Nanohardness of grains and grain boundaries in reactive spark plasma sintered dual-phase (Ti0.82Zr0.04Nb0.08Hf0.03Ta0.03)B2 +(Ti0.49Zr0.12Nb0.13Hf0.11Ta0.15)C high-entropy composite was investigated. The composite with a high relative density of 99.8%, consists predominantly of carbide ( 56.4 vol%) and boride ( 39.7 vol%) phases with average grain sizes of 2.2 mu m and 3.4 mu m of the carbide and boride phases, respectively. Most grain/phase boundaries show a continuous sharp 1.5 nm wide segregation of Fe, Co, and Ni impurities. Nanohardness was measured by nanoindentation on polished/non-deformed and worn/deformed surfaces. At non-deformed surface, the average hardness/Young's modulus of boride and carbide grains are 41.3 +/- 2.9 GPa/596 +/- 25 GPa and 38.3 +/- 2.3 GPa/553 +/- 24 GPa, respectively. At the vicinity of grain boundaries, the hardness/Young modulus is 37.3 +/- 2.5 GPa/600 +/- 32 GPa. At deformed surfaces, the average hardness of boride grains is higher and the average hardness of carbide grains is slightly higher compared to the values at non-deformed surfaces, with values of 42.4 +/- 3.9 GPa, and 38.4 +/- 2.4 GPa, respectively.

Superlattice architecture presents a promising strategy for the simultaneous enhancement of hardness and toughness in hard ceramic films. Here, we demonstrate the success of this approach in transition metal diboride films-materials whose inherent brittleness typically limits their applications. We combined Density Functional Theory (DFT)-based calculations and direct current magnetron sputtering to investigate the mechanical properties as a function of the bilayer period (A). Theoretical calculations for ZrB2/TaB2 cells (A = 1.4-8.2 nm) reveal a stabilizing effect with decreasing A and a significant increase in stiffness, peaking at A = 2.7 nm. Experimentally, ZrB2.6/TaB1.4 superlattice films deposited with A = 1.8-31.5 nm exhibit a structural transition characterized by the crystallization of disordered TaB2_y layers. This transition is accompanied by a remarkable increase in hardness from H = 34.1 +/- 1.9 to 47.2 +/- 2.3 GPa as A decreases to 3.4 nm. The hardening exceeds the estimations of Koehler's strengthening, suggesting multiple contributing effects: chemical bonding, boron diffusion at interfaces, Hall-Petch behavior, and compressive residual stress. At the same time, the fracture toughness increases to KIC= 4.6 +/- 0.3 MPa & sdot;m1/2 at A = 1.8 nm, attributed to coherent stresses at the ZrB2+x/ TaB2_y interfaces. This research demonstrates the effectiveness of superlattice architectures in diboride films and highlights the crucial role of nanostructure and stoichiometry.

This paper presents the design, fabrication, calibration, and comprehensive characterization of a homemade tri-axial fluxgate magnetometer. The magnetometer, utilizing a ring core configuration, was developed to measure ultra-low magnetic fields with high sensitivity and stability. Critical stages from material selection to sensor geometry optimization are discussed in detail. A series of critical characterization processes were conducted, including zero-field voltage determination, scale factor calculation, resolution measurement, noise analysis, bias assessment, cross-field effect evaluation, temperature dependency, and bandwidth determination. The sensor demonstrated a minimum detectable magnetic field resolution of 2.2 nT with a noise level of 1.1 nT/√Hz at 1 Hz. Temperature dependency tests revealed minimal impact on sensor output with a maximum shift of 120 nT in the range of 60 °C, which was effectively compensated through calibration to less than 5 nT. Additionally, the paper introduces a model function in matrix form to relate the magnetometer’s output voltage to the measured magnetic field, incorporating temperature dependency and cross-field effects. This work highlights the importance of meticulous calibration and optimization in developing fluxgate magnetometers suitable for various applications, from space exploration to biomedical diagnostics.

Titanium diboride (TiB2) is a promising candidate for high-temperature applications due to its chemical inertness, phase stability, and excellent mechanical properties. However, its typical nanocomposite microstructure with a B-tissue phase promotes low-temperature oxidation. In this study, we employ a dual approach to suppress B-tissue formation and enhance oxidation resistance: yttrium alloying, due to its strong oxygen affinity, and the use of high-power impulse magnetron sputtering (HiPIMS) to reduce boron content in the growing film. Two Ti1-xYxB2 +/-triangle coatings with similar to 9 at.% Y were deposited: overstoichiometric X-ray amorphous Ti0.68Y0.32B2.8 via conventional direct current magnetron sputtering (DCMS) and understoichiometric crystalline Ti0.76Y0.24B1.4 via HiPIMS. Thermally induced structural evolution and mechanical performance were analyzed using X-ray diffraction, scanning transmission electron microscopy, and nanoindentation. The X-ray amorphous coating crystallized above 900 degrees C into TiB2 and YB6 phases, while the HiPIMS coating retained its nanocolumnar, stacking fault-rich alpha-Ti1-xYxB2-triangle structure up to 1100 degrees C. The Ti0.68Y0.32B2.8 coating exhibited moderate hardness (similar to 28 GPa), whereas the Ti0.76Y0.24B1.4 coating reached superhardness (> 40 GPa) with higher Young's modulus (similar to 420 GPa). Both coatings showed improved oxidation resistance compared to TiB2, with delayed crystalline oxide formation above 700 degrees C, while slower oxidation kinetics was observed for the understoichiometric coating. These results demonstrate the effectiveness of alloying and highly ionized deposition techniques for tuning the structure and high-temperature performance of TiB2-based coatings.

In this work, we have investigated the microstructural evolutions and the phase transformations of a new near-beta alloy with a nominal composition of Ti-5.5Al-5V-5Mo-2.4Cr-0.75Fe-0.15O (weight percent), the TIMETAL 18 [here after called Ti-18]. The complete microstructural state of the Ti-18 during heat treatments, from as quenched metastable state, has been first investigated. The phase transformations have been studied by combination of X-ray diffraction analysis, metallurgical observations and electrical resistivity measurements. From a series of isothermal treatments, the first complete TTT diagram has been then established displaying three C-curves corresponding to different precipitation domains for alpha phase.

Magnetoresistance and magnetoimpedance studies were performed on (FexCoy)73Nb7Si5B15 ribbons in their as quenched amorphous state and after selected heat treatment in amorphous state as well as after partial nano-crystallization. The dependence of magnetoresistance (MR) and magnetoimpedance (MI) on the applied field has been determined with parametric control of stress.