Phase Region Research Articles

Study on the metallurgical mechanisms of inclusions in the FGH4096 alloy during electron beam smelting

In this study, the metallurgical mechanisms of inclusions during electron beam smelting (EBS) of a FGH4096 powder superalloy was investigated. The macroscopic morphology of the ingots, as well as the composition and structure of inclusions were studied. The effect of electron beam smelting parameters on the cooling rate, O/N content, number density and size of inclusions have been revealed. Besides, the mechanisms for inclusions removal and formation were elucidated. The results show that inclusions in the final solidification zone are mainly oxides (simple tetragonal CrO2, hexagonal Al2O3, and face-centered cube TiN), whereas the complex inclusions and carbon nitrides with Al2O3 and TiN as the nucleation cores are mainly present in the matrix. With the increase in smelting power and time, both the cooling rate and O/N content decsrease, and the smelting power shows a greater impact on the cooling rate. The number density of total inclusions increases with the increase in the smelting power. As the smelting time increases, the number density of total inclusions decreases, while the size of complex inclusions and carbon nitrides increases. This is attributed to the combined effect of cooling rate and O/N concentration in the alloy under different smelting parameters. Thermodynamic calculations indicate that Al2O3 forms in the solid-liquid phase region. The precipitation of TiN occurs when the alloy solidifies, and its precipitation temperature is higher than that of TiC. The lattice mismatch between Al2O3 and TiN is 8.14%, while that between TiC and TiN is 6.94%, which effectively promotes the heterogeneous nucleation of complex inclusions and carbon nitrides. The formation mechanisms of complex inclusions and carbon nitrides provide a theoretical basis for purification of superalloys by electron beam metallurgy.

The combined effects of uniaxial pressure and defects on the mechanism of martensitic transformation in pure iron: A molecular dynamics study

The as-produced martensitic steel fabricated by selective laser melting (SLM) is generally softer and weaker than the wrought specimen due to the residual austenite in the microstructure. To avoid additional post-heat treatment, this study proposes a strategy to reduce the residual austenite by applying additional pressure after each laser scanning. Therefore, the combined effects of uniaxial pressure and stacking faults (SFs) on martensitic transformation (MT) in the parent face-centered cubic (FCC) phase of pure Fe are investigated via molecular dynamics (MD) simulation. The simulation results show that the supercooling, uniaxial pressure, and pre-existing SF defects in the parent FCC phase provide chemical driving force, and mechanical driving force and reduce the energy barrier of MT, respectively. The Ms temperatures increase gradually with the pressure from 0 to 200MPa. The MT process consists of nucleation and growth. The heterogeneous nucleation occurs in the parent FCC phase with pre-existing defects and favoring intersecting-SF, SF, and defect-free FCC phase region in order. The homogeneous nucleation occurs in the parent FCC phase without pre-existing defect and the MT process is achieved by the growth and coalescence of the scattered crystal nucleus. The stress field generated by the dislocation lines at the intersecting region of SFs results in the lattice distortion of the atoms nearby, reducing the energy barrier of MT nucleation. The study verifies the feasibility of reducing residual austenite in SLM-ed martensitic steel by applying pressure during the cooling process of each layer.

The Effect of Refined Coherent Grain Boundaries on High-Temperature Oxidation Behavior of TiAl-Based Alloys through Cyclic Heat Treatment

The grain size of the full lamellae TiAl-based alloy changes from ~400 μm to ~40 μm through the precipitation of metastable structures by cyclic heat treatment. Based on this, two kinds of variant selection processes—coherent metastable γ variants precipitated during the air-cooling process and αs variants precipitated during the holding at a single α phase region process—are identified to promote the formation of refined Type I and Type II coherent grain boundaries. The oxidation tests at 1000 °C for 100 h show that the formation of refined coherent grain boundaries can greatly improve oxidation resistance by inducing the continuous multi-layer protective barrier consisting of (Ti, (Nb, Ta))O2, TiN, and Al(Nb,Ta)2. This protective barrier inhibits the inward diffusion of oxygen and nitrogen.

Experimental Investigation of Phase Equilibria in the Ti-Cr-V System at 1000–1200 °C

Ti-Cr-V-based alloys have been utilized across various domains, including aerospace structural and functional materials and hydrogen storage materials. Investigating the phase relations in the Ti-Cr-V system is significant in supporting the material design for these applications. In the present work, the isothermal sections at 1000, 1100, and 1200 °C for the Ti-Cr-V system were precisely determined through a systematic investigation using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The phase region of Cr2Ti was entirely elucidated for the first time. As the temperature decreased from 1200 to 1000 °C, the V solubility range of Cr2Ti increased from 5.3 wt.% to 10.0 wt.%, while the Ti solubility range essentially remained constant at approximately 31.0–33.9 wt.%. In addition, it was suggested that the stable structure of Cr2Ti was C36 at 1200 °C and C15 at 1000 and 1100 °C. The present work will support thermodynamic re-assessment research.

Constructing a Novel Moderately Modulus "Rigid-Flexible" Structure with Synergistic Reinforcement on the Carbon Fiber Surface to Enhance the Mechanical Properties of Carbon Fiber/Epoxy Composites at Elevated Temperatures.

To improve the mechanical performance of carbon fiber (CF)/epoxy composites in high-temperature environments, a moderately modulus gradient modulus interlayer was constructed at the interface phase region of composites. This involved the design of a "rigid-flexible" synergistic reinforcement structure, incorporating rigid nanoparticle GO@CNTs and a flexible polymer polynaphthyl ether nitrile ketone onto the CF surface. Notably, at 180 °C, compared to commercial CF composites, the CF-GO@CNTs-PPENK composites displayed a remarkable improvement in their mechanical characteristics (interfacial shear, interlaminar shear, flexural strength, and modulus), achieving enhancements of 173.0, 91.5, 225.7, and 376.4%, respectively. The principal reason for this the moderately modulus interface phase composed of GO@CNTs-PPENK (where GO and CNTs predominantly consist of carbon atoms with sp2-hybridized orbitals, forming highly stable C-C structures, while PPENK possesses a "twisted non-coplanar" structure), which exhibited resistance to deformation at high temperatures. Moreover, it greatly improved the mechanical interlocking, wettability, and chemical compatibility between CF and the epoxy. It also played a crucial role in balancing and buffering the modulus disparity. The interface failure behavior and reinforcement mechanisms of the CF composites were analyzed. Furthermore, validation of the presence of a moderately modulus gradient interlayer at the interface phase region of CF-GO@CNTs-PPENK composites was performed by using atomic force microscopy. This study has established a theoretical foundation for the development of high-performance CF composites for use in high-temperature fields.

Microstructural Characteristics and Properties of Laser-Welded Diamond Saw Blade with 30CrMo Steel.

In order to enhance the quality of diamond composite materials, this work employs a Cu-Co-Fe and Ni-Cr-Cu pre-alloyed powder mixture as a transition layer, and utilizes laser-welding technology for saw blade fabrication. By adjusting the laser-welding process parameters, including welding speed and welding power, well-formed welded joints were achieved, and the microstructure and mechanical properties of the welded joints were investigated. The results demonstrate that the best welding performance was achieved at a laser power of 1600 W and a welding speed of 1400 mm/min, with a remarkable tooth engagement strength of up to 819 MPa. The fusion zone can be divided into rich Cu phase and rich Fe phase regions, characterized by coarse grains without apparent preferred orientation. The microstructure of the heat-affected zone primarily consists of high-hardness brittle quenched needle-like martensite, exhibiting a sharp increase in microhardness up to 550 HV. Fracture occurred at the boundary between the fusion zone and the heat-affected zone of the base material, where stress concentration was observed. By adjusting the welding parameters and transition layer materials, the mechanical properties of the joints were improved, thereby achieving a reliable connection between diamond composite materials and the metal substrate.

Boron-doped high-entropy oxide toward high-rate and long-cycle layered cathodes for wide-temperature sodium-ion batteries

O3-type layered metal oxides hold great promise for sodium-ion batteries cathodes owing to their energy density advantage. However, the severe irreversible phase transition and sluggish Na+ diffusion kinetics pose significant challenges to achieve high-performance layered cathodes. Herein, a boron-doped O3-type high entropy oxide Na(Fe0.2Co0.15Cu0.05Ni0.2Mn0.2Ti0.2)B0.02O2 (NFCCNMT-B0.02) is designed and the covalent B–O bonds with high entropy configuration ensure a robust layered structure. The obtained cathode NFCCNMT-B0.02 exhibits impressive cycling performance (capacity retention of 95% and 82% after 100 cycles and 300 cycles at 1 and 10 C, respectively) and outstanding rate capability (capacity of 83 mAh g−1 at 10 C). Furthermore, the NFCCNMT-B0.02 demonstrates a superior wide-temperature performance, maintaining the same capacity level (113.4 mAh g−1@−20 °C, 121 mAh g−1@25 °C, and 119 mAh g−1@60 °C) and superior cycle stability (90% capacity retention after 100 cycles at 1 C at −20 °C). The high-entropy configuration design with boron doping strategy contributes to the excellent sodium-ion storage performance. The high-entropy configuration design effectively suppresses irreversible phase transitions accompanied by small volume changes (ΔV = 0.65 Å3). B ions doping expands the Na layer distance and enlarges the P3 phase region, thereby enhancing Na+ diffusion kinetics. This work offers valuable insights into design of high-performance layered cathodes for sodium-ion batteries operating across a wide temperature.

Flow behavior and dynamic recrystallization mechanism of a new near-alpha titanium alloy Ti-0.3Mo-0.8Ni-2Al-1.5Zr

A new near-α titanium alloy Ti-0.3Mo-0.8Ni-2Al-1.5Zr was designed based on Ti-0.3Mo-0.8Ni (TA10). The hot compression tests were carried out at temperatures of 800 ∼ 970 °C and strain rates of 0.01-5 s-1. The results show that the flow softening phenomenon in the α + β phase region is more distinct than that in the single β phase region. The Arrhenius constitutive models based on strain compensation in the α+β phase region and β phase region were established respectively, and the correlation coefficient between the predicted flow peak stress values and the experimental values reached 0.99365. The hot processing map of the alloy was established, the processing parameters of the peak efficiency: 800 ≤ T ≤ 818 °C, 0.01 ≤ ≤ 0.0235 s-1, and 960 ≤ T ≤ 970 °C, 0.01 ≤ ≤ 0.0213 s-1. The microstructure evolution and deformation mechanism of the compressed specimens were researched by electron backscatter diffraction (EBSD) technique. There were two nucleation mechanisms for dynamic recrystallization (DRX): sub-grains growth nucleation and high angle grain boundaries (HAGBs) bulging nucleation, the former was continuous dynamic recrystallization (CDRX), and the latter was discontinuous dynamic recrystallization (DDRX). The flow stress in the α+β phase region was softened by CDRX and dynamic recovery (DRV), while the principal deformation mechanisms in the β phase region are DRV and DDRX. The dislocation strain energy and recrystallization ability at different temperatures were quantitatively analyzed by the kernel average misorientation (KAM) and the geometrically necessary dislocation (GND), and the results showed that more complete recrystallization occurred at lower temperature in the α + β phase region. The HCP slip was principally completed by prismatic and pyramidal slip systems during the hot compression, while BCC was a mixed mode of , and multiple slips.

Modulation of microstructure and improvement in the mechanical properties of TiBw/Ti65 composites by rolling at different temperatures

The effect of rolling temperature on microstructure evolution and mechanical properties of as-sintered TiBw/Ti65 composites was systematically investigated. The results showed that at 900 °C (in the low α + β phase region), the matrix microstructure primarily exhibited a deformation structure. At 1000 °C (in the high α + β phase region), a bimodal structure was observed, and at 1100 °C (in the β phase region), a basket-weave structure emerged. Additionally, silicides precipitated at 900 °C were fine but grew and coarsened at 1000 °C, eventually dissolving almost completely into the matrix at 1100 °C. This behavior is attributed to the varying solubility of silicides in the α and β phases. With increasing rolling temperature, the dynamic recrystallization (DRX) mechanism within the TiBw/Ti65 composites transitioned from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). Rolling significantly enhanced the mechanical properties of the composites. The HR-900 composite exhibited the optimal strength-plasticity combination at room temperature, achieving an ultimate tensile strength (UTS) of 1415 ± 21 MPa and elongation (EL) of 6.2 ± 2.7%, mainly due to grain refinement and work hardening. Conversely, the HR-1100 composite demonstrated superior high-temperature mechanical performance, showing improvements of 37.18%, 27.05%, and 9.59% at 963 MPa (650 °C), 789 MPa (700 °C), and 560 MPa (750 °C), respectively, compared to those of the as-sintered materials. The strengthening mechanisms were fine-grain strengthening, dislocation strengthening, and load transfer strengthening of the as-rolled composites, and the primary strengthening mechanism shifts from dislocation to fine-grain strengthening as the rolling temperature increases.

Liquid-Liquid equilibrium measurements analysis of synthetic multicomponent solvent (n-Pentane, n-Hexane, n-Heptane, Cyclo-Hexane, Toluene)/Bitumen System: Implications for solvent-aided in-situ bitumen extraction

Understanding the Liquid-Liquid Equilibrium (LLE) of multicomponent solvent/bitumen systems is pivotal in optimizing in-situ bitumen extraction. While Vapor-Liquid Equilibria (VLE) of solvent-bitumen systems has been extensively studied, LLE data and predictive models for these mixtures, especially those involving synthetic multicomponent solvents, are scarce. This study provides comprehensive LLE measurements of bitumen and a multicomponent synthetic solvent (n-pentane + n-hexane + n-heptane + cyclo-hexane + toluene) conducted under controlled equilibrium conditions at temperatures of 295 to 352 K, solvent concentrations up to 70 wt% at 1.291 MPa. Application of common correlation used in the construction of solvent-aided process fluid models exhibited average absolute relative deviations (AARDs) of 0.37 % for density and 8.87 % for viscosity. We identified the boundaries marking the shift from homogenous single-phase liquid to two-phase (LLE) states, which occurs within the synthetic multicomponent solvent concentration range of 50 to 60 wt%. We also successfully constructed calibration curves to measure solvent concentrations in both phase regions. The molecular weight distribution and saturates, aromatics, resins, and asphaltene (SARA) fractionation of both liquid phases were determined, highlighting that the heavy liquid phase is primarily asphaltene (∼46 wt%). The insights gained from the measurements and analysis find applications in designing and optimizing solvent-assisted thermal recovery processes for bitumen extraction.

Simulation of nuclear fuel clad high-temperature ballooning under loss-of-coolant accident conditions considering anisotropic creep

Zirconium (Zr) alloys are standard clad material in commercial light water reactors. However, it is vulnerable to ballooning and burst under high-temperature conditions such as LOCA (Loss-Of-Coolant Accident), due to large internal/external pressure difference. Considering that clad ballooning is detrimental in terms of nuclear reactor safety especially for high-burnup fuel rod, high-fidelity numerical simulation of Zircaloy clad ballooning is desirable. This paper presented a finite-element based implementation for the simulation of Zircaloy clad ballooning. The developed simulation capability predicts progressive clad ballooning up to failure given empirical burst limits. The material models coupled together are phase transformation and high-temperature creep. Especially, anisotropic creep was considered for α phase Zircaloy. The implemented algorithm for stress update is implicit in time integration, which allows relatively large time step size to efficiently simulate the process that can last for hundreds of seconds. An analytic benchmark, the PUZRY ballooning and burst test, and the Hardy stress-rupture test were utilized to verify and validate the simulation capability. The anisotropic creep calculation conforms to the analytical solution. The comparison with PUZRY and Hardy test data shows that considering anisotropic creep in the α phase region is essential. 3D ballooning was also simulated by considering circumferential temperature difference for both conventional and novel annular clad designs. Interestingly, it is the first time to note that the risk of buckling failure is predicted for the double-cooled annular nuclear fuel clad during the accident condition, only after considering the anisotropic creep algorithm.

Trial- vs. cycle-level detrending in the analysis of cyclical biomechanical data

Biomechanical time series may contain low-frequency trends due to factors like electromechanical drift, attentional drift and fatigue. Existing detrending procedures are predominantly conducted at the trial level, removing trends that exist over finite, adjacent time windows, but this fails to consider what we term ‘cycle-level trends’: trends that occur in cyclical movements like gait and that vary across the movement cycle, for example: positive and negative drifts in early and late gait phases, respectively. The purposes of this study were to describe cycle-level detrending and to investigate the frequencies with which cycle-level trends (i) exist, and (ii) statistically affect results. Anterioposterior ground reaction forces (GRF) from the 41-subject, 8-speed, open treadmill walking dataset of Fukuchi (2018) were analyzed. Of a total of 552 analyzed trials, significant cycle-level trends were found approximately three times more frequently (21.1%) than significant trial-level trends (7.4%). In statistical comparisons of adjacent walking speeds (i.e., speed 1 vs. 2, 2 vs. 3, etc.) just 3.3% of trials exhibited cycle-level trends that changed the null hypothesis rejection decision. However 17.6% of trials exhibited cycle-level trends that qualitatively changed the stance phase regions identified as significant. Although these results are preliminary and derived from just one dataset, results suggest that cycle-level trends can contribute to analysis bias, and therefore that cycle-level trends should be considered and/or removed where possible. Software implementing the proposed cycle-level detrending is available at https://github.com/0todd0000/detrend1d.

Dissipative Particle Dynamics Study on the Phase Region of Spatial Gradient Materials Produced by Photoinduced Isomerization

AbstractSpatial gradient materials occupy an important research position in the field of functional materials with their unique porous structure. Gradient changes in pore size and density distribution have received extensive attention in the fields of biomimetic and smart materials. The gradient transition law is mathematically related to the driving force of isomerization reaction and component phase separation. In this study, a dissipative particle dynamics simulation is used to introduce photoisomerization reactions into the system. Lambert's law is used to construct a reaction model for the variation of light intensity with irradiation depth, and a gradient structure with a spatial transition law is obtained. The effects of the extinction coefficient ε, the initial reaction probability Pr0, and the interactions α(A,B) between the isomerized molecules as well as the viscosity on the formation of the gradient structure are investigated in detail. Furthermore, the mathematical proportionality between the size of the phase region and interfacial energy of the two phases is elucidated. This study provides preliminary computational insights into the factors affecting the photoinduced phase separation process of polymeric gradient materials. It may help to develop effective strategies to improve the phase separation and properties of polymer gradient materials in subsequent studies.

Intertwined crystal structure, magnetic, and charge transport properties in mixed valent A-site ordered manganite NdBaMn2O6

In the present work, we report a correlation between crystal structure, magnetic, and electrical properties in an exotic magnetic compound, NdBaMn2O6 having ∼92% ordering between Nd and Ba, investigated using temperature-dependent synchrotron x-ray diffraction (XRD), dc magnetization and transport measurements. Temperature-dependent XRD data reveals that the compound undergoes various complex crystallographic phase transitions from high-temperature (T > 320 K) P4/mmm phase to intermediate (320 K – 280 K) Cmmm phase to a mixed (Cmmm and P21am) phase (280 K – 220 K) and to low-temperature P21am phase (T < 220 K). It is found that these crystallographic phase compositions play a crucial role in controlling its magnetic and transport properties. Temperature-dependent dc magnetization data show a sharp drop at the onset of mixed phase (Cmmm + P21am) at 280 K followed by a broad hump at ∼ 220 K where mixed phase to P21am transition occurs, thus indicating a correlation between the structural and magnetic properties. The dc magnetization in the mixed phase region is calculated by considering a superposition of the magnetic moments of Cmmm and P21am phases weighted by the fraction of each phase, which exactly follows the experimental magnetization data. Temperature variation of resistivity data shows a jump at ∼260 K, a temperature corresponding to 50–50% phase composition of Cmmm and P21am phases. The compound shows insulating behavior over a whole temperature range as confirmed from the resistivity data. Further, application of magnetic field causes a shift of magnetic and transport transition temperatures which may be due to the magnetic field induced structural transition in the system.

Phase diagram of ternary Co–Fe–Ge system (I): Experimental

Co–Fe–Ge is an important material system for magnetic and catalyst applications. However, phase equilibria information of the Co–Fe–Ge ternary system is limited. Ternary Co–Fe–Ge alloys equilibrated at 950 °C were prepared. The microstructures, chemical compositions and crystal structure of each phase were determined. The phase equilibria isothermal section at 950 °C of the Co–Fe–Ge ternary system was then proposed. A continuous solid solution phase was formed between the Co5Ge3 and Fe5Ge3 phases and was labeled the β(Co,Fe)5Ge3 phase. There are five three-phase regions in the system at 950 °C. A wide α2 single-phase, and liquid phase regions with large composition ranges being confirmed at the Ge-poor and Ge-rich sides, respectively.

Microstructure and Properties of TiCp/Fe Hierarchical Composites Prepared by a New Pressure Infiltration Method.

TiCp/steel composites are conventionally produced via powder metallurgy. In this paper, a liquid pressure infiltration method was developed to prepare a kind of spherical hierarchical architectured composite, in which spherical TiCp-rich hard phase regions were uniformly dispersed in TiCp-free soft phase region. The microstructure and mechanical properties of the architectured composites were carefully studied and compared with the common composite, as well as the effect of TiCp fraction on the properties. The results show that architecturual design can effectively improve both the toughness and strength of the composites. With TiCp content increasing from 30% to 50%, both the bending strength and the impact toughness of the architectured composites first increase, then decrease, and reach the highest at 40% TiCp. The highest impact toughness reaches 21.2 J/cm2, being 6.2 times that of the common composite and the highest strength being 67% higher. The pressure infiltration method possesses adaptability to varying shapes and sizes of the products, allowing for large-scale preparation. Therefore, for the first time, the combination of pressure infiltration preparation and architectural design was applied to TiCp/steel composites.

Crosstalk reduction for Arrayed waveguide gratings on Silicon-on-Insulator platform

Ultracompact silicon-based arrayed waveguide gratings (AWGs) with low loss and low crosstalk are essential for on-chip optical interconnect and miniaturized spectroscopic analysis systems. In our previous research, we demonstrated the crosstalk reduction by utilizing constant projection period for phased array waveguide on the tangent line to the grating pole to reduce the imaging error induced by phased array waveguide end point positions [1] and using deep etching waveguides at the interface of free propagation region to further decrease the footprint of phase region of an AWG to reduce fabrication imperfections induced phase error [2]. Here we first study the effect of curved waveguides in the phased array of 16 × 400 GHz AWGs on the adjacent crosstalk of output channels. According to the AWGs made in our fabrication platform and the testing results of five dies from one wafer at different locations, the AWGs with equal length of single-mode curved waveguides have an average adjacent crosstalk level of ∼ 4 dB smaller than those with equal length of narrow single-mode waveguides composed of straight and curved waveguides in their phased array. Based on the design of equal curved waveguide length in phased array, in combination with our reported approaches on crosstalk reduction, 16 × 200 GHz, 8 × 800 GHz and 8 × 1250 GHz AWGs are fabricated. For characterization, five dies including all designs from different locations of the fabricated wafer are tested. Experimental results show that among these five dies, the best adjacent crosstalk levels are less than − 21.97 dB, −25.72 dB, −24.83 dB and the worst adjacent crosstalk levels are less than − 20.51 dB, −25.03 dB, −24.34 dB for 16 × 200 GHz, 8 × 800 GHz and 8 × 1250 GHz AWGs with FPR angle of 120°, respectively, within the passband width of 25 % channel spacing. The on-chip insertion losses for all output channels of these fabricated AWGs are less than 3 dB.

The unique failure behavior of Ni–Mo–Cr-Gd superalloy during hot compression at ultrahigh temperatures

The unique failure behavior of the Ni–Mo–Cr-Gd superalloy deformed at 0.01 s−1 and 0.5 strain with ultra-high temperatures has been investigated. The samples compressed at 0.01 s−1 and 0.5 strain are severely cracked at 1230 °C, and almost completely crushed at 1250 °C. The microstructure observations show that the divorced γ/Ni5Gd eutectic phase transforms into the lamellar γ/Ni5Gd eutectic phase, and the Ni5Gd phase disappears in the center of samples, especially at 1250 °C. Here, the eutectic transformation is attributed to the fact that the Ni5Gd phase melts and solidifies due to the temperature rise of local interface friction between the Ni5Gd phase and the γ matrix. Furthermore, the severe failure of samples and the unexpected disappearance of the Ni5Gd phases were ascribed to the interconnected localized melting regions of the Ni5Gd phase.

On Phase Transitions during Collisions near the Horizon of Black Holes

During particle collisions in the vicinity of the horizon of black holes, it is possible to achieve energies and temperatures corresponding to phase transitions in particle physics. It is shown that the sizes of the regions of the new phase are of the order of the Compton length for the corresponding mass scale. The lifetime is also on the order of the Compton time. It is shown that the inverse influence of the energy density in the electro-weak phase transition in collisions on the space–time metric can be neglected.

Effect of TiO2 addition on microstructure and mechanical properties of Al2O3 ceramic joints brazed with Ag‐CuO fillers

AbstractIn our work, 0.5 mol.% TiO2 was added to Ag‐xCuO (x = 2, 4, 8 mol.%) fillers whose compositions at 1050°C were in the L2 single liquid phase region, the boundary of the miscible phase region, and the L1+L2 miscible phase region, respectively. The role of TiO2 was derived by comparing the quenching microstructure of the fillers on the Al2O3 ceramics and the effect on the interfacial microstructure and shear strength of the joints before and after the addition of TiO2. The results showed that the TiO2 would dissolve into the CuO‐rich L1 liquid phase of the filler, leading it to spread outside the molten droplet. When brazing with Ag‐4CuO‐0.5TiO2 filler, the CuO at the joint interface almost completely disappeared, and the shear strength of the joint was significantly reduced. In contrast, the joint strength showed a small increase when using Ag‐8CuO‐0.5TiO2 filler, as the excess CuO at the interface of the brazed joint was reduced. When the filler composition was in the L2 single liquid phase region, CuO was diffusely distributed throughout the molten droplet. TiO2 was hardly contacted with CuO and its addition had no significant effect on the interfacial microstructure and the shear strength of the joints.