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Wire arc additive manufacturing (WAAM) has garnered significant attention in industries owing to its ability to produce complex geometrical components with lower production costs. In the present work, WAAM process was used to fabricate rectangular plates and cylindrical tubes from ER70S6 filler material based on the cold metal transfer technique. The microstructure of the rectangular plate was investigated at three different locations, viz., top, middle and bottom regions along the build direction (BD). It was characterized by the presence of ferrite and pearlite phases along with Mn and Fe rich carbide precipitates. The average grain size of the middle location was found to be marginally higher as compared to the other two locations which resulted into lower hardness in the former. The tensile properties were evaluated for three directions, i.e., 0°, 45° and 90° with respect to BD. The total elongation and strength were found to be slightly higher for the specimen deformed 90° with respect to BD. Furthermore, the performance of the additive manufactured components was analyzed through corrosion and compression tests. The corrosion current density and corrosion rate were found to be higher for the middle location as compared to the top and bottom locations owing to its higher pearlite fraction. The compression of tubes was carried out under axial and transverse loading conditions. Axisymmetric progressive folding of the tubes was observed under axial loading, whereas infinity shape formation was witnessed under transverse loading. The above deformation modes indicated the uniformity in mechanical properties of WAAM tubes without any discontinuity, and further suggested that these tubes could act as excellent energy absorbers. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM), a type of additive manufacturing is widely used for complex mold design, single‐part tool manufacturing, and prototyping. The FDM process, especially with fiber‐reinforced filament, induces intricate changes that influence microstructure and properties, highlighting the necessity for a thorough understanding to maximize FDM utilization. This study comprehensively examines microstructural changes and mechanical attributes in polyamide (PA) and carbon fiber‐reinforced polyamide (CF‐PA) before and after FDM printing. Through various characterization techniques including X‐ray diffraction, thermal gravimetric, differential scanning calorimetry, tensile testing, micro‐Computed Tomography (μ‐CT), and fractography, insightful perspectives were obtained. Results reveal substantial fiber breakage, resulting in a 33.03% decrease in the average fiber length from filament to printed parts. X‐ray μ‐CT scans illustrated a more pronounced fiber alignment in CF‐PA filament than in the CF‐PA printed sample. TG analysis confirms approximately 20 wt.% CF content in the filament, with negligible residue in pure PA filament and samples. DSC shows enhanced thermal stability with CF reinforcement, while XRD confirms amorphous behavior in filament and printed parts. Tensile tests reveal anisotropic properties in FDM samples. The addition of short CFs increases Young's modulus but decreases strength. Examination of fractured surfaces reveals different failure modes for filament and printed coupons. [ABSTRACT FROM AUTHOR]

In this paper, vacuum annealing has been adopted to introduce atomic cluster micro-regions inside Gd-based metallic microfibers to further explore the effect of the structural changes on the magnetocaloric properties and the mechanism which is systematically expressed. The experimental results indicate that the as-prepared Gd-based metallic microfibers have favorable amorphous formation ability and thermal stability. After annealing @ 380 °C, the maximum magnetic entropy change −ΔSmmax, refrigerating capacity (RC), and relative cooling power (RCP) values of the Gd-based metallic microfibers are 7.20 J/kg·K, 459.4 J/kg, and 588.7 J/kg, respectively. Combined with the transmission electron microscopy analysis results, the internal organizational order of the annealed microfibers is significantly altered, and the atomic clusters formed in localized regions, which reduce the magnetocrystalline anisotropy of the microfibers. While under the uni-action of an external magnetic field, the magnetic moment rotation state and magnetic domain structure distribution of the micro-region atoms will be changed obviously, thereby changing the general magnetic properties and magnetocaloric properties of the metallic microfibers. The above research results can promote the engineering application of Gd-based metallic microfibers in the field of magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Abstract Surfaces are commonly enhanced with wear-resistant coatings to improve their resistance to abrasion, erosion, and other forms of wear. These coatings play a crucial role in extending the lifespan and improving the performance of materials and components exposed to challenging conditions. The objective of the current study is to deposit thermally sprayed 3-layer TiC–12Co–10ZrO2/NiCoCrAlMo functionally graded coatings on SS410 substrates using atmospheric plasma spray. The results revealed that by employing appropriate ceramic proportions, the microhardness of graded coatings increased to 990.4 HV, which is approximately 3.21 times higher than that of the substrate. Furthermore, the tribological properties of graded coating exhibited superior resistance compared to the substrate, where process settings were varied. Specifically, graded coating samples subjected to the applied load, sliding distance, and sliding velocity showed improved wear resistance of 78.51%, 68.42%, and 76.66% respectively in extreme conditions compared with uncoated samples. The characterization of the worn surface revealed a sequential occurrence of wear mechanisms: abrasive, adhesive, and delamination. The formation of TiO2 and Cr2O3 tribo-oxide film protects the surface against the wear mechanism and is applicable in extreme wear environments.

One-step (F100) and three-step (F30-60-40) hot forging of Al0.35CoCrFeNi alloy was investigated to achieve a uniform equiaxed grain structure. In the as-cast and forged state, only a single-phase face-centered cubic structure was observed. The formation of twins, recrystallized and partially recrystallized grains in the volume of the samples was observed depending on used forging process. To predict uniform grain-size formation numerical simulation of the hot-forging process was used. The numerical model was calibrated and validated by means of measured compression experimental data of as-cast Al0.35CoCrFeNi alloy before forging. Thermal analysis using finite element analysis was used to simulate cooling of sample during the relocation from the furnace on the lower die. Simulations were run under different thermo-mechanical conditions and the regions for the formation of dynamically recrystallized grains were predicted. Room temperature mechanical properties were evaluated after F100 and F30-60-40 hot-forging process. The F30-60-40 hot forging optimized the grain size, which was evident in the very small dispersion of the room temperature mechanical properties in tension. Elongation after F30-60-40 hot forging increased by 17%. The correlation between temperature, equivalent stress, equivalent plastic strain, microstructure, tensile properties, and strain-hardening behavior is discussed. [ABSTRACT FROM AUTHOR]

The Al-Mg-Si alloy plate produced by traditional hot rolling has many defects such as complicated processes， long time and high cost， which seriously restricts the development of Al-Mg-Si alloy. Therefore， the Al-Mg-Si alloy plate produced by the twin-rolling casting process has attracted great attention in recent years. The twin-rolling casting process was used to prepare the Al-Mg-Si aluminum alloy plate， and the difference of microstructure at different positions of the plate and the influence on the performance were investigated. The results show that the grain morphology of the edge and the center of the plate is significantly different， the texture composition is complex， a large number of second phases are unevenly distributed along the grain boundary， and there is obvious element segregation inside the plate. According to the theoretical calculation， the contribution strength of texture strengthening at the edges of the twin-rolling casting plate is 10.7 MPa and the contribution strength of grain boundary strengthening is 86.8 MPa， while the contribution strength of texture strengthening in the center of the twin-rolling casting plate is 15.1 MPa and the contribution strength of grain boundary strengthening is 82.4 MPa. The contribution of plate texture and random texture to the strength is limited， and the strength difference between edge and center mainly depends on the grain boundary strengthening. Different degrees of dislocation tangles exist at the edge and the center， and the dislocation density at the edge is higher than that at the center， which is consistent with the statistical results of low angle grain boundaries. According to the characteristics of microstructure inhomogeneity of the plate， the theoretical guidance for the subsequent heat treatment system of the plate is provided through thermodynamic calculation.

Changes in structure and properties of resin matrix caused by water absorption is one of the key factors affecting the long-term durability of fiber reinforced polymer composites used in civil engineering. In the present study, the water diffusion and structural change in an epoxy resin were investigated experimentally through immersion in deionized water at 40, 60 and 80 °C for 135 days. Water absorption, thermal, mechanical and microstructure analysis tests were conducted to evaluate the long-term property evolution. It was found that the water absorption of epoxy resin followed a two-stage model, including an initial Fick's diffusion response and a subsequent relaxation response. Long-term hygrothermal exposure brought about the structural change of epoxy resin, which led to the significant degradation up to 8%–30% in the mechanical properties and 21% in glass transition temperature, respectively. The resin plasticization and hydrolysis was the key factors for the degradation of thermal and mechanical properties. It was proved that the plasticization effect was reversible with the remove of bonding water after the drying. Based on the Arrhenius equation, the long-term life of flexural strength in two service environments were predicted to provide the application guideline. The significant degradation of flexural strength was occurred at the initial exposure of 2000 days and then reached to the stable strength retention of 69.6%.

In this work we argue that the reverse martensitic transformation (MT) of the stress-induced martensite (SIM) of Fe–Mn–Si-based alloys for moderate prestrains occurs in essentially thermoelastic-like way, in contrast to non-thermoelastic MT of temperature-induced martensite (TIM). We compare, using a number of complementary experimental techniques, the temperatures and the kinetics of the reverse ε→γ martensitic transformation of SIM and TIM for commercial and model Fe–Mn–Si alloys after various thermomechanical treatments. We claim that two studied phenomena are generic in Fe–Mn–Si-based alloys of different compositions and microstructure: first, opposite to the conventional effect of stabilization of martensite by prestrain, the reverse MT during heating of alloys prestrained in bending and tension starts well below (up to 100 K) the start temperature of the reverse MT for the TIM of the same alloy. The difference between engineering temperatures of the start of the reverse transformation, As, for SIM and TIM reaches ca. 50 K, pointing to a need to consider different As for TIM and SIM, AsTIM and AsSIM. Second, the reverse transformations of TIM and SIM show very different kinetics. The reverse MT of SIM is diffuse over the temperature range exceeding 100 K. The reverse MT of TIM, on the contrary, is well localized within the temperature range of ca. 20 K. The experimental observations can be interpreted assuming that, due to the differences in the formation mechanisms of SIM and TIM, the latter shows non-thermoelastic behaviour, whereas the SIM shows similarities with the thermoelastic martensites stabilized by prestrain.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of polymers is desirable in the industries where weight reduction and corrosion resistance are required, such as in the automotive industry where weight reduction directly relates to fuel conservation. Acrylonitrile butadiene styrene (ABS) is a type of polymer used in aerospace, railway, automotive, and consumer goods industries. This research article investigates the use of friction stir welding (FSW) to join ABS polymer. Compared to traditional metal-based products, polymers offer better formability, design flexibility, and ease of processing. The process parameters were optimized based on tensile strength using Taguchi's L18 orthogonal array (OA). A maximum tensile strength of 19.4 MPa was obtained at a tool rotational speed of 224 rpm, a tool travel speed of 40 mm/min, external heat of 45 °C, and a tool shoulder diameter of 16 mm. Transmission electron microscopy was used to analyze the microstructural characteristics, while Vickers microhardness tester and tensometer were used to examine the mechanical properties. The strength of the joint was affected due to the butadiene rubber particles breaking or weakening in the stir zone). Moreover, to identify the location of failure, three additional tensile coupons were taken from Experiment No. 13, and a 1-mm-deep notch was machined in all of them at the Center, AS, and RS. The findings revealed that the tensile coupon with the notch at RS had a tensile strength of 19.4 MPa, which is 60% relative to the base material. The retreating side of Experiment No. 13 exhibited a Vickers microhardness of 14.3 HV, which was higher than the base material's Vickers microhardness of 13.8 HV, indicating that it became harder. [ABSTRACT FROM AUTHOR]

Ni–Cr–MoS2-based composite’s microstructure and wear behavior were examined in relation to compacting pressure and sintering temperature. The tribological performance of Ni-Cr–MoS2 composite against En32 martial is examined in this research in relation to the nodule count, particle count, and average area depending on the compacting pressure and sintering temperature. The green pallets were cylindrical in shape and had a diameter of 12.5mm × 30mm. They were pressed at room temperature (28∘C) with axial pressures of 220MPa, 275MPa, and 330MPa, then sintered in two batches at different sintering temperatures of 900∘C and 1000∘C. By using Image analysis, the amount of nodules, their size, particle counts, particle sizes, and lubricant flakes of developed composite are investigated. The typical nodule size ranges from 46 μm to 60 μm, and the average nodule percentage is between 67 and 79 present in Ni–Cr–MoS2-based composite. Particle counts ranged at present from 29 to 516 depending on the sintering temperature and compacting pressure. Up to 1.1472 μm, lubricant flake lengths were nearly the same for composite for the different compacting pressure and sintering. With varying compacting pressures and sintering temperatures, the coefficient of friction and wear rate varied for the developed Ni–Cr–MoS2 composite. The impact of the nodule, nodule counts, particle and particle size is also present on the developed composites for friction and wear. Minimum wear rate observed for composite sintered was under 1000∘C temperature, and maximum wear rate was 7.55E−8 mm3/Nm for low compacting pressure and 900∘C sintering temperature. [ABSTRACT FROM AUTHOR]

The AZ91 Mg alloy was surface melted by a DPSS Nd:YVO4 laser using different pulse lengths. Characterization of the Mg alloy and laser melted layers was accomplished utilizing XRD, SEM, and EDS. The impact of laser surface melting (LSM) on hardness and corrosion characteristics was investigated using hardness tester and potentiodynamic polarization test, respectively. The results indicated that LSM clearly reduced the crystallite size of α-Mg to be in the range of 206–251 nm for the laser melted layers compared to 369 nm for the Mg alloy. The highest melted layer thickness of 13.7 μm was obtained using a pulse length of 100 nm. The concentration of Al and Zn in the melted layers changed with increasing pulse length due to the evaporation of Mg. The hardness was enhanced due to the LSM, especially with a decrease in the pulse length owing to the rapid solidification where the highest hardness value of 89.1 HV0.1 was observed using a pulse length of 15 ns. The LSM significantly boosted the corrosion resistance of Mg alloy mainly owing to the increase in Al concentration. The corroded surface of all laser melted layers was characterized by a sponge-like structure. [ABSTRACT FROM AUTHOR]

Inconel 718 has good fabricability, high strength at elevated temperatures, and high corrosion resistance and is widely deployed in many aerospace and other high-performance applications. With the molten pool's rapid solidification during laser powder bed fusion (LPBF), the resulting microstructures differ from those expected in equilibrium conditions. Residual stresses, microsegregation, anisotropy, undesirable phases, layered structure, and lower mechanical properties are the challenges that must be addressed before LPBF-ed Inconel 718 parts can be industrially implemented. Heat treatment of Inconel 718 after the LPBF process is widely discussed in the literature, and the proposed heat treatment processes do not address all the challenges mentioned above. For this reason, specific heat treatments should be designed to achieve desired mechanical properties. Four different high-temperature heat treatment procedures were developed and tested in recent work to study the effect of various heat treatment parameters on the type of precipitates, grain size, room and elevated temperature mechanical properties, and creep properties of LPBF-ed Inconel 718. Two heat treatment procedures were designed to study the effect of eliminating the stress relief cycle and increasing the soaking time of solution heat treatment at the same hot isostatic pressing (HIP) and aging conditions. The other two heat treatment procedures were designed to study the effect of stress relief and aging parameters, with similar HIP and solution annealing parameters. The investigated heat treatment procedures showed the formation of equiaxed grain size and a significant amount of γ″ particles at the grain boundary in addition to primary carbide types (MC). Three different grain sizes could be obtained, starting with the same as-built microstructure by controlling post-process heat treatment parameters. The first type, coarse grain size (ASTM grain size No. G 3), suitable for creep application, was achieved by increasing the soaking time at the aging cycle. The second type, the formation of serrated grain boundaries suitable for good fatigue and creep properties, was achieved by decreasing the stress relief cycle's soaking time and temperature. The third type, fine grain size (ASTM grain size No. G 6), which is preferable for fatigue properties, was achieved by decreasing the soaking time at the solution annealing cycle. Among the different heat treatment conditions, the heat treatment with lower stress relief temperature and longer soaking time at solution annealing steps showed compromised equiaxed grain size with serrated grain boundaries, and it was selected for mechanical testing. The mechanical properties at room and elevated temperature (650 °C) and creep properties under constant axial stress of 690 MPa at 650 °C until failure were evaluated. The obtained elongation is > 2 × higher than the available properties in the AMS 5663 for wrought Inconel 718, AMS 5383 for cast Inconel 718, and ASTM F3055 for LPBF while maintaining a higher tensile strength above the average level found in the standards. It can be concluded that the performed heat treatment achieves higher mechanical properties. The values of UTS, YS, elongation, and reduction of area percentages are similar in the Z and XY orientations, revealing the presence of isotropic microstructure and uniform distribution of MC and γ″ precipitates. [ABSTRACT FROM AUTHOR]

This study presents a novel cost-effective Fe30Ni25Cr25Mo10Al10 high-entropy alloy with a dual-phase microstructure that was processed using cyclic closed-die forging (CCDF) at room temperature for a maximum of six passes. The as-homogenized alloy exhibited [CrMoFe]-rich dendrites with dual-size morphology dispersed in an almost uniform face-centered cubic (FCC) matrix. It was found that as the number of CCDF passes increased, leading to a more homogenous nanograin, there was an accumulation of dislocations, fragmentation of [CrMoFe]-rich dendrites, and enhanced distribution within the matrix. These conditions were conducive to the creation of a nanostructured Fe30Ni25Cr25Mo10Al10 alloy with superior mechanical properties. Texture analysis indicated that the prominent texture components for the Fe30Ni25Cr25Mo10Al10 alloy after six passes were Rotated Cube {001}, S {123}, and Dillamore {4 4 11}. After the sixth CCDF pass, the Fe30Ni25Cr25Mo10Al10 alloy exhibited the highest microhardness (∼ 974 HV) and the lowest wear rate (∼ (0.8 ± 0.1) × 10–5 mm3.N−1.m−1). Additionally, it was proposed that the development of the Rotated Cube {001} texture component contributed positively to enhancing wear resistance in the cost-effective high-entropy alloys. Considering the obtained results, it is reasonable to propose that CCDF processing is significant potential for the advancement of cost-effective nanostructured high-entropy alloys for industrial applications.

Abstract The study discussed the effects of different mineral incorporations and the curing time on the strength of modified magnesium phosphate cement (MPC) mortars through mechanical tests, mathematical model analysis and microstructure characterization. Fly ash (FA), silica fume (SF), and metakaolin (MK), which exhibit excellent durability and bonding properties, were used to modify the MPC. A quantitative relationship was established between the strength of modified MPC mortars and the mineral incorporation and curing time. First, the strength of each mineral-modified MPC mortar cured in air with different mineral incorporations and curing durations was evaluated. The strengths of MPC mortars containing 10% fly ash, 15% silica fume, and 10% metakaolin—which perform best in their incorporations—were compared to analyze the function of the three minerals. To establish the relationship between strength and mineral incorporation and curing time, three mathematical models, linear model, general nonlinear model, and data distribution shape nonlinear model (DDSNM), are commonly used for material property analysis based on statistics. DDSNM best describes the trend of strength change among the three models and the error is small for three minerals. Based on DDSNM, the influence of various minerals on the strength of MPC mortar was quantitatively evaluated by calculating the variable partial derivatives, and verified by scanning electron microscopy and X-ray diffraction. MK performs the best in improving the flexural strength performance of MPC, while SF performs the best in the compressive strength. FA-MPC has low sensitivity to dosage fluctuations and is easy to prepare.

Oxide dispersion strengthened (ODS) alloys, due to their high irradiation resistance and good mechanical properties at high temperatures, are promising for applications in Generation IV reactors, especially GFR, and fusion installations. However, the biggest challenge in applying ODS materials is related to fabrication techniques. This paper aims to evaluate powder metallurgy processing and the effect of small additions of oxide- and carbide-forming elements on the microstructure and mechanical properties of Fe–Cr–Al-based ODS alloys. The series of ODS alloys with Y2O3 and different additions of Ti and V was prepared by mechanical alloying (MA) and consolidated by spark plasma sintering (SPS), which is less often employed to fabricate ODS alloys than hot extrusion or hot isostatic pressing. The investigations were performed on MAed powders, bulk-sintered samples, and samples after homogenization annealing. The MAed powders reveal two body-centered cubic (bcc) alloyed phases with close lattice parameters. The sintered samples show a single bcc phase (a = 2.88–2.89 Å) matrix and a high-volume fraction of homogenously distributed nanometric oxide precipitates. The addition of vanadium and titanium leads to the formation of vanadium- and titanium-rich nanometric oxides and carbides. The bulk samples show fine grain and stable microstructure with an average grain size slightly below 1 µm. Moreover, after homogenization annealing and air cooling, the relative density slightly increases. Hardness after heat treatment is relatively stable, which was confirmed by nanoindentation and Vickers microhardness results. These experimental findings promise to develop Fe–Cr–Al-based ODS materials tailored for operation under harsh conditions in nuclear reactors. [ABSTRACT FROM AUTHOR]

The study discussed the effects of different mineral incorporations and the curing time on the strength of modified magnesium phosphate cement (MPC) mortars through mechanical tests, mathematical model analysis and microstructure characterization. Fly ash (FA), silica fume (SF), and metakaolin (MK), which exhibit excellent durability and bonding properties, were used to modify the MPC. A quantitative relationship was established between the strength of modified MPC mortars and the mineral incorporation and curing time. First, the strength of each mineral-modified MPC mortar cured in air with different mineral incorporations and curing durations was evaluated. The strengths of MPC mortars containing 10% fly ash, 15% silica fume, and 10% metakaolin—which perform best in their incorporations—were compared to analyze the function of the three minerals. To establish the relationship between strength and mineral incorporation and curing time, three mathematical models, linear model, general nonlinear model, and data distribution shape nonlinear model (DDSNM), are commonly used for material property analysis based on statistics. DDSNM best describes the trend of strength change among the three models and the error is small for three minerals. Based on DDSNM, the influence of various minerals on the strength of MPC mortar was quantitatively evaluated by calculating the variable partial derivatives, and verified by scanning electron microscopy and X-ray diffraction. MK performs the best in improving the flexural strength performance of MPC, while SF performs the best in the compressive strength. FA-MPC has low sensitivity to dosage fluctuations and is easy to prepare. [ABSTRACT FROM AUTHOR]

The use of process–microstructure–property relationships for cold spray can significantly reduce application development cost and time compared to legacy trial and error strategies. However, due to the heterogeneous microstructure of a cold spray deposit, with (prior) particle boundaries outlining consolidated splats (deformed particles) in the as-spray condition, the use of automated analysis methods is challenging. In this work, we demonstrate the utility of quantitative data developed from a convolutional neural network (CNN) for feature extraction of cold spray microstructures. Specifically, the power of CNN is harnessed to automatically segment the deformed particles, which is hardly accessible at scale with traditional image processing techniques. Deposits produced with various processing conditions are evaluated with metallography. Parameters related to particle morphology such as flattening ratio are also quantified and correlated to strength. [ABSTRACT FROM AUTHOR]

High‐nitrogen stainless bearing steel (HNSBS) is the most representative third‐generation aviation bearing steel, and the cleanliness and microstructure characteristics of bearing steel are crucial to its high performance and long service life. In this work, the effect of cerium addition on the cleanliness and microstructure characteristics of as‐cast HNSBS was systematically studied by combining microstructural characterization and thermodynamic analysis methods. The results show that with increasing Ce content, the cleanliness of steel first improved and then decreased, and Ce2O2S, Ce2O3 and CeN inclusions were generated successively. The Ce content should be controlled to ≈0.012 wt% to ensure that all Al2O3, MgO · Al2O3, and MnS inclusions were modified, and minimize the formation of large‐size Ce‐bearing inclusions. Furthermore, cerium addition refined the dendrite structure due to more nucleation sites for γ‐Fe and the enrichment of Ce in the liquid phase at solidifying front. The finer and more dispersed distribution in precipitates was ascribed to the reduction of growth space and Cr segregation, as well as the increase in effective nucleation sites. These results can offer theoretical guidance for inhibiting the formation of harmful inclusions in high‐nitrogen alloy systems and refining the microstructure of alloy systems containing M23(C, N)6 and M2(C, N) precipitates. [ABSTRACT FROM AUTHOR]

Purpose: This research presents experimental investigation into the performance improvement of dredged sediment (DS) stabilization with ternary alkali-activated materials (AAMs) based on fly ash (FA), ground granulated blast-furnace slag (GGBS), and desulfurization gypsum (DG) for use as embankment fill materials. Methods: The performance of stabilized DS was assessed through a series of pH, electrical conductivity (EC), and unconfined compressive strength (UCS) tests. Microstructure characterization was also conducted to reveal the performance improvement mechanism of stabilized DS. Results: The pH value of the stabilized DS exhibited a significant increase, reaching its peak at a DG content of 8%. This increase was attributed to the consumption of free water and the priority reaction of C-(A)-S–H. Subsequently, the pH value gradually decreased, primarily due to the consumption of OH− through Ca(OH)2 precipitation. Concurrently, the EC value steadily increased due to the rising Ca2+ concentration. Additionally, the UCS of the stabilized DS exhibited a noteworthy increase at a DG content of 8% and then showed a tendency to increase or decrease slightly with varying DG content, in line with the changes in pH value. Conclusions: The performance improvement of the stabilized DS was attributable to the cementation provided gels (i.e., geopolymer gel and C-(A)-S–H gel), along with the pore-filling of ettringite (AFt) in the alkaline environment. Conversely, the performance of stabilized DS deteriorated due to the presence of microcracks resulting from excessive AFt expansion. [ABSTRACT FROM AUTHOR]

Ion irradiation combined with nanoindentation is a promising tool for studying irradiation-induced hardening of nuclear materials, including reactor pressure vessel (RPV) steels. For RPV steels, the major sources of hardening are nm-sized irradiation-induced dislocation loops and solute atom clusters, both representing barriers for dislocation glide. The dispersed barrier hardening (DBH) model provides a link between the irradiation-induced nanofeatures and hardening. However, a number of details of the DBH model still require consideration. These include the role of the unirradiated microstructure, the proper treatment of the indentation size effect (ISE), and the appropriate superposition rule of individual hardening contributions. In the present study, two well-characterized RPV steels, each ion-irradiated up to two different levels of displacement damage, were investigated. Dislocation loops and solute atom clusters were characterized by transmission electron microscopy and atom probe tomography, respectively. Nanoindentation with a Berkovich indenter was used to measure indentation hardness as a function of the contact depth. In the present paper, the measured hardening profiles are compared with predictions based on different DBH models. Conclusions about the appropriate superposition rule and the consideration of the ISE (in terms of geometrically necessary dislocations) are drawn. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study examined mechanical properties of AA2024 alloy and its correlation between strain path and crystallographic texture. Accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB) were used to severely deform AA2024 alloys. Electron backscatter diffraction (EBSD) studies demonstrated that nano/ultrafine grains were formed by the strain routes after eight cycles. It was also found that the lamellar boundary spacing and the mean boundary spacing were ~ 360 ± 10 nm and 845 ± 10 nm after eight ARB cycles. In contrast to the ARB, the CARB specimen had equiaxed microstructures characterized by grains with a size of 150 and 100 nm. The CARB processed specimen exhibited a mean misorientation angle of 41.83° and a fraction of high angle grain boundaries of 78%, these values were 34.57° and 67% for ARB treated specimen, respectively. It was observed that the evolved texture is greatly affected by the strain paths. The ARB processed specimen revealed strong Copper {112} <111>, Dillamor {4 4 11} <11 11 8>, S {123} <634>, and Brass {011} <211> components. In contrast, the CARB processed specimen showed major texture with prominent Copper {112} <111>, Brass {011} <211>, Rotated Cube {001} <110>, S {123} <634>, and Goss {011} <100> components. In the CARB specimen, the Goss/Brass texture ratio was intensified and the mechanical properties were superior (tensile strength: 535 MPa, microhardness: 182 HV, elongation: 11.9%) compared with the ARB processed specimen (tensile strength: 455 MPa, microhardness: 145 HV, elongation: 9.2%). Further, the change in strain path did not significantly affect the intensity of Goss and Cube components, ruling out any further recrystallization tendency. [ABSTRACT FROM AUTHOR]

Ag-In intermetallic alloys were produced by using vacuum arc furnace. Differential Scanning Calorimetry (DSC) and Energy Dispersive X-Ray Spectrometry (EDX) were used to determine the thermal properties and chemical composition of the phases respectively. Microhardness values of Ag-In intermetallics were calculated with Vickers hardness measurement method. According to the experimental results, Ag-34 wt%In intermetallic system generated the best results of energy saving and storage compared to other intermetallic systems. Also from the microhardness results, it was observed that intermetallic alloys were harder than pure silver and Ag-26 wt% In system had the highest microhardness value with 143.45 kg/mm2. [ABSTRACT FROM AUTHOR]

SAF2507 duplex stainless steel (DSS) is often used as a structural component in ocean-going vessels and marine petroleum exploitation equipment, which require superior mechanical properties. In this study, we used cold rolling (CR) at room temperature with 55% or 80% deformation amounts and subsequent annealing at 1273 K in 1 min to prepare SAF2507 samples with a heterogeneous structure (HS) that was composed of ferrite and austenite phases with different grain sizes. Compared with the homogeneous structure samples, the yield strength of the HS samples increased, while the ductility did not decrease. The 55%-1273 and 80%-1273 samples exhibited the hetero-zone boundary-affected regions on both sides of the grain boundary, phase boundary, and twin boundary. This resulted in hetero-deformation-induced (HDI) strengthening and strain hardening of samples during tensile deformation, which improved the ultimate tensile strength of the HS samples while maintaining a good uniform elongation. In addition, the heterogeneous structure of DSS had better corrosion resistance than the initial sample of coarse grain (CG) structure; mainly because the HS samples had finer grains and more grain boundaries on the DSS surface than the CG structure, which is conducive to the formation of high-density passivation film on the surface of stainless steel. The current study provides a new method of material selection of some structural components with the demands of high strength and good ductility. [ABSTRACT FROM AUTHOR]

Geopolymer is an emerging green cementitious material that can be used to stabilize dredged clay (DC) as construction materials. This paper presented an experimental study on the effects of desulfurized gypsum (DG) on the mechanical properties (e.g., stress-strain characteristics, unconfined compressive strength (UCS) and water stability) of stabilized DC with high initial water content using the ternary geopolymer based on fly ash (FA), ground granulated blast-furnace slag (GGBS) and DG. Moreover, microstructure tests were conducted to elucidate the mechanism of the mechanical enhancement of the stabilized DC. The results clearly demonstrated that DG exerted a significant influence on the mechanical properties of the stabilized DC. Notably, the incorporation of DG led to a transition from ductile to brittle behavior and a notable increase in the deformation modulus (E50). DG effectively enhances the unconfined compression strength (UCS) of stabilized DC with a high initial water content. The peak UCS for the stabilized DC sample with an initial water content of 2.0wL reached 1632.9 kPa with the mass ratio of DG to solid waste FA and GGBS (i.e., D/S) of 8%. Stabilized DC at the low D/S ratio exhibited excellent water stability, while the stabilized DC at the D/S ratio of 8% retained the highest strength after water immersion. The threshold of the D/S ratio is determined to be 8%. Microstructure characterization revealed that the strength enhancement of the stabilized DC primarily relies on the cementation effect of geopolymer gel and crystalline C-(A)-S-H, along with the filling effect of ettringite. However, a significant amount of ettringite can lead to an expansion in the DC volume and disrupt the weak cementation bonding, ultimately causing a deterioration in strength.

The age-hardening behavior and precipitation evolution of an isothermal aged Mg−5Sm−0.6Zn−0.5Zr (wt.%) alloy have been systematically investigated by means of transmission electron microscopy (TEM) and atomic-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The Vickers hardness of the present alloy increases first and then decreases with ageing time. The sample aged at 200 °C for 10 h exhibits a peak-hardness of 90.5 HV. In addition to the dominant β0′ precipitate (orthorhombic, a = 0.642 nm, b = 3.336 nm and c = 0.521 nm) formed on {11-20}α planes, a certain number of γ” precipitate (hexagonal, a = 0.556 nm and c = 0.431 nm) formed on basal planes are also observed in the peak-aged alloy. Significantly, the basal γ” precipitate is more thermostable than prismatic β0′ precipitate in the present alloy. β0′ precipitates gradually coarsened and were even likely to transform into β1 phase (face centered cubic, a = 0.73 nm) with the increase of ageing time, which accordingly led to a gradual decrease in number density of precipitates and finally resulted in the decreased hardness and mechanical property in the over-aged alloys.

The rotavator blade, a part of an agricultural equipment rotavator, is used for the soil bed preparation. These blades have direct interaction with soil in agricultural land. Bad, rocky, gravel, sandy, and high rough-hard texture of soil are the main factor to damage the surface of the rotavator blade and a high wear rate is observed. This causes to decrease in the overall life of a rotavator blade. It also changes the geometry of the rotavator blade after a few operations, and that all effects the performance capability of this blade. Hence HVOF (High-velocity oxy-fuel) is used to modify the surface that improved wear resistance of the rotavator blade's surface. Feedstock powder used for the coating is WC–10%Co–4%Cr with Ni–20%Cr as a bond coat on 30MNCRB5 steel substrate (Rotavator blade's material). Six samples are prepared to test it on the Pin-On-Disc wear testing apparatus to determine the wear rate, weight loss, cumulative volume loss and linear wear rate, three bare 30MNCRB5 steel and three WC–10%Co–4%Cr coated samples are prepared with 8 mm diameter and 30 mm length in a cylindrical pin shape. Coated samples are characterized using the XRD (X-ray diffraction), SEM (Scanning electron microscope) with EDAX (Energy-dispersive spectroscopy), and X-ray mapping techniques. Worn out surfaces of bare 30MNCRB5 steel and WC–10%Co–4%Cr coated samples are investigated using the SEM (Scanning electron microscope) to study the microstructure of worn surface that helped out to identify the wear behavior. The HVOF (High-velocity oxy-fuel) spray coating drastically improved the surface to defend it from wear, and very less weight loss was seen in the WC–10%Co–4%Cr coated samples as compared to bare 30MNCRB5 steel material. Weight loss determined by the bare (30MNCRB5) material at 40N, 50N, 60N loads are 2.996 × 10−3 Kgm, 3.003 × 10−3 Kgm, 3.123 × 10−3 Kgm, and coated (WC–10%Co–4%Cr) sample at 40N, 50N, 60N loads are 0.006 × 10−3 Kgm, 0.030 × 10−3 Kgm, 0.038 × 10−3 Kgm respectively.

Slag containing lithium aluminate is analyzed for its microstructure. This refers to the mineralogical composition, shape and size of the target and matrix phase, orientation of the target phase, and porosity. To investigate the microstructure of the target phase, a representative sample is taken from the block and measured using the XCT. With the help of the two- and three-dimensional analysis, an insight into the complex structure can be gained. The target phase, in this case, lithium aluminate, has a dendritic structure with different orientations and thus also influences the microstructure of the matrix phase. This is composed of a mix of several minerals and amorphous components. Fine pores with a radius of 10–100 µm are found throughout the sample volume. The fracture behavior of the slag is estimated on the basis of the influencing factors that can initiate fracture in brittle materials or divert the path of the fracture. Since the mineralogical and thus also mechanical properties of the slag can be influenced by its production process, suggestions are given as to how slags should be structured in order to ensure a non-random fracture, which is required for the efficient liberation of the target phase in mechanical processing. [ABSTRACT FROM AUTHOR]

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• Precipitates of Mg-5Sm-0.6Zn-0.5Zr alloy were systematically investigated. • The dominant prismatic β 0 ′ phase was identified based on eight different SAED patterns. • The coexistence of basal γ " and prismatic β 0 ′ precipitates were revealed. • γ " precipitate is more stable than β 0 ′ precipitate in the present alloy. • Numerous β 0 ′ precipitates enhance the hardness and mechanical property. The age-hardening behavior and precipitation evolution of an isothermal aged Mg−5Sm−0.6Zn−0.5Zr (wt.%) alloy have been systematically investigated by means of transmission electron microscopy (TEM) and atomic-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The Vickers hardness of the present alloy increases first and then decreases with ageing time. The sample aged at 200 °C for 10 h exhibits a peak-hardness of 90.5 HV. In addition to the dominant β 0 ′ precipitate (orthorhombic, a = 0.642 nm, b = 3.336 nm and c = 0.521 nm) formed on {11-20} α planes, a certain number of γ" precipitate (hexagonal, a = 0.556 nm and c = 0.431 nm) formed on basal planes are also observed in the peak-aged alloy. Significantly, the basal γ" precipitate is more thermostable than prismatic β 0 ′ precipitate in the present alloy. β 0 ′ precipitates gradually coarsened and were even likely to transform into β 1 phase (face centered cubic, a = 0.73 nm) with the increase of ageing time, which accordingly led to a gradual decrease in number density of precipitates and finally resulted in the decreased hardness and mechanical property in the over-aged alloys. [ABSTRACT FROM AUTHOR]

Increasing the strength of metallic multilayered composites fabricated through accumulative roll bonding (ARB) is typically accompanied by a sacrifice in ductility. In the current work, we propose a strategy to achieve microstructural refinement and outstanding strength-ductility synergy in Al/Brass composites. Here, the aluminum matrix exhibits a bimodal grain distribution, consisting of fine equiaxed grains with an average size of ∼100 nm and ultrafine-elongated grains, in which the brass fragments were distributed uniformly. These microstructural features, introduced through cross accumulative roll bonding (CARB), provide synergistic strengthening effects. The CARB processed composite exhibits a mean misorientation angle of 43.16° and a fraction of high angle grain boundaries of 87%, compared to values of 38.02° and 79% for ARB processed specimen. The CARB processed composite demonstrates a major texture characterized by prominent Rotated Brass {110}, Rotated Goss {011}, and Rotated Cube {001} components. In contrast, the ARB processed specimen revealed strong Goss {011}, Rotated Goss {011}, Brass {011}, and S {123} components. The Copper {112} and S {123} components were nearly absent in the CARB processed composite, because both of them were unstable under the CARB regime. The CARB processed composite shows a tensile strength of 405 MPa and a remarkable elongation of 12.4% at ambient temperature, outperforming ARB processed specimen with a tensile strength of 335 MPa and elongation of 9.5%. These unique mechanical properties in the CARB processed composite are ascribed to the dislocation strengthening, bimodal grain size distribution, uniformity of the brass fragments, and quality of bonding at the interfaces.

Flexible rolling is important for increasing rolling production capacity. Since the wear rolls withdrawn and new rolls launched into the rolling process causing thermal deformation parameters variation, such as deformation temperature, strain rate, and strain. This paper studies the coupling behavior of static recrystallization (SRX), metadynamic recrystallization (MDRX), and thermal deformation parameters based on the double-pass thermal simulation experiments, analyzes the flow stress curves and reveals the variation law of recrystallization with thermal deformation parameters. The result shows that the second-pass flow stress of SRX is significantly dependent on the inter-pass time, deformation temperature and strain rate, Compared to MDRX, SRX requires time to nucleus of conception and is more influenced by initial strain. Considering the recovery effect and the multi-pass static softening solution algorithm of materials, the kinetic models of SRX and MDRX are established, and the predicted values of the models are in good agreement with the experimental values. The EBSD microstructure characterization technique is used to characterize the morphology of SRX and MDRX. The result shows that increasing inter-pass time, deformation temperature and strain rate can promote the SRX and MDRX process and improve static softening effect. Under the condition of constant deformation temperature and strain rate, increasing the initial strain can increase the SRX volume fraction. However, deformation temperature and strain rate have a more significant effect on the static softening than the initial strain. This paper provides a theoretical basis for designing and optimizing recrystallization behavior of flexible rolling gaps.

A comparative study on microstructures and mechanical properties of a low carbon Fe–Mn–Si steel with and without quenching pretreatment is performed to investigate the strength and plasticity enhancement mechanism. Microstructural analysis and 3D APT observation show that the lamellar microstructure obtained by introducing pre-quenching at 990 °C for 20 min prior to quenching and partitioning (Q&P) process mainly consists of ferritic laths, Mn-enriched tempered martensite and retained austenite with high mechanical stability. Mn enrichment in tempered martensite helps maintain a relatively high tensile strength. The refined alternative laths consisting of ferrite and tempered martensite share the same crystallographic orientation, which should be easier to hinder the crack propagation and delay the fracture. Compared to the polygonal-structured sample treated without quenching pretreatment, both higher frequencies of Σ3 CSL boundaries and higher volume fraction of stable retained austenite allow the pre-quenched sample exhibit an excellent strength-plasticity balance. The plasticity of the pre-quenched sample increases by nearly 90% and the product of strength and elongation (PSE) reaches higher than 24 GPa·%.

In this paper, vacuum annealing has been adopted to introduce atomic cluster micro-regions inside Gd-based metallic microfibers to further explore the effect of the structural changes on the magnetocaloric properties and the mechanism which is systematically expressed. The experimental results indicate that the as-prepared Gd-based metallic microfibers have favorable amorphous formation ability and thermal stability. After annealing @ 380 °C, the maximum magnetic entropy change −ΔSmmax, refrigerating capacity (RC), and relative cooling power (RCP) values of the Gd-based metallic microfibers are 7.20 J/kg·K, 459.4 J/kg, and 588.7 J/kg, respectively. Combined with the transmission electron microscopy analysis results, the internal organizational order of the annealed microfibers is significantly altered, and the atomic clusters formed in localized regions, which reduce the magnetocrystalline anisotropy of the microfibers. While under the uni-action of an external magnetic field, the magnetic moment rotation state and magnetic domain structure distribution of the micro-region atoms will be changed obviously, thereby changing the general magnetic properties and magnetocaloric properties of the metallic microfibers. The above research results can promote the engineering application of Gd-based metallic microfibers in the field of magnetic refrigeration.

The microstructure of Ti-6.5Al-2Zr-1Mo-1 V (TA15) alloy fabricated by laser powder bed fusion (LPBF) is characterized by the ultrafine α′ martensite with a high density of dislocations and twins, which is distinct to that of conventionally forged TA15 alloy. The α′ martensite in the as-built alloy transforms to stable α phase when annealing below the β transus, and meanwhile the dislocation density decreases and the α lamellae coarsen with increasing of annealing temperature. An excellent synergy of strength and ductility was achieved in the sample after designated heat treatments, which is better than that of the forged counterpart at both room temperature and 500 °C. In-situ tensile test at 500 °C demonstrated that the plasticity of as-built TA15 alloy was dominated by the formation of microscale shear bands (MSBs) between the α′ lamellae, which results in pronounced strain localization and limited tensile ductility. In the sample with coarsened α lamellae, it was found that the activation of pyramidal slip system at 500 °C effectively alleviated the strain localization and cracking tendency during mechanical loading, which is essential to achieve a desired balance of strength and ductility. These findings are helpful to promote the practical applications of LPBF near-α titanium alloys.

The proper reutilization of the phosphogypsum (PG) by-product derived from the production of phosphoric acid and recycled concrete aggregate (RCA) from waste concrete in roadbase materials is of great necessity and importance. This investigation tried seeking a new approach to reuse them to high quality, including turning PG into calcinated PG (CPG) via washing and calcination, as well as adopting sodium metasilicate nonahydrate (SMN) to strengthen the roadbase materials of cement-stabilized CPG and RCA. Upon the mix design, with a series of experiments including unconfined compressive strength, the wet–dry cycle, freeze–thaw cycle, and scanning electron microscopy, the comprehensive effects of PG treatment, the CPG to RCA mix ratio, SMN dosage, wet–dry cycle and freeze–thaw cycle on the road performance of roadbase materials were well evaluated, and the traffic bearing capacity and microstructure characteristics were also analyzed. The results demonstrate that the 7 d unconfined compressive strength of CPG/RCA roadbase materials can reach 5.34 MPa as the CPG and SMN dosage are 20% and 11%, respectively, which meets the requirements of an extremely and very heavy traffic grade. After five wet–dry cycles and freeze–thaw cycles, the resistance of the CPG/RCA roadbase materials to moisture and frost was significantly improved as 11% SMN was added. Meanwhile, SMN contributes to the reduction in crack width and densifies the microstructure of CPG/RCA roadbase materials. The research results can be used to provide new guidance for building more durable roadbase materials. [ABSTRACT FROM AUTHOR]

TiN/Ti multilayer coatings have great potential for application in improving aero-engine service lives in the sand environment. In this study, TiN/Ti multilayer coatings have been deposited on Ti6Al4V alloy by the magnetic filter cathode vacuum arc deposition technique. The microstructure, adhesion strength, microhardness and sand erosion properties of such coatings after different thermal cycling treatment at 500 °C have been characterized. The results showed that the adhesion strength decreased by 4.6, 4.6, and 41.5% for the coatings after treatments designated as 500-1, 500-2, and 500-3 (where 500 denotes the temperature in and -X denotes the number of cycles) compared with that of 500-0. The corresponding microhardness decreased by 13.5, 20.5, and 51.0%, and the erosion rate increased by factors of 2.51, 24.1, and 124.1. The degradation in mechanical properties was mainly attributed to the onset of surface oxidation, a loosening of the interface structure, and the development of interface microcracks. [ABSTRACT FROM AUTHOR]

This work is focused on creating coating layers made of a metakaolin-based geopolymer suspensions (GP)-formed Al matrix modified using H3PO4 acid with Al(OH)3 in isopropyl alcohol, named GP suspension I, and H3PO4 acid with nano Al2O3 in isopropyl alcohol, named GP suspension J. The selected GP suspensions were applied on aluminum and steel underlying substrates as single-layer coatings and multi-layer coatings, where multi-layer coatings included three and five layers that were polymerized by a curing process. Curing was divided into two types with every layer curing process and final layer curing process. For both GP suspensions I and J, the effect of the number of layers and the type of substrate on adhesion was investigated. The prepared samples on underlying substrates were characterized on the microscopy analysis including SEM for high-resolution images and 3D laser confocal microscopy (CLSM) for the 3D visualization of the coatings structure. Microscopy analysis showed structural defects such as porosity, cracks and peeling, which increase with a greater number of applied layers. However, these defects were only evident on a micro scale and did not seem to be fatal for the performance of the surface stability. The EDS mapping of the prepared layer showed inhomogeneity in the distribution of elements caused by the brush application. A grid test and thickness measurement were performed to complete the microscopy analysis. The grid test confirmed a very high adhesion of GP coatings on the aluminum substrate with a rating of one (only in one case was there a rating of two) and a lower adhesion on the steel substrate with the most frequent rating of three (in one case, there were ratings of two and one). The thickness measurement proved a noticeably thicker thickness of the prepared layer on the Fe substrate compared to the Al substrate by 20%–30% in the case of suspension I and by 70%–10% in the case of suspension J. The thickness of the layer also showed a dependence on the method of application and curing, as a thicker layer was always achieved when curing after the final layer of the GP suspension, compared to curing after each applied layer. The resulting single-layer and multi-layer thicknesses ranged from approx. 7 to 30 µm for suspension I and from approx. 3 to 11 µm for suspension J. A non-linear increase in thickness was also evident from the thickness measurement data. [ABSTRACT FROM AUTHOR]

The presence of macrozones (or micro-textured regions) in Ti-6Al-4V (Ti-64) was shown to be a potential cause to the onset of cold dwell fatigue which reduces fatigue life significantly. Past research has demonstrated the potential of using ultrasonic testing for macrozone characterization, with the variation of ultrasound attenuation, backscatter and velocity in the presence of macrozones. However, due to the complexity of the microstructure, some physical phenomena that were observed are still not well understood. In this study, we propose the use of finite-element polycrystalline models to provide us with a means to systematically study the wave-macrozone interaction. Through this investigation performed using two-dimensional models, we are able to identify important correlations between macrozone characteristics (size, shape and texture) and ultrasound responses (attenuation, backscatter and velocity). The observed behaviours are then validated experimentally, and we also highlight how this understanding can potentially aid with the characterization of macrozones in Ti-64 samples. [ABSTRACT FROM AUTHOR]

To investigate the effect of microwave irradiation on the rate of magnetite reduction while increasing the gas phase diffusion rate limit, the microstructure and kinetics of CO reduction of magnetite powder were studied. The investigation was conducted through microwave irradiation and conventional heating at 900~1100 °C. Under the two heating methods, the iron crystal is selectively reduced and gradually expanded along the direction normal to the length of the ore powder, forming a strip of iron crystal that penetrates the powder and expands outward across the width. The microwave field can effectively improve the sintering of minerals. The changes in Avrami exponents m and k in the reduction process were determined by combining the Johnson–Mehl–Avrami (JMA) model with the lnln method. The microwave field did not change the limiting step. Microwave irradiation proves to be the most effective means to enhance both the initial reduction rate and the rate during the primary iron crystal precipitation phase. The morphology of the iron crystal takes on a dense punctate shape, influenced by the rate of diffusion control. [ABSTRACT FROM AUTHOR]

Titanium alloys gain increasing importance in industry due to the expansion of advanced manufacturing technologies such as additive manufacturing. Conventional titanium alloys processed by such technologies suffer from formation of large primary grains and anisotropy of mechanical properties. Therefore, novel alloys are required. Herein, the effect of ternary alloying elements Fe and Cr on the Ti--6.4(wt%)Ni eutectoid system is investigated. Both elements act as eutectoid formers. Fe and Cr show sluggish transformation behavior, whereas Ni is an active eutectoid-forming element. Thereby, sluggish refers to slow and active to fast transformation kinetics. The focus of this work is on the combined addition of such elements studied under different heat-treatment conditions. It is shown in the results that largely varying microstructures can be generated resulting in hardness values ranging from 239 to 556 HV0.1. Moreover, the formation of a substructure within the α phase of direct aged alloys is observed. The formation mechanism of this substructure is investigated in detail. The mechanical properties are discussed based on the microstructural characteristics. The presence of intermetallic Ti2Ni phase increases the Young's modulus, whereas the presence of ω phase results in embrittlement. The results shed light upon the complex phase formation and decomposition behavior of titanium alloys based on Ti--6.4Ni. [ABSTRACT FROM AUTHOR]