Effect Of Thermomechanical Processing Research Articles

Effect of thermomechanical processing on the mechanical properties of CuZn10 alloy

Abstract The effects of thermomechanical processing on the grain size, tensile strength, and strain rate of a CuZn10 alloy were investigated. Microstructures of thermomechanically treated samples were introduced using a scanning electron microscope. The relationships between the flow stress, reduction ratio, annealing temperatures, and strain rates were detected for determination of activation energies and optimized thermomechanical parameters. The effect of grain size on the mechanical properties was examined by tensile and microhardness tests. The typical fractographs of samples after tensile tests were examined using a scanning electron microscope. It was observed that the annealing temperature and aging time have significant effects on the optimum grain size. Mechanical properties of the thermomechanically treated samples were improved by strain rate, deformation ratio, annealing temperature, and aging time.

Grain boundary modification and plasticization of pure nickel wires via torsion and annealing

Pure nickel wires are conducted to “torsion and annealing” grain boundary modification to study the effect of thermomechanical process (TMP) on grain boundary characteristics and plasticity. Compared with the initial sample, the elongation of the sample subjected to the optimal TMP increases by 103% while its tensile strength only reduces by 1.8%. A new micro index is presented to comprehensively indicate the coupling effect of grain size and grain boundary characteristic distribution on material plasticity. Numerous special boundaries generate during the initial recrystallization stage in TMP. The interfaces between recrystallization nuclei and the adjacent matrixes are basically incoherent Σ3ic boundaries. EBSD and TEM observations manifest that Σ3 boundaries, especially Σ3ic boundaries, have much weaker resistance on dislocation slip compared with random boundaries. The essence of plasticizing by GB modification is to make the material keep in the state that just completes recrystallization and contains as much as Σ3ic boundaries through coordinated TMP.

Effect of thermomechanical processing via rotary swaging on grain boundary character distribution and intergranular corrosion in 304 austenitic stainless steel

In the present work, the thermomechanical processing consisting of rotary swaging deformation and annealing treatment was performed to optimize the grain boundary character distribution (GBCD) of 304 austenitic stainless steel. To systematically investigate the effect of GBCD evolution on intergranular corrosion (IGC), double loop electrochemical potentiokinetic reactivation and electrolytic oxalic acid etch tests were employed. The experimental results show that the fraction of low-Σ coincident site lattice (CSL) boundaries increased from 58.1% to 74.0% for the specimen swaged to 0.06 true strain and then annealed at 1050 °C for 5 min duration. By characterizing the evolution of GBCD as a function of strain level in terms of low-Σ CSL boundaries fraction, average twin-related domain (TRD) size, average number of grain per TRD and fractal dimension of the maximum random boundary connectivity, the grain boundary engineering (GBE) microstructure was realized by the occurrence of prolific multiple twinning events during strain-induced boundary migration while static recrystallization has a detrimental effect on optimizing GBCD for the prolific of new strain-free grains with random boundaries. The IGC resistance of the GBE-treated 304 austenitic stainless steel is enhanced by inhibiting the nucleation and propagation of IGC cracks, resulting from the increase in the fraction of low-Σ CSL boundaries, especially Σ3 boundaries and the disruption of random boundary network connectivity.

Microstructural investigation of thermo-mechanically processed lithium slag for geopolymer precursor using various characterization techniques

Lithium slag is an emerging industrial waste due to the increasing demand for lithium rechargeable batteries attributed to the recent boom in the automobile industry and space exploration. It is extracted as a powder residue in sedimentary tanks after the refining process of lithium extraction. In this study, the effect of thermo-mechanical processing on the chemical reactivity of lithium slag is assessed by TESCAN Integrated Mineral Analyzer (TIMA), X-ray Fluorescence (XRF), Rietveld quantitative refinement techniques. The chemical, mineral, and crystallographic phase composition of processed lithium slag specimens were assessed and compared by XRF, TIMA, and Rietveld quantitative refinement techniques, respectively. The results of thermo-mechanical processing indicated that the mineral and crystallographic transformation of Spodumene to feldspars (Anorthite, Muscovite, Albite) occurred by crystallite agglomeration. The chemical reactivity of lithium slag is gauged in terms of amorphous alumino-silicates present in feldspars and unidentified phases. Characterization of unidentified phase is evident that it majorly contains micro-nano sized alumino-silicate rich particles with similar spectral signatures to that of feldspar, some fraction of it is aggregated into other phases due to its reactivity. The concentration of the amorphous phase is proportionate with the thermo-mechanical processing energy. However, the thermo-mechanical processing energy is also optimized based on the generation of amorphous phase and reduction in particle size. Therefore, the G1C700 processed regime resulted in one of the maximum amounts of amorphous phase (52.60%). The mineral phase transformation of Spodumene to Anorthite (+10.46%) and unidentified phase (+8.24%) along with D50 value of 13.26 µm, consequently releasing 0.45 kg of carbon emissions upon thermo-mechanical processing. Hence, G1C700 lithium slag is recommended for its use as a geopolymer precursor.

Boron and Thermomechanical Processing Effects on the Metallurgical Properties of a Niobium-Titanium High-Strength Low-Alloy Steel

Boron and Thermomechanical Processing Effects on the Metallurgical Properties of a Niobium-Titanium High-Strength Low-Alloy Steel

Effect of thermomechanical processing on microstructure characteristics of γ-TiAl-based alloy

In this study, the grain boundary character distribution (GBCD) of the γ-TiAl-based alloy was modified through the thermomechanical processing route. A compression test was conducted to identify the mechanical property improvements based on the grain boundary engineering (GBE) treatment. After multidirectional isothermal forging (MDIF) and annealing, the average grain size was refined to 20 µm. The length ratio of the low Σ (1 ≤ Σ ≤ 29) coincidence site lattice (CSL) boundaries increased to 64.01%, with the alloy exhibiting a higher compressive strength (2913 MPa) and maximum compression ratio (45.3%), owing to the strengthening mechanism of grain boundaries and dislocations. Consequently, the combination of MDIF and annealing could be used for grain refinement and tuning GBCD of γ-TiAl-based alloys.

Effect of Thermomechanical Processing on the Microstructures and Mechanical Properties of Cu-28Zn-2Al Alloys

This research was conducted to investigate the effect of thermomechanical process on microstructures and mechanical properties of Cu-28Zn-2Al alloys. Thermomechanical process was carried out by cold rolling process with 70% thickness reduction and followed by annealing process with variation temperature of 400°C, 500°C and 600°C. The result show that the β phase and shear bands are found in the samples. Further, cold rolling process can increase hardness of Cu-28Zn-2Al alloys from 100 to 172 VHN. The heat treatment with annealing process at 400°C tend to decrease the tensile strength of cold rolled samples from 695 to 472 MPa and more decreased until 422 MPa at 600°C. In contrast, annealing process at 400°C tend to increase the elongation from 10 to 28% and more increased up to 56% at 600°C. This phenomenon prove that the annealing process will increase ductility of cold rolled samples of Cu-28Zn-2Al alloys.

Effect of Thermo-Mechanical Processing on Grain Boundary Character Distribution and Sensitization of Austenitic Steel TP321

Effect of Thermo-Mechanical Processing on Grain Boundary Character Distribution and Sensitization of Austenitic Steel TP321

Effects of Thermomechanical Processing on Hydrogen Embrittlement Properties of UltraHigh-Strength TRIP-Aided Bainitic Ferrite Steels

The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength, low-alloy, transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were evaluated by conducting conventional tensile tests after hydrogen charging and constant load four-point bending tests with hydrogen charging. The 0.4 mass%C-TBF steel achieved refinement of the microstructure, improved retained austenite characteristics, and strengthening, owing to thermomechanical processing. This might be attributed to dynamic and static recrystallizations during thermomechanical processing in TBF steels. Moreover, the hydrogen embrittlement resistances were improved by the thermomechanical processing in TBF steels. This might be caused by the refinement of the microstructure, an increase in the stability of the retained austenite, and low hydrogen absorption of the thermomechanically processed TBF steels.

Characterising Correlations between Electric Conductivity and Structural Features in Rotary Swaged Al/Cu Laminated Conductors.

This study aims to characterize the correlations between electric characteristics and selected structural features of newly designed Al/Cu laminated conductors manufactured via room temperature rotary swaging. After swaging, the laminates with diameters of 15 mm were subjected to two different post-process annealing treatments. Structure analyses performed to evaluate the effects of thermomechanical processing were performed via scanning and transmission electron microscopies. Electric conductivity and resistivity of the laminates were experimentally measured and numerically simulated using models designed according to the real conditions. The results showed that the electric resistivity was affected by the grain size, bimodal grains’ distribution (where observed), the presence of twins, and, last but not least, dislocation density. Among the influencing factors were the area fractions of Al and Cu at the cross-sections of the of the laminated conductors, too. The results revealed that fabrication of the laminate via the technology of rotary swaging introduced more advantageous combinations of electric and mechanical properties than fabrication by conventional manufacturing techniques. The lowest specific electric resistivity of 20.6 Ωm × 10−9 was measured for the laminated conductor subjected to the post-process annealing treatment at 350 °C, which imparted significant structure restoration (confirmed by the presence of fine, equiaxed, randomly oriented grains).

Mechanical behavior and stability of dispersed retained austenite in thermomechanically rolled and isothermally-treated TRIP-aided multiphase steel

The effect of thermomechanical processing and cooling conditions on the microstructure and mechanical properties during multi-step interrupted tensile tests was investigated in 0.24C–1.55Mn-0.87Si-0.40Al multiphase steel. Two temperature variants of isothermal bainitic holdings at 450 and 350 °C were applied. The tensile tests were interrupted at strain levels of 5, 10, 15%. The microstructure was assessed using light and SEM microscopy. EBSD analysis was performed to determine the retained austenite (RA) distribution and size. Detailed calculations concerning the mechanical performance were performed including the Jaoul-Crussard's analysis. Multiphase steels with the high retained austenite fraction (ca. 15%) of different γ phase sizes below 4 μm in a ferritic-bainitic matrix (with an average size of <6 μm) have been obtained. The research showed that during martensitic transformation of RA, the grain undergoes fragmentation. It has been shown that for the proper use of the TRIP effect, it is necessary to produce the dispersed RA of different sizes in the structure instead of striving for maximum fragmentation, which is a commonly used practice. Obtaining too small grains in the microstructure blocks their transformation during deformation due to their too high stability. Obtaining grains of one size leads to the intensification of the TRIP effect at a given stage of deformation only, reducing the plasticity in the others. The corresponding different mechanical stability of the γ phase ensures a gradual martensitic transformation and beneficial strain hardening progress.

Quantitative morphological characterization of carbide inclusions in uranium metal

Uranium carbides (UCs) are prevalent inclusions in U metal that form during melting operations because of interactions with crucible walls and the casting chamber atmosphere. Although UCs have been studied extensively since the beginning of U metal foundry operations, there are still unknowns regarding the effects of thermomechanical processing on their sizes and morphology. Here, we present the results of a series of controlled cooling experiments with molten uranium to elucidate the effect of cooling rate on inclusion morphology in α-U. Samples were melted using a vacuum induction melter and manually cooled at rates of 2.5, 1.7, 1.1, 0.8, and 0.3 (± 1%) K/s from ∼1600 K to < 700 K in under 1 h. Subsequent scanning electron microscopy (SEM) was performed on cross sections of the samples, revealing a complex mixture of UC morphologies that are indicative of diffusion and growth influenced by the thermal processing of the U matrix. Image analysis using the morphological analysis of materials (MAMA) software showed that UC sizes generally grew larger with slower cooling rates, and the two slowest cooling rates noticeably affected the inclusion circularity and ellipse aspect ratio. These results indicate that UC morphology is sensitive to short cooling rates (< 1 h) and could therefore be controlled in the production of metallic nuclear fuels. Additionally, inclusion speciation and morphologies could potentially provide forensic clues about the processing history of unknown metal samples. Understanding the driving forces involved in UC morphology evolution is beneficial for evaluating metal fuels for next-generation nuclear reactors and for identifying signatures for nuclear forensics.

How the Thermomechanical Processing Can Modify the High Strain Rate Mechanical Response of a Microalloyed Steel.

The effects of thermomechanical processing (TMP) on the mechanical response of microalloyed steels subjected to dynamic loading conditions were examined. The deformation conditions in the thermomechanical laboratory rolling processes were selected on the basis of dilatometric tests. It allowed (with a constant value of total deformation) us to obtain microstructures with different compositions and morphology of the particular components. Several samples characterized by a particularly complex and unexpected representation of the obtained microstructures were selected for further research. Plastometric tests, i.e., compression and tensile tests, were performed under quasi-static loading with digital image correlation (DIC) analysis, and under dynamic loading on the Split Hopkinson Pressure Bar (SHPB) apparatus with strain rates of 1400 and 2000 s−1. Samples deformed in such conditions were subjected to microstructural analysis and hardness measurements. It has been observed that the use of various combinations of TMP parameters can result in the formation of specific microstructures, which in turn are the source of an attractive mechanical response under dynamic loading conditions. This opens up new possible areas of application for such popular structural materials which are microalloyed steels.

The effect of thermomechanical process on metallurgical and mechanical properties of 38MnVS6 micro alloyed steel

AbstractThis study aims to have the proper mechanical properties without applying any heat treatment process after hot forging by using 38MnVS6 micro alloyed steel in tow hook manufacturing which is used in automobiles. The effect of forging temperature and cooling rate on metallurgical and mechanical properties of micro alloyed steel is investigated. The samples of micro alloyed steel are forged at 800 °C, 850 °C, 900 °C, 1050 °C and cooled down at the rates of 0.75 °C/s and 1.5 °C/s. The forging temperature and the cooling rate have a significant effect on toughness by the experimental and numerical studies. The amount of ferrite increases with a decreasing forging temperature, and the toughness is improved by increasing the amount of ferrite. Also, by increasing the cooling rate after forging at 1050 °C, the acicular ferrite is observed which has a positive effect on both the toughness and strength of the micro alloyed steel.

Effects of thermo-mechanical process on phase transitions, hydrogen solubility and corrosion of Ta-modified Zr-1Nb alloys

The feasibility of using Ta as a minor alloying element in Zr-1Nb alloys is addressed in terms of phase stability and resistance to corrosion of the microstructure obtained with the following two thermomechanical processes after a water quenching from βZr: a) annealed at 570°C for 3840 h and b) a combination of intermediate annealing temperatures and cold rolled steps. Hydrogen solubility was also measured, but only in alloys with the first process. It was found, through calorimetric measurements, that an increase of Ta replacing Nb in the nominal alloy composition increases the α→(α+β) phase transformation temperature in agreement with an estimated increase in the enthalpy of formation of the βNb/Ta phase, ΔHβNb/Taf. As expected, the mass fraction of βNb/Ta measured in the rolled alloys is lower. Further, this diminution is larger in the alloys containing Ta due to the lower mobility of Ta and higher ΔHβNb/Taf. The growth of the oxide layer in each alloy, at 400°C steam up to 14 days, follows the predictor calculated as the ratio between the atomic concentrations of Nb plus Ta in the alloy and ΔHβNb/Taf. A slight decrease in hydrogen solubility was observed at low Ta content in the alloy.

Effect of thermo-mechanical processing on quench-induced precipitates morphology and mechanical properties in high strength AA7075 aluminum alloy

The effect of a novel thermo-mechanical process route on quench-induced precipitates morphology and mechanical properties of high strength AA7075 aluminum alloy is investigated in the present work. After solutionizing the probed material is hot formed and quenched at different tool temperatures ranging from 24 to 350 °C to determine the influence of different cooling rates. The strengthening mechanisms and precipitation morphology after aging are examined based on mechanical testing, microstructure observation and differential scanning calorimetry. The results demonstrate that the tool temperature, as a key element of the investigated process, affects significantly the material strength due to a fundamental change in the microstructure and the strain hardening behavior when exceeding a temperature limit. At tool temperatures from 24 to 200 °C only a slight decrease in tensile strength from 590 to 568 MPa is obtained. When increasing the tool temperature above 200 °C, up to 350 °C, the tensile strength drops to 336 MPa and the initial strain hardening rate θ0 increases. This behavior is linked to the change of quench-induced precipitates morphology and shape. TEM investigations revealed high fractions of semi coherent η’-phases for low and coarse η-phases for high tool temperatures causing a fundamental shift of strengthening mechanisms from predominantly particle shearing to a combination of bypassing and strain hardening by Orowan loops. High diffusion rates and local accumulation of solute atoms at grain boundaries during cooling led to the formation of large grain boundary precipitates during aging, even after high cooling rate using cooled tools.

Effect of Interstitial Elements on the Cryogenic Mechanical Behavior of FCC High Entropy Alloys

High entropy alloys (HEAs) with face-centered cubic (fcc) structure, namely equiatomic CoCrFeMnNi alloy, have attracted considerable attention because of impressive cryogenic mechanical properties – strength, ductility, and fracture toughness. Further increase of the properties can be achieved, for example, by proper alloying. A particularly attractive option is the addition of interstitial elements like carbon or nitrogen. In present work, a series of CoCrFeMnNi-based alloys with different amounts of C and N (0-2 at.%) was prepared by induction melting. The alloys doped with C had lower Cr content to increase the solubility of carbon in the fcc solid solution. It was revealed that the solid solution strengthening effect of both C and N is significantly increased when the testing temperature decreases from 293K to 77K. The effect of thermomechanical processing on the structure and mechanical properties of the alloys is analyzed.

Effect of Severe Forging and Rolling on the Microstructure and Mechanical Properties of Al–Mg–Sc–Zr Alloy

The effect of thermomechanical processing combining one- or two-step isothermal multidirectional forging (MF) and sheet rolling on the structure and mechanical properties of alloy 1570C (Al–5Mg–0.18Mn–0.2Sc–0.02Zr (wt %)) was studied. One-step MF was performed at a temperature of 325°C to a true strain (e) of about 12. In two-step MF, deformation was continued at 250°C to e ≈ 6 (total strain of about 18). Subsequent warm rolling with a total strain e ≈ 1.6 (relative strain of about 80%) was carried out at the corresponding temperatures of each MF step, and cold rolling was performed at room temperature. In both MF steps, relatively uniform (ultra)fine-grained structures with a grain size of 2.2 and 1.9 μm, respectively, were obtained. Subsequent warm rolling led to further grain refinement, whereas cold rolling ensured the formation of highly work-hardened (ultra)fine-grained structures with high densities of lattice dislocations. The best combination of technological and service properties, including strength, plasticity, superplasticity, and thermal stability, was reached in sheets after one-step (higher temperature) MF. Lowering the deformation temperature in the second MF step ensured further alloy strengthening, but impaired its room-temperature rollability and led to an essentially complete degradation of the superplasticity of the obtained sheets.

Effect of Thermo-Mechanical Processing on the Corrosion Behavior of Fe−30Mn−5Al−0.5C TWIP Steel

Electrochemical corrosion of thermo-mechanically processed (TMP) and recrystallized Fe−30Mn−5Al−0.5C twinning-induced plasticity (TWIP) steels containing 30 wt.% Mn was studied in a 1.0 wt.% NaCl electrolyte solution. The alkaline nature of the corrosion products containing manganese oxide (MnO) increases the dissolution kinetics of the TWIP steel in acid media, obtaining Mn2+ cations in solution, and producing the hydrogen evolution reaction (HER). X-ray photoelectron spectroscopy (XPS) surface analysis revealed an increased Al2O3 content of 91% in the passive layer of the recrystallized TWIP steel specimen, while in contrast only a 43% Al2O3 was found on the TMP specimen. Additionally, the chemical composition of the surface oxide layer as well as the TWIP alloy microstructure was analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The results indicate an enhanced corrosion attack for the TMP high-Mn TWIP steel.

Extra-strengthening in a harmonic structure designed pure titanium due to preferential recrystallization phenomenon through thermomechanical treatment

The effect of thermomechanical processing (TMP), consisting of cold rolling followed by annealing, on the microstructure and mechanical properties of Harmonic Structure designed commercially pure Ti (HS–Ti) was studied. The TMP of HS-Ti led to the evolution of a peculiar preferentially recrystallized structure, localized in the Shell and Shell-Core interface regions. The underlying mechanism for such a unique microstructural evolution in the TMP HS-Ti has been proposed and discussed. The TMP treated HS-Ti specimens exhibited considerably higher strength values and comparable ductility with respect to its conventional homogeneous structured Ti (Homo-Ti) and as-sintered HS-Ti counterparts. The present work demonstrated that it is feasible to further enhance the superior mechanical properties of harmonic-structured materials through controlling the volume fraction and the grain size of the Core/Shell via controlling TMP parameters.