Decrease In Hardness Research Articles

Sheet-based friction stir additive manufactured 6061 aluminium alloy: Microstructure, texture evolution and mechanical properties

A 6061 Al alloy build consisting of 3 additive layers was successfully fabricated using a sheet-based friction stir additive manufacturing process. The study focused on analyzing the microstructure and texture characteristics in the central regions of each layer and the thermal mechanical affected zones (TMAZs) beneath the stir zones (SZs). Mechanical properties of the final multilayered build were also analyzed. The results revealed that, following plastic deformations and thermal cycles, the equiaxed grains formed in the central region of layer 2 were the finest (∼7.9 μm) among the three layers, attributed to the highest degree of recrystallization. Additionally, the average grain size of the TMAZs further decreased to ∼4.0 μm due to lower frictional heat generated by the tool pin. Furthermore, the geometrically necessary dislocation densities of the TMAZs showed a slight increase compared to those of the central regions. In terms of textures, shear and deformation textures were predominant in the central regions, while shear texture dominated the TMAZs. The primary precipitates found at the center of the SZs included β, β′, Q′, Al8Fe2Si and (Fe,Mn,Cr)3SiAl12. Besides, the yield strength and ultimate tensile strength of the build drop significantly to 119.7 MPa and 204.6 MPa, respectively. Moreover, a non-monotonic decrease in hardness as the increase of distance from the top of build could be found, due to the existence of numerous grains with soft orientations and the intense dissolution and coarsening of β” and β’ phases.

Development of new β Ti-10-Mo-Mn alloys for biomedical applications

Metallic biomaterials play a crucial role in various biomedical applications, particularly in developing implants and prostheses. Hence, this study aimed to produce and analyze the structure, microstructure, hardness, and preliminary cytotoxicity of Ti-10Mo-xMn system alloys (with x ranging from 0 to 8 wt%) intended for biomedical applications as biomaterials. The alloys underwent thorough characterization, including chemical composition analysis through EDS measurements, mapping, and density assessments. Structural and microstructural analyses were conducted using x-ray diffraction (XRD), Rietveld refinement, optical (OM), and scanning electron microscopy (SEM), while Vickers microhardness testing provided insights into mechanical properties. Rapid cytotoxicity tests via MTT were also performed to assess biocompatibility. Results indicated that the produced alloys exhibited good quality and homogeneity regarding chemical composition. Adding Mn to the Ti-10Mo alloy facilitated the formation of the β phase, transforming it from a biphasic (α" + β) to a single-phase alloy.Moreover, Mn-induced reductions in lattice parameters and average crystallite size of the β phase were observed due to the smaller atomic radius of substituting Mn than Ti. Despite a decrease in hardness attributed to β phase formation, all alloys demonstrated non-cytotoxic behavior in cell adhesion and viability assays, with values exceeding 70 %. Overall, these findings highlight the potential of Ti-10Mo-xMn alloys as viable biomaterials, warranting further exploration and development in biomedical engineering.

Technology for Blending Recombined Flour: Substitution of Extruded Rice Flour, Quantity of Addition, and Impact on Dough.

In a previous study, rice bread was prepared using a combination of rice-wheat mixed flour. To investigate the impact of the partial adoption of extruded rice flour (ERF) on mixed flour (MF) and mixed dough (MD), the effects of adding ERF on the pasting, mixing characteristics, texture, and water retention of the MF and MD were examined by a rapid visco analyzer (RVA), Mixolab, texture profile analysis (TPA), and a low-field nuclear magnetic resonance analyzer (LF-NMR). The PV, TV, BD, FV, and SV of the MF declined as the incorporated amount of ERF increased. There was no significant difference in the PT at the 5-15% addition level (p < 0.05), but it showed an increasing trend at the 20-30% level (p < 0.05). The incorporation of ERF led to a significant increase in the water absorption (WA) of the MD, while the DT, ST, C2, C3, C4, and C5 exhibited a declining trend. The texture analysis revealed a significant decrease in the dough hardness with the addition of ERF, with a 55% reduction in the hardness of the 30% improved mixed dough (IMD), and the cohesiveness increased significantly (p < 0.05). The IMD was mainly composed of weakly bound water. The content of weakly bound water increased with the ERF amount.

Mechanical Properties of Newly Developed Flowable Composite Derived from Rice Husk at Different Monomer Ratios

An ideal flowable composite (FC) requires good mechanical properties to fulfill its role as a dental restorative material and ensure durability and clinical efficacy, with these properties being influenced by different monomer ratios. The study aimed to evaluate the mechanical properties of the newly developed FC on Vickers hardness, flexural strength, and flexural modulus at different monomer ratios. The newly developed FC employed nanohybrid silica from rice husk and zirconia as fillers, and the ratio of urethane dimethacrylate to triethylene glycol dimethacrylate (UDMA:TEGDMA) at 20:80, 30:70, 50:50, 60:40, 80:20 and 90:10 as monomers. Filtek Supreme Ultra Flowable Restorative, Revolution Formula 2, and G-aenial Universal Flo served as control groups. The data were statistically analyzed using one-way ANOVA with post-hoc Bonferroni test. Generally, the higher UDMA ratio in the newly developed FCs exhibited higher mechanical properties. All newly developed FCs demonstrated a significant decrease in Vickers hardness than control groups. The flexural strength values at ratios of 50:50, 60:40, 80:20, and 90:10 were comparable with control groups and passed the International Organization for Standardization 4049 requirement. Meanwhile, the flexuralmodulus of the newly developed FC at the ratio of 90:10 was comparable to Revolution Formula 2. In summary, the differences in monomer ratios affect the mechanical properties of the newly developed FCs. The improved mechanical properties at ratios of 80:20 and 90:10 could potentially substitute sustainable dental restorative materials, subjected to further investigations.

Unraveling cereal physical barriers composed of cell walls and protein matrix: Insights from structural changes and starch digestion

Physical barriers composed of cell walls and protein matrix in cereals, as well as their cooking changes, play important roles in starch digestion. In this study, the physical barriers of native and cooked highland barley (HB), brown rice (BR), and oats (OA) kernels and their contribution to starch digestion were investigated. The resistant starch content was similar in cereal flours, but varied among cooked kernels (HB > BR > OA: 45.05 %, 10.30 %, and 24.71 %). The water adsorption, gelatinization enthalpy, and decrease in hardness of HB kernels were lower than those of OA and BR kernels. Microstructural observations of native kernels showed that HB had the thickest cell walls. After cooking, the lowest cell wall deformation and a dense continuous network developed from the protein matrix were observed in HB kernels. During digestion, undigested starch granules encapsulated by the stable cell walls and strong protein network were observed in HB kernels, but not in BR or OA kernels. Furthermore, the heavily milled HB kernels still had more resistant starch than the intact OA and BR kernels. Therefore, the physical barriers of HB kernels exhibited stronger inhibition of starch gelatinization and digestion. Differences in cereal physical barriers led to various inhibitory effects.

Evaluation of the efficacy of various remineralization agents and grape seed extract on microhardness and lesion depth of primary tooth enamel: An in vitro study.

This study evaluated the efficacy of grape seed extract (GSE) on the remineralization of primary tooth enamel alone or in combination with remineralizing agents. The initial microhardness value of 90 primary tooth enamel samples was calculated; then, the samples were demineralized. The post-demineralization hardness of the samples was measured and the samples were randomly divided into 6 groups as follows: G1: negative control, G2: GSE, G3: NaF, G4:Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), G5: GSE+NaF, and G6: GSE+CPP-ACP (n=15). Oral environment pH cycle was applied and hardness measurements were repeated after treatments. The samples were stained with 1% rhodamine B dye and sectioned, and the lesion depth was measured. Statistical significance was set at P<0.05. The hardness decrease of the GSE and GSE+NaF groups was less than the other groups (P<0.05). The decrease was also less in the other groups than in the control group (P>0.05). GSE showed a positive effect when combined with NaF in maintaining microhardness but did not show the same effect when combined with CPP-ACP (P<0.05). Concerning penetration depth, all the groups had statistically lower values than the control group (P<0.05). The lowest penetration rates were observed in the GSE+NaF and GSE+CPP-ACP groups (P<0.05). The lowest hardness decrease was observed in the GSE and GSE+NaF groups, and the lowest penetration rates were observed in the GSE+NaF and GSE+CPP-ACP groups. It has been determined that a 15% GSE solution might be used as an alternative to fluoride in primary tooth remineralization and can increase the effectiveness of fluoride when used together.

Elucidating the evolution of pore structure, microstructural damage, and micromechanical response in cement pastes containing microencapsulated phase change materials under freeze-thaw conditions

As climate variability intensifies the frequency and severity of freeze-thaw cycles, the development of cementitious materials capable of withstanding these harsh conditions becomes increasingly crucial. This research focuses on the potential of Microencapsulated Phase Change Materials (MPCMs) to enhance the durability of Hardened Cement Paste (HCP) in the face of such challenges. Specifically, this paper evaluates the influence of MPCMs on evolution of pore microstructure, damage, and micromechanical response in HCP subjected to extended freeze-thaw cycles, utilizing Low-Temperature Differential Scanning Calorimetry (LTDSC), X-ray Tomography (XRT), and micro-indentation. LTDSC results indicate a lower ice-crystallization temperature and a significant reduction in ice formation in MPCM-integrated HCP. Micro-indentation experiments reveal that while the control HCP undergoes substantial decreases in indentation hardness (35 %) and Young's modulus (37 %) after 180 cycles, the MPCM samples show much lower losses (only 9 % loss in hardness and 7 % loss in Young's modulus for 20 % MPCM inclusion). XRT image analysis reveals that MPCMs mitigate pore enlargement, preserve a stable pore size distribution, and effectively reduce the risk of increased interconnected porosity in HCP when subjected to extended freeze-thaw cycles. Crack analysis demonstrates that control HCP samples exhibit significant crack propagation with increased freeze-thaw cycles, while samples with 10 % MPCM inclusion show only slight crack initiation, and those with 20 % MPCM inclusion maintained their structural integrity with virtually no crack progression after 180 freeze-thaw cycles. These findings underscore the potential of MPCMs to improve the durability of HCP against freeze-thaw damage, offering key insights for designing more robust materials.

Eliminating the soft zone for grade 91 steel weldment via enhancing prior austenite grain size of the intercritical heat-affected zone

The soft zone is deemed unwanted for grade 91 steel weldments as it constitutes a cracking-sensitive region deleterious for long-term creep performance. In the present work, formation mechanisms of the soft zone in grade 91 steel weldments have been elucidated and an approach for its elimination has been proposed. It has been demonstrated that a soft zone forms within the intercritical heat-affected zone (ICHAZ) after post-weld tempering. Post-weld normalizing and tempering enables the elimination of the soft zone. Further analysis reveals that the ICHAZ of the as-welded specimen possesses a mixed structure, consisting of over-tempered martensite and fresh martensite with a fine prior austenite grain size. During post-weld tempering, the increase in grain size and the reduction in dislocation density are the main factors contributing to the decrease in hardness. The recrystallization rate of the ICHAZ is faster than that of other regions, resulting in a decrease in hardness from 350.8 HV0.3 to 204.6 HV0.3 and the formation of the soft zone. Increased prior austenite grain size in the ICHAZ, achieved through post-weld normalizing and subsequent tempering, facilitates the formation of tempered martensite and prevents the formation of the soft zone.

The aging-hardening behavior of short-time in high pressure die casting AlSi9MgMnZn alloy

Short-time aging is an effective industrial technique for enhancing the mechanical properties of high pressure die cast (HPDC) aluminum alloy components. However, the evolution of precipitation behavior during short-time aging of HPDC alloys remains unclear. In this study, the short-time aging behavior of HPDC AlSi9MgMnZn alloy was investigated. The results show that the AlSi9MgMnZn alloy exhibits effective aging-hardening, with an increment in hardness of approximately 30 HV through the optimal short-time aging treatment (aged at 180 °C for 120 minutes). Higher aging temperatures led to reduced peak hardness and rapid over-aging above 220 °C. The microstructure observation indicates that the peak short-time aging promotes the simultaneous precipitation of β″ precipitates, GP zones and nano Si phases. The contribution of different strengthening mechanisms to hardness was estimated, implying that the coexistence of β″ precipitates and GP zones can provide a positive contribution to aging-hardening during short-time aging. Moreover, as the aging temperature increases, the appearance of β′ precipitates reduces the strengthening effect, leading to a decrease in hardness.

Research on a new type of ureteral stent material Zn-2Cu-0.5Fe-xMn with controllable degradation rate

The placement of ureteral stents plays a crucial role in the treatment of ureteral strictures, therefore requiring high material performance standards. In addition, depending on the etiology of ureteral strictures, there are significant differences in the retention time of ureteral stents, thus requiring different degradation rates for the stents. Therefore, it is crucial to develop stent materials with high performance and controllable degradation rates. This study explores the potential of Zn-2Cu-0.5Fe-xMn alloy as a ureteral stent material, utilizing the antibacterial effect of copper ions, the strengthening effect of Fe element on Zn-based alloys, and the accelerated degradation effect of Mn element. The research found that with the increase in Mn content, the average grain size of the alloy and the size of (Fe, Mn)Zn13 phase gradually increased, leading to a decrease in hardness. The corrosion rate of the alloy increased with the increase in Mn content, attributed to changes in grain size and standard electrode potential differences between elements. Due to the antibacterial effects of Zn ions and Cu ions, the Zn-2Cu-0.5Fe-xMn alloy exhibits good anti-stone formation capabilities. Furthermore, the alloy also demonstrates acceptable cytotoxicity. Therefore, the Zn-2Cu-0.5Fe-xMn alloy is expected to become an important implant material in urological surgery.

The Effect of Cigarettes Smoke on the Color and Properties of a Silicone for Maxillofacial Prostheses.

Although deterioration of silicone maxillofacial prostheses is severely accentuated in smoking patients, the phenomenon has not been systematically studied. To address a gap in the literature concerning the stability of maxillofacial prostheses during service, in this contribution, the effect of cigarette smoke on the aspect and physical properties of M511 silicone elastomer was evaluated. The aspect, surface, and overall properties of the silicone material, pigmented or not, were followed by AFM, color measurements, FTIR, water contact angle measurements, TGA-DTG and DSC, hardness and compression stress-strain measurements. The types of the contaminants adsorbed were assessed by XRF, ESI-MS, MALDI-MS, and NMR spectral analyses. Important modifications in color, contact angle, surface roughness, local mechanical properties, and thermal properties were found in the silicone material for maxillofacial prostheses after exposure to cigarettes smoke. The presence of lead, nicotine, and several other organic compounds adsorbed into the silicone material was emphasized. Slight decrease in hardness and increase in Young's modulus was found. The combined data show important impact of cigarette smoke on the silicone physical properties and could indicate chemical transformations by secondary cross-linking. To our knowledge, this is the first study making use of complementary physical methods to assess the effect of cigarette smoke on the aspect and integrity of silicone materials for maxillofacial prostheses.

Effect of carboxymethyl cellulose incorporation to gelatin‐sunflower oil bigel on the physicochemical and structural properties

AbstractBigels are innovative and appealing heterogeneous matrices composed of two structured‐gel (hydrogel and oleogel) phases, which suitable for the entrapment of both hydrophilic and lipophilic active agents. As structuring the bigel phases using convenient materials can enhance the main characteristics, this study aimed to develop bigel system based on a hybrid hydrogel consisting of gelatin and carboxymethylcellulose (CMC). The impact of incorporating various concentrations of CMC (0, 0.5, 1, 2, and 3% w/w) into gelatin‐based hydrogel at a constant organogel/hydrogel ratio of 60:40 was investigated on bigel properties. The integration of gelatin and CMC significantly affected the solvent holding capacity (SHC), microstructure, rheology, thermal, and textural properties. The results showed that bigel samples containing gelatin‐CMC had lower SHC compared to gelatin‐based samples. The integration of CMC to bigel formulation resulted in a significant decrease in hardness, cohesiveness, and adhesiveness also smooth texture. Differential scanning calorimeter (DSC) analysis of the bigels showed a descending trend in melting point from 99.07 to 98.60°C for bigel samples as the CMC concentration increased from 0% to 2%. This was followed by an increase in melting temperature (100.95°C) in the bigel containing 3% CMC. Particle size distribution data indicated that the droplet sizes of the bigels increased with the incorporation of CMC into the hydrogel phase, without displaying a distinct concentration‐dependent trend. The rheological characteristics of strain sweep, frequency sweep, and loss factor affected by gelatin/CMC concentration. Overall obtained results highlight that CMC incorporation to gelatin plays a crucial role in bigel offering different textural, rheological and thermal properties. So that carefully selection and optimization of gelatin and CMC concentrations in hydrogel phase are essential for tailoring the mechanical strength and stability of bigels for various applications such as drug delivery, cosmetic, and food industries. Regarding the desired properties of CMC, it could be recommend to use by combination with gelatin to create a structure–function aimed bigels.

The impact of BBr3/TiCl4 ratios on the microstructural and mechanical characteristics of TiBN coatings deposited using a pulsed-PACVD technique

This study aimed to investigate the impact of precursor ratios on both the microstructural and tribological characteristics of TiBN coatings. Using the PACVD process, TiN, TiB2, and three variations of TiBN coatings with adjusted BBr3/TiCl4 ratios were applied onto H13 substrates. The coatings were characterized using XRD, FESEM, TEM, AFM, nanoindentation, and nanoscratch methods to analyze their microstructural properties, surface morphology, and mechanical behavior. The findings revealed that the TiBN coatings possessed a nanocomposite structure with TiN crystals dispersed within the BN matrix, which is amorphous. Moreover, the augmentation of the BBr3/TiCl4 ratio from 0 to 1/3 resulted in a significant rise in the hardness value, from 13.4 GPa to 25.7 GPa. However, a further increase in the ratio from 1/3 to 3/3 resulted in a decrease in hardness to 14.4 GPa because cracks were formed in the deposited coating. In comparison, the TiB2 coating exhibited a higher hardness of 19.7 GPa due to strong TiB bonds within the coating. The TiBN coating, applied with a BBr3/TiCl4 ratio of 1/3, demonstrated the lowest wear volume of 0.10 × 10−18 m3, attributed to its higher hardness and smoother surface texture.

Surface microstructure evolution and enhanced properties of Ti-6Al-4V using scanning electron beam

Enhanced surface properties of the Ti-6Al-4V alloy are crucial for optimizing its overall performance and reliability. In this study, scanning electron beam treatment was employed to enhance its surface properties. The results demonstrate a nonlinear decrease in hardness with increasing depth, while the surface microhardness increased to 422.6 HV0.1, representing a 1.4 times enhancement compared to the substrate. The wear volume was decreased from 0.5045 mm³ before treatment to 0.2498 mm³, resulting in a >2 times enhancement in wear resistance. Additionally, the corrosion current density of the treated material decreased by an order of magnitude, while the corrosion potential and charge transfer resistance increased. These improvements in surface properties can be attributed to the treatment with a scanning electron beam, which induces phase transformation and refines the microstructure into more acicular α' phases. This process enhances surface hardness and facilitates the formation of a more robust passive layer, thereby enhancing the material's wear resistance and corrosion resistance. This study provides valuable insights and methodologies for enhancing the surface properties of Ti-6Al-4V alloy.

Chlorine Dioxide Delays Enzymatic Browning in Postharvest Cherimoya and Enables Establishment of Kinetics Substrate Model

Cherimoya (Annona squamosa L.) is a nutrient-rich fruit. However, it is not easy to store because of its susceptibility to browning. In order to prolong the storage period of cherimoya, the fruit was treated with chlorine dioxide (ClO2) at different concentrations (20, 40, 60, 80, and 100 mg L−1) and stored at 15 °C for 8 days. The quality and biochemical indexes of the fruit were investigated using a chromameter, high-performance liquid chromatography and scanning electron microscopy, etc. The results showed that all the treatments with various concentrations of ClO2 could delay the increase in the browning index, loss of weight, and decrease in hardness. Meanwhile, ClO2 treatment effectively reduced the consumption of starch, titratable acids, and phenolics as well as inhibited the polyphenol oxidase (PPO) activity and enzymatic oxidation. It can be seen from the Fourier transform infrared spectrum (FTIR) that the C=O stretching peak at 1731 cm−1 disappeared at a ClO2 concentration of 60 mg L−1. We think the ClO2 treatment may inhibit the oxidation of phenol to quinone. According to the Arrhenius formula, the values of the apparent activation energy (Ea) for enzymatic browning reaction were estimated. The Ea with catechol in cherimoya pericarp and flesh were 67.00 and 47.83 kJ mol−1, respectively. It was found that the phenolic enzyme reaction with catechol has a much smaller Ea and a higher affinity for PPO. Therefore, treatment with ClO2 at a suitable concentration for cherimoya stored at 15 °C could effectively maintain fruit quality and prolong the storage period; the most appropriate concentration is 60 mg L−1.

Friction weldability of ultrafine-grained titanium grade 2

The paper presents the results of an experimental study of the friction weldability of Titanium Grade 2 with ultrafine-grained (UFG) microstructure obtained by hydrostatic extrusion and rotary swaging (HE+RS). High-speed friction welding with different rotational speed (n) values was used as a joining method. The best properties were obtained for n=7000 rpm. Metallographic observations confirmed the formation of a continuous friction joint with a changed microstructure of the base material in the thermal-mechanical affected zone (TMAZ) and a friction weld (FW). The results of the mechanical properties showed the greatest decrease in hardness in the TMAZ. The friction welded joint had an 18 % lower tensile strength value than initial state UFG Titanium Grade 2 after the HE+RS process (with UTS=1050 MPa).

Tomato seed fractions enriched muffins: functional, textural, and qualitative characterisation

SummaryThe current study was undertaken to investigate the use of tomato seed oil (TSO) and defatted tomato seed meal (DTSM) individually and in combination for muffin preparation in an effort to utilise the fruit waste generated during food processing and harness its nutritional potential. The incorporation of DTSM and TSO at 0–25% led to a significant increase in the baking yield and weight of muffins, with a more pronounced effect in the case of DTSM‐incorporated muffins. Based on organoleptic evaluation, muffins with incorporation of DTSM and TSO at 20% and 15%, respectively, were most acceptable. Therefore, muffins (DTSM 20 + TSO 15) were prepared with DTSM and TSO replacement at 20% and 15%, respectively. The combined effect of DTSM and TSO resulted in a dietary fibre increase of 61.57% as compared to the control (wheat flour and margarine‐based muffins). As per texture profile analysis, the addition of DTSM led to a significant decrease in hardness, whereas a rise was noted for TSO‐incorporated muffins. Storage studies of muffins for 7 days in low‐density polyethylene pouches indicated no significant degradation in quality parameters. The results obtained in the study confirmed the efficient utilisation of tomato seed fractions for the preparation of nutritionally enriched muffins.

Thermal runaway of Li-ion batteries caused by hemispherical indentation under different temperatures: Battery deformation and fracture

Thermal runaway (TR) of Li-ion batteries (LIBs) presents a disastrous safety hazard and a significant barrier to the wider adoption of electric vehicles (EVs). Internal short circuit (ISC) induced by mechanical abuse is one of the causes of battery TR. This paper uses hemispherical indentation tests to trigger ISC in the battery at different temperatures and studies the battery deformation and fracture mode. Results show as the initial temperature increases, the battery hardness and strength decrease, and the fracture mode of the laminar structure changes from shear fracture to localized rupture. In the shear fracture mode, the ISC homogeneously heats the battery, and it does not directly trigger TR. In the localized rupture mode, the ISC is only induced at the layers close to the indenter and generates a hot spot exceeding 200 °C, leading to the initiation of TR. Therefore, the mechanical properties of batteries under different conditions need to be studied in more detail to develop batteries that are safer under mechanical abuse.

Effect of Phase Composition Variation of Oxy–Nitride Composite Ceramics on Heat Resistance and Preservation of Strength Parameters

The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of long-term thermal exposure, accompanied by the processes of oxidation and softening. The relevance of this research consists of determining the influence of the phase composition of ceramics on the change in their strength and thermophysical parameters, on the basis of which, we can draw a conclusion about the optimal composition of composite ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant structural materials. During this study, the dynamics of the changes in the phase transformations of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by the thermal annealing of the samples, was established. According to the assessment of the phase transformations with variations in the ratio of the components, it was found that thermal annealing in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an orthorhombic Al2(SiO4)O phase and an elevation in its contribution at concentrations above 0.5 M, which causes a rise in the thermophysical parameters and resistance to high-temperature degradation. During the heat resistance tests, it was found that the formation of the composite ceramics with the Si3N4(SiO2)/Al2(SiO4)O/Al2O3 phase composition results in an increase in the stability of their strength properties when exposed to thermally induced oxidation, which has a negative impact on their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2(SiO4)O phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation resistance of strength properties by more than 4–7 times, in comparison with the softening data established for single-component ceramics.

An integrated exploration from microstructure to mechanics in austenite to pearlite transformation of high carbon steel under high magnetic fields

The effects of a high magnetic field (12 T) on the microstructural evolution and mechanical properties of high carbon steel during isothermal pearlitic transformation at 720 °C were investigated. The application of a high magnetic field effectively promotes pearlitic transformation and leads to a reduction in the lamellar spacing and the geometrically necessary dislocation density (GND) as well as to a slight increase in the grain size of the pearlite, which leads to a decrease in hardness. This is because the magnetic field reduces the magnetic Gibbs energy of ferrite and cementite, resulting in an increase in the driving force of phase transformation, which shortens the pearlite maturation time and reduces the nucleation barriers of pearlite, thereby accelerating the growth rate of pearlite. In addition, the interfacial energy of ferrite/cementite was found to be increased by the magnetic field from the thermodynamic point of view, and the mechanism of action of the magnetic field -induced precipitation of cementite in the form of particles and short rods was elucidated. The present work will enhance the understanding of the mechanism of magnetic field-induced phase transformation in iron-based materials.