The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up...The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.展开更多
Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the...Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the mechanical properties of nanocomposites, such as the nanolayer, matrix and nanolayer/matrix interface. How to contribute to the mechanical properties of nanocomposite film is a very complex problem. In this paper, these factors are analyzed based on the addition amount and fracture mechanics. The results indicate that the specimen at 20 wt% MMT breaks prematurely with a fracture strength （σb = 78 MPa） much lower than that （σb = 128 MPa） at the 1 wt% MMT. However, the Young＇s modulus （3.2 GPa） of the former is higher than that （1.9 GPa） of the latter. Fractography also indicates that the brittle cracking formed in high content addition is the main cause of failure but microscopically ductile fracture morphology still exists locally. And for the trace element addition, the smaller threading slipping veins are evenly distributed on the entire fracture section of these films. Therefore, these characteristics would presumably be associated with both the concentration effects of size of nanocomposite sheets and the increasing deformation harmony in nanolayers.展开更多
文摘The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.
基金Project supported by the National Basic Research Program of China (No.2004CB619304)the Hundred TalentsProgram of Chinese Academy of Sciences, Key Research Programme of Beijing City Science and Technology Committee(No.H020420020230).
文摘Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the mechanical properties of nanocomposites, such as the nanolayer, matrix and nanolayer/matrix interface. How to contribute to the mechanical properties of nanocomposite film is a very complex problem. In this paper, these factors are analyzed based on the addition amount and fracture mechanics. The results indicate that the specimen at 20 wt% MMT breaks prematurely with a fracture strength （σb = 78 MPa） much lower than that （σb = 128 MPa） at the 1 wt% MMT. However, the Young＇s modulus （3.2 GPa） of the former is higher than that （1.9 GPa） of the latter. Fractography also indicates that the brittle cracking formed in high content addition is the main cause of failure but microscopically ductile fracture morphology still exists locally. And for the trace element addition, the smaller threading slipping veins are evenly distributed on the entire fracture section of these films. Therefore, these characteristics would presumably be associated with both the concentration effects of size of nanocomposite sheets and the increasing deformation harmony in nanolayers.
