High Temperature Deformation Properties Research Articles

Influence of Alloying Elements Content on High Temperature Properties of Ti-V-Cr and Ti-Al-V Series Titanium Alloys: A JMatPro Program Calculation Study

For the issues of high temperature performance affected by the alloying elements content in Ti-V-Cr and Ti-V-Cr alloys, the thermodynamic calculation method based on JMatPro program was applied in this study. The research is mainly focused on the analysis of phase composition, thermodynamic parameters and mechanical properties of Ti-Al-V and Ti-V-Cr series alloys with different element proportions under high temperature environment. Those obtained results show that the proportion of Al in Ti-Al-V alloys has a great influence on the high temperature properties. Increasing the content of Al not only increases the transformation temperature of β single-phase structure and delays the transformation process of α/β microstructure to β single-phase structure, but also helps to improve the high temperature thermal conductivity and elastic deformation resistance of the alloy. In Ti-V-Cr alloys, the influence of V element on high temperature properties is mainly focused on the improvement of thermal conductivity and high temperature deformation properties, while the influence of Cr element is relatively weak. Besides, adding a small amount of Al element to Ti-V-Cr alloy can further improve the thermal conductivity of the alloy. The Young’s modulus of the Ti-V-Cr alloy increases when 0.3%-1% of C element is added. Finally, the effect of Si element on the high temperature elastic deformation of the alloy is relatively weak.

Evaluation of High-Temperature Creep Deformation Properties of Warm-Mix Recycled Asphalt Mixture Based on Improved Flow Number

Evaluation of High-Temperature Creep Deformation Properties of Warm-Mix Recycled Asphalt Mixture Based on Improved Flow Number

Impression creep deformation behaviour of FSWed AA6061 at various weld zone

ABSTRACT Impressioncreep (IC) tests were performed at three welded regions viz: nugget zone (NZ), thermo-mechanical affected zone (TMAZ) and heat affected zone (HAZ) at 326°C, 359°C and 378°C of furnace temperature and equivalent stresses of 24MPa, 28MPa and 32MPa respectively. The high temperature deformation properties were estimated by employing power law creep equation and the results were compared with the base material (BM). The rate controlling mechanism of IC process at each selected area and its correlation with the microstructural evolution throughout FSW and IC procedures were realised. The steady-state creep rate of NZ was estimated to be the highest and of BM was the lowest. The other creep parameters such as the stress exponents and the apparent activation energy for the IC process were calculated at each localised zones for the welded material and were compared with the BM. The creep deformation was found to be homogeneous at all the selected testing areas and was of dislocation type. Creep rate was found to be affected by the grain size and testing temperature. Detail microstructural analysis of the samples before and after the IC test was performed by optical microscope.

High-temperature deformation properties of CuCr0.6 alloy

High-temperature deformation properties of CuCr0.6 alloy

Mechanical and high-temperature deformation properties of Ti–43.5Al–3V–2Nb alloy

We studied mechanical properties and deformation behavior of Ti–43.5Al–3V–2Nb alloy at high-temperatures. Stress–strain curves demonstrated standard work-hardening and flow-softening characteristics,and the data obtained from these curves were used to obtain a corresponding formula to calculate activation energy (which was qual to 565 kJ mol−1). Dynamic materials modeling was used to develop a processing map with a true strain equal to 0.6. Ti–43.5Al–3V–2Nb alloy with an equiaxed structure has a wide processing window. Instability zones were in the 1000 °C–1050 °C and >0.5 s−1. Flow-soft mechanism in the unstable region is related to stress-relaxation due to the incompatible deformation of each phase. Flow-soft mechanism in the safe region is related to the dynamic recrystallization and dynamic recovery of γ, α and β polymorphic modifications. Heat treatment at 1235 °C for 60 min/AC + 900 °C/6 h/FC improved room-temperature tensile properties of the forged alloy significantly: tensile strength was 920MPa and tensile ductility was 2.5%. Thus, the alloy demonstrated excellent combination of high strength and ductility after this heat-treatment. Heat-treated Ti–43.5Al–3V–2Nb alloy also maintained tensile strength higher >820 MPa up to 750 °C.

In situ scanning electron microscopy-based high-temperature deformation measurement of nickel-based single crystal superalloy up to 800 °C

In situ observation and measurement of high-temperature deformation of hot-section materials in scanning environments is helpful in understanding the microscopic failure and fracture mechanisms of these materials and estimating their safe life cycles. However, in situ high-temperature measurements in a scanning electron microscopy (SEM) environment pose major challenges in high-efficiency heat source design, establishment of stable high-contrast microscopic images, and quantitative measurement of the deformation fields in the high-temperature environment. New methods and approaches must be therefore developed for quantitative measurement of these high-temperature mechanical properties. This article reports use of in situ SEM to measure the high-temperature deformation and fatigue properties of a nickel-based single crystal superalloy (NBSCS) up to 800 °C. A conductive heating source has been constructed based on numerical calculations of the thermal field inside the SEM chamber and analysis of the secondary electron spectrum and thermionic emissions received by the detector. Al2O3 nano-scale particles were coated on the NBSCS surfaces and were used to form speckle patterns to measure the deformation of NBSCS from room temperature up to 800 °C via a digital image correlation technique. The stable spatial geometric configuration and enhanced interfacial strength between the Al2O3 particles and the sample surface with increasing temperature validate the developed high-temperature speckle patterns. Tensile and fatigue experiments are performed for NBSCS samples using the developed system. Full-field displacements are obtained near the notch root and in situ fatigue crack propagation is reported in the temperature range from 600 °C to 800 °C.

Evaluation of deformation properties of asphalt mixture using aggregate slip test

Asphalt mixture is a multiphase particulate material composed of aggregate, asphalt and filler. The deformation property of asphalt mixture is an external reflection of aggregate slip behaviour. To evaluate the high-temperature deformation properties of asphalt mixture, an aggregate slip device was developed and aggregate slip tests were conducted on five asphalt mixtures for different gradations under different test conditions. Four evaluation parameters, the slip failure load (Fs), the slip failure deformation (Ds), slip modulus parameter (M) and slip energy index (SEI), were obtained according to the load–displacement curves. The relationship between these parameters and rut depth (RD) was analysed. The effects of test temperature and asphalt content on slip resistance of asphalt mixture are studied in this research. The results indicate that the parameter Fs has limitations for large nominal maximum particle-size mixture, and SEI is an effective parameter to evaluate the aggregate slip properties for different nominal maximum particle-size asphalt mixtures. SEI has the strongest relationship to RD, which is the best parameter to evaluate the slip deformation behaviour of asphalt mixture. With the increase in asphalt content, SEI has a peak value and a valley value. When the optimum asphalt content is used in asphalt mixture, aggregate skeleton effect and asphalt cohesive force can both reach a high level, and asphalt mixture has the best deformation resistance.

High-Temperature Compressive Properties of TiC-Added Mo-Si-B Alloys

High-temperature compressive properties of two TiC-added Mo-Si-B alloys with nominal compositions of Mo-5Si-10B-7.5TiC (70Mo alloy) and Mo-6.7Si-13.3B-7.5TiC (65Mo alloy) (at.%) were investigated. The alloys were composed of four constituent phases: Mo solid solution (Moss), Mo5SiB2, (Mo,Ti)C, and (Mo,Ti)2C. The primary phases of the 70Mo and 65Mo alloys were Moss and T2, respectively. The compressive deformability of the 65Mo alloy was significantly limited even at 1600°C because of the elongated, coarse primary T2 phase, whereas the 70Mo alloy had good compressive deformability and a high strength in the test-temperature range of 1000–1600°C; the peak stresses were 1800 MPa at 1000°C, 1230 MPa at 1200°C, and 350 MPa at 1600°C. At and above 1200°C, the peak stress values were more than double those of Mo-6.7Si-7.9B, Ti-Zr-Mo, and Mo-Hf-C alloys. The plastic strain in the 70Mo alloy at temperatures lower than the ductile–brittle transition temperature of T2 was generated by plastic deformation of not only Moss but also of (Mo,Ti)C and (Mo,Ti)2C. This work indicates that (Mo,Ti)C and (Mo,Ti)2C play an important role in determining the high-temperature strength and deformation properties of TiC-added Mo-Si-B alloys.

듀플렉스 스테인레스 소재의 고온 변형 안정성 및 어닐링 온도에 따른 특성 분석

The aim of this study was to analyze high temperature deformation stability and properties of duplex stainless steels(DSS) according to annealing temperature. In order to analyze high temperature deformation stability, a number of compression tests were carried out with a stain rate of 10 s~10 s up to a compression ratio of 50% in a temperature range of 950°C-1300°C. The analysis of high temperature deformation stability of DSS was performed based on the Ziegler model. In order to analyze the high temperature properties of DSS, annealing treatments were conducted by isothermal holding for 1 hr at 950°C to 1300°C with 50°C intervals followed by water cooling. The hardness and tensile tests were performed on specimens with different volume fractions of constituent phases, such as austenite, ferrite and sigma. The hardness and tensile strength of 2507 according to the annealing temperature are better than those of 2205. The strain rate sensitivity and Ziegler parameter are higher in 2205 than in 2507 as a whole, which implies that 2205 is better than 2507 in terms of forgeability at high temperature. (Received January 25, 2012)

502 7075アルミニウム合金の摩擦撹拌接合継手の撹拌部における高温変形特性

502 7075アルミニウム合金の摩擦撹拌接合継手の撹拌部における高温変形特性

Dependence of heating rate in PCAS on microstructures and high temperature deformation properties of γ-TiAl intermetallic alloys

The effect of heating rate in Resistance Sintering on resulting microstructures and properties was not widely explored. For the purpose of obtaining γ-TiAl alloys with fine grains, synthesis of coarse pre-alloyed TiAl powders was carried out with relatively high heating rate on self-built similar sintering device named pulse current auxiliary sintering apparatus (PCAS). The effect of heating rate on microstructures and high temperature ductility was investigated. And high temperature tensile behavior and fractography were compared between the two obtained original microstructures. The results show that relatively high heating rate is beneficial for obtaining fine-grained microstructures. And the resultant intermetallic alloy with equiaxed near gamma microstructures exhibits superplastic properties at relatively low temperature.

High strain rate superplasticity in continuous cast Al–Mg alloys prepared via friction stir processing

Friction stir processing (FSP) is very effective in refining the grain size of as-cast alloys. In this work, the effect of five FSP conditions on the high-temperature deformation properties of a continuous cast Al–Mg alloy has been investigated. It was observed that FSP broke down the cast structure and refined the grain size to less than 3 μm, enabling tensile elongation of over 800% at 530 °C with a strain rate of 3 × 10−2 s−1.

Effect of texture on the high temperature mechanical properties of Nb–1%Zr alloy

High temperature deformation properties of Nb–1%Zr alloy were evaluated with a special emphasis on the texture effect. Fully recrystallized Nb–1%Zr samples with different crystallographic textures were prepared by annealing 80% cold-rolled foil at 1500 °C for 2 h. Subsequent tensile tests at 1100 °C showed that the sample oriented in the rolling direction is about 20% stronger than that oriented 30° to the rolling direction.

611 Co-Ni-Cr系超高弾性合金の再結晶と高温変形特性(オーガナイズドセッション : 超成形・超塑性と材料)

611 Co-Ni-Cr系超高弾性合金の再結晶と高温変形特性(オーガナイズドセッション : 超成形・超塑性と材料)

高強度Ａｌ‐Ｚｎ‐Ｍｇ‐Ｃｕ系Ｐ／Ｍ合金押出材のミクロ組織微細化と高速超塑性特性

The effects of thermo-mechanical treatment (TMT) on grain refining and high temperature deformation properties have been investigated for the alloy with chemical composition of Al–9.6Zn–3.0Mg–1.4Cu–0.04Ag–0.4Zr in mass% fabricated by hot-extrusion from rapidly solidified powders The present TMT consisted of aging at 498 K for precipitation of T phase (Mg32(Zn, Al)49) and subsequent warm rolling at the same temperature. Due to aging up to 7.2 ks at 498 K, extremely fine T phase precipitated homogeneously in the matrix. At the next warm rolling step, those fine precipitates contributed to form the uniform dislocation cell structure with high number density. The microstructure analysis by means of XRD and TEM made clear that their dislocation cell structure recrystallized continuously and transformed to very fine (sub-) grain structure with average size of 0.45 μm at the tensile testing temperature of 718 K. The fine grain structure was stabilized by the distribution of fine Al3Zr particles. Thus the high strain rate superplastic behavior realized for the warm rolled specimens after aging at 498 K for about 7.2 ks. On the other hand, the warm rolled specimens after aging at 498 K for the longer time than 18 ks formed a very coarse grain structure and resulted in a poor superplasticity. The reason has been discussed on the basis of discontinuous recrystallization theorem.

金属化合物の粉末冶金と諸物性 ＨＩＰ法により製造したＴｉＢ２−ＴｉＡｌ複合材料の高温変形特性

金属化合物の粉末冶金と諸物性 ＨＩＰ法により製造したＴｉＢ２−ＴｉＡｌ複合材料の高温変形特性

微細結晶粒を有するSUS304の高温変形挙動に及ぼす残留マルテンサイトの影響

The high temperature deformation properties of two stainless steels, austenite single phase and austenite/martensite dual phases have been studied. These two materials were not conventionally produced but reversely transformed into austenite phase from martensite phase which was induced by large plastic deformation on austenitic stainless steel SUS304 (similar to AISI304) below the temperature of Md point.Tensile tests on both alloy sheets with initial grainsize refined below 1μm by such above processing have been conducted at different temperatures from 923K to 1023K at strain rates ranging from 3.0 × 10-5to 1.0 × 10-2 s-1. These both materials exhibit a maximum elongation exceeding 200 pct with very low flow stress. The dual phase material shows more elongation and less flow stress in comparison with the single phase material, and the lower testing temperatures or the higher strain rates, the larger this tendancy becomes clearly. This is the reason why a slight martensite phase which is included in the dual phase material prevents the grain size of austenite phase from coasening during large deformation.

High- temperature deformation properties of nial single crystals

The high-temperature deformation properties of stoichiometric NiAl single crystals have been studied in the temperature range from 850 °C and 1200 °C. We have established a basic data set for and have explored the high-temperature deformation characteristics of this intermetallic compound. The results provide a basis for determining the controlling mechanisms of high-temperature deformation. Constant stress tension creep and constant stress or constant strain rate compression experiments were conducted on crystals oriented with loading axes along the “hard,” [001] orientation, where no driving force exists for glide ofb = (001) dislocations, and along various “soft” orientations, [223], [111], and [110], where deformation can occur by the glide of these dislocations. In addition to these monotonie tests, high-temperature deformation transients were studied using stress relaxation, strain rate change, and stress change experiments. These transient deformation experiments were conducted in an effort to further elucidate the mechanisms that control high-temperature deformation of this material. The steady-state deformation properties of these differently oriented single crystals can be characterized by creep activation energies that all coincide, within experimental error, with the activation energy for diffusion of Ni in NiAl, 308 ± 10 kJ/mol. The stress dependence of steady-state deformation can be characterized with stress exponents that range from about 9 at 850 °C to about 4 at 1200 °C. At all temperatures and stresses, the soft oriented crystals creep about two orders of magnitude faster than the hard oriented crystals at the same stresses and temperatures. Soft oriented crystals loaded along [223] and [111] axes tested in both tension creep and constant stress or constant strain rate compression are found to deform at the steady-state rate from the very beginning of the deformation experiment. Crystals with these orientations exhibit virtually no evidence of strain hard-ening. Transients associated with stress changes suggest that deformation is limited primarily by the mobility of dislocations and not by dislocation interactions. These characteristics of deformation are consistent with the operation of easyb = (001) glide processes in these crystals. Crystals loaded along [110] exhibit small deformation transients which indicate both sluggish dislocation motion and some substructure formation. We speculate that cross-slip of dislocations from {110} to {010} planes is responsible for this effect. Deformation in hard oriented crystals provides evidence for both mo-bility and substructure controlled deformation. Creep in hard oriented crystals is characterized by a dramatic sigmoidal transient suggesting very low dislocation mobility. However, the strain hardening observed in monotonic tests and the transient responses suggest that deformation is also limited by a dislocation substructure that forms during deformation. These findings support the conclusion, explored fully in a forthcoming article, that creep deformation in the hard orientation is controlled by the motion and interaction ofb = (101) dislocations.

High Temperature Deformation of Single Crystals of NiAl

The high temperature deformation properties of single crystals of stoichiometric NiAl have been studied in tension creep and in constant strain rate compression at temperatures between 850 and 1200°C. Samples were tested in a “soft”, [223], orientation and the “hard”, [001], orientation. The samples exhibit a strong orientation dependence of the strength and show other revealing deformation characteristics. The activation energy for steady state flow in both hard and soft orientations is near that for lattice self diffusion. Soft oriented crystals reach steady state rapidly and develop little dislocation substructure. Deformation of these soft oriented crystals occurs by the glide of b= dislocations. The creep curves of hard oriented crystals show pronounced sigmoidal creep, suggesting that the dislocations move in a sluggish manner, multiply in the early stages of creep and, ultimately, lead to strain hardening. Hard oriented crystals also develop extensive dislocation substructure during creep. This dislocation substructure is composed of b= dislocations, which have no resolved shear stress for glide. Evidence for {101} glide in hard oriented crystals is presented and a model is developed by which the decomposition of gliding b= dislocations can produce the observed b= dislocation networks. The increased creep resistance of hard oriented crystals compared to soft oriented crystals is described in terms of the differences in dislocation mobility and substructure formation for deformation in these directions.

Creep and high temperature deformation of titanium aluminide alloys: influence of α2 phase distribution and B2 phase decomposition

The high temperature deformation properties of a titanium aluminide alloy Ti-24at.%Al-11at.%Nb-2at.%V-1at.%Mo have been studied as a function of the microstructural distribution of α 2 and B2 phases. Controlled annealing treatments were given as initial starting conditions in order to obtain different volume fractions of the α 2 phase. These materials were used to study creep and compression properties at 700°C. Decomposition of the B2 phase was observed to occur during the high temperature exposure of the deformation tests. The stress and temperature-dependent parameters determining the high temperature deformation process have been confirmed to depend on the microstructural distribution.