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Abstract: Composites produced in nature, such as mollusk shells, bones, etc., are renowned for their unique structures and excellent properties. In this paper the microstructure and mechanical properties of the shell of Conus betulina Linnaeus are investigated. The results indicate that the mechanical properties of the shell are anisotropic. After removal of the organic protein in the shell, the three-point bending strength significantly decreases, to about 1/20th or 1/30th of the original value. The organic matrix plays an important role in the hierarchical structure of the conch shells, as it promotes load transfer between adjacent aragonite layers. [Copyright &y& Elsevier]

High borated steel sheets containing 0.25 wt% to 4.0 wt% boron including hypoeutectic (0.28 wt% B and 2.11 wt% B), eutectic (2.43 wt% B) and hypereutectic (4.01 wt% B) compositions were tried to be fabricated by a novel strip casting technology, and the effects of boron content on sub-rapid solidification behavior and subsequent microstructural evolution together with mechanical properties was studied. It was found that the morphology of borides depended greatly on the boron content. When increasing boron, the morphological change of borides was network-like → grainy → cluster-like → plate-like. Various orientation relationships between different morphological borides and γ-Fe in as-cast steels were also identified. After subsequent hot-rolling and solution-treating, ultra-fine (<10 μm) borides were obtained in hypoeutectic and eutectic steels. Benefiting from that, excellent mechanical properties was achieved, which was much better than that of steels prepared by traditional ingot casting. Particularly, when the boron content approached eutectic composition, of which the effect on the microstructure and mechanical properties was more sensitive. The steels containing 2.11 wt% and 2.43 wt% boron exhibited different morphological borides with a total elongation of 14.1% and 8.0%, respectively. Moreover, a thin hypereutectic borated steel sheet was also prepared, but the borides were very large and the total elongation was very low. The correlation between microstructure and strength was clarified based on the Hall-Petch behavior and intermetallic strengthening effect. Smaller γ-grains and higher volume fraction of borides were responsible for higher strength. The plastic behavior of steels was influenced by strain-hardening rate that was determined by the volume fraction of γ-Fe matrix. A better sustainable strain-hardening capability was beneficial to extend the stage of uniform deformation and enhance the ductility. In addition, the mechanical properties of steels were also decided by the fracture mechanism that was dominated by the size of borides. [ABSTRACT FROM AUTHOR]

This study investigated the features of grain boundary regions in a Ni-based superalloy which underwent creep deformation. Large grain boundary zones were denuded in fine γʹ precipitates but contained coarsened microscale γʹ rods. The coarsening direction of these rods was along the <110> of the γ matrix and γʹ precipitates. The orientation of the grain boundary zone was the same as that of the adjacent grain behind the migrating boundary. This result indicated that the formation of these zones was accompanied by the migration of the grain boundary. Then, numerous slip features were observed through detailed local disorientation analysis. It is proposed that the driving force for the grain boundary migration was the local stress induced by the dislocation creep. The dissolution–reprecipitation of the precipitates at the boundary migration front resulted in the directional coarsening of the γʹ rods. [ABSTRACT FROM AUTHOR]

To manufacture hard-to-deform intermetallics and their components at high temperatures and for a short-time, a novel additive sintering method based on solid-state powder densification is proposed, which aims to achieve the fabrication and joining of intermetallics. In this study, the sintering and joining of NiAl/NiAl and NiAl/TiAl alloys were conducted using this method. The results show that good bonding was achieved between similar intermetallics of NiAl/NiAl. Nevertheless, due to the formation of brittle phases, defects were observed in the bonding interface of the NiAl/TiAl alloy. An interlayer of V was employed to optimize the microstructure of the interface, which can prevent the formation of the brittle phase and improve the property of the interface. • A additive sintering method is proposed to manufacture dissimilar-material component. • The method can achieve fabrication and joining of dissimilar material simultaneously. • V foil as interlayer eliminates brittle IMCs at the joining interface of NiAl/TiAl. • The NiAl/V/TiAl sample shows significantly improved interfacial property. [ABSTRACT FROM AUTHOR]

For fabricating NiAl thin-walled component and improving its high-temperature strength, a novel layered NiAlV composite sheet/cone consisting of NiAl(V) layer, NiAl–V hypereutectic layer and V (NiAl) layer have been successfully prepared using forming-reaction of laminated Ni/Al/V foils. Compared with pure NiAl, the ultimate tensile strength (UTS) of the NiAlV composite at 1000 °C is increased by 177%, which is mainly attributed to the solution strengthening and precipitation strengthening of V element. The obtained results provide a new approach for synergetic controlling shape and property of NiAl-based thin-walled component. • A forming-reaction method was proposed for fabricating closed cross-section thin-walled NiAl-based components. • Novel NiAlV composite sheet/cone consisting of different layer morphologies were successfully prepared. • The ultimate tensile strength of NiAlV composite was 201.6 MPa at 1000 °C (177% higher than pure NiAl). [ABSTRACT FROM AUTHOR]

The high-temperature anisotropy and microstructure evolution mechanisms of the rolled TA32 titanium alloy sheet were studied. The hot deformation behaviors of the TA32 sheet along the rolling direction (RD), diagonal direction (DD), and transverse direction (TD) were studied by the uniaxial tensile tests in the temperature range of 700–900 °C and the strain rate range of 0.0001–0.1 s-1. The anisotropic coefficients were calculated by interrupted tensile tests. The microstructure and texture characteristics were observed by electron backscatter diffraction (EBSD) characterization. The effects of dislocation slip, texture evolution, dynamic recrystallization (DRX), and grain morphology on high-temperature anisotropy were comprehensively studied. Results show that the TD sample exhibited the largest peak strength and the DD sample displayed the highest elongation. The r -values decreased with increasing temperature and decreasing strain rate, and increased with increasing strain. The dominant dislocation slip modes of RD, DD, and TD samples were prismatic slip, the coupling of basal and prismatic slips, and pyramidal slips, respectively. The DRX mechanism of TA32 titanium alloy during hot deformation was the combined effects of DDRX (discontinuous dynamic recrystallization) and CDRX (continuous dynamic recrystallization), and DDRX could weaken the anisotropy. The grain growth and refinement caused by thermal effect and DRX led to the decrease and increase of r -value, respectively. In addition, the room-temperature tensile strength of the TD deformed sample showed the largest drop compared with the initial sheet, which can be attributed to the accumulation of damage and the increase of basal texture in the TD sample during the hot working. [ABSTRACT FROM AUTHOR]