Search Results (35)

This study explored the effects of the finishing deformation temperature on the microstructure and properties of CrVNb micro-alloyed steel following thermomechanical processing (TMP). The investigation encompassed the influence of the deformation temperature on the ferrite grain size, precipitate characteristics, hardness and flow stress. The microstructure characterization was performed using optical and electron microscopy techniques. The results show that decreasing the deformation temperature refined the ferrite grains, though a bimodal ferrite grain structure formed when the deformation temperature fell to about 100 °C below the Ar3 temperature. Additionally, lower deformation temperatures increased the number density of strain-induced precipitates (SIPs), whereas the density of finer precipitates (random and interphase precipitates (IPs)) decreased. The highest hardness was observed in a sample deformed at 950–850 °C temperatures. These findings highlight the impact of the finishing deformation temperatures on the microstructural and mechanical properties, providing valuable insights for optimizing steel processing conditions. Full article

Microstructure control, especially the elimination of microtexture in Ti alloys such as Ti-6Al-4V and TIMETAL 834, is important to improve the fatigue life. In most research, small samples measuring 8–10 mm in diameter and 12–15 mm in height are utilized. However, the cooling rates of these small samples are always quite rapid, whereas the cooling rates of larger engine components, are relatively slow. Therefore, in this study, microstructural change involving different thermomechanical processing (TMP) was investigated using large TIMETAL 834 samples of 80 mm in diameter and 100 mm in height. The samples were forged at 940 and 1000 °C using a 1500 t forging simulator and heat treated at 900 and 1000 °C. Our goal is to attain a macroscopic understanding that connects the processing, microstructure, and fatigue life. The significant microstructure difference is that the deformed microstructure remains in the small sample due to rapid cooling, while the formation of a bimodal structure or an α phase globularization progressed in the large samples by diffusion during slow cooling. Improvement in the fatigue life was obtained by the 85% forging at 1000 $°$C. This is due to the refinement of the α grains and active slip in microtexture by alignment of the c-axis of α grains far from the tensile axis. Full article

Biobased foams have the potential to serve as eco-friendly alternatives to petroleum-based foams, provided they achieve comparable thermomechanical and physical properties. We propose a facile approach to fabricate eco-friendly cellulose nanofibril (CNF)-reinforced thermomechanical pulp (TMP) fiber-based foams via an oven-drying process with thermal conductivity as low as 0.036 W/(m·K) at a 34.4 kg/m³ density. Acrodur^®, iron chloride (FeCl₃), and cationic polyacrylamide (CPAM) were used to improve the foam properties. Acrodur^® did not have any significant effect on the foamability and density of the foams. Mechanical, thermal, cushioning, and water absorption properties of the foams were dependent on the density and interactions of the additives with the fibers. Due to their high density, foams with CPAM and FeCl₃ at a 1% additive dosage had significantly higher compressive properties at the expense of slightly higher thermal conductivity. There was slight increase in compressive properties with the addition of Acrodur^®. All additives improved the water stability of the foams, rendering them stable even after 24 h of water absorption. Full article

Thermomechanical processing (TMP) of ferritic–martensitic (FM) steels, such as HT9 (Fe–12Cr–1MoWV) steels, involves normalizing, quenching, and tempering to create a microstructure of fine ferritic/martensitic laths with carbide precipitates. HT9 steels are used in fast reactor core components due to their high-temperature strength and resistance to irradiation damage. However, traditional TMP methods for these steels often result in performance limitations under irradiation, including embrittlement at low temperatures (<~430 °C), insufficient strength and toughness at higher temperatures (>500 °C), and void swelling after high-dose irradiation (>200 dpa). This research aimed to enhance both fracture toughness and strength at high temperatures by creating a quenched and tempered martensitic structure with ultrafine laths and precipitates through rapid quenching and unconventional tempering. Mechanical testing revealed significant variations in strength and fracture toughness depending on the processing route, particularly the tempering conditions. Tailored TMP approaches, combining rapid quenching with limited tempering, elevated strength to levels comparable to nano-oxide strengthened ferritic alloys while preserving fracture toughness. For optimal properties in high-Cr steels for future reactor applications, this study recommends a modified tempering treatment, i.e., post-quench annealing at 500 °C or 600 °C for 1 h, possibly followed by a brief tempering at a slightly higher temperature. Full article

The present study evaluates the mold fungal resistance of newly developed loose-fill thermal insulation materials made of wheat straw, corn stalk and water reed. Three distinct techniques for the processing of raw materials were used: mechanical crushing (Raw, ≤20 mm), thermo-mechanical pulping (TMP) with 4% NaOH and steam explosion pulping (SEP). An admixture of boric acid (8%) and tetraborate (7%) was applied to all processed substrates due to their anti-fungal properties. The fourth sample group was prepared from SEP substrates without added fungicide (SEP*) as control. Samples from all treatments were separately inoculated by five different fungal species and incubated in darkness for 28 days at 28 °C and RH > 90%. The highest resistance to the colonization of mold fungi was achieved by TMP and SEP processing, coupled with the addition of boric acid and tetraborate, where molds infested only around 35% to 40% of the inoculated sample area. The lowest mold fungi resistance was detected for the Raw and SEP* samples, each ~75%; they were affected by rich amount of accessible nutrients, suggesting that boric acid and tetraborate additives alone did not prevent mold fungal growth as effectively as in combination with TMP and SEP treatments. Together, the achieved fungal colonization scores after combined fungicide and pulping treatments are very promising for the application of tested renewable materials in the future development of thermal insulation products. Full article

Dislocation slips, twinning, shear banding (SBs), strain localization, and martensite formation are a few deformation modes that are activated in BCC metals and alloys. Strain, strain rate, and deformation temperature are other parameters that determine the activation of deformation modes in BCC alloys. This review focuses on several BCC alloys, such as beta-titanium (β-Ti), tantalum (Ta), and ferritic stainless steels (FSSs), all of which exhibit differences in deformation behavior. These alloys often undergo thermo-mechanical processing (TMP) to enhance their mechanical properties. TMP leads to the evolution of deformation-induced products, such as SBs, strain-induced martensite (SIM), strain localizations, and mechanical/deformation twins (DTs) during plastic deformation, while also influencing crystallographic texture. The deformation modes in β-Ti depend upon the stability of the β-phase (i.e., β-stabilizers); low-stability alloys show the formation of SIM along with slips and twins, whereas in highly stable β-Ti alloys, only slip+twin modes are observed as the primary deformation mechanisms. In the case of Ta, slip activity predominantly occurs on {110} planes, but it can also occur on planes with the highest resolved shear stress. The breakdown of Schmid’s law or non-Schmid behavior for Ta and Ta-W alloys has been discussed in detail. The cold rolling (CR) of FSSs results in the formation of ridges, which is an undesirable phenomenon leading to very low formability. The microstructures of the rolled sheets consist of elongated ferrite grains with in-grain SBs, which are preferentially formed in the γ-fiber-oriented grains. The formation of finer grains after recrystallization improves both the mechanical properties and ridging resistance in FSS. Therefore, this review comprehensively reports on the impact of TMP on the microstructural and crystallographic texture evolution during the plastic deformation and annealing treatment of β-Ti, Ta alloys, and FSSs in BCC materials, using results obtained from electron microscopy and X-ray diffraction. Full article

Due to environmental concerns regarding single-use plastic materials, major efforts are being made to develop new material concepts based on biodegradable and renewable resources, e.g., wood pulp. In this study, we assessed two types of wood pulp fibres, i.e., thermomechanical pulp (TMP) and Kraft pulp fibres, and tested the performance of the fibres in wet-moulding and thermopressing trials. Kraft pulp fibres appeared to retain more water than TMP, increasing the dewatering time during wet-moulding and apparently increasing the compression resistance of the pulp during thermoforming. Additionally, cellulose nanofibres (CNF) were added to the pulps, which improved the mechanical properties of the final thermopressed specimens. However, the addition of CNF to the pulps (from 2 to 6%) had a further decrease in the dewatering efficiency in the wet-moulding process, and this effect was more pronounced in the Kraft pulp specimens. The mechanical performance of the thermoformed specimens was in the same range as the plastic materials that are conventionally used in food packaging, i.e., modulus 0.6–1.2 GPa, strength 49 MPa and elongation 6–9%. Finally, this study demonstrates the potential of wood pulps to form three-dimensional thermoformed products. Full article

Despite the high corrosion resistance of austenitic stainless steels (SSs), a significant reduction of stress corrosion cracking (SCC) resistance has been reported in cases of high residual stress and metastable microstructural features. In this study, the effect of thermo-mechanical processing (TMP) on the initiation and propagation of SCC in 304L SS was studied. To better understand the SCC mechanisms, three TMPs conditions—welded, solution annealed at 1050 °C for tens of seconds, and straightened—were used. The research focused on analyzing the initial microstructure, residual stress, and hardness along the depth direction to assess SCC resistance and establish correlations with the observed SCC modes. Experimental results demonstrated that transgranular SCC was observed in regions exhibiting elevated residual stress induced by welding and straightening processes. Furthermore, the presence of strain-induced martensite transformation and slip bands formed during plastic deformation were identified as additional factors contributing to the susceptibility of SCC. The study findings highlighted that the magnitude and distribution of residual stresses, in conjunction with microstructural evolution, could be varied depending on the specific TMP condition, leading to different SCC susceptibilities, cracking modes, and directions. Full article

Grain boundary engineering (GBE) is considered to be an attractive approach to microstructure control, which significantly enhances the grain-boundary-related properties of face-centered cubic (FCC) metals. During the twinning-related GBE, the microstructures are characterized as abundant special twin boundaries that sufficiently disrupt the connectivity of the random boundary network. However, controlling the grain boundary character distribution (GBCD) is an extremely difficult issue, as it strongly depends on diverse processing parameters. This article provides a comprehensive review of controlling GBCD during the twinning-related GBE of FCC materials. To commence, this review elaborates on the theory of twinning-related GBE, the microscopic mechanisms used in the optimization of GBCD, and the optimization objectives of GBCD. Aiming to achieve control over the GBCD, the influence of the initial microstructure, thermo-mechanical processing (TMP) routes, and thermal deformation parameters on the twinning-related microstructures and associated evolution mechanisms are discussed thoroughly. Especially, the development of twinning-related kinetics models for predicting the evolution of twin density is highlighted. Furthermore, this review addresses the applications of twinning-related GBE in enhancing the mechanical properties and corrosion resistance of FCC materials. Finally, future prospects in terms of controlling the GBCD during twinning-related GBE are proposed. This study will contribute to optimizing the GBCD and designing GBE routes for better grain-boundary-related properties in terms of FCC materials. Full article

Research on multi-pass hot processing of 7075 Al-alloy was rarely discussed. This study aims to design and evaluate different thermomechanical processing strategies (TMPS) to produce 3 mm-thick sheets of 7075 Al-alloy. A physical simulation was performed using the hot compression test of a Gleeble 3500 to study flow mechanisms and microstructural evolution, while an experimental investigation was carried out using a rolling mill to examine the effect of TMPS on the mechanical properties. Four hot forming strategies were designed and tested at a constant strain rate of 0.1 s⁻¹ over a temperature range of 200–450 °C. These strategies involved applying a constant amount of deformation of 65–70% in single (SP), double (DP), triple (TP), and quadruple (QP) passes of thermomechanical processing to study the influence of multi-pass thermomechanical processing on the final mechanical properties and industrial feasibility. The microstructure analysis showed a significant refinement and more uniform distribution of precipitates with an increasing number of passes, as observed through optical micrographs and the full width at half maximum (FWHM)-position relationship of XRD data. The results indicate that QP is the optimum strategy for producing the best mechanical properties in the shortest production time. Full article

Near-α Ti alloys find themselves in advanced aeroengines for applications of up to 600 °C, mainly as compressor components owing to their superior combination of ambient- and elevated-temperature mechanical properties and oxidation resistance. We evaluated, ranked, and selected near-α Ti alloys in the current literature for high-temperature applications in aeroengines driven by decision science by integrating multiple attribute decision making (MADM) and principal component analysis (PCA). A combination of 12 MADM methods ranked a list of 105 alloy variants based on the thermomechanical processing (TMP) conditions of 19 distinct near-α Ti alloys. PCA consolidated the ranks from various MADMs and identified top-ranked alloys for the intended applications as: Ti-6.7Al-1.9Sn-3.9Zr-4.6Mo-0.96W-0.23Si, Ti-4.8Al-2.2Sn-4.1Zr-2Mo-1.1Ge, Ti-6.6Al-1.75Sn-4.12Zr-1.91Mo-0.32W-0.1Si, Ti-4.9Al-2.3Sn-4.1Zr-2Mo-0.1Si-0.8Ge, Ti-4.8Al-2.3Sn-4.2Zr-2Mo, Ti-6.5Al-3Sn-4Hf-0.2Nb-0.4Mo-0.4Si-0.1B, Ti-5.8Al-4Sn-3.5Zr-0.7Mo-0.35Si-0.7Nb-0.06C, and Ti-6Al-3.5Sn-4.5Zr-2.0Ta-0.7Nb-0.5Mo-0.4Si. The alloys have the following metallurgical characteristics: bimodal matrix, aluminum equivalent preferably ~8, and nanocrystalline precipitates of Ti₃Al, germanides, or silicides. The analyses, driven by decision science, make metallurgical sense and provide guidelines for developing next-generation commercial near-α Ti alloys. The investigation not only suggests potential replacement or substitute for existing alloys but also provides directions for improvement and development of titanium alloys over the current ones to push out some of the heavier alloys and thus help reduce the engine’s weight to gain advantage. Full article

In this study, we present the effects of 0.004~0.098 wt% Zr and thermo-mechanical processing (TMP) on the microstructure and mechanical properties of the China RAFM steel, CLAM, as a feasibility study for improving mechanical properties. The inclusions in ingots were characterized using optical microscope (OM) and scanning electron microscope (SEM), which could be classified as fine simple particles and large complex particles. The complexity of the alloy’s inclusion composition increases with the increasing Zr concentration. The higher the Zr content, the more complex the composition of inclusions in the alloy. The average diameter of inclusions in 0.004Zr steel was the smallest, which was 0.79 μm and the volume fraction was 0.018%. The highest yield strength, tensile strength, elongation, and impact energy of 0.004Zr alloy at room temperature were 548.3 MPa, 679.4 MPa, 25.7%, and 253.9 J. The structure of the TMPed steels was all tempered martensite. With the increase in tempering temperature, the yield and tensile strength of the experimental steel gradually decreased, while the elongation and impact energy gradually increased. The 0.004ZrD and 0.004ZrH alloys had the best yield strength and impact energy, which were 597.9 and 611.8 MPa and 225.9 and 243.3 J, respectively. In addition, the alloys showed good thermal stability during the aging at 600 °C for 1500 h. It was discovered that TMP is a simple and practical industrial technique that could successfully enhance the mechanical properties of CLAM steel without sacrificing impact toughness. Full article

The main objective of this study was to develop cellulose nanofibers from the thermomechanical pulp (TMP) of Radiata Pine (Pinus radiata D. Don), and for this, a one-step micro-grinding process was used. The newly developed material was called thermomechanical pulp nanofibers (TMP-NF). In the first instance, a determination of the constituents of the TMP was carried out through a chemical characterization. Then, TMP-NFs were compared with cellulose nanofibers (CNF) by morphological analysis (Scanning Electron Microscopy, SEM, and Atomic Force Microscopy, AFM), X-ray Diffraction (XRD) and Fourier-Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR). In addition, films were developed from TMP-NF and CNF using a vacuum filtration manufacturing method. For this study, 0.10, 0.25, 0.50, and 1.00% dry weight of CNF and TMP-NF were used as continuous matrices without organic solvents. The films were characterized by determining their morphological, physical, surface properties, and mechanical properties. The main results showed that morphological analysis by SEM and AFM for the fractionated sample indicated a fiber diameter distribution in the range of 990-17 nm and an average length of 5.8 µm. XRD analysis showed a crystallinity index of 90.8% in the CNF, while in the TMP-NF, it was 71.2%, which was foreseeable. FTIR-ATR analysis showed the functional groups of lignin and hemicellulose present in the TMP-NF sample. The films presented apparent porosity values of 33.63 for 1.00% solids content of CNF and 33.27% for 0.25% solids content of TMP-NF. The contact angle was 61.50° for 0.50% solids content of CNF and 84.60° for 1.00% solids content of TMP-NF. Regarding the mechanical properties, the modulus of elasticity was 74.65 MPa for CNF and 36.17 MPa for TMP-NF, and the tensile strength was 1.07 MPa for CNF and 0.69 MPa for TMP-NF. Although the mechanical properties turned out to be higher in the CNF films, the TMP-NF films showed improved surface characteristics as to surface hydrophobic and apparent porosity. In addition, the easy and rapid obtaining of TMP nanofibers makes it a promising material that can be used in biologically based nanocomposites. Full article

Controlling the formation of the β′ (Al₃Zr) phase is pivotal for regulating the recrystallization and thus the mechanical properties of the spray formed 2195 (Al-Cu-Li) alloy. In a conventional “homogenization-extrusion” process, the precipitation of β′ is severely affected by the presence of the T₁(Al₂CuLi) phase in the as-deposited alloy, leading to an inhomogeneous distribution of the β′ phase. In the present work, we propose a new thermomechanical processing (TMP)—swapping the order of the homogenization and extrusion processes. The microstructures and properties of the new proposed TMP were systematically studied at various stages of the alloy treatment and compared with the out of the conventional TMP. It was revealed that the introduction of the extrusion process on the as-deposited alloy can break the continuous network of primary phases and dissolve the T₁ phase, promoting a uniform distribution of the β′ phase during subsequent two-step homogenization. During solution treatment, the new TMP is more effectively in suppressing the formation of a coarse grain layer at sheet surface, while after final peak aging, the new TMP produces a lower alloy strength but a higher elongation, due mainly to the smaller thickness reduction during deformation. The new proposed TMP technique provides a new insight into regulating the mechanical properties of Al-Cu-Li alloys. Full article

Thermomechanical pulp (TMP) fibres can serve as renewable, cost-efficient and lightweight reinforcement for thermoplastic polymers such as poly(lactic acid) (PLA). The reinforcing ability of TMP fibres can be reduced due to various factors, e.g., insufficient dispersion of the fibres in the matrix material, fibre shortening under processing and poor surface interaction between fibres and matrix. A two-level factorial design was created and PLA together with TMP fibres and an industrial and recyclable side stream were processed in a twin-screw microcompounder accordingly. From the obtained biocomposites, dogbone specimens were injection-moulded. These specimens were tensile tested, and the compounding parameters statistically evaluated. Additionally, the analysis included the melt flow index (MFI), a dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and three-dimensional X-ray micro tomography (X-$\mathsf{\mu }$CT). The assessment provided insight into the microstructure that could affect the mechanical performance of the biocomposites. The temperature turned out to be the major influence factor on tensile strength and elongation, while no significant difference was quantified for the tensile modulus. A temperature of 180 °C, screw speed of 50 rpm and compounding time of 1 min turned out to be the optimal settings. Full article