Ti_3Al+Si+Nb alloys containing Ti_5Si_3 have the potential in ductility improvements. In this paper, the fracture mechanism of this alloy is under investigation. Three kinds of alloys in the as rolled condition were p...Ti_3Al+Si+Nb alloys containing Ti_5Si_3 have the potential in ductility improvements. In this paper, the fracture mechanism of this alloy is under investigation. Three kinds of alloys in the as rolled condition were prepared for determination of KIC values and calculation of J-resistance curves. The results show that the morphology of Ti_5Si_3 has a great influence on the KIC. values of the alloys and crack growth resistance. The fracture mechanism is controlled by Ti_5Si_3 particles.展开更多
The corrosion behavior of corrosion resistant steel(CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel(CS) using corrosion loss, polarization curves, X-ray diffract...The corrosion behavior of corrosion resistant steel(CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel(CS) using corrosion loss, polarization curves, X-ray diffraction(XRD), scanning electron microscopy(SEM), electron probe micro-analysis(EPMA), N2 adsorption, and X-ray photoelectron spectroscopy(XPS). The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-Fe OOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO2, Cu2O, CrOOH, NiFe2O4, and Ni2O3, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.展开更多
The high strength and toughness of natural materials are mainly determined by a combination of mechanisms operating at different length scales,which can be used as a strategy to reduce the intrinsic brittleness of cer...The high strength and toughness of natural materials are mainly determined by a combination of mechanisms operating at different length scales,which can be used as a strategy to reduce the intrinsic brittleness of ceramics.Inspired by the architectures of bamboo,the polycrystalline cubic boron nitride/hexagonal boron nitride(PcBN/hBN)fibrous monolithic ceramics with a long fiber arrangement structure was constructed with PcBN fiber cells and hBN cell boundaries,and its crack resistance responses and tribological performances were investigated.The composite ceramic failed in a non-brittle manner with the rising resistance curve(R-curve)behavior,which was attributed to multiscale crack effects in the hierarchical architecture.The maximum crack growth toughness was extremely high(approximately 21 MPa×m^(1/2)),corresponding to a 270%increase over the crack initiation toughness.Excellent fracture resistance could be retained even above 1000℃.Moreover,the composite ceramic exhibited low and stable friction coefficients(approximately 0.33)when paired with a Si_(3)N_(4)pin at high temperature(1000℃),owing to the lubrication function of hBN cell boundaries with weak van der Waals forces and a small amount of liquid B_(2)O_(3)produced.As a result,a synergistic improvement of mechanical and tribological properties at high temperature(1000℃)was realized by combining bionic structure and tribological design.It provides important theoretical and technical support for expanding the application of self-lubricating composite ceramics in harsh environments.展开更多
The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and ene...The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) attached to SEM. Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP. The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels. The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels. The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size. The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about 0.002% oxygen and 0.004% sulfur. Solid-soluble content of rare earth in steels was (14-20)×10-6, which can act as a micro-alloying element. The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test. Their corrosion rates were obtained respectively. The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods. The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth. Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation. The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.展开更多
The influences of Ca and Y additions on the microstructure and corrosion resistance of vacuum die-cast AZ91 alloys were investigated by optical microscope,electron scanning microscope,weight-loss test,and electrochemi...The influences of Ca and Y additions on the microstructure and corrosion resistance of vacuum die-cast AZ91 alloys were investigated by optical microscope,electron scanning microscope,weight-loss test,and electrochemical corrosion experiment.The results indicate that the Ca or Ca and Y additions refined the microstructure and decreased the amount of Mg17Al12 phase on grain boundaries in the alloys.Meanwhile,the addition of Ca and Y led to the formation of network Al2 Ca phase and rod-like Al2 Y phase,improved the corrosion resistance of AZ91 magnesium alloy.Compared with AZ91 alloy,the corrosion rate of AZ91–1.5Ca–1.0Y alloy was decreased to 16.2%,and its corrosion current density was dropped by one order of magnitude after immersion in 3.5 wt% NaCl solution for 24 h.展开更多
Zr and its alloys have excellent mechanical properties as new structural material,but in specific application environment,its corrosion resistance still needs to be further explored.In this work,double glow plasma sur...Zr and its alloys have excellent mechanical properties as new structural material,but in specific application environment,its corrosion resistance still needs to be further explored.In this work,double glow plasma surface alloying technique was used for copperizing on pure Zr surface.Besides,X-ray diffraction(XRD),scanning electron microscope(SEM) and energy dispersion spectrum(EDS) were employed to characterize the samples.Furthermore,research was also conducted on the polarization curve of the samples in different solutions.Copperizing on surface can improve corrosion resistance of pure Zr in 3.5 % Na Cl and 0.5 moláL-1Na OH solutions.Especially in 0.5 moláL-1Na OH solution,the corrosion resistance can achieve significant improvement.However,copperizing has no influence on the improvement of corrosion resistance of pure Zr in 0.5 moláL-1H2SO4 solution.The results may provide new insight into way for improving the corrosion property of zirconium alloys.展开更多
文摘Ti_3Al+Si+Nb alloys containing Ti_5Si_3 have the potential in ductility improvements. In this paper, the fracture mechanism of this alloy is under investigation. Three kinds of alloys in the as rolled condition were prepared for determination of KIC values and calculation of J-resistance curves. The results show that the morphology of Ti_5Si_3 has a great influence on the KIC. values of the alloys and crack growth resistance. The fracture mechanism is controlled by Ti_5Si_3 particles.
基金the funding support from the National Natural Science Foundation of China(No.51571027)
文摘The corrosion behavior of corrosion resistant steel(CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel(CS) using corrosion loss, polarization curves, X-ray diffraction(XRD), scanning electron microscopy(SEM), electron probe micro-analysis(EPMA), N2 adsorption, and X-ray photoelectron spectroscopy(XPS). The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-Fe OOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO2, Cu2O, CrOOH, NiFe2O4, and Ni2O3, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.
基金This work was supported by the National Natural Science Foundation of China(Grant No.52005486)the Science and Technology Planning Project of Chengguan District of Lanzhou City(Grant No.2021JSCX0030)the Major National R&D Projects(Grant No.J2019-IV-0020-0088)。
文摘The high strength and toughness of natural materials are mainly determined by a combination of mechanisms operating at different length scales,which can be used as a strategy to reduce the intrinsic brittleness of ceramics.Inspired by the architectures of bamboo,the polycrystalline cubic boron nitride/hexagonal boron nitride(PcBN/hBN)fibrous monolithic ceramics with a long fiber arrangement structure was constructed with PcBN fiber cells and hBN cell boundaries,and its crack resistance responses and tribological performances were investigated.The composite ceramic failed in a non-brittle manner with the rising resistance curve(R-curve)behavior,which was attributed to multiscale crack effects in the hierarchical architecture.The maximum crack growth toughness was extremely high(approximately 21 MPa×m^(1/2)),corresponding to a 270%increase over the crack initiation toughness.Excellent fracture resistance could be retained even above 1000℃.Moreover,the composite ceramic exhibited low and stable friction coefficients(approximately 0.33)when paired with a Si_(3)N_(4)pin at high temperature(1000℃),owing to the lubrication function of hBN cell boundaries with weak van der Waals forces and a small amount of liquid B_(2)O_(3)produced.As a result,a synergistic improvement of mechanical and tribological properties at high temperature(1000℃)was realized by combining bionic structure and tribological design.It provides important theoretical and technical support for expanding the application of self-lubricating composite ceramics in harsh environments.
基金Project supported by Shandong Natural Science Foundation (ZR2010EQ017)
文摘The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) attached to SEM. Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP. The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels. The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels. The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size. The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about 0.002% oxygen and 0.004% sulfur. Solid-soluble content of rare earth in steels was (14-20)×10-6, which can act as a micro-alloying element. The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test. Their corrosion rates were obtained respectively. The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods. The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth. Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation. The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.
文摘The influences of Ca and Y additions on the microstructure and corrosion resistance of vacuum die-cast AZ91 alloys were investigated by optical microscope,electron scanning microscope,weight-loss test,and electrochemical corrosion experiment.The results indicate that the Ca or Ca and Y additions refined the microstructure and decreased the amount of Mg17Al12 phase on grain boundaries in the alloys.Meanwhile,the addition of Ca and Y led to the formation of network Al2 Ca phase and rod-like Al2 Y phase,improved the corrosion resistance of AZ91 magnesium alloy.Compared with AZ91 alloy,the corrosion rate of AZ91–1.5Ca–1.0Y alloy was decreased to 16.2%,and its corrosion current density was dropped by one order of magnitude after immersion in 3.5 wt% NaCl solution for 24 h.
基金financially supported by the National Basic Research Program of China (No.2013CB733000)the National Natural Science Foundation of China (Nos.51271161,51271162 and 51434008)
文摘Zr and its alloys have excellent mechanical properties as new structural material,but in specific application environment,its corrosion resistance still needs to be further explored.In this work,double glow plasma surface alloying technique was used for copperizing on pure Zr surface.Besides,X-ray diffraction(XRD),scanning electron microscope(SEM) and energy dispersion spectrum(EDS) were employed to characterize the samples.Furthermore,research was also conducted on the polarization curve of the samples in different solutions.Copperizing on surface can improve corrosion resistance of pure Zr in 3.5 % Na Cl and 0.5 moláL-1Na OH solutions.Especially in 0.5 moláL-1Na OH solution,the corrosion resistance can achieve significant improvement.However,copperizing has no influence on the improvement of corrosion resistance of pure Zr in 0.5 moláL-1H2SO4 solution.The results may provide new insight into way for improving the corrosion property of zirconium alloys.