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The mechanical properties and cavitation erosion-corrosion behavior of directed energy deposition (DED) and as-cast nickel-aluminum bronze (NAB) alloys in 3.5 wt% NaCl solution were investigated. The DED-produced NAB alloy showed a finer microstructure, and the content of κ phases significantly decreased, improving yield strength (increased by 27.76%) and elongation (increased by 54.89%) of NAB alloy. The DED-produced NAB exhibited a more uniform microstructure, fewer high-angle grain boundaries (HAGBs), and twin boundaries (∑3), resulting in a weakened synergistic effect between corrosion and mechanical attack. Compared with the as-cast counterpart, the mass loss rate of DED-produced NAB decreased by 74.77%. ● Nickel-Aluminum Bronze components were fabricated by directed energy deposition. ● Differences in microstructure between DNAB and the CNAB were discussed. ● Fine and uniform microstructure of DNAB enhanced its mechanical properties. ● DNAB exhibited better cavitation erosion and -corrosion resistance than CNAB. [ABSTRACT FROM AUTHOR]

The effect of nano diamond (ND) content on the microstructure, mechanical properties, and thermal conductivity of ZK60+ x (x = 0, 0.05, 0.1, 0.15, 0.2 wt.%) ND composites were investigated. The microstructures of ND/ZK60 composites were observed, which indicated that the nanoscale MgZn 2 and ND particles distributed evenly in the α-Mg matrix. The tensile yield strength (TYS) and compressive yield strength (CYS) of the composites first increased remarkably and then decreased with further increasing the ND content. Due to the surface area of the matrix-diamond interface increased and the grains sizes of composites decreased with the amount of ND increase, which cause the coefficient of thermal expansion (CTE) of the composites reduced significantly. Meanwhile, the thermal conductivity of the composite material decreases from 129 W·m −1·K −1 to 116 W·m −1·K −1 with the content of ND increasing from 0.05% to 2.0%. The thermal conductivity of the composites increases to the maximum and then decrease with the increase of temperature (in temperature range of 273 - 573 K). The ZK60+0.05 ND showed superior mechanical and thermal conductivity property, TYS of 343.97 MPa, CYS of 341.74 MPa, elongation of 15.71%, CTE of 7.3 × 10−6 K −1, and thermal conductivity of 129 W·m −1·K −1 at room temperature. It is demonstrated that the ND content has an obvious influence on the microstructure, mechanical properties, and thermal conductivity of ND/ZK60 composites. [ABSTRACT FROM AUTHOR]

The wire-arc additive manufacturing (WAAM) was used to develop Ni-Al bronze (NAB) alloys for naval application. Compared with as-cast NAB, the microstructure of as-fabricated NAB is finer, the precipitation of the κ Ⅰ is suppressed, more uniform distribution of elements, and most β′-phase transformates to α + κ Ⅲ eutectic structures. Additively manufactured sample reveals a lower corrosion current (0.0149 ± 0.0014 mA·cm−2) than the counterpart (0.0162 ± 0.004 mA·cm−2). After immersion for 30 days, since the film formed on the additively manufactured NAB contains more Al 2 O 3 and Ni, the mass loss of WAAM-produced NAB alloys decreased by 35.21% compared to the cast samples. • Nickel-Aluminum Bronze components were fabricated by wire-arc additive manufacturing. • Differences in κ-phases formation between WAAM-produced NAB and cast was discussed. • WAAM-produced samples showed fine microstructure and uniform element distribution. • The more Al 2 O 3 and Ni in the oxide film formed on the WAAM-produced samples. • WAAM-produced NAB exhibited lower corrosion rate and better corrosion resistance. [ABSTRACT FROM AUTHOR]

MFI-type zeolite membranes on hollow fibers are fabricated by a facile secondary growth method. The microstructure of the membranes is systematically manipulated by tuning the seed size, seed morphology and the structure-directing agent content. The as-synthesized MFI-type zeolite membranes are thoroughly characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, water contact angle, pervaporation and gas permeation tests. High quality thin membranes (~3 μm) can be obtained on alumina hollow fibers by using appropriate seed size and morphology ( e.g. , 500 nm coffin-shaped crystals), and certain low TPA + content ( e.g. , TPA + /Si=0.05), achieving a separation factor as high as 58 with a high flux of 9.8 kg m −2 h −1 for pervaporation of a 5 wt% ethanol aqueous solution at 60 °C. A linear decrease relationship between the total flux and the separation factor is obtained. The high pervaporation performance of the membranes can be ascribed to their dense membrane layer and low concentration polarization effect owing to their particular microstructures. [ABSTRACT FROM AUTHOR]

A TC4/TA2 honeycomb structure was fabricated using Selective Laser Melting. The study primarily investigates the impact of process parameters on the mechanical properties of as-built TC4 and TA2, as well as the correlation between microstructure and mechanical properties in as-built TC4/TA2. The resulting composite displays a heterogeneous structure of acicular α′ and columnar β grains, and exhibits superior mechanical properties with a maximum tensile strength of 1081 MPa and an average elongation of approximately 14 %. These outstanding mechanical properties are attributed to the strengthening effect of acicular α′ martensite and synergistic effect between dissimilar materials. The anisotropy of the mechanical properties of heat-treated TC4/TA2 decreased, which is attributed to the transformation of the columnar grains to the basket-waving structure and equiaxed structure. • The TC4/TA2 honeycomb structure was fabricated by the Selective Laser Melting (SLM). • The unique scanning strategy caused the microstructure on the sop surface to exhibit a checkerboard pattern. • The temperature gradient and G/R value played an important role in the epitaxial growth of columnar grains. • The reasons for the difference in mechanical properties of the as-built part in different directions were explained. [ABSTRACT FROM AUTHOR]

The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu element within the cell boundary phase, and the gradient of Cu distribution increases with aging time, together with coercivity. However, the fundamental origin of such Cu gradient distribution is not clear. In this work, the element redistribution and interfacial stress change during the aging process were simultaneously analyzed by employing typical Sm(Co bal Fe 0.16 Cu 0.08 Zr 0.03) 7.6 magnets with and without slow cooling. The increased atomic diffusion after slow cooling leads to a narrow width and large Cu distribution gradient of 1:5H phase, contributing to a high coercivity. Meanwhile, the lattice mismatch at the 1:5H/2:17R interface along 〈 1 ¯ 010〉 2:17R direction was enhanced in the magnet with slow cooling, giving rise to a large interfacial stress. Such interfacial stress was found, via physical chemistry analysis, to contribute to the gradient of Cu distribution in the 1:5H phase. The combined analysis of transmission electron microscopy, geometric phase analyses, and micromagnetic simulations reveal the presence of the interfacial stress together with a large concentration and gradient of Cu distribution in the 1:5H phase can improve the coercivity. These findings provide new considerations for the design of high-performance 2:17-type SmCo magnets. [Display omitted] [ABSTRACT FROM AUTHOR]

Broadband electromagnetic microwave absorbing materials with low density are highly demanded and faced with a development challenge for the critical applications into military stealth technology and electromagnetic pollution protection. Tailoring micro-structures and compositions of carbon-based multifunctional materials is a promising strategy to satisfy the expectation. Herein, we have firstly introduced nonmagnetic Cu element to tune microstructure, chemical composition of agglomerated Cu–Ni bimetallic alloys nanoparticles in gumdrop-cake-like CuNi/C nanofibers for the usage of high-quality light microwave absorbing materials, which can integrate the advantages of carbon nanofibers and CuNi nano solid solution particles. The CuNi/C nanofiber calcined at 650 °C temperature remarkably achieves a −55.1 dB strong reflection loss at 13.4 GHz frequency and a 7.5 GHz broad bandwidth (RL ≤ −10.0 dB) at 3 mm matching thickness, exhibiting a superior microwave absorption performance. This work demonstrates that introducing nonmagnetic Cu element could provide an effective way to improve the electromagnetic performance of carbon-based composites through tuning their microstructure. [ABSTRACT FROM AUTHOR]

In this study, CoCrFeNiMo 0.2 high entropy alloy (HEA) was successfully prepared by laser-powder bed fusion (LPBF). The superior mechanical properties were achieved in the as-printed sample, with the yield strength, ultimate tensile strength, and fracture elongation determined as 776 MPa, 929 MPa and 37.4%, respectively. The as-printed sample exhibits a single-phase face-centered-cubic (FCC) structure without precipitating out a second phase. The microstructural feature of epitaxial columnar grain growth with <001> texture in the as-printed sample can be observed. And the strengthening mechanism of the as-printed sample was also carefully studied. Moreover, the corrosion resistance of the as-printed sample in 3.5 wt% NaCl solution is better than 316L and 304 stainless steel. • CoCrFeNiMo 0.2 HEA with a single-phase FCC structure was successfully prepared by LPBF. • LPBF-built sample shows an excellent tensile strength of ∼ 0.93 GPa together with the fracture elongation of ∼ 37%. • LPBF-built sample has the best corrosion resistance relative to the 316L and 304 stainless steel. [ABSTRACT FROM AUTHOR]

Directed energy deposition (DED) process can enable rapid and low-cost manufacturing of large-scale high-strength AA2219 Al-6.3 wt%Cu alloy components, displaying broad prospects for structural lightweighting in aerospace applications. However, a high tendency to prominent porosity defects and inhomogeneous layered microstructure are intrinsically present in DED-processed Al-Cu alloy, leading to significant performance degradation and anisotropy. Herein, we demonstrate a robust DED process to fabricate high-quality formed AA2219 alloy deposits, based on in-situ synthesized TiC-containing wires and an ultrasonic-frequency pulsed (UFP) arc. The effects of in-situ synthesized submicron-scale TiC particles (average diameter 0.7 ± 0.4 µm) in microstructural evolution and mechanical performance were comparatively investigated through multi-scale microstructural characterization and mechanical property measurement. The introduction of TiC particles into the as-deposited AA2219 component results in a homogeneous refined equiaxed microstructure with an average α-Al grain diameter of 23.4 ± 2.9 µm, and a dramatical elimination of porosity defects. After undergoing a T6 solution and aging treatment, the TiC-reinforced AA2219 deposit demonstrates excellent resistance against grain coarsening, porosity defects growth, and particle segregation. Moreover, the introduced TiC particles lead to a noticeably enhanced precipitation hardening behavior. A homogeneous precipitation microstructure of dispersed θ′-Al 2 Cu particles with an average diameter of 84.1 ± 34.5 nm and a high fraction of 9.8 ± 2.5 vol% was obtained in the heat-treated AA2219 deposit. Based on the as-built multiscale homogeneous microstructure, the heat-treated deposit embedded with TiC particles exhibits a synergy of unprecedented tensile strength of 501 ± 14 MPa and excellent ductility of 9.6 ± 3.3%. [Display omitted] • A well-formed AA2219 alloy was fabricated via wire+arc directed energy deposition. • Introducting TiC particles results in homogeneous refined equiaxed microstructure and suppressed porosity. • Heat-treated TiC p /2219 deposit exhibits a synergy of strength and ductility. [ABSTRACT FROM AUTHOR]

3D-printed composites have promising potential for applications as structural or functional parts in different engineering fields. However, due to the presence of pores and weak interface interactions, 3D-printed parts have weaker mechanical performance than traditional processed ones. In recent years, polypropylene (PP) emerged as a new 3D printing material with enormous potential. In this work, two PP-based composites (PP/EPR(ethylene-propylene-rubber) and PP/EPDM(ethylene-propylene-diene-monomer)/talc) were chosen to study the effects of extrusion temperature and layer thickness on the quasi-static and dynamic behavior of 3D-printed PP-based composites. The results obtained in this study indicated that the processing induced voids have a significant impact on the mechanical properties of printed specimens as they could cause stress concentration and trigger crack propagation. A smaller layer thickness and a moderate printing temperature could reduce pore size and porosity in the printed parts and consequently increase their mechanical properties. Compared to the response under quasi-static loading, the apparent strength and modulus for both materials under dynamic compression were much higher. Under impact loading, polypropylene-based composites exhibited different rupture characteristics caused by the different reinforcement. • Dynamic behavior of 3D-printed polypropylene (PP)-based composites was investigated. • Processing induced voids have a significant impact on the mechanical properties of printed specimens. • A smaller layer height and a moderate printing temperature could reduce pore size and porosity in the printed parts. • Under impact loading, PP-based composites exhibited different rupture features caused by the different reinforcement. [ABSTRACT FROM AUTHOR]

Additively Manufactured structural components would often serve the impact environment while sufficient efforts have not been paid on their dynamic response. In this study, cold metal transfer wire and arc additive manufacturing (CMT-WAAM) process was used to fabricate 316 L stainless steel and initial well-aligned coarse austenitic columnar crystals with 〈100〉 texture along deposition direction were developed. Samples of as-built 316 L were subjected to dynamic compressions with various strain rates and strains by split hopkinson pressure bar (SHPB). The as-built 316 L dynamically exhibits ~50% higher yield strength and twice elastic modulus than quasi-static condition. Twinning acts as main deformation mode whereas strain induced martensitic transformation has not been found. Microstructure evolution upon progressive strains at similar high strain rates reveals continuously increase in the population of deformation twins associated with a gradual decrease in average twin thickness from 120 nm to 20 nm. Average twin thickness as the key physical parameter from evolving microstructures and flow behavior are well fitted using empirical equation. A careful texture analysis suggests a remarkable transition from initial 〈100〉 ||CD (compression direction) to the component 〈110〉 ||CD. Our findings provide the mechanistic insights into understanding the dynamic behavior of additively manufactured stainless steel. Unlabelled Image • Microstructure evolution upon progressive strains of additively manufactured 316 L during dynamic process is revealed. • Average twin thickness as the key physical parameter from evolving microstructures and flow behavior are well fitted. • Texture evolution reflects a transition from initial 〈100〉||CD (compression direction) into strong 〈110〉 ||CD component. [ABSTRACT FROM AUTHOR]

Abstract A designed Cr-Mn-N wire with 0.99 wt% of nitrogen content (HNS0.99) was used to make high nitrogen austenite stainless steel parts by introducing CMT wire and arc additive manufacturing (CMT-WAAM) method. The solidification behaviour, microstructure evolution, inclusions and tension properties were studied both in the as-built and post heat treatment conditions. Excellent tension properties parts with high nitrogen content were successfully produced. Ferrite-austenite (FA) and austenite-ferrite (AF) solidification models were revealed in the as-built microstructure of two different areas, inner layer area (ILA) and partial melting area (PMA), respectively, and the former predominated the microstructure. Amorphous inclusion islands and microspherical inclusions made by MnO were found. The increasing density of the latter in 0.1-1 μm diameters was detrimental to the tensile properties because the matrix-inclusion surfaces acted as the preferred nucleation sites for Cr 2 N during heat treatment. Due to the stable austenite and the nitrogen work hardening effect, planer dislocation-arrays predominated the dislocation slip model which, to some extent, diminished the strength anisotropy in different directions. However, the ferrite dendrites caused the diversity of UTS and elongation by acting as tunnels for cracks in the horizontal direction samples. Graphical abstract Unlabelled Image Highlights • High nitrogen austenite stainless steel parts were successfully made by CMT-WAAM process with excellent tension properties. • The increased density of inclusions (0.1-1μm) surrounding by Cr2N was detrimental to tension properties after heat treatment. • Migration of δ-γ boundaries during high-temperature short-time heat treatment reveals a great promotion of the YS and UTS. • YS and UTS anisotropies were largely reduced due to the stable austenite matrix and nitrogen work hardening effect. [ABSTRACT FROM AUTHOR]