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In this study, electric current effects on the densification, microstructure, and properties of W-Mo-Cu alloy fabricated by large current electric field sintering (LCS) were investigated. The apparent sintering activation energy for densification (ASAED) was calculated to decrease from 72.01  kJ/mol to 24.02 kJ/mol with the increased electric current from 30,000 A to 50,000 A, thereby enhancing the sinterability of the W-Mo-Cu mixed powder and improving the densification of W-Mo-Cu alloy. The experimental results also proved that the elevated electric current optimized the microstructure and properties of the W-Mo-Cu alloy. Moreover, XRD and TEM results suggested that electric current had a significant effect on the phase transformation of the alloy, while the varying electric current did not affect the phase type. Besides W, Mo, and Cu phases, the W-Mo-Cu alloy prepared by LCS contains three new phases, i.e., Cu 0.4 W 0.6 intermetallic compound, Mo-Cu solid solution, and W-Mo solid solution, none of which are present in an equilibrium state.

The influence of manufacturing parameters (particle size fractions of powder, compaction pressure, sintering temperature) of titanium hydride TiH 2 on the microstructural evolution and corrosion resistance of porous titanium in inorganic acids (20 wt.% HCl and 40 wt.% H 2 SO 4 solutions) was investigated. It was shown that the porosity was fixed in the powder metallurgy titanium regardless of the manufacturing parameters. By decreasing particle size fractions of powder (from 100–200 μm to 0–100 μm) and increasing compaction pressure (from 150 MPa to 650 MPa) and sintering temperature (from 1050°C to 1350°C), the porosity of titanium was decreased from 5.1% to 1.1%. It was determined that a decrease of the porosity improves the anticorrosion properties of sintered titanium investigated by potentiodynamic polarization and static immersion tests. The highest corrosion resistance in the inorganic acids was obtained for porous titanium (1% porosity), which was pressed at 650 MPa and sintered in a vacuum at a temperature of 1350°C.

Optimizing temperature-kinetic heating conditions is an important component of powder technology. This problem is especially acute in heterogeneous systems, where in addition to traditional issues of contact formation, it is necessary to consider the patterns of heterodiffusion, which determine the phase composition and affect the processes of loosening according to the Kirkendall and Frenkel effects. The results of DTA, dilatometric and x-ray studies were subsequently used to optimize the technological modes of hot forging. The effects thermo-kinetic parameters of heating and hot forging temperature on compaction and physico-mechanical properties of iron aluminide were examined. A comparison of the results of studies of forged samples that were heated at different speeds and forged at the same temperature shows the insignificant advantages of slow heating at low forging temperatures, where the process of phase formation and the formation of a high-quality contact has not yet been completed. At higher forging temperatures and additional annealing, these differences practically disappear. Considering the technological difficulties of slow heating, it is advisable to use rapid heating to temperatures of 1100–1220°C, hot forging at these temperatures and subsequent annealing at temperatures of 1300°C for 30 min as the basic mode of thermo-mechanical treatment.

Tungsten trioxide (WO 3 ) nanoparticles were prepared by the citric acid method, using ammonium paratungstate as the tungsten source, and doped with rare earth europium (Eu) under various pH values and Eu content. The microstructure, morphology, and luminescence properties of the prepared samples were characterized by XRD, SEM, and a fluorescence spectrometer. The results show that Eu 3+ doped WO 3 nanoparticles were successfully obtained by the citric acid method, the prepared nanoparticles were spherical and rhomboidal, and the average particle size of the prepared samples reached 56 nm. The excitation spectrum consisted of a series of linear excitation peaks in the range of 250–550 nm. The strongest excitation peak was located at 543 nm, which belongs to the 7 F 0  →  5 D 1 transition of Eu 3+ .

Being a widely used building material in marine structure, concrete is susceptible to freeze–thaw (F–T) damage in high-latitude marine conditions, which can easily affect the safety and the lifetime of marine infrastructures. This paper investigates the mechanical properties and frost durability of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PFRGC) with bentonite and fly ash before and after frost damage. The mechanical properties of PFRGC were revealed through cubic compressive, flexural and axial compressive strength. The frost durability of PFRGC was also studied through the relative dynamic modulus of elasticity (RDEM). Furthermore, the acoustic emission (AE) technique was adopted to provide real-time monitoring of the damage progress. Meanwhile, the microstructure was characterized by SEM to illustrate the mechanism of macroscopic property degradation. The results show that the compressive strength continued to decrease with increasing fly ash (FA) incorporation when the bentonite admixture was 0%, while the compressive strength of the concrete reached a maximum when FA/C was 1.8 at higher bentonite admixtures (3% and 6%). At the same time, the mechanical and physical performance of PFRGC decreased with freeze–thaw cycles. The AE characteristics were tightly correlated with the progress of damage and stress–strain curves.

The dual-phase titanium alloy Ti6Al4V, presents overall top performance for most-used weight reduction titanium alloy usage in aerospace production, but its general applications have not been fully realized because its resistance to local plastic deformation, friction and wear are unsatisfactory. In a bid to enhance the known shortcomings, Ti6Al4V matrix composites (TMCs) with advanced refractory nitride reinforcements were synthesized by spark plasma sintering. The effects of single (3 wt.%) and double (1.5 wt.% each) reinforcements of nanograde hexagonal boron nitride ( h -BN), titanium nitride (TiN) and aluminium nitride (AlN) on the microstructure, phase constituents, nanomechanical and tribological performance of the sintered TMCs were investigated. Microstructure and phase analyses showed that sintered TMCs consist of crack-free microstructures with practically no notable visible defects or impairing intermetallic phases, suggesting that no adverse particle–matrix interfacial reactions occurred during sintering. Nanoindentation and tribology tests generally revealed remarkable improvements in hardness, elastic modulus and wear resistance through each reinforcement type on the sintered TMCs in decreasing order of influence from 3 wt.% h -BN, to 1.5 wt.% of h -BN and AlN, followed by 1.5 wt.% of h -BN and TiN, then 1.5 wt.% of TiN and AlN, to 3 wt.% AlN and finally, 3 wt.% TiN.

The method of carbothermal pre-reduction of WO 3+ solid phase carburization was used to prepare WC nano-powder. The effects of particle size of carbon black (type C1: 100–300 nm; type C2: ~ 55 nm) on the reduction kinetics, as well as particle size and morphology evolution of the products were investigated. During the carbothermal pre-reduction of WO 3 , the contact area between C2 and WO 3 was larger than that of C1 after ball-milling treatment, which effectively accelerated the reduction reaction. In addition, the partial pressure of the gaseous by-product CO affected the phase transition and morphology evolution of the products. Therefore, a predominant region diagram of W-C-O system under different temperatures and partial pressures of CO was constructed. The results showed that, as the partial pressure of CO increased, the reduction and carbonization reactions proceeded more easily. Moreover, in the temperature range of 1000 ~ 1100°C, the reduction order of WO 3 was WO 3  → W 18 O 49  → WO 2  → W → WC. Finally, the carbothermal reduction products were used as the raw material to prepare WC powder by carbonization reaction. The results showed that the carbonized products obtained by small-sized carbon black had a smaller particle size. This work provides theoretical guidance for preparing WC powder with controllable size.

Fe-15Cr-2Mn-1.5Al metal matrix composites (MMCs) reinforced with TiB 2 and CrFeB were synthesized from a Fe, Cr, Mn, Al, Ti, and B powder mixture at 1100°C and 50 MPa for 15 min using an in situ spark plasma sintering (SPS) method. A mechanical alloying process was used to improve the activity and uniformity of the composite powder. The reinforced phase and matrix were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The mechanical properties of the steel-based MMCs were also measured by compression and microhardness. The results showed that the in situ synthesized reinforcements of steel-based MMCs were Cr-rich M 2 B-type boride (CrFeB) and TiB 2 , and the matrixes were α-Fe. CrFeB addition improved the plastic deformation capacity and weakened the compressive strength as well as the hardness. The plastic deformation capacity of the (15 vol.% M 2 B + 10 vol.% TiB 2 )/Fe-15Cr-2Mn-1.5Al composite equaled ~ 14.3%, which was almost double that of the TiB 2 /Fe-15Cr-2Mn-1.5Al composite (~ 7.5%). The compressive strength and hardness of the TiB 2 /Fe-15Cr-2Mn-1.5Al composite equaled ~ 2971 MPa and 781 ± 15 HV, respectively, while the compressive strength and hardness of the (15 vol.% M 2 B + 10 vol.% TiB 2 )/Fe-15Cr-2Mn-1.5Al composite equaled ~ 2576 MPa and 659 ± 15 HV, respectively.

The time-consuming experimental process currently required to optimize process parameters for the selective laser melting (SLM) of new materials is still a major hurdle in adopting this technology for various materials. A clear solution is using numerical modelling to predict the required process parameters. Although literature and the authors’ work indicate that part-scale melt pool modelling is currently computationally expensive, some studies indicate that the accurate modelling of single tracks can be an effective way of determining optimal process parameters. This article reports on efforts to apply this approach to the Ti6Al4V alloy. Experimental and simulation results were obtained for a broad range of laser powers and scanning speeds to investigate the accuracy of the model. Thereafter, the effects of changing various simulation parameters on the accuracy of the model concerning simulated melt pool dimensions were investigated to find parameters that could be responsible for inaccuracies. These parameters were found to include the temperature-dependent absorptivity of the material, the evaporation pressure coefficient, and the surface tension temperature-dependent coefficient. It is concluded that, provided accurate values could be obtained for the simulation parameters, single-track SLM simulations could be a powerful tool in determining process parameters for materials.

Taking aeolian sand powder concrete as the research object, this study uses nuclear magnetic resonance, nanoindentation and scanning electron microscope to explore its micropore, mechanical and morphological characteristics and establishes the correlation between the micromechanical parameters, pore parameters and pore diameter and the relative dynamic elastic modulus of aeolian sand powder concrete. According to the gray system theory, the gray prediction model of service life of aeolian sand powder concrete based on carbonization is established. The results show that the hardness in micromechanical properties and the porosity in pore parameters have great effects on the deterioration damage process of aeolian sand powder concrete and ordinary concrete, but the effects of pores with different pore diameters are different, Harmless holes < 20 nm have a great impact on ordinary concrete, and less harmful holes between 20 nm and 50 nm have a great impact on aeolian sand powder concrete. The corrosion resistance of aeolian sand powder concrete surface is intact, while the ordinary concrete pores are damaged to varying degrees. The goodness of fit between the gray prediction model of carbonation in the service life of aeolian sand powder concrete and the measured results reaches 0.9883, which meets the requirements.