High-temperature Uniaxial Compression Research Articles

High Temperature Uniaxial Compression and Stress–Relaxation Behavior of India-Specific RAFM Steel

India-specific reduced activity ferritic martensitic steel (INRAFM), a modified 9Cr-1Mo grade, has been developed by India as its own structural material for fabrication of the Indian Test Blanket Module (TBM) to be installed in the International Thermonuclear Energy Reactor (ITER). The extensive study on mechanical and physical properties of this material has been currently going on for appraisal of this material before being put to use in the ITER. High temperature compression, stress–relaxation, and strain-rate change behavior of the INRAFM steel have been investigated. The optical microscopic and scanning electron microscopic characterizations were carried out to observe the microstructural changes that occur during uniaxial compressive deformation test. Comparable true plastic stress values at 300 °C and 500 °C and a high drop in true plastic stress at 600 °C were observed during the compression test. Stress–relaxation behaviors were investigated at 500 °C, 550 °C, and 600 °C at a strain rate of 10−3 s−1. The creep properties of the steel at different temperatures were predicted from the stress–relaxation test. The Norton’s stress exponent (n) was found to decrease with the increasing temperature. Using Bird–Mukherjee–Dorn relationship, the temperature-compensated normalized strain rate vs stress was plotted. The stress exponent (n) value of 10.05 was obtained from the normalized plot. The increasing nature of the strain rate sensitivity (m) with the test temperature was found from strain-rate change test. The low plastic stability with m ~ 0.06 was observed at 600 °C. The activation volume (V*) values were obtained in the range of 100 to 300 b3. By comparing the experimental values with the literature, the rate-controlling mechanisms at the thermally activated region of high temperature were found to be the nonconservative movement of jogged screw dislocations and thermal breaking of attractive junctions.

Improvement of Magnetostrictive Properties of Fe-15mol%Ga Alloy by Texture Formation during High Temperature Uniaxial Compression Deformation

Improvement of Magnetostrictive Properties of Fe-15mol%Ga Alloy by Texture Formation during High Temperature Uniaxial Compression Deformation

High-Temperature Deformation Processing Map Approach for Obtaining the Desired Microstructure in a Multi-component (Ni-Ti-Cu-Fe) Alloy

An equiatomic NiTiCuFe multi-component alloy with simple body-centered cubic (bcc) and face-centered cubic solid-solution phases in the microstructure was processed by vacuum induction melting furnace under dynamic Ar atmosphere. High-temperature uniaxial compression experiments were conducted on it in the temperature range of 1073 K to 1303 K (800 degrees C to 1030 degrees C) and strain rate range of 10(-3) to 10(-1) s(-1). The data generated were analyzed with the aid of the dynamic materials model through which power dissipation efficiency and instability maps were generated so as to identify the governing deformation mechanisms that are operative in different temperature-strain rate regimes with the aid of complementary microstructural analysis of the deformed specimens. Results indicate that the stable domain for the high temperature deformation of the multi-component alloy occurs in the temperature range of 1173 K to 1303 K (900 degrees C to 1030 degrees C) and (epsilon) over dot range of 10(-3) to 10(-1.2) s(-1), and the deformation is unstable at T = 1073 K to 1153 K (800 degrees C to 880 degrees C) and (epsilon) over dot = 10(-3) to 10(-1.4) s(-1) as well as T = 1223 K to 1293 K (950 degrees C to 1020 degrees C) and (epsilon) over dot = 10(-1.4) to 10(-1) s(-1), with adiabatic shear banding, localized plastic flow, or cracking being the unstable mechanisms. A constitutive equation that describes the flow stress of NiTiCuFe multi-component alloy as a function of strain rate and deformation temperature was also determined. (C) The Minerals, Metals & Materials Society and ASM International 2015

Texture Formation in AZ91 Magnesium Alloy during High-Temperature Uniaxial Compression

Texture development in Magnesium alloy AZ91 having a weak (0001) texture before deformation is studied by uniaxial compression tests at 673K and 723K, strain rates ranging from 5.0×10-4s-1 to 5.0×10-2s-1 up to a strain of -1.0. The fiber texture is formed in all of the deformation conditions. The main component of the texture varies depending on deformation conditions. The position of maximum axis density varies depending on final stress. It is concluded that the (0001) fiber texture develops by continuous dynamic recrystallization.

Fe-3mass%Si合金の高温単軸圧縮変形中に生じる優先動的結晶粒成長による集合組織形成に及ぼすP添加の影響

Fe-3mass%Si合金の高温単軸圧縮変形中に生じる優先動的結晶粒成長による集合組織形成に及ぼすP添加の影響

Effect of Deformation Condition on Texture Formation in Fe-3Mass%Si Alloy during High-Temperature Uniaxial Compression Deformation

High temperature uniaxial compression tests are conducted in order to clarify the effect of test conditions to the evolution of microstructures and textures. Fiber texture with {001} and {111} (compression plane) is formed as major and minor component, respectively. In contrast to the deformation at room temperature, axis density at ‹001› is higher than that at ‹111›. EBSD observation shows that the mean grain size of ‹001› oriented grain is larger than the grain with the other orientation. This suggests the development of {001} fiber texture in Fe-3%Si can be attributed to the preferential growth of ‹001› oriented grain, being similar to the behavior of Al solid solution reported before. The orientations of the preferentially grown grains in the both alloys can be understood on the basis of the same hypothesis proposed by two of the authors. In many cases, high angle boundaries (15°∼) are serrated. It is suggested that the serration corresponds to the existence of small angle boundary (2°∼15°). EBSD measurements suggest that small angle grain boundaries in ‹111› oriented grain give local driving force to grain boundary migration into ‹111› oriented grain, and the boundaries in ‹001› oriented grain retard the migration. Examination of the texture sharpness at a strain of -1.0 shows that axis density at ‹001› develops with an increase in temperature and a decrease in strain rate. This suggests that homogeneous distribution of dislocations contributes to the development of ‹001› orientation.

On the gas pressure forming of aluminium foam sandwich panels: Experiments and numerical simulations

Forming of light-weight highly stiff aluminium foam sandwich (AFS) panels into complex 3D components would mark a development in the manufacturing of these materials. In this work, gas pressure forming of AFS panels is investigated experimentally and using numerical simulations. Deformation behaviour of AFS panels is studied during high-temperature uniaxial tension and compression, and constitutive models are developed and incorporated into FE simulations of the gas pressure forming process. Simulation results and experimental observations show reasonable agreement and demonstrate the possibility of forming AFS panels to significant deformations while maintaining considerable core porosity.

Texture Development in Ferritic Steels during High Temperature Uniaxial Compression Deformation

Texture formation during uniaxial compression at elevated temperatures in Fe-3mass%Si and 430 stainless steel is studied. The behavior is analyzed in relating to the understanding on the texture development in Al-Mg solid solution alloy at high temperatures. It is found that the fraction of {001} (compression plane) is much higher than that of {111} both in Fe-3%Si and 430 steel, which is different from the deformation at room temperature. In Fe-3%Si, the fraction of {001} becomes higher at higher temperatures and with lower strain rates. EBSD measurement suggests that the development of {001} is attributed to the preferential growth of {001} oriented grains. In the case of 430 steel, no obvious deformation condition dependence of {001} development is seen, probably due to the fine particles pinning the grain boundaries.

Deformation and crystallization of Zr-based amorphous alloys in homogeneous flow regime

The purpose of this study is to experimentally investigate the interaction of inelastic deformation and microstructural changes of two Zr-based bulk metallic glasses (BMGs): Zr41.25Ti13.75Cu12.5Ni10Be22.5(commercially designated as Vitreloy 1 or Vit1) and Zr46.75Ti8.25Cu7.5Ni10Be27.5(Vitreloy 4, Vit4). High-temperature uniaxial compression tests were performed on the two Zr alloys at various strain rates, followed by structural characterization using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Two distinct modes of mechanically induced atomic disordering in the two alloys were observed, with Vit1 featuring clear phase separation and crystallization after deformation as observed with TEM, while Vit4 showing only structural relaxation with no crystallization. The influence of the structural changes on the mechanical behaviors of the two materials was further investigated by jump-in-strain-rate tests, and flow softening was observed in Vit4. A free volume theory was applied to explain the deformation behaviors, and the activation volumes were calculated for both alloys.

Texture development of Ca 3Co 4O 9 thermoelectric oxide by high temperature plastic deformation and its contribution to the improvement in electric conductivity

High temperature uniaxial compression is conducted on Ca 3Co 4O 9 layered cobaltite, in order to achieve a thermoelectric oxide with low resistivity by the development of (0 0 1) texture. It is found that flow stress varies depending on deformation temperature and strain rate. Development of a sharp texture having the maximum (0 0 1) pole density of about 33 times as high as the random level is achieved. It is found that the high temperature compression process is quite effective for the simultaneous achievement of densification and (0 0 1) texture development. It is experimentally confirmed that resistivity decreases drastically by the construction of a sharp (0 0 1) texture.

Al-Mg 固溶体合金の高温単軸圧縮変形における集合組織形成におよぼす溶質雰囲気の効果

Al-Mg 固溶体合金の高温単軸圧縮変形における集合組織形成におよぼす溶質雰囲気の効果

Anisotropy of the hot plastic deformation of Ti–6Al–4V single-colony samples

The critical resolved shear stresses (CRSSs) and flow curves for the seven possible slip systems in Ti–6Al–4V with a lamellar microstructure were determined via high-temperature uniaxial compression testing. For this purpose, samples with a rectangular cross section were cut from single colonies grown using a float-zone technique and then tested at 815 °C. Each sample was oriented for single slip along one of seven different slip systems in the alpha phase; i.e., one of the three 〈 1 1 2 ¯ 0 〉 { 1 0 1 ¯ 0 } (prism 〈 a〉), the three 〈 1 1 2 ¯ 0 〉 { 0 0 0 1 } (basal 〈 a〉), or the 〈 c + a〉 (pyramidal) systems was activated by orienting specific samples to have the highest Schmid factor on that particular system. Measurements of the CRSS at yielding and the subsequent flow behavior revealed a strong dependence of mechanical behavior on colony orientation/activated slip system. The anisotropy in the CRSS and the tendency for flow softening at large strains was rationalized on the basis of the Burgers orientation relationship between the alpha (hcp) lamellae and the beta (bcc) matrix and hence the orientation of alpha slip directions relative to those in the beta phase.

Determination and Interpretation of Texture Evolution during Deformation of a Zirconium Alloy

Abstract Worldwide, crystal plasticity models are currently developed to predict texture development during processing of material. Such models require a precise knowledge of the active deformation mechanisms. The activation energy for certain deformation modes will change with temperature and also depend on the chemistry of the alloy as well as the microstructure. Deformation mechanisms were studied in ZIRLO™ during room and high-temperature uniaxial compression testing. Materials with a strong crystallographic basal texture and a more random texture due to β-quenching were investigated with the aim of establishing the effect of temperature, microstructure, and texture on the active deformation modes during the initial stages of deformation. First, specimens were strained at room temperature, 180°C and 300°C to 2 % and 5 % or 10 % total strain and subsequently analyzed by Electron Back Scatter Diffraction (EBSD) to determine the texture evolution. It was found that a dramatic texture change was observed for all testing temperatures in the strongly textured specimen after only 5 % total strain, which can only be understood in terms of tensile twinning of {10 1¯2} ⟨1¯011⟩ being active mainly at room temperature and compressive twinning of {11 2¯2} ⟨1¯1¯23⟩ being operational at room and elevated temperature. The β-quenched specimens did not show any evidence of texture change when strained to 10 %. In-situ intergranular strains were measured by time-of-flight neutron diffraction during continuous compressive loading. This information enabled the development of a crystal plasticity finite element model (CPFEM), which was subsequently used to predict the stress state in individual grains. It was found that in the strongly textured material the spread of intergranular strain in the {0002} grain family (normal pointing towards the ND direction) results in some grains being in compression even though the mean stresses are tensile, which could explain the activation of the observed compressive twinning. The crystal plasticity model also demonstrated that the observed texture changes in the strongly textured material, including those at high temperature, cannot be explained by slip alone even when ⟨c+a⟩ slip is considered. In addition, the model showed that the dramatic difference in yield strength of the two conditions studied here cannot be solely attributed to the difference in texture but that grain size plays an important role.

Texture development in Bi 1.5Pb 0.5Sr 1.7Y 0.5Co 2O 9− δ layered cobaltite by high-temperature compression deformation and its effect on thermoelectric properties

Texture development in Bi 1.5Pb 0.5Sr 1.7Y 0.5Co 2O 9− δ (BPSYO) layered cobaltite by plastic deformation is examined experimentally by high-temperature uniaxial compression, in order to develop a method to reduce the resistivity of thermoelectric cobaltite by controlling the spatial arrangement of the (0 0 1) conductive CoO 2 layers. It is found that the present oxide can be plastically deformed up to a true strain of −2.2 at 1113 K with strain rates in the order of 10 −5 s −1. It is concluded that high-temperature compression is effective both for densification and texture development. Evolution of (0 0 1) (compression plane) texture is experimentally confirmed as expected from the crystal structure, where a dislocation that has a small Burgers vector may move in the (0 0 1) plane. The formation of a sharp (0 0 1) texture results in a reduction in resistivity to about one-tenth of that of the specimen without texture. The estimated value of the dimensionless thermoelectric figure of merit is 0.11 at 973 K, which is close to the practical level of a thermoelectric material.

Deformation behavior of TiAl intermetallic compounds and orientation control by reactive diffusion and high-temperature uniaxial compression deformation

To determine the optimum method of producing TiAl intermetallic compounds with an oriented lamellar microstructure the authors applied reactive diffusion and high-temperature deformation in a two-phase state on Ti-43 mol.%Al and Ti-46 mol.%Al. The reactive diffusion process produces an α single-phase state with orientations that reflect the texture of the starting titanium foils; the high-temperature deformation aims to rotate the lamellar interface by means of preferential activation of the crystal slip systems that are parallel to the interface. The reactive diffusion process can effectively control the texture in an α single-phase state, though many voids are formed at the initial stages of reactive diffusion. Furthermore, after the heating process for the construction of the lamellar microstructure, uniaxial compression at 1323 K is quite effective for ensuring that the lamellar interface is rotated parallel to the compression plane. Finally, the deformation causes about one half of all the lamellae to be arranged within 20 degrees of the compression plane.

Microstructure evolution and texture development during high-temperature uniaxial compression of magnesium alloy AZ31

Texture development in magnesium alloy AZ31 was studied by uniaxial compression tests at temperatures, strain rates and final strains ranging from 573 to 773 K, 1.0 × 10 −3 to 5.0 × 10 −5 s −1 and −0.2 to −1.5, respectively. Fiber texture was formed in all of the deformation conditions. The main component of the texture varied depending on deformation conditions; it appeared about 33–38° away from the basal pole after the deformation at higher temperatures and lower strain rates. This can be attributed to the increased activity of the secondary pyramidal slip system. With a decrease in temperatures and an increase in strain rate, the tilting angle of the main component (compression plane) from the basal pole decreased down to about 20°. Construction of a basal fiber texture was detected after deformations at the lowest temperature and high strain rates.

高配向性ラメラ組織を有するＴｉ‐４３ｍｏｌ％Ａｌ金属間化合物の創製とクリープ特性

Various processes consisting of high temperature deformation and heat treatment are experimentally examined on Ti-43mol%Al in order to control the lamellar arrangement in TiAl intermetallic compound. High temperature uniaxial compression in α+γ as well as α2+γ two phase state is effective to rotate the lamellar interface to the position parallel to the compression plane. The high temperature compression in α2+γ two phase state results in the formation of many cracks along the lamellar colony boundaries while no cracks are observed when the compression is made in the α+γ two phase state. Deformation in the two phase state deduce the formation of many single phase grains along the colony boundaries. It is found that the heat treatment at the temperature slightly higher than that for high temperature deformation in the α+γ two phase region is effective to eliminate the single phase grains. Compression creep tests are performed on two kinds of specimen having different lamellar arrangement; one has the lamellar interface parallel to the compression direction and the other has the interface inclined about 45° to the compression direction. The specimen having the lamellar interface parallel to the compression direction shows the creep rate much lower than that of the other.

Structure and mechanical properties of Mg–Zn–misch metal alloys solidified at different cooling rates

The influence of cooling rate on the mechanical properties and structure evolution of Mg–Zn–misch metal alloys has been investigated. The sequence of structural changes has been correlated with stress—strain curves determined from high temperature uniaxial compression tests. Two regions of work hardening have been identified on the stress—strain curves, described by the Ludwigson equation σ=K1 ϵn1±Δ. Microstructural examination at various levels of deformation has been carried out on selected specimens. In the first region of deformation, the appearance of traces of slip lines was observed inside the grains. In the second region, a network of eutectic precipitates located around the grains had undergone fragmentation, enabling the propagation of deformation by transcrystalline slip across two or more grains. Based on results of the present investigation, optimal properties of the alloys for application at elevated temperatures have been established.

The microstructure and plasticity of Ni-AI-Fe alloys

Although intermetallic compounds form a very important group of materials, their properties have been insufficiently investigated yet. The nonstoichiometric intermetallic NiA1 compound is mentioned among useful constructive materials for high temperature applications. Many attempts to increase its poor ductility were undertaken by micro- and macroalloying, most promising results were reported for the Fe addition. The present investigation was carried out to determine the influence of the Fe and small titanium and boron additions on the phase composition, microstructure and mechanical chracteristic, particularly with respect to the feasibility to high temperature deformation on Ni-AI-Fe-Ti-B alloys. The Ni-A1-Fe-Ti-B alloys, containing 35.8 at.% A1 and 3,6-8,6-17.6 at.% Fe were prepared from high purity components and Al master alloy containing Ti2B particles, by melting in a Balzers furnace and casting. After the homogenization in the β-phase temperature range and long-time annealing at 1023 K, high temperature uniaxial compression test were performed. The sequence of structural changes has been correlated with mechanical characteristics of high temperature deformation process, determined in uniaxial compression tests. Two ranges of work hardening were identified on the stress-strain curves. It has been found that the first range of the deformation corresponds to intergranular slip system operating within individual grains, while the second one is connected with transgranular slip.

Texture analysis of L1 2 Al 66Mn 3Ti 25 intermetallic compound deformed at high temperatures

The authors investigated the deformation characteristics and microstructure change of L1[sub 2] Al[sub 66]Mn[sub 9]Ti[sub 25] by high temperature uniaxial compression tests. Three regimes appeared in the dynamics restoration process, depending on the flow stress level. When the flow stress is higher or lower, dynamic recovery is the dominant dynamic restoration process, while dynamic recrystallization is predominant at the intermediate stresses. Texture examination showed that three kinds of fiber texture developed corresponding to the difference in the dynamic restoration process. Evaluation of the pole figure suggested that the main components of the texture are close to [110], [110] + [111] and [111] for higher, intermediate and lower stress regimes, respectively. In this paper, crystallographic characteristics of the textures formed in the lower and higher stress regimes are examined by calculating the orientation distribution function, in order to understand the mechanism of texture formation.