The low valence electron concentration(VEC)Al_(x)CoCrFeNiSi(x=0.5,1.0,1.5 and 2.0)high-entropy alloys(HEAs)were designed by the fundamental properties of the constituent elements and prepared by vacuum arc melting met...The low valence electron concentration(VEC)Al_(x)CoCrFeNiSi(x=0.5,1.0,1.5 and 2.0)high-entropy alloys(HEAs)were designed by the fundamental properties of the constituent elements and prepared by vacuum arc melting method.The effects of Al addition on the crystal structure and microstructure were investigated.The microhardness and wear property were also researched.The results showed that the microstructure transformed from dendritic crystal to equiaxed crystal.It was found that FCC phase gradually decreased with the increasing Al content and disappeared until in a composition of 1.0 in Al_(x)CoCrFeNiSi HEAs.Little FCC phase was found with continuously adding Al,while the phase fraction of BCC increased from 85.0% to 91.8%,and VEC decreased from 7.00 to 6.14.The microhardness was increased gradually from 598 up to 909 HV with addition of Al from 0.5 to 2.0.It was the same of the compressive strength results,which improved from 1200 to 1920 MPa.The wear coefficient and mass loss were in line with mechanical properties evolution,which was attributed to the microstructure transformation into equiaxed crystal and the increase in BCC phase.展开更多
ZrO2-MgO-YzO3-CaO-Al203 composites with a multiphase microstructure were fabricated by die pressing process and sintered at various thermal programs. The microstructure of this polycrystalline was examined to clarify ...ZrO2-MgO-YzO3-CaO-Al203 composites with a multiphase microstructure were fabricated by die pressing process and sintered at various thermal programs. The microstructure of this polycrystalline was examined to clarify the role of A1203 on grain growth. Environmental scanning electron microscopy （ESEM） micrographs revealed that spinel was beneficial to refine grain. The effect of thermal treatment on the formation of monoclinic phase was discussed. It can be found that, the grain size and the fraction of the monoclinic phase in this partially stabilized zirconia（PSZ） increases after heat treatment at 1 150 ℃. The temperature of heat- treatment, not the time for holding, is the governing factor of the fraction of monoclinic phase.展开更多
We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corre...We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corresponding capillary absorption of CAC-anhydrite mortars were revealed.The composition and microstructure of efflorescence-causing substances were investigated by optical microscope,in-situ Raman spectroscopy,scanning electron microscope,energy dispersive spectrometer,thermogravimetric analysis,and differential scanning calorimetry,at multi-scales.Results indicate that,besides the calcium carbonate,ettringite is another main component of efflorescence-causing substances.Compared with the neat CAC mortars,the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure.In addition,methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system.展开更多
基金financially supported by the Natural Science Foundation of Liaoning Province(No.2019-MS-247)the Liaoning Revitalization Talents Program(XLYC1807178).
文摘The low valence electron concentration(VEC)Al_(x)CoCrFeNiSi(x=0.5,1.0,1.5 and 2.0)high-entropy alloys(HEAs)were designed by the fundamental properties of the constituent elements and prepared by vacuum arc melting method.The effects of Al addition on the crystal structure and microstructure were investigated.The microhardness and wear property were also researched.The results showed that the microstructure transformed from dendritic crystal to equiaxed crystal.It was found that FCC phase gradually decreased with the increasing Al content and disappeared until in a composition of 1.0 in Al_(x)CoCrFeNiSi HEAs.Little FCC phase was found with continuously adding Al,while the phase fraction of BCC increased from 85.0% to 91.8%,and VEC decreased from 7.00 to 6.14.The microhardness was increased gradually from 598 up to 909 HV with addition of Al from 0.5 to 2.0.It was the same of the compressive strength results,which improved from 1200 to 1920 MPa.The wear coefficient and mass loss were in line with mechanical properties evolution,which was attributed to the microstructure transformation into equiaxed crystal and the increase in BCC phase.
文摘ZrO2-MgO-YzO3-CaO-Al203 composites with a multiphase microstructure were fabricated by die pressing process and sintered at various thermal programs. The microstructure of this polycrystalline was examined to clarify the role of A1203 on grain growth. Environmental scanning electron microscopy （ESEM） micrographs revealed that spinel was beneficial to refine grain. The effect of thermal treatment on the formation of monoclinic phase was discussed. It can be found that, the grain size and the fraction of the monoclinic phase in this partially stabilized zirconia（PSZ） increases after heat treatment at 1 150 ℃. The temperature of heat- treatment, not the time for holding, is the governing factor of the fraction of monoclinic phase.
基金Funded by the National Key Research and Development Program of China(No.2022YFC3803400)National Natural Science Foundation of China(Nos.52378255,52278270)+1 种基金Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Fundamental Research Funds for the Central Universities and the Experimental Center of Materials Science and Engineering in Tongji University。
文摘We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corresponding capillary absorption of CAC-anhydrite mortars were revealed.The composition and microstructure of efflorescence-causing substances were investigated by optical microscope,in-situ Raman spectroscopy,scanning electron microscope,energy dispersive spectrometer,thermogravimetric analysis,and differential scanning calorimetry,at multi-scales.Results indicate that,besides the calcium carbonate,ettringite is another main component of efflorescence-causing substances.Compared with the neat CAC mortars,the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure.In addition,methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system.
