Search

The compromise between strength and plasticity has greatly limited the potential application of particles reinforced magnesium matrix composites (MMCs). In this work, the Ti particles reinforced AZ31 magnesium (Mg) matrix composites achieved simultaneous improvement in strength, elongation and wear resistance. The Ti particles reinforced AZ31 composites were fabricated by ultrasonic-assisted stir casting with hot extrusion. The results showed that a strong interfacial bonding was obtained at Ti/Mg interface because of the formation of semi-coherent orientation relationship of TiAl/Mg, TiAl/Al 2 Ti and Al 2 Ti/Mg interfaces. The as-extruded 6 wt.%Ti/AZ31 composite presented the best compressive mechanical properties and wear resistance with ultimate tensile strength, elongation and wear rate of 327 MPa, 20.4% and 9.026 × 10−3 mm3/m, obviously higher than those of AZ31 alloys. The enhanced mechanical properties were attributed to the grain refinement and strong interfacial bonding. The improved wear resistance was closely related to the increased hardness of composites and the formation of protective oxidation films. • Ti particles refine the grain size of Ti/AZ31 composites. • A strong interfacial bonding forms at Ti/Mg interface. • Ti/AZ31 composites get an increase in strength, elongation and wear resistance. [ABSTRACT FROM AUTHOR]

A 3‐layered composite plate is innovatively fabricated via composite rolling of 1.6 wt% B stainless steel surrounded by two layers of boron‐free steels. The tensile properties of composite and non‐composite plates are comparatively tested and analyzed. Besides, the microstructure evolution of the investigated plates is characterized in detail. It is found that the composite specimens exhibit higher tensile elongation comparing with that of non‐composite specimens. Specifically, the engineering strain of the 1050 °C × 30 min solution‐treated specimens reaches to 12.5 ± 0.8% which is 2.5–3.0 times as high as that of non‐composite specimens. In addition, the as‐cast lamellar borides break into bar‐shaped structures in hot rolled plates, however, their morphology and distribution hardly change after solution treatment. Besides, the transition regions between the core and clad layers are formed and characterized by medium‐sized recrystallized grains and fine borides in the solution‐treated composite specimens. The enhancement mechanism of tensile elongation is mainly analyzed in term of the geometrical restriction of necking in the composite plate during tensile deformation. This paper provides a promising method to effectively enhance the tensile fracture elongation for these metallic materials with poor plasticity like high borated stainless steels. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiAlV sheet was prepared by magnetron-sputtering and foil-reaction process. • Solid-liquid reaction is applied without pressure to accelerate the process. • The tensile strength of NiAl-1.01V alloy was 128.9 % higher than pure NiAl at 1000 °C. To prepare NiAl sheets with improved high-temperature strength, the V layers with different thicknesses were deposited on the single-side of Ni foils by magnetron sputtering and then the hot-pressing of laminated Ni(V)/Al foils were carried out. A NiAlV sheet consisting of V precipitates and NiAl matrix was successfully prepared using this reaction technique of laminated foils. The NiAlV alloy prepared by microalloying method can obtain better mechanical properties (166.4 MPa) and retain considerable fracture strain (54.5 %) at high temperature. [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]

• The paramagnetic structure of HPNb alloy change into ferromagnetic after carburization. • The M 23 C 6 carbides are replaced by carbon-rich M 7 C 3 carbides in carburization zone. • The carburized tube furnace tubes become brittle after carburization. • Carburization reduced the high temperature creep strength of HPNb alloy tube. The structure characteristics and mechanical properties of as-cast and carburized HPNb alloy tubes were investigated in this paper. Through magnetism test by the vibrating sample magnetometer, we find that the paramagnetic structure of as-cast HPNb alloy tubes has changed into ferromagnetic structure after carburization. Electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) analyses show that the M 23 C 6 type carbide transformed into M 7 C 3 type carbide in carburization zone. Due to the coarser primary carbides and blocky-shaped secondary carbides after carburization, the ductility and toughness of the ethylene cracking furnace tubes are very low and become brittle. At high temperature, the tensile strength and yield strength of carburized tube are higher than those of as-cast tube, but the tensile elongation is lower. Owing to the microstructure degradation, the creep strength of HPNb alloy decreased after carburization. Hence, the carburization also could lead to the decrease of the remnant life of the pyrolysis furnace tubes. [ABSTRACT FROM AUTHOR]