Effect Of Thermomechanical Treatment Research Articles

Effect of thermo-mechanical treatment on Ti–Ta-Hf high temperature shape memory alloy

The microstructure, martensitic transformation and mechanical/functional properties of Ti–Ta-Hf alloys with various thermo-mechanical treatments were investigated. The results reveal that the hot-rolling could refine the grain size and introduce a certain number of defects, resulting in the disappearance of martensitic transformation. The as-casted and solution treated Ti–Ta-Hf alloys were composed of α'' martensite phase and smaller volume of β phase. In contrast, the grain size of solution treated Ti–Ta-Hf alloy was slightly less than that of as-casted Ti–Ta-Hf alloy. This should be responsible to the higher yield stress and superior strain recovery characteristics for solution treated Ti–Ta-Hf alloy. The yield stress for the dislocation slip and the maximum recoverable strain of solution treated Ti–Ta-Hf alloy were 723 ​MPa and 5.06%, respectively.

Effect of thermomechanical treatment on the microstructure and mechanical properties of Si-containing oxide dispersion strengthened reduced activation ferritic steel synthesized via mechanical alloying and spark plasma sintering

Abstract The present work describes the effect of thermo-mechanical treatment on the microstructure, and its subsequent effect on the mechanical properties of Si-containing oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel. ODS-RAF steel powder mixture with a nominal composition of Fe-14Cr-2W-0.3Ti-1Si-0.3Y2O3 was mechanically alloyed up to 50 h and subsequently consolidated via spark plasma sintering (SPS) at 900 °C followed by thermo-mechanical treatment (TMT) at 850 °C. Microstructural study revealed that the sintered sample consisted of ultrafine grains (0.35 µm) along with nano-size particles (Cr2TiO4, SiO2, and Y2Ti2O7) distributed in the matrix. This sintered sample exhibited excellent mechanical properties such as Vickers hardness (600 VHN), compressive strength (1795 MPa), and total elongation (21%), which is ascribed to the presence of ultrafine grains and nano-size particles. The thermo-mechanically treated sample exhibited an increase in the density by 2.7% and a reduction in the grain size by 23%. Consequently, the Vickers microhardness, compressive strength, and failure elongation of the sintered sample improved by 13%, 37%, and 19%, respectively, upon thermo-mechanical treatment.

Effect of thermomechanical treatment on MX phase precipitation behavior in CLAM steel

Reduced Activation Ferritic/Martensitic (RAFM) steels are the preferred first wall structural materials in nuclear fusion experimental reactors at this stage, which puts forward high requirements for its creep properties. Previous references point out that the main factor for the creep resistance of RAFM steel is the massively precipitated MX phases in the matrix. Thermomechanical treatment (TMT) technology can promote the precipitation of a large number of nano-sized MX phases, and has great potential for improving the creep strength of RAFM steels. In this paper, China Low Activation Martensitic (CLAM) steel is taken as the research object, and four different thermomechanical treatment processes are designed for comparison. The purpose is to deepen our understanding of the effects of austenitization temperature, deformation temperature and strain on the precipitation of MX phases. It is found that the number density of MX phase after TMT increases by two orders of magnitude, and the average particle size decreases by about 79% when the austenitization temperature increases from 1000 to 1150 °C, while the effect of deformation temperature and strain is relatively small; after TMT, the specimen with the largest number and the smallest size of MX phase has the best creep performance, and vice versa.

Effect of thermo-mechanical treatment and strontium addition on workability and mechanical properties of Al Si Cu casting alloy

In this study, the potential application of Al-Si-Cu aluminum alloy (ALDC12), which is widely used in the high-pressure die-casting (HPDC) process, for fabricating a wrought product was evaluated. The effects of thermo-mechanical treatment and Sr addition on the microstructure, workability, and mechanical properties of the ALDC12 alloy were investigated in detail. The introduction of thermo-mechanical treatment significantly reduced the interconnectivity of the brittle eutectic Si phase formed during solidification and average grain size. Therefore, the uniformly distributed spherical Si particles and fine grain size considerably improved both the strength and ductility of the ALDC12 alloy. Furthermore, the addition of Sr effectively modified the eutectic Si phase in the casting process, which significantly reduced the occurrence of edge cracks in the subsequent rolling step and further improved the mechanical properties of the final sheets. Consequently, through microstructural control of the ALDC12 aluminum alloy by the thermo-mechanical treatment and Sr addition, it was possible to obtain suitable workability and significantly improved mechanical properties compared with those of cast products.

Influence of thermo-mechanical treatment on mechanical properties and shape memory effect of CuAlNiMnTi shape memory alloys

Shape memory alloys (SMAs) are vital in many advanced applications, such as micro-electro-mechanical systems (MEMS). Therefore, this work aimed at studying the effect of thermo-mechanical treatment in conjunction with alloying elements modification on improving the mechanical properties and shape memory effect (SME) of Cu–Al–Ni SMAs. In this study, the samples were divided into two groups: the first group was solution treated at 900 °C for 30 min. (S.T), and the other group was hot-rolled at 900 °C followed by solution treatment at 900 °C for 30 min. (H.R.S.T). The results showed that the hardness of the samples decreased with increasing the percent of Ni. In addition, the DSC investigations revealed that the martensite start temperature (Ms) decreased by 50–60 °C compared to the predicted Ms reported in the literature. Surprisingly, the alloying additions as well as thermo-mechanical treatment achieved a tensile elongation up to 22%, and a tensile fracture stress up to 600 MPa. Moreover, the shape recovery ratio exceeded 97%.

Effect of Thermo-Mechanical Treatment on Ductility of Cu–0.29 mass%Zr Alloy Wires

Effect of Thermo-Mechanical Treatment on Ductility of Cu–0.29 mass%Zr Alloy Wires

Influence of Thermomechanical Treatments on Corrosion of Carbon Steel in Synthetic Geopolymer Fly Ash Pore Solution

In this study the effect of thermomechanical treatments in chloride induced pitting corrosion is presented for carbon steel rebars exposed to synthetic fly ash (FA) pore solution. Due to the likely phase transformations that steel reinforcements in concrete experience during the event of a fire, the understanding of the corrosion behavior of such phases is key in predicting the stability of the structure. The motivation for this study arrives from the scarce literature regarding the corrosion behavior of thermomechanically treated steel reinforcements in FA environments and the need for further investigation to understand its mechanism. In order to better understand the effects on the corrosion behavior electrochemical measurements including cyclic potentiodynamic polarization curves (CPP) and electrochemical impedance spectroscopy (EIS) were used. It was found that quenched specimens showed enhanced corrosion kinetics as their icorr values were higher, being of 3.18 × 10−5 and 2.20 × 10−5 A/cm2 for water and oil quenched compared to 2.13 × 10−6 A/cm2 for the as-received. Furthermore, the effective capacitance of the double layer (Ceff,dl) showed the lower stability of the passive film for the quenched specimens, with values of 1.11 × 10−3 µF/cm2 for the as-receive sample that decreased to 8.12 × 10−4 µF/cm2 for the water quenched sample. The anodic charge transfer coefficient in the synthetic FA alkaline pore solution changes from 0.282 to 0.088, for the as-received and water quenched rebars specimens, respectively. These results indicate a lower energy barrier for the anodic dissolution reaction of quenched specimens, indicating that martensite and bainite microstructures promote corrosion process. Enhanced corrosion was found on quenched samples presenting martensite and bainite microstructure as showed by the increased pith depth, with values of 5 μm compared to 1 μm observed in the as-received samples.

The effect of thermo-mechanical treatment on the formation of T1 phase and δ′/θ′/δ′ composite precipitate in an Al-Cu-Li-Mg alloy

The T1-precipitates and δ′/θ′/δ′ composite precipitates are the two primary strengthening precipitates and co-exist in the age-hardened 3rd generation AlLi alloys. The relative proportion of these two types of precipitates formed in the alloys is strongly dependent of the thermo-mechanical-treatment (TMT) processes applied. In the present study, using electron microscopy and properties characterization, the competitive precipitation behaviors of these two types of precipitates in an Al-4.0Cu-0.9Li-0.2Mg (wt.%) alloy, and the property of the alloy were investigated systematically in relation to TMT processes employed. It is shown that a 5% pre-deformation can promote the formation of T1 precipitates but depress the δ′/θ′/δ′ composite precipitates, which improves the strength but decreases the plasticity of the alloy significantly. A pre-natural-aging will promote the fine δ′/θ′/δ′ composite precipitates and T1 precipitates to form uniformly during subsequent artificial aging, improving the strength while maintaining good plasticity. A pre-artificial-aging at 180 °C will depress the formation of T1 precipitates, and greatly reduce the plasticity of the alloy. Our study indicates that when the T1 and the δ′/θ′/δ′ precipitates are equally developed, the alloy may achieve optimized properties.

EFFECT OF SEVERE PLASTIC DEFORMATION ON RADIATION HARDENING OF T91 FERRITIC-MARTENSITIC STEEL

Effect of thermomechanical treatment on radiation hardening behavior in T91 ferritic-martensitic steel was evaluated. An applying of severe plastic deformation (SPD) by the “upsetting-extrusion” method and subsequent heat treatment led to a considerable grain refinement, crushing of martensite lamellas, reduction of MX carbides size and their more uniform distribution. Nanoindentation measurements of SPD-modified steel revealed a 1.4-fold increase in the hardness relative to the initial steel. Irradiation response of modified steel was examined after 1.4 MeV Ar+ ion irradiations in the dose range of 10…45 displacements per atom (dpa) at room temperature and 460 °C. Microstructure characterization was performed by means of transmission electron microscopy (TEM). It was found that dislocation loops and nano-sized argon bubbles dominated the damage microstructure after ion irradiation. The effects of SPD-induced transformations as well as nano-bubbles formation are discussed regarding to the hardening phenomenon observed in irradiated steel.

Effect of Thermomechanical Treatment on Functional Properties of Biodegradable Fe-30Mn-5Si Shape Memory Alloy

The structure, martensitic γ ↔ e transformation temperatures, Young’s modulus, mechanical properties, and electrochemical behavior of Fe-30Mn-5Si (wt pct) biodegradable shape memory alloy subjected to various thermomechanical treatments (TMT) comprising hot rolling or cold rolling with post-deformation annealing were characterized by optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, tensile testing, open circuit potential, and polarization curves measurements in Hanks’ solution, as compared to reference heat treatment. The optimum combination of mechanical properties (low Young’s modulus, high tensile strength, and appropriate ductility) for biomechanical compatibility was obtained after TMT with hot rolling at 600 and 800 °C due to the formation of favorable dynamically polygonized and recrystallized structures and decrease in the γ↔e transformation starting temperature down to the human body temperature. The TMT did not show a significant effect on the corrosion rate as compared to the appropriate corrosion rate after the reference heat treatment. It is concluded that the TMT with hot rolling at 600 or 800 °C, which provides an optimum combination of the required corrosion rate in the simulation body fluid with high biomechanical compatibility, can be considered a promising treatment of Fe-30Mn-5Si biodegradable alloy for bone implants.

Опыт изготовления штамповок из титановых сплавов в производственных условиях ФГУП "ВИАМ"

The purpose of the study was to reveal the effect of various technological aspects of manufacturing titanium alloy ВТ8 (VT8) forgings under isothermal conditions on a press with a force of 1600 kN. The starting material was OST 1 90266--86 and OST 1 90107--73 VT8 (ВТ8) alloy bars. For the forgings obtained from these rods, the score and background of the macrostructure, the type of microstructure, short-term strength, elongation, contraction and impact toughness at room temperature were determined. For forgings made from an OST 1 90266--86 bar, the effect of thermomechanical treatment on the level of properties was additionally evaluated, namely, half of the forging was recalibrated. The microstructure of the forgings which were made by thermomechanical treatment and aged was additionally investigated using scanning electron microscopy. Findings of research show a direct dependence of the quality of the final semi-finished product on the quality of the original bar. It has been established that lowering the punching temperature to the level of Tpp -- 150 °С leads to insufficient development of the structure of the deformed material over the cross section, and results in the presence of large grains from the initial bar. So, on forgings made from an OST 1 90266--86 bar, the following level of mechanical properties was achieved: σv ≥ 1000 MPa, δ ≥ 11 %, ψ ≥ 20 %, KCU ≥ 40.3 J / cm2

Effect of Thermomechanical Treatments on the Mechanical Properties of New Low-Cost Ti-Fe-Nb-Zr Alloys

The development of new low-cost alloys composed of common elements that show high biocompatibility and mechanical properties matching with human bone is the target of many researches recently. Design and controlling the mechanical properties of newly developed set of Ti-xFe-3Zr-yNb (x=3-8 & y=2-3, at.%) low-cost alloys through applying different thermomechanical treatments is the aim of this work. Fe-content in the present designed alloys is changing in the range 3 to 8 at.%. The hardness and Young's modulus of the alloys were measured for the alloys in the solution treated, hot rolled and subsequent ageing at 400 °C and 550 °C. The phases separation and hence hardness of the aged alloys at 400 °C and 550 °C are highly dependent on the Fe-content in the alloy. The Young's modulus of the alloys is also changing with the Fe-content and heat treatment, where lowest modulus (~80GPa) is shown in the Ti-5Fe-3Zr-3Nb alloy in the solution treated condition.

Evolution of Carbides during Prestrain and Tempering

The effect of thermo-mechanical treatment on the microstructural evolution of low carbon micro-alloyed high strength steel was studied by combining prestrain with tempering (PST) in this paper. It was found that the prestrain causes the dislocation to plug up around the grain boundary and carbide, resulting in carbide boundary fragmentation. Moreover, it breaks the thermo-dynamic equilibrium between the matrix and carbide, induces the dissolution of carbon in the high energy state, and then changes the distribution of carbon in the matrix. In the subsequent tempering process, the precipitation regularity of carbide was changed, which promoted the precipitation carbide at low temperature. The influence of carbide precipitation on dislocation can be divided into two stages: the first stage was precipitation induced creep, which promoted stress relaxation; the second stage was precipitation pinning dislocation, which improved material strength and inhibited stress relaxation.

Effect of thermomechanical treatment on the microstructure and mechanical properties of a low-carbon low-alloy steel

The effect of thermomechanical treatment on the microstructure, tensile strength and impact toughness of low-carbon low-alloy steel is considered. The developed microstructure is characterized by grain elongation along the rolling direction. Both the yield strength and the ultimate tensile strength increase with a decrease in test temperature. The ultimate strength at room temperature is 797 MPa, and at 77 K the ultimate strength increases to 1198 MPa. The steel samples subjected to tempforming exhibit impact toughness of KCV = 410 J/cm2 at room temperature. A decrease in the test temperature to 233 K leads to a slight decrease in the KCV value to 340 J/cm2. It should be noted that the impact specimens are not completely fractured even at a test temperature of 233 K, suggesting higher real values of impact toughness.

Effect of thermomechanical treatment on structure and properties of metastable Ti-25Nb-8Sn alloy

Effect of thermomechanical treatment on structure and properties of metastable Ti-25Nb-8Sn alloy

FEM study of internal stresses evolution in prestressing strands

This paper describes the results of modeling when the processes of stranding, reduction, straightening and thermo-mechanical treatment (TMT) of prestressing strands were simulated with the help of finite-element method. The distribution of residual stresses used in the simulation models refers to the stresses created at the preliminary stage of wire drawing. The simulation study looked at the effect of thermo-mechanical treatment on the internal wire stresses: residual stresses resultant from the drawing process and further stranding stresses. All studied methods demonstrated a positive effect not only in terms of eliminating internal stresses, but also from the point of view of their redistribution. Reduction of a strand in a solid tool at the ratios of 1–3 % allows to create tensile stresses at the surface of the wire and retain compressive stresses in its core. Straightening in a 5-roller group helped reach a double relaxation in outer wires. TMT, a process combining different physical effects, enabled to control within a broad range the redistribution of residual stresses in steel that was subjected to prior drawing at high deformation ratios. Such residual stresses occur as a result of stranding stresses that accompany the stranding operation and can affect the geometry of the strand. The study showed that tension as a TMT parameter plays a greater role in the elimination of longitudinal residual stresses. That’s why, at the minimum tension, almost no redistribution of residual stresses occur either in the central or in the near-surface layers irrespective of the TMT temperature regime applied. However, when the tension exceeding 70 kN is applied at the temperatures of 380–400 °C, the central and surface residual stresses balance off in the wire or almost disappear. This research was carried out under the Decree No. 220 dated 9th April 2010 of the Government of the Russian Federation (Contract No. 075-15-2019-869 dated 12th May 2019) and was funded by the Russian Science Foundation (Project No. 20-69-46042 dated 20th May 2020) and by the Russian Ministry of Education and Science with the goal of developing high-tech production (contract nos. 02.G25.31.078, December 1, 2015; and MK204895, July 27, 2015).

Characterization of ductile phase toughening mechanisms in a hot-rolled tungsten heavy alloy

Tungsten heavy alloys (WHAs) are a type of ductile phase toughened alloy that are becoming increasingly interesting as an alternative to polycrystalline tungsten for fusion reactor plasma facing material components due to their balanced strength and ductility. To justify their use in the extremely harsh environment of a fusion reactor, understanding detailed microstructural features of WHAs associated with their mechanical property changes is necessary. A 90W-7Ni-3Fe WHA alloy has been chosen to investigate the effect of thermomechanical treatment and microstructural manipulation on the overall effectiveness of deformation accommodation in these bi-phase metallic composites. Both in-situ tensile testing and 3D microstructural analysis of the samples reveal a predominance of microcracking at tungsten grain boundaries that are blunted and arrested by the ductile phase, while there remains little to no instances of interfacial debonding. Thermomechanical treatment of this alloy is found to alter the spherical brittle phase domains into elongated plates, drastically reducing the ductile phase connectivity, and changing the nature of material deformation. Characterization of the ductile phase toughening mechanisms in these materials has provided deeper insight into the underlying physics governing material behavior in these alloys; revealing a surprising interfacial strength between the different phases.

The effect of thermomechanical treatments on the properties of powder metallurgy Ti–5Fe alloy

In this study, the low-cost Ti–5Fe alloy was fabricated by a combination of sintering plus thermomechanical treatment (TMT). The primary aim is to improve the tensile properties of the recently widely studied powder metallurgy Ti-xFe alloys made by the press and sinter process. The effect of hot forging or extrusion and subsequent annealing treatment on the microstructure and mechanical properties of the Ti–5Fe alloy was therefore studied. TMT from temperatures in the β-phase field severely changes the microstructure of the sintered alloy. The substantial deformation of the β-grains and the formation of fine α-phase have a significant effect on the mechanical properties. The yield and ultimate tensile strengths of the TMT alloys reach high values, from 1050 MPa to over 1200 MPa. The subsequent heat treatment results in the modification of the α-phase morphology and the partial loss of the crystallographic texture, leading to the enhancement of the elongation to values above 20%, despite of the high oxygen content of the alloy.

Characterization of Ductile Phase Toughening Mechanisms in a Hot-Rolled Tungsten Heavy Alloy

Tungsten heavy alloys (WHAs) are a type of ductile phase toughened alloy that are becoming increasingly interesting as an alternative to polycrystalline tungsten for fusion reactor plasma facing materials due to their balanced strength and ductility. To justify their use in the extremely harsh environment of a fusion reactor, understanding detailed microstructural features of WHAs associated with their mechanical property changes is necessary. A 90W-7Ni-3Fe WHA alloy has been chosen to investigate the effect of thermomechanical treatment and microstructural manipulation on the overall effectiveness of deformation accommodation in these bi-phase metallic composites. Both in-situ tensile testing and 3D microstructural analysis of the samples reveal a predominance of microcracking at tungsten grain boundaries that are blunted and arrested by the ductile phase, while there remains little to no instances of interfacial debonding. Thermomechanical treatment of this alloy is found to alter the spherical brittle phase domains into elongated plates, drastically reducing the ductile phase connectivity, and changing the nature of material deformation. The manipulation of microstructures via hot rolling or other deformation processing may be the precursor to more effective materials for nuclear fusion applications.

Effects of thermomechanical treatment on the microstructure, precipitation strengthening, internal friction, and thermal stability of Al–Er-Yb-Sc alloys with good electrical conductivity

Rare-earth elements improve the mechanical properties of aluminum owing to the formation of the L12-structured nanoprecipitates providing the precipitation strengthening effect. The precipitates type, size, and number density depend on the alloy chemical composition and a thermomechanical treatment regime. It is essential to develop the alloys and treatments, providing a combination of the enhanced mechanical strength and a high level of electrical conductivity. This study investigates the influence of thermomechanical treatments on the microstructure, precipitation strengthening, mechanical properties, and electrical conductivity of Al–Er-Yb-Sc alloys with differing Sc content. An as-cast structure of the alloys studied consists of a supersaturated aluminum solid solution and Al3(Er,Yb) phase particles of eutectic origin with the particle thickness of 50–200 nm. A significant strengthening during post-deformation annealing is achieved by precipitation of L12-Al3(Sc,Er,Yb) phase dispersoids of 4–8 nm in size. The mechanical spectroscopy method is successfully used to understand the precipitation kinetics of the studied alloys in comparison with analogous Al-Yb-Y-Sc alloys. This method is highly sensitive to lattice defects parameters, i.e., recrystallization and precipitation kinetics. High-scandium alloys demonstrate an increase of the hardness and tensile strength and insignificant changes in the internal friction background level during post-deformation annealing of cold-worked samples at 300 °C. The yield strength of the Al–Er-Yb-Sc alloys after post-deformation annealing is 142–231 MPa, elongation-to-failure is 3.6–13.5%, and electrical conductivity is 54.8–60.9% IACS, dependent on scandium content and annealing parameters. The studied alloys exhibit high thermal stability of the tensile properties, which remains unchanged during annealing at 300 °C for 100 h.