Mg-8Li-1Al-0.5Sn (wt%) alloy was prepared by casting and deformed by hot extrusion in this study. The microstructure and mechanical properties of as-cast and extruded alloys were studied by OM, SEM, ...XRD, and the tensile test. The results show that the Mg-8Li-1Al-0.5Sn alloy consists of α-Mg (hcp), β-Li (bcc), LiMgAl2, Mg2Sn, Li2MgSn phases. After hot extrusion, the β-Li phase was refined, and Mg2Sn compounds were distributed uniformly in the matrix. The yield strength and ultimate tensile strength of extruded specimen reach to 240MPa and 322MPa respectively at room temperature. At 423K (150°C), the ultimate tensile strength arrives at 220MPa for extruded alloy. The strength of Mg-8Li-1Al-0.5Sn alloy is higher than many traditional Mg-Li alloys.
The aim of this paper is to investigate the mechanism of an electric current-assisted superplastic deformation on 3Y-TZP in an oxygen-lean atmosphere. The experiments were performed with different ...electric currents in the range of 0~5 A. The results show that the flow stress of 3Y-TZP during the deformation was significantly decreased by the combination of Joule heating and the applied current effect. The microstructures of the deformed specimens were all equiaxed grains without an obvious preferential grain growth. The stress exponent n = 2.05~2.61 suggested that the dominant deformation of 3Y-YZP with/without the electric current was grain boundary sliding at 1400 °C. The activation energy of the deformation which decreased from 465 kJ mol−1 to 315 kJ mol−1 by the electric current indicated that the lattice diffusion of Zr cation during the deformation was enhanced. And the deformation rate of 3Y-TZP with the electric current may be controlled by the grain boundary diffusion of Zr cation.
An experimental investigation on the fretting wear of Ti–6Al–4V was conducted using a self-designed test machine. The wear morphologies and the cracking phenomena of as-received and shot-peened ...specimens were comparatively analyzed by the combining the applications of a laser scanning confocal microscope and a scanning electron microscope. The results showed that shot-peening exhibited an increase in the wear volume during the early fretting wear period, while it reduced the material loss in the long-term fretting wear process. The dominant wear mechanism was transformed from adhesion/peeling to delamination in both the as-received/shot-peened specimens. The wear rates under the peeling and delamination mechanism was explained by the equivalent friction coefficient of the contacting point and the thickness of cracked surface layer. The optimal strengthening effect was obtained under a moderate shot-peening intensity of 0.3 mmA, which produced a proper curvature radius of asperity and a good combination between hardness and toughness of the surface material.
•A fretting test device is designed for the fretting wear experiments of Ti-6Al-4V.•Shot-peening leads to an increase of material loss in the early fretting stage.•Shot-peening reduces the fretting wear volume for the long-term fretting process.•The dominant wear mechanism is transformed during fretting process.•The optimal effect is obtained under a moderate shot-peening intensity.
Fusarium
wilt is an important disease of many food crops and often causes serious damages to yield and food quality. Consequently, numerous studies mainly focused on exploring the control strategy ...for
Fusarium oxysporum
as well as the mechanism of interaction between the
F. oxysporum
and other beneficial soil microorganisms. In this study, we have screened and identified an efficient biocontrol strain from the soil with infection of
F. oxysporum
f. sp.
momordica
(referred to as Fom),
Talaromyces purpurogenus
Q2 (referred to as TpQ2), which could be effective to reduce relative abundance of the rhizospheric Fom, leading to a significant decrease of
Fusarium
wilt disease incidence in bitter gourd during the greenhouse and field trails. TpQ2 can reduce the relative abundance of rhizospheric Fom through inhibition of growth and development of Fom. During the co-cultivation of TpQ2 and Fom, we confirmed that TpQ2 could significantly suppress the growth and development of Fom through disturbing the normal hyphae shape and function of the cell walls of Fom
via
secreting cell wall–degrading enzymes and suppression of the expression of cell wall biosynthesis genes, such as
FomCFEM
. In the meantime, TpQ2 showed a strong negative correlation with
F. oxysporum
in soil and positive correlation with beneficial indigenous microorganisms that had significant negative correlation with
Fusarium
populations, such as
Streptomycetes, Lysobacter
, and
Sphingobium.
To summarize, TpQ2 has a good biocontrol efficacy on
Fusarium
wilt of bitter gourd. The biocontrol mechanisms of TpQ2 on
Fusarium
wilt are complex and diverse.
Copper and its alloys are used widely in marine environments, and anisotropic corrosion influences the corrosion kinetics of copper. Corrosion of copper in an electrolyte containing Cl- is described ...as a dissolution-deposition process, which is a prolonged process. Therefore, it is laborious to clarify the corrosion anisotropy in different stages. In this paper, electrochemical impedance spectroscopy (EIS) following elapsed open circuit potential (OCP) test with 0 h (0H), 24 h (24H) and 10 days (10D) was adopted. To exclude interruptions such as grain boundary and neighbor effect, single crystal (SC) Cu(100) and Cu(111) were employed. After 10D OCP, cross-sectional slices were cut and picked up by a focused ion beam (FIB). The results showed that the deposited oxide was Cu
O and Cu(100)/Cu(111) experienced different corrosion behaviors. In general, Cu(100) showed more excellent corrosion resistance. Combined with equivalent electrical circuit (EEC) diagrams, the corrosion mechanism of Cu(100)/Cu(111) in different stages was proposed. In the initial stage, a smaller capacitive loop of Cu(111) suggested preferential adsorption of Cl- on air-formed oxide film on Cu(111). Deposited oxide and exposed bare metals also played an important role in corrosion resistance. Rectangle indentations and pyramidal structures formed on Cu(100)/Cu(111), respectively. Finally, a perfect interface on Cu(100) explained the tremendous capacitive loop and higher impedance (14,274 Ω·cm
). Moreover, defects in the oxides on Cu(111) provided channels for the penetration of electrolyte, leading to a lower impedance (9423 Ω·cm
) after 10D corrosion.
The effect of shot peen forming on the corrosion-resistant of 2024 aluminum alloy in a salt spray environment was studied with an electrochemical workstation. The surface morphology and cross ...sectional morphology of the original and shot peen-formed sample were studied by a scanning electron microscope. After shot peen forming, the salt spray corrosion resistance of 2024 aluminum alloy was worsened (the corrosion rates of the original alloy and the shot peen-formed alloy were 0.10467 mg/(cm
·h) and 0.27333 mg/(cm
·h), respectively, when the salt spray corrosion time was 5 h). The radius of capacitive reactance arc of the sample subjected to shot peen forming was smaller than that of the original sample. When the salt spray corrosion time was 5 h, the doping density (
) of the original alloy was 2.5128 × 10
/cm
. After shot peen forming, the
of the alloy increased to 15 × 10
/cm
. For the shot peen-formed sample, pitting corrosion first occurred in the crater lap zone and became severe with salt spray time. The cross sectional morphology of both original and the shot peen-formed samples shows that severe intergranular corrosion occurred in the salt spray environment. However, for the original sample, the intergranular corrosion distribution was lamellar. For shot peen-formed sample, the intergranular corrosion distribution was network.
Nickel-based alloy coating was deposited on AISI 304L stainless steel substrate using plasma transferred arc welding (PTAW). Microstructure and tribological characteristics of the coating were ...studied. The as-deposited microstructure mainly consists of Ni-rich γ (Ni, Fe) phase, Cr7C3, CrB, Cr3C2, M23C6, Ni3B, and Ni3Si. Compared with that of the 304L stainless steel substrate, the wear resistance of the coating greatly improves. The wear test demonstrates that the wear mechanism depends on wearing time and applied load. When the wearing time is short, the wear mechanism is abrasive wear under low load and adhesive wear under high load. When the time is relatively long, the wear mechanisms are adhesive wear and oxidation wear under low load; fatigue wear appears under high load.
► The surfacing of Ni50 alloy was deposited on the surface of 304L by PTAW process. ► The microstructure and tribological characteristic of the surfacing were researched. ► The wear resistance of as-deposited surfacing had been greatly improved. ► The main wear mechanism depended on the wearing time and the applied load.
Ti2AlNb-based composites are a great choice for achieving high-temperature properties by introducing reinforcement to meet engineering application requirements. In this study, Ti–22Al–25Nb (at.%) ...alloys and nano-Al2O3/Ti–22Al–25Nb composites were prepared by mechanical alloying (MA) and hot pressing (HP). The effects of sintering temperature on the microstructure and mechanical properties of Ti–22Al–25Nb alloys and Ti2AlNb-based composites were investigated. The sintering temperature effectively regulated the morphology and size of the primary O phase. The addition of Al2O3 particles refined the grain size of the matrix and precipitates, and it induced the phase transformation. When the sintering temperature reached 1350 °C, Ti–22Al–25Nb alloys and Ti2AlNb-based composites obtained a fine and uniform equiaxed microstructure. The hardness and ultimate compressive strength of the composite first increased and then decreased with increasing sintering temperature. Since the addition of Al2O3 particles promoted the precipitation of the ultrafine acicular O phase from the B2 phase, the composite sintered at 1350 °C had the optimal mechanical properties. The hardness of the Ti–22Al–25Nb alloy and Ti2AlNb-based composite was 4.12 GPa and 5.1 GPa, respectively. The ultimate compressive strength of the composite at room temperature (RT) and 650 °C was 2642.3 MPa and 2462.5 MPa, which was 25.8% and 9.6% higher than that of the Ti2AlNb alloy. The strengthening mechanism of the composites mainly includes dispersion strengthening and Orowan strengthening of the nano-Al2O3 particles, as well as precipitation strengthening of the acicular O phase. This study provides a theoretical guidance for designing Ti2AlNb-based composites with excellent high-temperature properties.
In this study, the compressive deformation of zirconia toughened alumina (ZTA) ceramics doped with different amounts of TiO2 dopants were investigated in the temperature range of 1300–1400 °C to ...evaluate the stress exponent (n value) and apparent deformation activation energy (Q value). With 0–8 wt.% TiO2 dopants, the n values and Q values of the TiO2-doped ZTA ceramics were calculated as 2–3 and 605–749 kJ/mol, respectively. Moreover, three grain boundary features were observed in these deformed materials, named the clean grain boundary, thin liquid phase grain boundary, and thick liquid phase grain boundary. Based on the deformation behavior and microstructure evolution, it was found that the lower apparent activation energy and higher strain rate of TiO2-doped ZTA ceramics are intensively related to the grain boundary feature.
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