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Zinc (Zn) alloys have recently revolutionized and shown promising usage for degradable biomedical implants (BMI). However, due to the low strength of pure Zn, its application in the biomedical industry was limited. In the current research, an innovative biodegradable Zn-0.4Li-0.4Cu alloy produced by laser powder bed fusion (LPBF) with good mechanical properties was investigated. The Zn-0.4Li-0.4Cu alloy showed superior mechanical properties (tensile strength at 296 MPa, yield strength at 260 MPa, and after heat treatment elongation at 8.3 %), a record for biodegradable Zn alloys, as a consequence of grain refinement, second-phase precipitation of intermetallic compounds, and solid solution strengthening. The impacts of Cu and Li on the microstructures, mechanical behaviors, corrosive behavior and deterioration rate of the Zn-0.4Li-0.4Cu alloy were studied. The addition of Cu and inherent fast-cooling rate of the LPBF process are favorable for promoting the nucleation events, leading to the refinement of grains. In addition, the formation of the second-phase precipitates (CuZn 4 and ZnLi 4) in the matrix was founded to further improve the mechanical properties. Moreover, the alloy showed a consistent degradation manner and a suitable degradation rate of 0.023 mm/year. Based on the findings shown above, the biodegradable Zn-0.4Li-0.4Cu alloy can be a potential candidate for vascular stents and medical applications due to its excellent mechanical properties and adequate degrading behavior. • The Zn-0.4Li-0.4Cu alloy produced by laser powder bed fusion (LPBF) demonstrated exceptional mechanical properties, with a tensile strength greater than 296 MPa, and elongation of 8.3 %. • The superior mechanical properties of the as-LPBF-built Zn-0.4Li-0.4Cu alloy can be attributed to the morphology and distribution of the intermetallic compounds and dislocations. • The novel biodegradable Zn-0.4Li-0.4Cu alloy is a promising candidate for fabricating degradable biomedical implants due to its strength, reasonable ductility, and satisfactory degradation rate. [ABSTRACT FROM AUTHOR]

Si-rich Mo-Si-B powders (Mo-62Si-5B at%) were deposited on Nb-Si based alloy by laser cladding assisted with ultrasonic vibration. The obtained coatings mainly consist of MoSi 2 and (Mo, X) 5 Si 3 (X = Nb and Ti). With the introduction of ultrasonic vibration during laser cladding, the lath-shaped MoSi 2 phase transforms into cellular gradually. Meanwhile, the discrepancy on the microstructure of the top region and the bottom region is eliminated gradually, indicating that the cavitation and acoustic streaming of ultrasonic vibration not only refines the microstructure, but also homogenizes the element and phase distribution in the coatings. High-temperature oxidation experiment at 1250 ℃ were conducted to assess the oxidation resistance of the coatings. Compared with Nb-Si alloy, the coated specimens have much lower oxidation weight increase. Furthermore, with the assistance of ultrasonic vibration, the oxidation resistance of the coating is enhanced further. The oxide scales on the coatings consist of two layers: an upper amorphous aluminoborosilica with TiO 2 particles dispersed and a lower crystalline SiO 2 layer. With the introduction of ultrasonic vibration, the microstructure of the coatings is refined, resulting in more phase and grain boundaries in the coatings. Therefore, the diffusion of the elements to the surface is accelerated and the protective oxide scale can be formed quickly. • Si-rich Mo-Si-B coatings were prepared on Nb-Si based alloy by laser cladding assisted with ultrasonic vibration. • The ultrasonic vibration refines the microstructure and homogenizes the phase distribution in the coatings. • The oxide scale on the coatings consists of an upper amorphous aluminoborosilica and a lower crystalline SiO 2 layer. • The ultrasonic vibration improves the oxidation resistance of the coatings because of more phase and grain boundaries. [ABSTRACT FROM AUTHOR]

W-based composites with the different immiscible second phases (Cu and Cu10Sn) were prepared by laser powder bed fusion (LPBF). The immiscible W phase and Cu/α-Cu phases were prone to separate during LPBF. The melted W phase could easily fuse together and form W matrix, and Cu or α-Cu phase distributed within the gaps among W phase. Cu or α-Cu phase can provide a gradient cooling way for the solidification of W phase through the transformation of 'solid-liquid-gas' during LPBF. The evaporation of Cu or Sn accelerated the heat dissipation, which caused the grain refinement of W. Higher thermal conductivity of Cu than α-Cu leads to the relative finer grain size of W phase in W-Cu composite. The heat conduction direction between W phase and Cu/α-Cu also affected the grain morphology. Heat continued transferred from W to Cu/α-Cu induced the columnar grain growth of W, the interlacing distribution of W and Cu/α-Cu made the growth of W columnar grains radiate out from the center Cu/α-Cu phase. Remarkable, cracks were severely restrained in W phase simultaneously although W phase melted completely. This is not only related to improvement of strength and ductility of W caused by grain refinement, but also because of the interlacing distribution of W and Cu/α-Cu phases, which could effectively reduce the stress degree in W phase during LBPF. [Display omitted] • W-Cu and W-Cu10Sn composites with free crack were successfully prepared by LPBF. • W phase formed skeleton structure in both W-Cu and W-Cu10Sn composites. • The addition of Cu/ Cu10Sn induced the grain refinement of W phase. [ABSTRACT FROM AUTHOR]

• Mo-10Si-(0, 5, 10, 15)B (at.%) alloys were prepared by vacuum arc-melting technique. • The effect of B content on phase constitution was discussed and the microstructure evolution was illustrated. • The relationship between the microstructure of the alloys and the mechanical properties was established. • The oxidation resistance of the alloys was evaluated and the mechanism of oxidation resistance was studied. The Mo-10Si-(0, 5, 10, 15)B (at.%) alloys located in Mo ss (Mo solid solution) +Mo 3 Si +T2 (Mo 5 SiB 2) region were prepared by arc melting. The effect of B content on the microstructure, microhardness, fracture toughness and oxidation resistance of the alloys was studied. In the Mo-10Si alloy, there are primary Mo ss and peritectic Mo 3 Si phases. With the addition of B, (Mo ss + T2) binary and (Mo ss + T2 + Mo 3 Si) ternary eutectics emerge in Mo-10Si-(5, 10)B alloys. For Mo-10Si-15B alloy, primary Mo ss disappears and the microstructure is only composed of binary and ternary eutectics. With the increase of B content, the proportion and grain size of Mo ss decrease. The microhardness of alloys increases with the increase of B content due to the increasing intermetallics. The fracture toughness of alloys decreases obviously in single-edge notched three-point bending testing (SENB) and the fracture mode transforms from transgranular fracture to intergranular fracture because of the refinement of Mo ss. In the high-temperature oxidation test at 1250 °C, the oxidation weight loss of the alloys decreases with the addition of B due to the densification of the borosilicate layer. [ABSTRACT FROM AUTHOR]

Almost fully dense AlCrFeNiV HEA consisting of face-centred-cubic (FCC) solid solution and L1 2 nano phase was prepared from gas-atomized alloy powder with optimized selective laser melting (SLM) processing parameters. Microstructure characterization reveals the presence of hierarchical structures including columnar grains, sub-grains, L1 2 nano phase and dislocations in SLMed HEA. Unique columnar grains ranging from several tens of microns up to 200 μm grow along the direction of the temperature gradient. High cooling speed and non-equilibrium solidification during SLM process induced the formation of sub-grains in every columnar grain, accompanied with the heterogeneous distribution of dislocations and L1 2 nano phase. The SLMed AlCrFeNiV HEA exhibited an outstanding combination of high strength (ultimate tensile strength ∼1057.47 MPa) and excellent ductility (plastic strain ∼30.3%). The characteristic hierarchically heterogeneous structure contributes to the increase of strength without losing ductility. The sub-grains contribute significantly to the enhanced strength through dislocation hardening. The excellent ductility is correlated with the progressive work-hardening mechanism regulated by the heterogeneous distribution dislocation and L1 2 nano phase within sub-grains. Image 1 • Almost fully dense AlCrFeNiV HEA was fabricated by SLM. • SLMed HEA consists of FCC phase and L1 2 nano phase. • SLMed HEA shows hierarchically heterogeneous microstructure. • SLMed HEA exhibits high ultimate tensile strength of 1057.47 MPa and plasticity of 30.3%. [ABSTRACT FROM AUTHOR]

Abstract For the aim of thermal barrier application in vehicle engines, a specific FeCrNbBSiC cored wire of consideration was produced to fabricate amorphous coating by wire-arc spraying. The microstructure and thermal conductivity of the as-deposited coating were characterized in detail. The results show that the FeCrNbBSiC coating (FB coating) primarily consists of amorphous phase owing to the combination of proper composition design and rapid quenching of wire-arc spraying. However, a fraction of crystalline phases coexists with the amorphous matrix, due to the both effects of partially incomplete alloying and continuous annealing. Depending on the expected amorphous structure, thermal conductivity of the developed FB coating is as low as 2.15 W/mK at room temperature, almost half of the referenced 316L stainless steel coating (SS coating, 4.20 W/mK), and displays relatively slow and limited increase with elevated temperature up to 500 °C. By means of temperature distribution analysis, an obviously higher temperature is found on the top surface of FB coating covered piston, which implies a benefit of enhancing heat energy conversion. Simultaneously, the temperature of aluminium alloy substrate could also be reduced by covered coating as the role of thermal insulation. Therefore, the wire-arc sprayed FeCrNbBSiC amorphous coating developed here with excellent thermal barrier performance and economic advantage could be a promising innovation and candidate for metal-based thermal barrier coatings applied in vehicle engines. Highlights • Innovative scheme of metal-based thermal barrier coatings was designed. • Wire-arc sprayed FeCrNbBSiC amorphous coating with high T x was obtained. • Incomplete alloying and continuous annealing result in crystalline phases formed. • Amorphization endows excellent thermal barrier ability for this coating (κ = 2.15 W/mK). • Application of this coating improves power efficiency and protects substrate effectively. [ABSTRACT FROM AUTHOR]

Abstract Cu-10Sn alloy with body-center-cubic (BCC) lattice structure was fabricated through selective laser melting (SLM). The geometry of SLMed BCC lattice Cu-10Sn alloy (rod diammeter ∼300 μm, length ∼700 μm) was in good agreement with the design model. Similar with the nearly full density Cu-10Sn alloy, columnar also constituted the majority parts of the lattice structure Cu-10Sn, but exhibited various morphologies due to the different grain growth orientation under thermal effect. The gowth orientation of columnar grain in the rods oriented to the as-fabricated layer due to the higher thermal conductivity of the as-fabricated layers. Graphical abstract Image 1 Highlights • Cu-10Sn alloy with BCC lattice structure was fabricated through SLM. • The geometry of BCC lattice Cu-10Sn alloy was in good agreement with the design model. • The BCC lattice Cu-10Sn exhibited various grain morphologies under thermal effect. • The gowth orientation of columnar grain in the rods oriented to the as-fabricated layer. [ABSTRACT FROM AUTHOR]

Amongst the structural materials for high temperature applications that are currently in the focus of research, high entropy alloys (HEAs) exhibit very promising features, such as high strength, good fracture toughness, high temperature phase stabilities and excellent resistance against softening at elevated temperatures. Key influencing factors for high temperature applications are the mechanical properties at elevated temperatures as well as the oxidation behavior of a given material. Al x CrFeCoNi alloys have been mostly investigated among different HEAs. However, up to now there are limited reports dealing with the oxidation behavior of Al x CrFeCoNi–based HEAs, especially with respect to the effect of Si-alloying on the oxidation behavior at elevated temperatures. In this study, the oxidation behavior of two HEAs, Al 0.6 CrFeCoNi and Al 0.6 CrFeCoNiSi 0.3 , were comparatively investigated at T = 800 °C, 900 °C and 1000 °C in air to determine the effect of Si-alloying. The results show that oxidized layers typically consist of Cr 2 O 3 /spinel and Al 2 O 3 with an underlying Al-depleted zone. AlN was found inside the Al-depleted zone with the exception of Al 0.6 CrFeCoNiSi 0.3 oxidation at T = 800 °C. However, Si alloying only positively influenced the oxidation behavior at T = 800 °C. Here, it promoted the formation of a continuous Al 2 O 3 layer. The Si-alloying did not enhance the oxidation resistance at T = 900 °C and 1000 °C. [ABSTRACT FROM AUTHOR]

A multiple grain size distributed Al-based composite was fabricated through ball milling the amorphous powder mixed with pure Al powder followed by spark plasma sintering. The composite consisted of amorphous/nanocrystalline, submicron grain and micron grain, exhibiting outstanding mechanical properties. The superior strengthen effect of the amorphous/nanocrystalline region contributed to the exhibiting specific strength (5.66 × 10 5 Nm/kg) of the composite. The orderly plastic deformation occurred within FCC-Al micron grain region and submicron grain region during compression. And the progressive deformation restrained the strain localization and unstable propagation of the crack, leading to the plastic deformation (4.3%) of the composite. [ABSTRACT FROM AUTHOR]