Explore the vast range of titles available.

ABSTRACT Titanium alloys are widely used in aerospace, biomedical and energy applications, but the low hardness and limited plastic deformation resistance of commercially pure titanium (CP‐Ti) remain key limitations. In this study, Ti‐yAl‐1Mo (y = 3, 5 and 7 wt.%) alloys were fabricated via plasma‐activated sintering and evaluated using instrumented nanoindentation. All alloys achieved near‐full densification and exhibited predominantly α‐Ti with minor β‐Ti and localised Mo‐rich regions, consistent with composition‐driven phase evolution. Nanoindentation revealed a strong composition‐dependent improvement in mechanical response: at 100 mN, hardness and elastic modulus increased from 2.5396 GPa and 113.6 GPa (CP‐Ti) to 5.4139 GPa and 149.8 GPa for Ti‐7Al‐1Mo. A similar trend persisted at 200 mN, with a slight hardness reduction attributed to the indentation size effect. Yield strain and yield pressure values further confirmed enhanced plastic deformation resistance. One‐way ANOVA verified that these improvements are statistically significant. The combined α‐stabilising and β‐stabilising effects of Al and Mo highlight the effectiveness of dual alloying in tailoring the nanomechanical properties of near‐α titanium alloys.

In present work, Fields Activated Sintering Technology (FAST), has been applied to successfully sinter the high-entropy alloy (HEA) samples. Based on the analysis of the microstructure, relative density and microhardness of the sintered HEA samples, the influence of sintering temperature and pulsed magnetic field treatment (PMT) has been investigated. In terms of performance, HEA samples fabricated using PMT-powder sintering exhibit superior properties compared to UT-powders. Regarding elemental distribution, pre-treating the powders with a pulsed magnetic field can enhance the uniformity of the alloyed powder components. Furthermore, elevated sintering temperatures have been observed to substantially accelerate the densification process, thereby improving the relative density of the sintered samples.

Low-temperature co-fired ceramics (LTCCs) are dielectric materials that can be co-fired with Ag or Cu; however, conventional LTCC materials are mostly poorly thermally conductive, which is problematic and requires improvement. We focused on ZnAl2O4 (gahnite) as a base material. With its high thermal conductivity (~59 W·m−1·K−1 reported for 0.83ZnAl2O4–0.17TiO2), ZnAl2O4 is potentially more thermally conductive than Al2O3 (alumina); however, it sinters densely at a moderate temperature (~1500 °C). The addition of only 4 wt.% of Cu3Nb2O8 significantly lowered the sintering temperature of ZnAl2O4 to 910 °C, which is lower than the melting point of silver (961 °C). The sample fired at 960 °C for 384 h exhibited a relative permittivity (εr) of 9.2, a quality factor by resonant frequency (Q × f) value of 105,000 GHz, and a temperature coefficient of the resonant frequency (τf) of −56 ppm·K−1. The sample exhibited a thermal conductivity of 10.1 W·m−1·K−1, which exceeds that of conventional LTCCs (~2–7 W·m−1·K−1); hence, it is a superior LTCC candidate. In addition, a mixed powder of the Cu3Nb2O8 additive and ZnAl2O4 has a melting temperature that is not significantly different from that (~970 °C) of the pristine Cu3Nb2O8 additive. The sample appears to densify in the solid state through a solid-state-activated sintering mechanism.

In this paper, titanium matrix composites with in situ TiB whiskers were synthesized by the plasma activated sintering technique; crystalline boron and amorphous boron were used as reactants for in situ reactions, respectively. The influence of the sintering process and the crystallography type of boron on the microstructure and mechanical properties of composites were studied and compared. The densities were evaluated using Archimedes’ principle. The microstructure and mechanical properties were characterized by SEM, XRD, EBSD, TEM, a universal testing machine, and a Vickers hardness tester. The prepared composite material showed a high density and excellent comprehensive performance under the PAS condition of 20 MPa at 1000 °C for 3 min. Amorphous boron had a higher reaction efficiency than crystalline boron, and it completely reacted with the titanium matrix to generate TiB whiskers, while there was still a certain amount of residual crystalline boron combining well with the titanium matrix at 1100 °C. The composite samples with a relative density of 98.33%, Vickers hardness of 389.75 HV, compression yield strength of up to 1190 MPa, and an ultimate compressive strength of up to 1710 MPa were obtained. Compared with the matrix material, the compressive strength of TC4 titanium alloy containing crystalline boron and amorphous boron was increased by 7.64% and 15.50%, respectively.

Electrical field activated sintering technology combined with micro-forming (Micro-FAST), as a new rapid powder sintering/forming method, is used to fabricate FeCo alloy parts. The successfully prepared FeCo parts have a high saturation of 214.11 emu/g and a low coercivity of 16 Oe, and these values are 20% and 10% higher than that of commercially available FeCoV alloy parts on the saturation and coercivity respectively. During the sintering process, the high current application shortened the densification time and enhanced the uniformity of the microstructure significantly. The grain sizes of FeCo alloys were in a range of 5–6 µm, and good isotropy was also shown. The low angle grain boundary (LAGB) accounted for more than 30% and the low angle misorientation accounted for more than 30% of the sample parts. Furthermore, the formation of the nano B2 phase was promoted during the Micro-FAST, and the size of the B2 phase was about 5 nm. The coherent interface between α and B2 was conducive for reducing the coercivity. As a consequence, the outstanding microstructure formed by Micro-FAST makes the FeCo alloys have high saturation and low coercivity.

In this work, W/HfC composite materials were synthesized using plasma activated sintering. The influence of the sintering temperature and HfC weight fraction on the relative density, microstructure and compression strength were investigated. The results demonstrated that the sintering temperature and the HfC content significantly affected the microstructure of W/HfC composites. Moreover, the grain size of the W/HC composites decreased and the mechanical properties were improved remarkably due to the addition of HfC. The majority of HfC particles reacted with oxygen impurities to generate HfO2, which purified the grain boundaries and refined the grain size of the W matrix. The optimum content of HfC is 2 wt%, at which a high compressive strength of 1.98 GPa and a high strain of 34.7% were obtained.

The method for activated sintering of reaction-bonded boron carbide by diffusion doping of boron carbide powder particles with amorphous boron was developed. On the basis of X-ray phase analysis, it is shown that under the conditions of activated sintering in the presence of boron the formation of the B 12 (B, C, Si) 3 phase occurred. According to the results of microstructural studies of the material, it is proved that on the surface of polycrystals there is a diffusion layer saturated with boron and silicon, which surrounds each particle. It is found that the structure of obtained ceramics based on boron carbide by doping with boron and silicon, represents the boron carbide grains penetrated by needle crystals of secondary silicon carbide. It has been experimentally proved that this nature of the structure leads to an increase in the fracture toughness of the material in 2–3 times compared to the existing sintered reaction-bonded boron carbide. This allows us to use the material for creating heat-proof coatings for hypersonic spacecraft.

This study formed a hard TiAlSiWN coating layer using Ti, Al, Si and W raw powders that were mechanically alloyed and refined. The TiAlSi and TiAlSiW coating targets were fabricated using a pulse current activated sintering process in a short time with the optimal sintering conditions. The optimized sintering condition was obtained by controlling process parameters such as temperature, pressure, heating rate and pulse ratio (on/off). The coating targets were successfully deposited on the WC substrate to form the TiAlSiN and TiAlSiWN nitride nano-composite structures by an arc ion plating process and also, their coating layers were compared according to the addition of W element. The microstructures of the nitride nano-composite coating layer were analyzed, focusing on the distribution of the crystalline phases, amorphous phases (Si3N4), and growth orientation of the columnar crystal depending on the addition of W element. The mechanical properties of the coating layers were exhibited a hardness of approximately 3000 kg/mm2 and adhesion of about 117.77 N in the TiAlSiN. In particular, the TiAlSiWN showed excellent properties with a hardness of more than 4300 kg/mm2 and an adhesion of about 181.47 N, respectively.

Additive manufacturing (AM) is a broad definition of various techniques to produce layer-by-layer objects made of different materials. In this paper, a comprehensive review of laser-based technologies for polymers, including powder bed fusion processes [e.g. selective laser sintering (SLS)] and vat photopolymerisation [e.g. stereolithography (SLA)], is presented, where both the techniques employ a laser source to either melt or cure a raw polymeric material. The aim of the review is twofold: (1) to present the principal theoretical models adopted in the literature to simulate the complex physical phenomena involved in the transformation of the raw material into AM objects and (2) to discuss the influence of process parameters on the physical final properties of the printed objects and in turn on their mechanical performance. The models being presented simulate: the thermal problem along with the thermally activated bonding through sintering of the polymeric powder in SLS; the binding induced by the curing mechanisms of light-induced polymerisation of the liquid material in SLA. Key physical variables in AM objects, such as porosity and degree of cure in SLS and SLA respectively, are discussed in relation to the manufacturing process parameters, as well as to the mechanical resistance and deformability of the objects themselves. Graphic abstract

One challenge for the commercial development of solid oxide fuel cells as efficient energy-conversion devices is thermo-mechanical instability. Large internal-strain gradients caused by the mismatch in thermal expansion behaviour between different fuel cell components are the main cause of this instability, which can lead to cell degradation, delamination or fracture 1 – 4 . Here we demonstrate an approach to realizing full thermo-mechanical compatibility between the cathode and other cell components by introducing a thermal-expansion offset. We use reactive sintering to combine a cobalt-based perovskite with high electrochemical activity and large thermal-expansion coefficient with a negative-thermal-expansion material, thus forming a composite electrode with a thermal-expansion behaviour that is well matched to that of the electrolyte. A new interphase is formed because of the limited reaction between the two materials in the composite during the calcination process, which also creates A-site deficiencies in the perovskite. As a result, the composite shows both high activity and excellent stability. The introduction of reactive negative-thermal-expansion components may provide a general strategy for the development of fully compatible and highly active electrodes for solid oxide fuel cells. Highly active but durable perovskite-based solid oxide fuel cell cathodes are realized using a thermal-expansion offset, achieving full thermo-mechanical compatibility between the cathode and other cell components.