature range from 25 to 430 °C. Mechanical properties after extrusion show that the composite samples have strength values superior to that of the matrix alloy at ambient temperature. At elevated temperatures the results indicate that the composites exhibit good strength retention up to 300 °C, above which the strengthening effect of SiCp disappears as the temperature is increased. The strain rate sensitivity “m” was observed to be 0.11 for the matrix alloy, 0.13 and 0.07 for the composites with 10 and 20 vol.% SiCp, respectively, at a test temperature of 430 °C in the strain rate range from 4 × 10 –5 to 4 × 10– 2 s– 1.

Influence of Zr on grain orientation, texture, and mechanical properties in hot- and warm-rolled FeCrAl alloys

Iron–chromium–aluminum (Fe–Cr–Al) alloys have great potential application as an accident-tolerant fuel cladding material in light-water reactors. It has excellent processing ability, resistance to steam oxidation at high temperatures (HTs), and irradiation swelling-resistance. It is necessary to improve the room- and high-temperature mechanical properties and reveal the strengthening mechanism. In this study, we analyzed the effect of Zr on the microstructure and room- and high-temperature tensile properties of hot- and warm-rolled FeCrAl alloys. The results show that the Laves phase could be effectively stabilized by Zr addition, and the proportion of low-angle grain boundaries increased. Moreover, the yield strength at room and high temperatures of the samples after Zr addition were improved, owing to the precipitation and sub-grain boundary strengthening by Zr. In addition, Zr changed the grain orientation, but had no relevance to the number of easier activated slip systems. The movable dislocation cannot slip during high-temperature tensile tests because of the pinning effect of the dynamic precipitated Laves phase, which could be the reason for the decrease in elongation at high temperatures. • Zr addition stabilized the Laves phase effectively in Fe–Cr–Al alloys. • Zr addition increased the proportion of LAGBs in hot and warm rolled Fe–Cr–Al alloys. • Zr addition did not influence the number soft orientation grains in Fe–Cr–Al alloys. • The elongation of Fe–Cr–Al alloys decreased at the high temperature tensile tests.

Evolution of Iron-Rich Intermetallics and its Effect on the Mechanical Properties of Al-Cu-Mn-Fe-Si Alloys after Thermal Exposure and High-Temperature Tensile Testing

Evolution of Iron-Rich Intermetallics and its Effect on the Mechanical Properties of Al-Cu-Mn-Fe-Si Alloys after Thermal Exposure and High-Temperature Tensile Testing

Study on mechanical behavior and microstructure evolution of Al-Mg-Li alloy during electropulsing assisted uniaxial tensile

The mechanical behavior and microstructure evolution of Al-Mg-Li alloys under the effect of electric current was investigated using an electropulsing-assisted uniaxial tensile (EAUT) test combined with microstructure observations. It was found that the localized Joule heating-induced microscale high temperature at the grain boundaries in the necking zone significantly accelerated the grain boundary weakening when necking occurred, which resulted in rapid intergranular fracture and relevant decrease in elongation. Electropulsing induced continuous dynamic recrystallization (CDRX) in the both side layers and the discontinuous dynamic recrystallization (DDRX) in the intermediate layers of the Al-Mg-Li sheet during EAUT testing at 460 °C and higher, promoting the formation of newly near-equiaxed recrystallized grains and weakening of β-fiber texture components. For the conventional high temperature tensile test, only a small amount of recrystallized grains formed along the grain boundaries of the coarse parent grains under the control of DDRX. The occurrence of CDRX during EAUT was substantially attributed to the promoted effect of electropulsing on dislocation glide and climb, which resulted from the combined effect of microscale localized Joule heating around dislocations and the electro-induced enhancement effect on vacancy diffusion.

Hot Deformation Behavior and Strain Rate Sensitivity of 33MnCrB5 Boron Steel Using Material Constitutive Equations

In this paper, the constitutive equation parameters (Johnson–Cook parameters) of the 33MnCrB5 material were determined with the help of tensile tests. Initially, Johnson–Cook (JC) model was used for performing the simulations of the sample with finite element analysis with the help of ANSYS software. For these operations, the sample was first used at a certain temperature (24 °C) and low strain rates (10−1, 10−2, 10−3 s−1) and quasi-static tensile tests were performed. Then, high temperature tensile tests were performed with strain rate values of 10−3 s−1 at temperatures of 300 °C, 600 °C, and 900 °C, respectively. Finally, JC parameters belonging to test materials were found in accordance with the results obtained from the high temperature tensile and quasi-static tests. In the last stage, the results obtained from the simulation software for the yield stress, maximum stress, and elongation values were compared with the experimental results. As a result, deviation values for quasi-static tests are calculated as 5.04% at yield stress, 5.57% at maximum stress, and 5.68% at elongation, while for high temperature, yield stress is 9.42%, maximum stress is 11.49% and the elongation value is 7.63%. The accuracy of JC parameters was verified with the comparison made with the obtained data.

Effects of Stabilizing Heat Treatment on Properties of Simulated Microstructures in the Heat-Affected Zone of 347H Stainless Steel

In this paper, two kinds of heat affected zone (HAZ) simulation structures of 347H stainless steel, which are coarse grain zone (CGZ) and unmixed zone (UZ), were prepared by thermal simulator. The material properties of toughness, reheat crack susceptibility and intergranular corrosion susceptibility of the two kinds of HAZ simulation structures were studied by impact test, high temperature tensile test, electrochemical potentiodynamic reactivation (EPR) test and micro morphology test. The result shows that CGHAZ had better toughness. But after the stabilizing heat treatment, it was weakened while that of the UZ was enhanced. The reheat crack susceptibility of the CGZ and UZ both increases after stabilization heat treatment, and the tendency of the UZ are more obvious. Stabilizing heat treatment has a certain effect on the prevention of sensitization process, which can improve the intergranular corrosion resistance of the material. Stabilizing heat treatment is double-edged to 347H HAZ, and it needs combined with the specific situation to used.

The High-Temperature Tensile Test of Quartz Fiber Fabric- Reinforced Resin Composites

The tensile properties of quartz fiber fabric-reinforced resin composites at high temperature were studied. The effects of specimen type and dimension, temperature loading procedure, holding time and loading rate on the tensile properties of the composites at high temperatures were analyzed through series of comparative experiments, the tensile test parameters were determined. Chinese national standard for high-temperature tensile property testing of the composites was compiled based on the data collected. According to the established standard, the tensile testing at 500°C was carried out. Compared with the tensile properties at room temperature, the tensile strength and tensile modulus of the composite at high temperature decreases significantly, with the tensile strength decreasing by about 42.32% and the tensile modulus decreasing by about 24.18%. This is mainly due to the high temperature which causes part of the resin matrix to pyrolyze and detach from around the fiber, thus losing the integrity of the material. In addition, this national standard for high-temperature tensile properties has some general applicability to different types of fiber-reinforced resin composites.

Numerical and experimental investigations of built orientation dependent Johnson–Cook model for selective laser melting manufactured AlSi10Mg

Powder bed fusion based additive manufacturing techniques involve melting or sintering of powder particles via laser beams to join them in order to attain desired shapes. This study aims to provide basis for material constitutive parameters of widely used aluminum alloy AlSi10Mg alloy. Initially, tensile samples of AlSi10Mg alloy samples were manufactured by using SLM technology. Afterwards, through quasi-static and high temperature tensile tests, an attempt has been made to determine the Johnson–Cook material model of AlSi10Mg. in order to conduct quasi-static tensile tests, strain rates of 10−3 s−1, 10−2 s−1 and 5 × 10−2 s−1 were considered and tests were conducted at ambient temperature. Whereas, for high temperature tensile tests 24, 150, 300 °C temperature values were considered at the reference strain rate value of 10−3 s−1. The numerically simulated tensile results achieved by using the established Johnson–Cook model were then compared with experimental results. It was observed that the maximum error between the test and simulation results was around of 7.5%. The error percentage is well within the acceptable, thus proving the accuracy of the established material model.

Comparison of Mechanical and Microstructural Properties of as-Cast Al-Cu-Mg-Ag Alloys: Room Temperature vs. High Temperature

Unfolding the structure–property linkages between the mechanical performance and microstructural characteristics could be an attractive pathway to develop new single- and polycrystalline Al-based alloys to achieve ambitious high strength and fuel economy goals. A lot of polycrystalline as-cast Al-Cu-Mg-Ag alloy systems fabricated by conventional casting techniques have been reported to date. However, no one has reported a comparison of mechanical and microstructural properties that simultaneously incorporates the effects of both alloy chemistry and mechanical testing environments for the as-cast Al-Cu-Mg-Ag alloy systems. This preliminary prospective paper presents the examined experimental results of two alloys (denoted Alloy 1 and Alloy 2), with constant Cu content of ~3 wt.%, Cu/Mg ratios of 12.60 and 6.30, and a constant Ag of 0.65 wt.%, and correlates the synergistic comparison of mechanical properties at room and elevated temperatures. According to experimental results, the effect of the precipitation state and the mechanical properties showed strong dependence on the composition and testing environments for peak-aged, heat-treated specimens. In the room-temperature mechanical testing scenario, the higher Cu/Mg ratio alloy with Mg content of 0.23 wt.% (Alloy 1) possessed higher ultimate tensile strength when compared to the low Cu/Mg ratio with Mg content of 0.47 wt.% (Alloy 2). From phase constitution analysis, it is inferred that the increase in strength for Alloy 1 under room-temperature tensile testing is mainly ascribable to the small grain size and fine and uniform distribution of θ precipitates, which provided a barrier to slip by deaccelerating the dislocation movement in the room-temperature environment. Meanwhile, Alloy 2 showed significantly less degradation of mechanical strength under high-temperature tensile testing. Indeed, in most cases, low Cu/Mg ratios had a strong influence on the copious precipitation of thermally stable omega phase, which is known to be a major strengthening phase at elevated temperatures in the Al-Cu-Mg-Ag alloying system. Consequently, it is rationally suggested that in the high-temperature testing scenario, the improvement in mechanical and/or thermal stability in the case of the Alloy 2 specimen was mainly due to its compositional design.

Dynamic Softening and Hardening Behavior and the Micro-Mechanism of a TC31 High Temperature Titanium Alloy Sheet within Hot Deformation.

TC31 is a new type of α+β dual phase high temperature titanium alloy, which has a high specific strength and creep resistance at temperatures from 650 °C to 700 °C. It has become one of the competitive candidates for the skin and air inlet components of hypersonic aircraft. However, it is very difficult to obtain the best forming windows for TC31 and to form the corresponding complex thin-walled components. In this paper, high temperature tensile tests were carried out at temperatures ranging from 850 °C to 1000 °C and strain rates ranging from 0.001 s−1 to 0.1 s−1, and the microstructures before and after deformation were characterized by an optical microscope, scanning electron microscope, and electron back-scatter diffraction. The dynamic softening and hardening behaviors and the corresponding micro-mechanisms of a TC31 titanium alloy sheet within hot deformation were systematically studied. The effects of deformation temperature, strain rate, and strain on microstructure evolution were revealed. The results show that the dynamic softening and hardening of the material depended on the deformation temperature and strain rate, and changed dynamically with the strain. Obvious softening occurred during hot tensile deformation at a temperature of 850 °C and a strain rate of 0.001 s−1~0.1 s−1, which was mainly caused by void damage, deformation heat, and dynamic recrystallization. Quasi-steady flowing was observed when it was deformed at a temperature of 950 °C~1000 °C and a strain rate of 0.001 s−1~0.01 s−1 due to the relative balance between the dynamic softening and hardening. Dynamic hardening occurred slightly with a strain rate of 0.001 s−1. Mechanisms of dynamic recrystallization transformed from continuous dynamic recrystallization to discontinuous dynamic recrystallization with the increase in strain when it was deformed at a temperature of 950 °C and a strain rate of 0.01 s−1. The grain size also decreased gradually due to the dynamic recrystallization, which provided an optimal forming condition for manufacturing thin-walled components with the desired microstructure and an excellent performance.

Study on high temperature plasticity of Q390 microalloyed steel

In this paper, the effect of Al and Ti on the high temperature plasticity of Q390 microalloyed steel was studied. The high temperature tensile tests of two Q390 steels with different contents of aluminum and titanium (0.02%Al-0.01%Ti and 0%Al-0.02%Ti) were carried out on Gleeble 3800 thermal simulation test machine. The high temperature plasticity of the two steels was compared and analyzed by calculation of shrinkage ratio, fracture morphology and energy spectrum of the precipitates. The study indicated: The toughness of 0%Al-0.02%Ti steel is 12%-35% higher than that of 0.02%al-0.01%Ti steel in the III brittleness temperature zone. Aluminum has a negative effect on the high temperature plasticity of microalloyed steel, while titanium has a positive effect on the high temperature plasticity of microalloyed steel. Therefore, the surface quality of Q390 microalloyed steel is improved when Q390 is adopted the composition of 0%Al-0.02%Ti steel.

Study on controlled rolling and cooling process of CH1T steel High speed wire 1# shaoguan steel

Under the background that the high-grade industrial wire rod such as cold heading steel is mainly developed in the first line of Shaoguan Iron and Steel Co., Ltd., the controlled rolling and controlled cooling process of ultra-low carbon cold heading steel ch1t is studied in this paper. A large number of high-temperature tensile tests for CH1T are carried out on Gleeble 3800 thermal simulation testing machine, and the high-temperature plastic characteristics of CH1T and stress-strain curves at different temperatures are obtained, At the same time, the transformation points Ac1, Ac3, Ar1 and Ar3 of ch1t steel and the dynamic CCT curve were measured, and the process improvement measures were formulated on the basis of experimental research. The field practice shows that the proposed process improvement measures have greatly improved the problem of low yield of ch1t cold heading steel in the first high line of Shaoguan Iron and Steel Co., and achieved remarkable economic benefits.

Microstructure evolution and fracture mechanism of a TiAl–Nb alloy during high-temperature tensile testing

A TiAl–Nb alloy was prepared by casting, and its tensile properties and microstructure evolution at different temperatures were investigated. The results show that the brittle-ductile transition temperature (BDTT) of the alloy is 880–920 °C. At low temperatures, deformation mainly occurs in the γ lamellae and coarsening γ phase between the lamellar colonies. As the temperature increase in the transitory stage, a small number of dislocations may pass through the interface from the coarsening γ phase into the γ lamellae. During the brittle stage, the dislocation and dislocation array bow out from the phase interface, and twins are emitted from the phase interface, which may contribute to the accommodation of stress concentration. During the ductile stage, the γ lamellae coarsen due to the thinner and smaller α2 lamellae dissolving and phase boundary transfer. The dislocations interact with the dislocation walls to form subboundaries in the γ lamellae and transform into equiaxed crystals by dynamic recrystallization (DRX), which increases the plasticity of the alloy. With the transition from the brittle model to the ductile model, the fracture mode of the alloy changes from the mixed fracture mode of transgranular fracture and translaminar fracture to intergranular fracture.

Correlation of microstructure and mechanical properties of Ti2AlNb manufactured by SLM and heat treatment

Ti2AlNb intermetallic has a promising application in aeronautics and aerospace industries due to its high strength-to-weight ratio and high creep resistance at an elevated temperature. Selective laser melting (SLM) of this material has been emerging recently. The correlation of its microstructure and mechanical properties after the SLM and heat treatment determines the application of this material. In this paper, the process window of SLM for Ti2AlNb was determined. Characteristics of lath, acicular and grain boundary (GB) precipitates were studied after different heat treatments. The relation of solution heat treatment (SHT) temperature on the size and volume fraction of precipitates before and after aging treatment (AT) were established. High-temperature tensile test of the SLMed and heat-treated intermetallic were conducted. A relation between microstructure and mechanical properties was proposed. The change of the tensile strength and elongation at elevated temperature were rationalized. The results show that for the SLMed sample the dominating B2 phase led to a good room temperature ductility, but at 650 °C the continuous precipitation along the GB deteriorated the tensile strength and ductility. After SHT (920 °C) + AT, the maximum elongation (El) at 650 °C was significantly increased due to the precipitation of large-sized lath O+α2 phase. After SHT (1000 °C) + AT, the maximum ultimate tensile strength (UTS) of the tensile test at 650 °C increased to 820 MPa due to the precipitated acicular O phase.

Mechanical Properties and Resistance Coefficient of Carbon Steel during Fire

AbstractRecently, serious fire accidents have occurred on bridges. For example, the 9‐Mile Overpass located near Detroit, MI, USA, experienced serious damage, where the steel‐concrete composite girder bridge fell down. To avoid future instances of such events, we need to understand the effect of the decrease in hardness of carbon steel during fire on structural characteristics, and to clarify the collapse mechanism of a bridge. Fifty years ago, the Japan Society of Steel Construction (JSSC) defined the mechanical properties of carbon steel up to 900 °C. However, recently, there have been bridge fire incidents where the heat has exceeded an estimated 1000 °C. Therefore, it is necessary to conduct the high temperature tensile test above 900 °C. In Japan, the design method has changed from the allowable design method to the limited design method, and a fire design method for the safety, serviceability and restorability of bridges has not been established. In near future, we seek to clarify the resistance coefficient for fire design. Herein, we carry out the high temperature tensile test to determine the relationship between strength and temperature, and propose a resistance coefficient for fire design based on these results. The 1 % yield strength of SM400 (minimum tensile stress: 400 N/mm2) decreased on average by 26 % at 500 °C, and on average by 94 % at 1100 °C. It was found that the elongation of carbon steel is greatest at 800 °C.

Effect of Ni-interlayer on zinc-assisted liquid-metal-induced-embrittlement susceptibility of 22MnB5 galvanized steel

In this study, in-situ heat treatment and high-temperature tensile tests were performed to investigate the effect of an Ni-interlayer on the zinc-assisted liquid-metal-induced-embrittlement (LMIE) susceptibility of 22MnB5 galvanized steel. The heat treatment results indicated that the Ni-interlayer delays the diffusion between liquid Zn and steel substrate, and it can modify the phase composition of the coating. The high-temperature tensile test results showed that the strength and ductility of the 22MnB5 galvanized steel increased as the Ni-electroplating time increased, indicating that the Ni-interlayer could improve the strength and ductility of the 22MnB5 galvanized steel. The fracture type of the galvanized steel was brittle, while that of the Ni-interlayer galvanized steel was ductile, additionally, a U-shaped crack extending to the steel substrate was observed near the fracture of the galvanized steel, whereas no cracks extending to the steel substrate were observed near the fracture of the Ni-interlayer galvanized steel. In general, the Ni-interlayer can reduce the susceptibility of zinc-assisted LMIE; moreover, when the Ni layer was electrodeposited for 8 min, the property of the Ni-interlayer galvanized steel was found to be comparable to those of bare steel.

Influence of Post Weld Heat Treatment on the Grain Size, and Mechanical Properties of the Alloy-800H Rotary Friction Weld Joints.

This study evaluated the microstructure, grain size, and mechanical properties of the alloy 800H rotary friction welds in as-welded and post-weld heat-treated conditions. The standards for the alloy 800H not only specify the composition and mechanical properties but also the minimum grain sizes. This is because these alloys are mostly used in creep resisting applications. The dynamic recrystallization of the highly strained and plasticized material during friction welding resulted in the fine grain structure (20 ± 2 µm) in the weld zone. However, a small increase in grain size was observed in the heat-affected zone of the weldment with a slight decrease in hardness compared to the base metal. Post-weld solution heat treatment (PWHT) of the friction weld joints increased the grain size (42 ± 4 µm) in the weld zone. Both as-welded and post-weld solution heat-treated friction weld joints failed in the heat-affected zone during the room temperature tensile testing and showed a lower yield strength and ultimate tensile strength than the base metal. A fracture analysis of the failed tensile samples revealed ductile fracture features. However, in high-temperature tensile testing, post-weld solution heat-treated joints exhibited superior elongation and strength compared to the as-welded joints due to the increase in the grain size of the weld metal. It was demonstrated in this study that the minimum grain size requirement of the alloy 800H friction weld joints could be successfully met by PWHT with improved strength and elongation, especially at high temperatures.

Alloying effect of Mg on microstructure and mechanical properties at 300 °C of Al–5Cu–1Mn–0.5Ni heat-resistant alloy

The effect of Mg alloying on microstructure and mechanical properties at 300 °C of Al–5Cu–1Mn–0.5Ni heat-resistant aluminum alloy was investigated by microstructure observation and tensile test. Alloying with 0.5 wt%Mg addition considerably increases the yield strength at 300 °C of samples at as-cast, as-solutionized and as-aged states. It also greatly enhances the strengthening effects from solution and ageing treatments, however, simultaneously, decreases the elongation greatly. During the solidification process of the alloy with Mg addition, a great amount of whisker-like Al–Cu–Mg compound phase is formed at the eutectic boundary zones in the form of ridge configuration, which is determined as AlCuMg intermetallic compound by TEM. During the solution treatment, this whisker-like AlCuMg phase is completely dissolved into Al matrix that leads to a remarkable rise in the increment of yield strength at 300 °C by solution strengthening. The alloying of Mg has a significant influence on the precipitation behavior during the ageing treatment, for examples, promoting the formation of finer θ′′ particles and a great number of Cu–Mg atomic clusters. During high temperature tensile test, theses clusters evolve into fine cube-like Al5Cu2Mg particles with orthorhombic structure. It is the significant microstructure evolution induced by alloying of Mg that leads to the great rise in yield strength at 300 °C. Addition of Mg in Al–Cu–Mn–Ni alloy dose not lead to the formation of meta-stable or stable S phase, but whisker-like AlCuMg and cube-like Al5Cu2Mg compounds are determined by TEM.