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Severe erosion wear is found on valve spools, which threatens the safety and reliability of these units. The use of the plasma beam spraying surfacing method can significantly improve the corrosion resistance and sealing performance of hydraulic valve spools, reduce material waste, and reduce maintenance costs. The effects of the co-addition of CeO2 and SiC particles on the morphology, surface cracks, microstructure, precipitated phases, and wear property of plasma-beam-sprayed Fe55-based coatings on 1025 steel were investigated using OM, EDS, ultra-deep field microscopy, and a wet sand rubber wheel friction tester, respectively. The dendrite exhibited a directional growth pattern perpendicular to the substrate and the transitional states of the microstructure with the co-addition of CeO2 and SiC particles. CeO2 or SiC reduced the liquid phase diffusion coefficient DL of Cr and C and resulted in a decrease in the G/R ratio. The dendrites changed into equiaxed grains. The main phase composition of the Fe55 welding layer was Cr7C3, γ-Fe. The martensite in the surfacing layer and the carbides formed Cr7C3, which can improve the hardness of the surfacing layer. The grain boundaries consisted mainly of a reticular eutectic structure. The uniform distribution of the Cr7C3 hard phase in the Fe55+1.5 wt% SiC+0.01 wt% CeO2 resulted in a uniformly worn surface. The sub-wear mechanisms during the friction process were micro-ploughing and micro-cutting. The hardness and toughness of Fe55+1.5 wt% SiC+0.01 wt% CeO2 were well-matched, avoiding excessive micro-cutting and microplastic deformation. A low content of CeO2 could lead to the formation of equiaxed grain and effectively improve the uniformity of the microstructure. The wear-resistant layer of Fe55+1.5 wt% SiC+0.01 wt% CeO2 can effectively improve the service life and long-term sealing performance of the valve spools. [ABSTRACT FROM AUTHOR]

High-entropy alloys have been proved to be potential candidate materials in the biomedical field due to their balanced mechanical properties and excellent biocompatibility. The effects of atomic ratios on the as-cast microstructural evolution, mechanical properties, and electrochemical property of TiZrTaNbSn high-entropy alloys were studied systematically. The crystal structure of TiZrTaNbSn high-entropy alloys is single BCC phase, and the microstructural evolution is based on atomic ratio. The dendric structure, peritectic structure, pseudo eutectic and equiaxed grain, which are associated with element segregation, can be obtained by non-equal atomic ratio. Ti30Zr20Ta20Nb20Sn10 alloy demonstrates a high compressive strength and fracture strain, which are 2,571.8 MPa and 12%, respectively, and the fracture behavior is quasi-cleavage faults. The Ti45Z35Ta5Nb5Sn10, Ti30Zr20Ta20Nb20Sn10 and Ti35Zr25Ta15Nb15Sn10 alloys show excellent corrosion resistance according to Nyquist diagram, polarization curves and corrosion morphology. Compared with TiZrTaNbSn alloy, the corrosion rate of Ti45Zr35Ta5Nb5Sn10 alloy increases by about 98.9%. It can be concluded that non-equal atomic ratios are effective for microstructure control and performance optimization. [ABSTRACT FROM AUTHOR]

• The TGA and MD simulations are used to explore the influence of Na 2 O on the volatilization of fluoride. • The mechanism of the effect of Na 2 O on melt volatilization is analyzed in detail. • Providing a substantial theoretical and experimental basis for the volatilization of fluoride. Volatilization of fluorides is a common phenomenon and an environmental concern in metallurgy, welding, glass, and other industries. In order to understand the effect of Na 2 O on the volatilization behavior of fluorides in molten slags, thermogravimetric analysis together with molecular dynamic (MD) simulation was employed in the present study. The MD simulation results are consistent with the thermogravimetric analysis (TGA). That is, the increase of Na 2 O promotes the volatilization of fluoride. Investigation of melt microstructure showed that the diffusion of Na+ plays a key role in the volatilization of fluoride. The main contributing microstructural factors to the diffusion coefficient of Na+ are the extent of polymerization in Si O and Ca F networks and the Na F clustering. Collectively, this research offered a thorough understanding of the microstructure and process of fluorine volatilization in molten slags. [ABSTRACT FROM AUTHOR]

• Titanium/steel laminated composites form a tooth-like interface. • Stress can induce interface element diffusion at room temperature. • Shear stress induce the formation of nanocrystalline/amorphous mixed interface. • Normal stress induce the formation of interfacial transition zone. Titanium/steel laminated composites form a tooth-like interface which is subjected to alternating shear/normal stresses during cold roll bonding process. Interfacial shear stress promotes atomic diffusion and gives birth to nano-grains, resulting in an interface mixed with nanocrystalline and amorphous region. Interfacial normal stress introduces high dislocation density, resulting in an interfacial transition zone. [ABSTRACT FROM AUTHOR]

In the present work, the effects of aging treatment on the microstructures of a TC18 alloy are studied. The influence of aging treatment on the tensile properties and failure mechanisms is systematically analyzed. It is found that the size and morphology of the primary α (αp) phases are insensitive to aging temperature and time. Furthermore, the aging temperature and time dramatically influence the precipitation of the secondary α (αs) phases. Massive αs phases precipitate and gradually coarsen, and finally weave together by increasing the aging temperature or extending the aging time. The variations in αp and αs phases induced by aging parameters also affect the mechanical properties. Both yield strength (YS) and ultimate tensile strength (UTS) first increase and then decrease by increasing the aging temperature and time, while ductility first decreases and then increases. There is an excellent balance between the strengths and ductility. When the aging temperature is changed from 450 to 550 °C, YS varies from 1238.6 to 1381.6 MPa, UTS varies from 1363.2 to 1516.8 MPa, and the moderate elongation ranges from 9.0% to 10.3%. These results reveal that the thickness of αs phases is responsible for material strengths, while the content of α phases can enhance material ductility. The ductile characteristics of the alloy with coarser αs phases are more obvious than those with thinner αs phases. Therefore, the aging treatment is helpful for the precipitation and homogeneous distribution of αs phases, which are essential for balancing the strengths and ductility of the studied Ti alloy. [ABSTRACT FROM AUTHOR]

Steel fiber-reinforced ultra-high-performance concrete (UHPC) is becoming an important type of concrete reinforcement. After mixing with the reinforced steel fibers, the UHPC has perfect flex resistance, shear strength, crack resistance, shock resistance, and anti-seepage. In this study, the influence of straight, corrugated, and hooked brass-coated steel fibers (BCSFs) on the microstructure, mechanical properties, and crack expansion mechanism of ultra-high-performance concrete (UHPC) with varying content of 1–6 wt.% under different curing times were investigated. Field emission scanning electron microscopy and energy dispersive X-ray spectrometry were employed to characterize the microstructure of the BCSF-reinforced UHPC mix specimens. X-ray computed tomography was employed to determine the porosity of the BCSF-reinforced UHPC mix specimens. The obtained results indicate the flexural strength and compressive strength of BCSF-reinforced UHPC mix specimens are enhanced, along with increasing the content of BCSFs reinforcement with different shapes (straight, corrugated, and hooked). The embedded BCSFs play a major role in the adhesive property and stress transfer of the BCSFs–UHPC matrix interface. Different from many studies, the flexural strength of mix UHPC with straight BCSFs is higher than those with corrugated and hooked BCSFs. However, the compressive strength of UHPC with corrugated BCSFs is higher than those with straight and hooked BCSFs. The flexural strength of mix UHPC with 6 wt.% straight BCSFs at 28 days reaches the maximum value of 26.2 MPa, and the compressive strength of UHPC with 6 wt.% corrugated BCSFs at 28 days reaches the maximum value of 142.3 MPa. With the increase in straight BCSF content from 1 wt.% to 6 wt.%, the porosity in mix UHPC reduces gradually from 18.4% to 8.3%. The length of average crack spacing is dependent on the straight BCSF content. With the increase in straight BCSF content from 1 wt.% to 6 wt.%, the average crack length reduces gradually from 34.2 mm to 12.1 mm, and the average crack width reduces gradually from 0.78 mm to less than 0.1 mm. During crack extension, part of the energy in the UHPC mixture specimen with the 6 wt.% BCSF content flows into the crack tip region converted into the work dissipated during the bridging process. The crack propagation resistance of the UHPC mixture with straight BCSFs was improved compared with those with corrugated and hooked BCSFs. The bond strength between the BCSFs and UHPC matrix was enhanced by using vibrational mixing, and the brass film coated on the BCSFs contributes to increase the flexural and compressive strength of the UHPC mixture. [ABSTRACT FROM AUTHOR]

During the automatic powder‐feeding process, the hollow granulated mold fluxes are easily broken due to insufficient granule strength, which leads to dust pollution and the deterioration of the properties of mold fluxes during the continuous casting. Herein, a drum‐type granule strength testing device, laser granule size analyzer, and scanning electron microscope are used to analyze the attrition mechanism of three kinds of hollow granulated mold fluxes and the effect of microstructure on the attrition mechanism. The results show that: 1) the result of the drum‐type granule strength test is in good agreement with the practical application effect of mold fluxes; 2) abrasion has dominated the breakage of three kinds of mold fluxes and the dust pollution is caused by the generation of a large number of granules with granule sizes ranging from 20 to 80 μm; 3) the uniform and dense surface film structure on the surface of mold flux effectively inhibits the abrasion and improves the granule strength of mold flux; and 4) the difference in granule size and solubility of different raw materials in the spray granulation process leads to the deposition of Na2CO3, binder, and carbon black on the surface to form the film structure. [ABSTRACT FROM AUTHOR]