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Cu Fe alloys with high iron content (Fe > 10 wt%) are a class of promising copper alloys with high strength and high conductivity. However, the strength and conductivity trade-off dilemma is a longstanding problem in the high iron content Cu Fe alloys owing to macro-segregation of iron particles and incomplete precipitation of solid solution iron atoms in the traditional casting process. We adopted a comprehensive strategy of designing the ultra-fine dual structures with fine copper grains and micro-nano iron particles, and adding phosphorus element to induce solid solution iron atoms precipitation to break through the above bottleneck. In this study, Cu 20Fe alloys with 0.05–1.0 wt% P were prepared through powder metallurgy process. The results showed that the addition of P promoted the precipitation of soluble Fe atoms, reduced oxygen content, and activated sintering. Ultimately, the strength and conductivity of cost-effective Cu 20Fe alloys were significantly improved. The annealed Cu 20Fe 0.1P alloys possess unprecedented comprehensive properties with 608 MPa tensile strength and 65.2% IACS electrical conductivity, which were 7.8% and 19.8% higher than the Cu 20Fe alloys, respectively. The annealed Cu 20Fe 1.0P alloys achieved 59.7% IACS electrical conductivity, increased by 10% compared to Cu 20Fe alloys. The results broke the conventional understanding that increasing P content deteriorated material properties. The influence of P on the microstructure and properties of powder metallurgy Cu 20Fe alloys was investigated in detail. These findings provide new insight into overcoming the dilemma of the inverted relationship between the strength and conductivity of copper alloys. • Simultaneous enhancement of the mechanical and electrical properties of Cu 20Fe alloys by introducing phosphorus. • The Cu 20Fe 0.1P alloys possess unprecedented comprehensive properties and property-costs. • The influence of P on the microstructure and properties of powder metallurgy Cu 20Fe alloys was investigated in detail. [ABSTRACT FROM AUTHOR]

In this study, porous calcium silicate (CaSiO 3) scaffolds were prepared by 3D gel-printing (3DGP) method and Fe 3 O 4 water-based magnetic fluids (WMFs) were prepared by phacoemulsification compound chemical coprecipitation method. Fe 3 O 4 WMFs were coated on CaSiO 3 scaffolds surface to prepare Fe 3 O 4 /CaSiO 3 composite scaffolds. The effect of WMFs with different Fe 3 O 4 concentrations on porous CaSiO 3 scaffolds was studied. The composition and morphological characteristics of porous scaffolds were analyzed by using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis. The magnetic properties were tested by vibrating sample magnetometer (VSM). The stability of Fe 3 O 4 WMFs coatings and the degradability of composite scaffolds were tested by immersing them in simulated body fluid (SBF). The results show that when Fe 3 O 4 concentration was 5.4% (w/v), the composite scaffolds had the highest saturation magnetization of 69.6 emu/g and the best stability in dynamic SBF. It is obviously that Fe 3 O 4 WMFs coatings can be used for bone tissue engineering scaffolds repairing. [ABSTRACT FROM AUTHOR]

Graphite flakes (GFs) in the GF/Cu composites generally fail to exert the advantage of the negative coefficient of thermal expansion (CTE) on account of the weak interfacial bonding between GFs and Cu. In this work, a rivet-joint strategy is adopted to surmount the dilemma. By introducing submicron Mo particles into the Cu matrix through the chemical synthesis process, various GF/Cu composites with the improved alignment of GFs via the method of tape-casting and hot-pressing sintering have been prepared. Due to the combined effects of Mo particle strengthened Cu and the rivet-joint interfacial architecture deriving from the in-situ synthesized Mo x C, optimized thermal/mechanical properties of GF/Cu–Mo composites have been achieved. The 50 v o l % GF/Cu composite with 1 w t % Mo shows the in-plane thermal conductivity of 598 W ⋅ m − 1 ⋅ K − 1 and the through-plane CTE of −2.92 × 10 − 6 K − 1 (25–100 ∘C). Simultaneously, the bending strength is 40 % higher than the 50 v o l % GF/Cu composite. This strategy could promote the development of composites with improved combined structural and functional properties. [ABSTRACT FROM AUTHOR]

Abstract Metal-organic frameworks (MOFs) appear as promising candidates for microwave absorbing materials with a low density as well as tunable electromagnetic parameters. In this study, a facile strategy to fabricate microwave absorbing materials has been demonstrated by introducing metallic Ni nanoparticles into carbon matrix which takes advantage of extremely porous structure. The magnetic Ni composition in the final products can be controlled, which offers an effective way to tune electromagnetic properties. Interfacial polarization is considered to be one of the most important attenuation mechanisms, which can be changed by increasing the interface area and electrical conductivity. When the filler loading of Ni/NiO/Cu@C composite in paraffin matrix is only 10 wt%, a minimum reflection loss of −38.1 dB is achieved at a layer thickness of 3.2 mm. The low density of the filler loading can be guaranteed by enhancing the conduction loss and impedance matching. [ABSTRACT FROM AUTHOR]

[Display omitted] • Close-coupled nozzles for gas atomization with different gas Mach number at the outlet were designed. • The structure of gas field and the profile of gas pressure and velocity were analysed by CFD. • The cooling and solidification process of metal droplets were analysed calculated by finite difference method. • Fe-6.5wt.%Si powder was prepared and close-coupled nozzles with higher Mach number can produce finer powder. Gas velocity is a key parameter regulating the particle size and the cooling rate of the gas atomized powder applied in additive manufacturing, metal injection molding, thermal spraying, and soft magnetic composites. In this paper, on basis of the well-designed close-coupled nozzles with different gas Mach numbers at the outlet, the gas field structure was simulated by Computational Fluid Dynamics (CFD) software, and the process of cooling and solidification of Fe-6.5 wt% Si metal droplets was calculated by finite difference method. The results show that with the increase of Mach number, both the gas velocity downstream and the pressure at the base of melt delivery tube tip rise, whereas the mass flow rate of the melt decreases. The nozzles with high Mach number can produce finer powder with higher cooling rate. The median diameter of the powder prepared by the nozzle with Mach numbers of 1.0, 1.5, 2.0, and 2.5 is 44.9, 39.0, 32.5, and 29.1 μm, respectively, and the corresponding cooling rate of the metal droplet with a diameter of 80 μm is 2.85 × 104, 2.98 × 104, 3.32 × 104, and 3.50 × 104 K/s, respectively. This work provides new ideas and suggestions for the preparation of metal powder with small particle size at high cooling rate. [ABSTRACT FROM AUTHOR]

3D gel-printing (3DGP) is a novel manufacturing technology, which builds a 3D component by depositing and gelating metal slurry layer by layer. In this paper, the hydroxyethyl methacrylate (HEMA) based slurries with WC-20Co solid loading of 47–56 vol% were directly formed by 3DGP and then sintered in a vacuum furnace. The WC-20Co slurries exhibited suitable fluidity and shear thinning behavior, which were beneficial for 3DGP forming process. The effects of 3DGP processing parameters, such as the internal diameter of print nozzle and filling rate, on the surface roughness and dimensional accuracy of as-printed green bodies were studied. The influence of solid loading on rheological property of WC-20Co slurry, green density, sintered density and mechanical properties of sintered samples were also investigated. The results show that the samples can be printed with good shape, appropriate precision and homogeneous microstructure. The sintered samples have good shape retention and uniform microstructure. The density, hardness and transverse rupture strength of the optimal sample were 13.55 g/cm 3 , HRA 87.7 and 2612.8 MPa, respectively. 3DGP has unique advantages in near-net forming for complex shape WC-20Co components. [ABSTRACT FROM AUTHOR]

Powder metallurgy methods such as additive manufacturing are often employed to fabricate bulk refractory alloys with high-melting temperature, nevertheless, it still remains a challenge to produce high-quality refractory high-entropy alloy (RHEAs) powders. In this work, we found that hydrogen absorption can embrittle the NbTaTiZr RHEA and promote intragranular fracture due to segregation of hydrogen atoms at grain boundaries. Synergistic effects of the hydrogenation temperature and time on the pulverization behavior of the NbTaTiZr RHEA were investigated, and the relation between grain sizes in the original ingots and particle sizes in the pulverized powders was explored. The present findings not only provide a highly efficient approach to produce high-quality powders of alloys with high-melting points, but also shed light into understanding hydrogen embrittlement of RHEAs. • The RHEA was easily pulverized after hydrogenation. • The particle size distributions of the pulverized powders matched those of the grain sizes. • An orderly transition from grains to powders was established. [ABSTRACT FROM AUTHOR]

• High-plasticity PM Ti material with high O content is prepared with ZrO 2 addition. • The strength-ductility trade-off dilemma of PM titanium alloy is broken. • Ti-1.0 wt% ZrO 2 sample (0.56 wt% O) has UTS of 824 MPa and EL. of 15%. • Zr and O atoms fully dissolve in the Ti matrix, leading to lattice constant change. • The strengthen effect of ZrO 2 is calculated as 146.7 MPa/wt% ZrO 2. [Display omitted] High-plasticity titanium materials with high oxygen content were prepared by powder metallurgy (PM) and hot rolling, using pure Ti and ZrO 2 powder as raw materials. Completely dissolved oxygen and zirconium atoms resulted in the lattice constant change, thereby increasing the strength. Although the oxygen content was up to 0.56 wt% (much higher than the oxygen threshold of 0.33 wt%), PM Ti still exhibited high plasticity. The Ti-0.5 wt% ZrO 2 sample (0.43 wt% O) had UTS of 737 MPa and EL. of 28%, while the Ti-1.0 wt% ZrO 2 sample (0.56 wt% O) had UTS of 824 MPa and EL. of 15%. Compared to pure Ti, the addition of 0.5 wt% ZrO 2 resulted in a noticeable increase in UTS (increased by 9%) and EL. (increased by 19%). The strength-ductility trade-off dilemma of PM Ti alloy was broken. The formation of fine and equiaxed dynamic recrystallized grains may be one of the reasons that increased the ductility. The reinforcement effect of ZrO 2 was calculated as 146.7 MPa/wt% ZrO 2. [ABSTRACT FROM AUTHOR]

FeCoNi concentrated solid-solution alloys (CSAs) and its modified version strengthened by in-situ formed nano-sized particles are successfully manufactured through mechanical alloying and spark plasma sintering method. Both the as-milled powders and the bulk materials are of single face-centered cubic structure. After sintering and heat treatment, grains are refined by 68% with the addition of oxides. In oxide dispersion strengthened (ODS) FeCoNi CSAs, the majority of nano-sized particles with diameter ranging from a few to ~ 40 nm are uniformly distributed in the matrix, and most of them are identified as Y 2 Ti 2 O 7. Electron backscattered diffraction results reveal that the recrystallization process is suppressed due to the existence of the nano-sized particles. The size and distribution of oxide particles in the matrix can be controlled by adjusting experiment parameters of the mechanical alloying process and annealing treatment. Refined grains and high-density nano-sized particles result in enhanced compressive yield strength for ODS-FeCoNi CSAs at room temperature and 700 °C, which is 1295 MPa and 127 MPa, respectively. Image 1 • Nano-sized oxide particles were introduced into FeCoNi based ternary alloys by mechanical alloying. • Nano-sized particles with diameter ranging from a few to ~40 nm are evenly distributed in matrix and identified as Y 2 Ti 2 O 7. • Both the as-milled powders and the bulk materials are of single face-centered cubic structure. • High compressive yield strength is obtained at RT and 700 °C for ODS-FeCoNi CSAs, which is 1295 and 127 MPa, respectively. [ABSTRACT FROM AUTHOR]

Abstract High-quality Ti 2 AlNb alloys were prepared from blended elemental powders via cold isostatic pressing and pressureless vacuum sintering. When sintered at 1200 °C, the Ti-23Al-17Nb alloy attained a very high relative density (98.7%) and low contents of interstitials (0.1 wt% O, 0.03 wt% N and 0.005 wt% H). Three crystalline phases – B2, α 2 , and orthorhombic (O) – were observed in a fine and homogeneous microstructure in the sintered samples. The fine microstructure and low interstitials account for the good mechanical properties achieved: approximately 941 MPa of ultimate tensile strength, 862 MPa of yield strength and 11.7% of elongation. Highlights • Ti-23Al-17Nb with high relative density (98.7%) was prepared by vacuum sintering from blend elemental powder. • The as-sintered Ti-23Al-17Nb has low interstitials, about 0.1 wt% of O, 0.03 wt% of N and 0.005 wt% of H. • The mechanical properties of as-sintered Ti-23Al-17Nb is about 941 MPa in UTS, 862 MPa in YS and 11.7% in elongation. [ABSTRACT FROM AUTHOR]

Abstract An integration technology was employed to prepare TiC-TiB 2 strengthening coating on aluminum alloys, with the combination of Self-propagating high-temperature synthesis (SHS) and Vacuum-expendable pattern casting (VEPC). During the VEPC process, the Ti-C-B 4 C-TP SHS reaction was ignited by molten Al alloy, resulting in the simultaneous obtainment of TiC-TiB 2 SHS coating with the cast Al alloy. Specifically, Teflon (PTFE) as reaction promoter was introduced into the SHS system to guarantee the reaction to be ignited successfully. With 3.8 wt% PTFE addition, homogeneous and dense TiC-TiB 2 coating microstructure was obtained. Compared to the matrix, the hardness of the surface coating increased from 80 HB to 284 HB. And, the weight loss decreased from 533 mg to 52 mg at load of 20 N, indicating the significant improvement of wear resistance. In addition, a comprehensive bonding strength of 160 MPa was achieved. The proposed method for preparing hard coating on Al alloys broadens their industry application, where higher hardness and better wear resistance are required. Graphical abstract fx1 Highlights • In-situ synthesis of TiC-TiB 2 composite coating on Al alloy. • Teflon (PTFE) was employed as a promoter to ignite Ti-C-B 4 C reaction during Al alloy casting process. • The hardness and wear resistance has been significantly improved. • Reaction mechanism was outlined with the help of thermodynamic analysis. • One promising method has been proposed for production of strengthening coating on Al alloy. [ABSTRACT FROM AUTHOR]

LaNiO 3 thin film coated Li-rich cathode Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 material is fabricated for the first time using the facile sol-gel process. Morphology, structure and battery cycle performance of the LaNiO 3 -coated Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 is characterized by a series of tests. LaNiO 3 coating was synthesized by the sol-gel process and uniformly covered powder surface. By coating proper amount of LaNiO 3 , the initial Coulombic efficiency, discharge capacity, rate capability and cycle performance are significantly improved, while the charge transfer resistance reduces. The initial Coulombic efficiency of 3 wt% LaNiO 3 -coating samples reaches the maximum of 70% and 65% at 0.1 C and 1 C rates, respectively. The 3 wt% LaNiO 3 -coating electrode has the highest initial charge/discharge capacity of 405.4/285.1 mAh g −1 at 0.1 C rate (1 C = 250 mA g −1 ), while 5 wt% LaNiO 3 -coating delivers the maximum value of 264.1/165.1 mAh g −1 at 1 C. The cycling performance profiles demonstrate that at 1 C rate, the 3 wt% LaNiO 3 -coated electrode exhibits higher discharge specific capacity of 207.6 mAh g −1 and cyclic stability of 190.3 mAh g −1 92% capacity retention after 50 cycles compared with pristine and other content LaNiO 3 . The film resistance and charge transfer resistance both decrease after coating with LaNiO 3 . LaNiO 3 is an efficient modifier to enhance electrochemical performance of Li-rich cathode materials. [ABSTRACT FROM AUTHOR]

In this study, in-situ tensile deformation behavior of powder metallurgy (PM) Ti6Al4V alloys was investigated to analyze the crack initiation and propagation. Accordingly, the fracture mechanisms of the as-sintered and forged PM alloys were summarized. At the initial stage of plastic deformation, cracks appeared in the stress concentration area of pores in the as-sintered Ti6Al4V alloy, and the crack propagation direction was along the phase boundary. Due to the existence of pores, early fracture was obtained, resulting in low elongation of 6.3%. After forging, the crack initiation occurred between α lamellar structure, and the propagation direction was along the lamellar direction. The fine lamellar structure in different directions in the forged PM Ti6Al4V alloy can hinder the crack propagation, thus improving the plasticity. As a result, better comprehensive mechanical performance was obtained in the forged sample, with UTS of 960 MPa, YS of 850 MPa, and EL of 16%. • In-situ tensile deformation behavior of PM Ti6Al4V alloys was studied. • Porosity was the main reason for the crack initiation and propagation. • The driving force of fracture was normal stress in the sintered sample. • Fine α lamellae with different orientations hindered the crack propagation. • The driving force of fracture was shear stress in the forged sample. [ABSTRACT FROM AUTHOR]

In this study, 3D gel printing based on a low molecular mass organic gel system was employed to fabricate complex-shaped Ta parts. As opposed to a polymeric gel system, this system was initiated by heat transition. To obtain suitable printing slurry with 62 vol% solid content, 2.5 wt% resin was introduced to improve green body strength and 0.55 wt% oleic acid was added to modify the viscosity. As a result, the printed samples had relatively good surface quality without defects or pores observed on the surface. Ta particles were closely bound by dibenzylidene sorbitol (DBS) gelators. After sintering, a uniform shrinkage was obtained with a shrinkage of 11%, but the surface quality of the as sintered samples was improved. Sintering decreased the surface roughness from 4.0 μm to 2.8 μm. Besides, the as-sintered Ta samples had a relatively dense and homogenous microstructure. The relative density of the as-sintered sample was about 98%. Therefore, 3D gel printing is a promising method to prepare complex-shaped Ta parts with minimal material waste. Unlabelled Image • Ta parts with a relative density of about 98% was prepared by 3D gel printing. • Low molecular mass organic gel system was introduced in to 3D gel printing. • The printed Ta parts had good surface quality and high dimensional accuracy. • One promising method was proposed to prepare complex-shaped Ta parts. [ABSTRACT FROM AUTHOR]