Effect Of Thermomechanical Treatment Research Articles

Effect of Thermo-mechanical Treatment on High Temperature Tensile Properties and Ductile–Brittle Transition Behavior of Modified 9Cr-1Mo Steel

In the present work, a modified 9Cr-1Mo steel is subjected to normalizing and tempering treatment with or without an intermediate rolling, which was carried out at 1050 °C in austenitic phase and 550 °C in metastable austenitic phase. The tempering was carried out at 700 °C and 750 °C to improve the strength by precipitation hardening and refining the microstructure. The ductile to brittle-transition temperature (DBTT) and tensile properties have been evaluated at 20 °C, 550 °C and 650 °C for the material subjected to various thermomechanical treatments. Rolling performed in austenitic phase showed improvement in the upper shelf energy and reduction in the DBTT compared with the material rolled in metastable austenitic phase. Rolling in metastable austenitic phase improved the yield strength at elevated temperature (39 pct at 20 °C, 31 pct at 550 °C and 91 pct at 650 °C) and was accompanied by a reduction in ductility (21 pct at 20 °C, 32 pct at 550 °C and 35 pct at 650 °C) compared with the as-received condition. The influence of grain size, low angle boundaries and precipitates on DBTT and high temperature strength has been studied using EBSD and TEM analyses. An increase in high temperature strength is found to increase with the area fraction of fine M23C6/MX precipitates, whereas low angle boundaries and effective grain size influenced the DBTT behavior. The combined effect of precipitation strengthening and strain hardening leads to improvement in the high temperature mechanical strength while maintaining adequate toughness. The effect of aging (for 72 hours at 650 °C) on heat-treated and -rolled samples showed a small decrease in yield strength at 20 °C. A decreasing trend of fracture toughness is observed with the increase in yield strength.

Effect of thermo-mechanical treatment on microstructural evolution and mechanical properties of a superelastic Ti–Zr-based shape memory alloy

Achieving a combination of good superelastic performance and high strength in the bio-functional nickel-free Ti-based shape memory alloys is always required for the superelastic biomedical devices. For achieving this combination, in this paper, the thermo-mechanical treatment's influence on the microstructural development, mechanical performance and superelastic behavior of a Ti–45Zr–8Nb–2Sn (at.%) shape memory alloy was studied by using X-ray diffraction (XRD), transmission electron microscope (TEM), and tensile tests. 773 K and 823 K annealed specimens after cold rolling showed (β+α) two-phase microstructure. The grain size increased from 0.11 μm in 773 K annealed specimen to 125 μm in 1173 K solution-treated specimen. A maximum recovery strain of 5.4% was achieved at room temperature in the 1073 K annealed specimen due to some extent of the favorable recrystallization texture together with reasonable grain size but the tensile strength was 830 MPa. A combination of a large recovery strain of 5.0%, a high tensile strength of 1030 MPa and good ductility with fracture strain of 13.2% was achieved at room temperature in the 823 K annealed specimen due to the fine β grains of 0.74 μm, which can be beneficial for biomedical applications.

On the Impact of Texture and Grain Size on the Pseudoelastic Properties of Polycrystalline Fe\u2013Ni\u2013Co\u2013Al\u2013Ti Alloy

The effects of thermomechanical treatments on crystallographic texture and grain size evolution and their impact on the pseudoelastic properties in Fe41–Ni28–Co17–Al11.5–Ti2.5 (at.%) were studied in the present paper. The results show that cold rolling leads to brass-type texture in this alloy, which is typical for low stacking fault energy materials. Thermal treatments up to 1300 °C were conducted and it is shown that the presence of β-phase helps to control grain growth. After the dissolution of the secondary phase induced by heat treatment at higher temperatures, a strong {230}〈001〉 recrystallization texture evolves in cold rolled samples already upon imposing medium reduction ratios. Finally, good pseudoelastic properties are found in conditions being characterized by adequate texture and grain sizes spanning over the entire thickness of the samples tested.

Effect of thermomechanical treatment on the aggregation behaviour and colloidal functionality of β-Lactoglobulin at high concentrations

Thermomechanical treatment of β-Lactoglobulin (βLG) protein systems at concentrations above 50% (w/w) leads to the formation of aggregates stabilised by disulphide bonds and non-disulphide covalent bonds. Although thermomechanically treated samples had lower solubility, depending on the treatment conditions, the viscosity of dispersions containing 10% untreated and treated βLG increased from 0.01 Pa·s to 300 Pa·s, respectively. Additionally, the interfacial tension at the oil-water interface decreased from 13.5 mN m−1 to 11 mN m−1 depending on treatment conditions, probably due to the presence of native and small water-soluble aggregates in the continuous phase. Consequently, the emulsions prepared with treated samples were more stable and showed smaller Sauter mean diameters. Furthermore, samples with high degree of aggregation showed an increased thermal stability and formed cold-set gels when dispersed in water. In contrast, heating dispersions of partially aggregated samples resulted in the formation of heat-set gels due to a second gelation process.

Improving the in vitro digestibility of rice starch by thermomechanically assisted complexation with guar gum

The effects of thermomechanical treatment and guar gum (GG) addition on the in vitro digestibility of rice starch have been investigated. Rice starch added with GG at concentrations of 0, 0.025, 0.05, 0.075, or 0.10 g/100 g (wet basis) was subject to a micro-extrusion process. The in vitro digestibility, predicted glycemic index (pGI), and multi-scale structures (granule, lamellar, crystalline, and molecular structures) were examined. Micro-extruded rice starch (MERS) with GG presented reduced digestion rate and pGI, a higher degree of structural ordering, and altered crystalline, single-helical and double-helical structures. Using Pearson correlation analysis, the relationships among extrusion, the molecular interaction and multi-scale structure, and the digestibility were established. The content of resistant components (RC) was positively correlated with crystallinity (r = 0.836, p < 0.05), fractal dimension (r = 0.966, p < 0.05), A-type crystallinity (r = 0.954, p < 0.01), V-type crystallinity (r = 0.987, p < 0.05), R1045/1022 (r = 0.987, p < 0.05), single-helix content (r = 0.897, p < 0.05), and double-helix content (r = 0.991, p < 0.01); and was negatively correlated with pGI (r = −0.947, p < 0.05). Overall, this study showed that thermomechanical treatment assisted the complexation of GG with starch, which could be an effective means to improve the resistant properties of rice starch.

Effect of Thermo-mechanical Treatment on Microstructure and Mechanical Properties of Two-phase TiNbO Alloy

We designed the composition of alloy with Ti-8Nb-0.5O (at. %) and fabricated in high vacuum arc-melting furnace. This work was focused on the effect of thermomechanical treatment on microstructure and mechanical properties. Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), X-ray Diffraction analysis (XRD), Micro Vickers Hardness Tests and Tensile Tests were utilized to characterize the alloys. The annealing temperature has a significant effect on the microstructure and mechanical properties of TiNbO alloy. When the alloy was annealed at 300℃, 400℃ or at hot-rolled state, there were just α and β phases in the alloy. When the alloy was annealed at 500℃, 600℃, the alloy recrystallized and harmful ω phase appeared, which increased the modulus and strength of the alloy greatly. When the alloy is annealed at 700℃, the alloy recrystallized completely without ω phase. When we accelerated the cooling rate after annealed, the martensitic transformation appeared, which restrained the appearance of ω phase and reduced the modulus.

Effects of thermomechanical treatment on grain refinement, second-phase particle dissolution, and mechanical properties of 2219 Al alloy

Abstract An improved thermomechanical treatment, which included 50% hot deformation at 440°C, 10% cold predeformation at 25°C, and a subsequent heat treatment (solution, 2.5% cold deformation and aging treatment), was performed on 2219 Al alloy forgings. For comparison, a 2219 Al alloy forging was also manufactured using the conventional process, which involved 50% hot deformation at 440°C and a subsequent heat treatment. The evolution of the microstructures of the forgings during the treatments and their final mechanical properties were evaluated. A large number of Al2Cu particles were formed during the hot-deformation process. Further, tangled dislocation structures were formed around these particles after 10% cold deformation in the forging manufactured by the improved process, resulting in a significant grain refinement during the solution treatment because of particle stimulated nucleation as well as a weakened texture. In addition, more coarse Al2Cu particles dissolved into the Al matrix during the solution treatment in the case of the forging subjected to the improved treatment, because the tangled dislocation structures promoted the dissolution of these particles, thus increasing the density of the precipitates after T8-aging. The forging manufactured by the improved treatment exhibited a higher ultimate tensile strength (by 34.3 MPa), higher yield strength (by 43.2 MPa), and significantly lower anisotropy, as well as improved elongations in the axial and radial directions (lower-performance directions).

Strengthening mechanisms of ultrafine grained copper alloys

Cu-Cr-Zr alloys are characterized by an excellent combination of strength and electrical conductivity and are applied as structural materials in various electrical/electronic devices. The microstructure design of Cu-Cr-Zr alloys, the effect of thermomechanical treatment based on severe plastic deformation, and physical mechanisms providing high strength and electrical conductivity are investigated. The main structure-property relations in Cu-Cr-Zr alloys are considered. The dissolution of the dispersed particles during severe plastic deformation and an increase in the dislocation density, as well as the effect of heat treatment after deformation on the mechanical and electrical properties are discussed.

Effect of thermomechanical treatment on the mechanical and microstructural evolution of a β-type Ti-40.7Zr–24.8Nb alloy

In this study, the microstructural evolution and mechanical properties of a newly developed Ti-40.7Zr–24.8Nb (TZN) alloy after different thermomechanical processes were examined. As-cast TZN alloy plates were solution-treated at 890 °C for 1 h, after which the thickness of the alloy plates was reduced by cold rolling at reduction ratios of 20%, 56%, 76%, and 86%. Stress-induced α” formation, {332} <113> β mechanical twinning, and kink band formation were observed in the cold-rolled TZN alloy samples. In the TZN sample after cold rolling at the 86% reduction ratio plus a recrystallization annealing at 890 °C for 1 h, the deformation products of a stress-induced α” phase, {332}<113> β mechanical twinning, and kink bands disappeared, resulting in a fine, equiaxed single β phase. The alloy samples exhibited elongation at rupture ranging from 7% to 20%, Young's modulus ranging from 63 to 72 GPa and tensile strength ranging from 753 to 1158 MPa. The TZN alloy sample after cold rolling and recrystallization annealing showed a yield strength of 803 MPa, a tensile strength of 848 MPa, an elongation at rupture of 20%, and an elastic admissible strain of 1.22%, along with the most ductile fractures during tensile testing.

The effect of thermomechanical treatment on the microstructure and mechanical properties of high Mn–Cr austenitic steels

AbstractIt was shown that new high-manganese austenitic steels can be used as an alternative to conventional Ni–Cr austenitic steels especially in vacuum vessels. In this study, a nickel-free austenitic steel with chemical composition of 24 wt.% Mn, 10 wt.% Cr, 0.13 wt.% C and trace elements of Si, Ti, V, W, and Al was hot-rolled at 950 and 1100 °C to different strains. Microscopic observations, X-ray diffraction, tensile, impact and microhardness tests were performed to characterize the microstructural aspects and mechanical properties. A small amount of chromium carbide was found on the grain boundaries of this fully austenitic steel. The results showed that the microstructure and mechanical properties of hot rolled manganese austenitic steel are affected by the dynamic recrystallization and twinning phenomena. Also, by changing the grain morphology from equiaxed to elongated, strength and hardness increased, and the impact toughness and ductility were reduced.

Effect of Thermomechanical Treatments on the Phases, Microstructure, Microhardness and Young's Modulus of Ti-25Ta-Zr Alloys.

Titanium and its alloys currently are used as implants, possessing excellent mechanical properties (more suited than stainless steel and Co-Cr alloys), good corrosion resistance and good biocompatibility. The titanium alloy used for most biomedical applications is Ti-6Al-4V, however, studies showed that vanadium and aluminum cause allergic reactions in human tissues and neurological disorders. New titanium alloys without the presence of these elements are being studied. The objective of this study was to analyze the influence of thermomechanical treatments, such as hot-rolling, annealing and solution treatment in the structure, microstructure and mechanical properties of the Ti-25Ta-Zr ternary alloy system. The structural and microstructural analyses were performed using X-ray diffraction, as well as optical, scanning and transmission electron microscopy. The mechanical properties were analyzed using microhardness and Young’s modulus measurements. The results showed that the structure of the materials and the mechanical properties are influenced by the different thermal treatments: rapid cooling treatments (hot-rolling and solubilization) induced the formation of α” and β phases, while the treatments with slow cooling (annealing) induced the formation of martensite phases. Alloys in the hot-rolled and solubilized conditions have better mechanical properties results, such as low elastic modulus, due to retention of the β phase in these alloys.

The effect of thermo-mechanical treatment of moso bamboo (Phyllostachys Pubescens) on its sorption and physicomechanical properties

The aim of this study was to examine some properties of heat-treated (200 °C) and densified (treated) bamboo. Density (ρ), equilibrium moisture content (EMC), sorption hysteresis (H), swelling (S), and Brinell hardness (HB) were examined and compared with untreated bamboo (Phyllostachys sp.) and common oak (Quercus robur L.). The density of heat-treated bamboo (ρ = 1170 kg/m3) was higher than that of untreated bamboo (ρ = 850 kg/m3) and oak wood (ρ = 670 kg/m3). The sorption isotherms were parameterized with the Guggenheim-Anderson-deBoer (GAB) model. Treated bamboo showed lower EMC than untreated bamboo and oak wood in the entire hygroscopic range. The swelling anisotropy index of treated bamboo was the lowest (1.09). The mean HB of treated bamboo (HB=132 MPa) was significantly higher than that of oak and untreated bamboo.

Effect of thermomechanical treatment on the microstructures and mechanical properties of an ultrafine grained steel using bainite starting microstructure

AbstractThe cold rolling and subsequent annealing of microstructures with a high percentage of bainite is one of the promising thermomechanical treatments for grain refinement in low-alloy steels. In this research, the bainite microstructure was formed in the steel DIN 1.5715 by austenitizing at 1143 K followed by quenching in a salt-bath at 688 K. The specimens were then cold rolled to 90 % reduction in thickness followed by annealing at 773–923 K for different times. An ultrafine grained ferrite microstructure was developed possessing the best strength–ductility balance after 90 % cold rolling followed by annealing at 923 K for 2 400 s.

Effect of thermo-mechanical treatment on microstructure and tensile properties of 2219ScMg alloy

An improved high temperature performance of 2219 aluminium alloys through thermo-mechanical treatments having additions of 0.8 wt% Sc and 0.45 wt% Mg is presented. The copper mould chill cast alloy designated as 2219ScMg is processed through two different routes. In the first route, designated here as HMCR process, the alloy is homogenised at 530 °C and cold rolled, while in the second route, designated here as HRCR process, the cast alloy is directly rolled sequentially under hot and cold conditions. The evolution of the microstructure and strength are examined throughout the processes. The formation of L12 ordered Al3Sc and Al3(Sc, Zr) precipitates of average size 10 ± 5.5 nm (radius) takes place during solidification. In the HMCR process, homogenization of the alloy at 530 °C results in an increase in the number density of these precipitates in addition to partial dissolution of copper in the Al matrix. Subsequent cold rolling of the alloy introduces strain hardening. The same thing happens during hot rolling at 300 °C in HRCR process but the size of the Al3Sc/Al3(Sc, Zr) precipitates is smaller. The subsequent cold rolling again strain hardens the alloy. In addition to excellent room temperature 0.2% proof stress of ∼500 MPa in both the processes, outstanding elevated temperature (200 °C) 0.2% proof stress of 345 MPa in HMCR and 312 MPa in HRCR is obtained. Thermal stability of the alloy at elevated temperature is enhanced by the Sc and Mg segregation at the Al/θ′ interface and the formation of a small amount of Ω phase.

On the effect of thermo-mechanical treatment on creep deformation and rupture behaviour of a reduced activation ferritic-martensitic steel

Creep deformation and rupture behaviour of a reduced activation ferritic-martensitic (RAFM) steel subjected to thermo-mechanical treatment (TMT) is studied and compared with those of conventional normalized and tempered (N + T) steel. In TMT processing, the steel is warm rolled and aged in austenite phase field at 973 K before the martensite transformation on cooling and is then tempered at 1038 K. The TMT processing renders the steel with higher dislocation density, refinement in lath structure and large quantity of finer M23C6 and MX precipitates than those in the N + T steel. Creep tests are carried out at 823 K over the stress range 180–300 MPa. TMT processing of the steel decreases its minimum creep rate (ε˙min) with corresponding increase in time to onset of tertiary stage of creep deformation, rupture life (tr) and creep rupture ductility (εf). The stress exponent value (n), obtained from minimum creep rate vs. stress plot, increases upon TMT processing, indicating high resistance to creep deformation than in the N + T steel. Resisting stress as estimated based on the Lagneborg and Bergman method is found to increase on TMT processing and is associated with high damage tolerance parameter, defined asλ=εf/(ε˙min.tr). Enhanced creep deformation and rupture strength of the TMT steel, compared to N + T steel, is attributed to the microstructural refinement. Post-creep microstructural investigations show higher microstructural stability of the steel on TMT processing and are in line with the observed high damage tolerance parameter (λ), longer time to onset of tertiary creep and rupture life.

Effect of Thermo-Mechanical Treatment on the Microstructure Evaluation and Mechanical Properties of Fe-20Mn-12Cr-3Ni-3Si Damping Alloy.

This study was carried out to investigate the effect of thermo-mechanical treatment on the microstructure of Fe-20Mn-12Cr-3Ni-3Si damping alloy. Dislocation, αʹ, and ε-martensite were formed by thermo-mechanical treatment. The intersections of the surface relief and specific direction due to martensitic transformation were generated by thermo-mechanical treatment. They were then reversed to austenite with an ultra-fine grain size of less than 5 μm by annealing treatment at 700°C for 20min. The volume fractions of dislocation, αʹ, and ε-martensite were increased with the cycle number of thermo-mechanical treatment. In five-cycle number thermo-mechanical treated specimens, more than 45% of the volume fraction of ε-martensite and less than 3% of the volume fraction of α΄-martensite were attained. Therefore, in this article, the effect of thermo-mechanical treatment is briefly introduced, and these phenomena are explained in terms of the grain refinement of austenite, αʹ, and ε-martensite distribution and homogeneous dislocation distribution.

Evaluation of the Effect of Thermo-mechanical Treatment on the Resistance of Commercial OSB to Decay Fungi

insertion of chemical agents, which are subject to leaching when exposed to weathering. In this context, the thermo-mechanical modification seeks to increase the durability of wood, without polluting the environment. Samples of untreated and thermo-mechanically treated Oriented Strand Board (OSB) were exposed to the attack of rotting fungi. Both untreated and treated samples were classified as resistant to the attack of T. versicolor (white-rot). To the attack of G.trabeum (brown-rot), the untreated samples were classified as moderate resistance, and the treated samples as resistant. The results of mass loss showed that the thermo-mechanical treatment caused an increase of 19.34 % (white-rot) and 43.03 % (brown-rot) in the OSB resistance, and also improved the OSB resistance class from moderately resistant to resistant to brown-rot fungi.

Effect of Thermomechanical Treatment on the Formation of Gradient Structure and Mechanical Properties in a Disk Made of Powder-Metallurgy Nickel-Based Superalloy

The process of obtaining a gradient structure by thermomechanical treatment (TMT) has been demonstrated using the example of a model disk workpiece made of the powder-metallurgy (PM) EP741NP nickel-based superalloy. The TMT included the main deformation leading to the development of recrystallization and the formation of a fine-grained microstructure, heat treatment in a gradient temperature field, additional deformation, and final strengthening heat treatment. In the disk workpiece after TMT, a gradient structure was obtained: a “necklace” structure in the peripheral part and a fine-grained “microduplex” structure in the center. The estimation of mechanical properties of samples cut out at different distances from the axis of symmetry of the disk workpiece showed that the central part of the disk is characterized by enhanced strength and ductility, and the peripheral part possesses enhanced high-temperature strength and impact toughness. The obtained results indicate that the approach used is promising for achieving a gradient structure and gradient mechanical properties in disks made of PM nickel based superalloys.

Effect of Thermomechanical Treatment on Acicular Ferrite Formation in Ti–Ca Deoxidized Low Carbon Steel

Transformation behaviors and mechanical properties under thermomechanical treatment conditions of Ti–Ca deoxidized low carbon steel were studied in comparison to Al–Ca treated steel. A thermomechanical simulation and a hot rolling experiment were carried out. Inclusions and microstructures were characterized, and the transformation mechanism was analyzed. The results indicated that typical inclusions in Ti–Ca deoxidized steel were TiOx-MnS-Al2O3-CaO, TiOx-MnO-Al2O3-CaO, and TiOx-MnS, which were effective for acicular ferrite (AF) nucleation. Acicular ferrite formation temperature decreased with an increase in cooling rate. A fine AF dominant microstructure was formed under a high driving force for the transformation from austenite to ferrite at lower temperatures. A high deformation of 43–65% discouraged the formation of acicular ferrite because of the increase in austenite grain boundaries serving as nucleation sites. The fraction of high-angled grain boundaries that acted as obstacles to cleavage cracks was the highest in the sample cooled at 5 °C/s because of full AF structure formation. The hardness increased significantly as the cooling rate increased from 2 to 15 °C/s, whereas it decreased under the condition of deformation because of the formation of (quasi-)polygonal ferrite. By applying accelerated water cooling, the mechanical properties, particularly impact toughness, were significantly improved as a result of fine AF microstructure formation.

Effect of Thermo-Mechanical Treatment on the Damping Capacity of Alloy with Deformation Induced Martensite Transformation

This study investigates the effect of thermo-mechanical treatment on the damping capacity of the Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. Dislocation, α’ and ε-martensite are formed, and the grain size is refined by deformation and thermo-mechanical treatment. With an increasing number cycles in the thermo-mechanical treatment, the volume fraction of ε-martensite increases and then decreases, whereas dislocation and α’-martensite increases, and the grain size is refined. In thermo-mechanical treated specimens with five cycles, more than 10 % of the volume fraction of ε-martensite and less than 3 % of the volume fraction of α’-martensite are attained. Damping capacity decreases by thermomechanical treatment and with an increasing number of cycles of thermo-mechanical treatment, and this result shows an opposite tendency for general metal with deformation induced martensite transformation. The damping capacity of the thermomechanical treated damping alloy with deformation induced martensite transformation greatly affect the formation of dislocation, grain refining and α’-martensite and then ε-martensite formation by thermo-mechanical treatment.