The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
C K Sha - One of the best experts on this subject based on the ideXlab platform.
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microstructural feature thermal shock resistance and isothermal oxidation resistance of nanostructured zirconia coating
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Wenyang Wang, C K ShaAbstract:Nanostructured and conventional zirconia coatings on superalloys have been deposited to show thermal shock resistance and oxidation resistance by atmospheric plasma spraying. The results showed that the nanostructured zirconia coating mainly contained two kinds of microstructures, nanosized zirconia particles embedded in the matrix and micrometer-sized Columnar Grain structures of zirconia similar to those of conventional zirconia coating. Compared with the conventional zirconia coating, the nanostructured coating is denser and has finer and less porous structure and fewer microcracks with higher thermal shock resistance and isothermal oxidation resistance. With increasing zirconia coating thickness from 100 to 500 μm, the thermal shock resistance of both nanostructured and conventional coatings decreased. The increased properties of nanostructured zirconia coating are related to improved toughness and decreased porosity and microcrack of the coating.
Sharvan K Kumar - One of the best experts on this subject based on the ideXlab platform.
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relation of sn whisker formation to intermetallic growth results from a novel sn cu bimetal ledge specimen
Journal of Materials Research, 2009Co-Authors: L Reinbold, Nitin A Jadhav, E Chason, Sharvan K KumarAbstract:Sn whisker formation was studied in a “bimetal ledge specimen” that consisted of a uniform layer of Sn that was covered by Cu on only half the sample. Whiskers are observed to grow in the Cu-free region of the sample, which is attributed to stress generated by the diffusion of Sn atoms along the network of Columnar Grain boundaries. The Sn diffusion is driven by intermetallic growth, but the whisker density extends out much further than any measurable Cu concentration. Whiskers were also observed to grow in the Cu-coated region by punching through the overlayer, leaving a Cu-Grain on the tip of the Sn whisker.
Jianlei Cui - One of the best experts on this subject based on the ideXlab platform.
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influence of Columnar Grain microstructure on thermal shock resistance of laser re melted zro2 7 wt y2o3 coatings and their failure mechanism
Surface & Coatings Technology, 2015Co-Authors: Zhengjie Fan, Kedian Wang, Xia Dong, Wenqiang Duan, Xuesong Mei, Wenjun Wang, Jianlei CuiAbstract:Abstract In this study, influence of Columnar Grain morphology on thermal shock resistance of laser re-melted ZrO 2 -7 wt.% Y 2 O 3 thermal barrier coatings (TBCs) has been researched. The influence of variation in Columnar Grain microstructures on the fatigue mechanism of laser re-melted coatings in thermal shock experiments has been investigated. The thermal shock experiments have confirmed the positive effect of small Grain size on thermal fatigue life. This is thought to have resulted from an increase in the number of Grain boundaries that restrict the Grain motion during deformation. Further, “void effect” could be responsible for promoting peeling of the laser re-melted coatings when spallation is less than 10% because it can cause a relatively large tensile stress between the Columnar Grains and the underlying splats. However, it is found to have negligible effect on the shedding of LRCs shed when the spallation percentage is 20% or more because the remaining LRCs are relatively homogeneous having less or no voids. The presence of separate columns and large intergranular clearance may have allowed better compliance of stress through free-movement of the individual Columnar Grains. There are many more restrictions on stress relaxation. An additional moving resistance is found to be present at the undulate intergranular interfaces for the irregular gear-like Columnar Grains with small inter-crystalline space and large intergranular contact area. The one-piece structure with pseudo-Columnar Grains was found to improve the thermal cycle lifetime slightly. It is believed to be due to its relatively lower strain tolerance as well as lower fracture toughness as compared to that of the structure with separate Columnar Grains.
Q. Liu - One of the best experts on this subject based on the ideXlab platform.
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Deformation strain inhomogeneity in Columnar Grain nickel
Scripta Materialia, 2005Co-Authors: Andrew Godfrey, D. Juul Jensen, Q. LiuAbstract:Abstract A method is presented for determination of the local deformation strain of individual Grains in the bulk of a Columnar Grain sample. The method, based on measurement of the change in Grain area of each Grain, is applied to 12% cold rolled nickel. Large variations are observed in the local strain associated with each Grain.
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macroscopic subdivision of Columnar Grain aluminium with 001 uv0 orientations following low strain deformation
Scripta Materialia, 2001Co-Authors: Andrew Godfrey, Wei Liu, Q. LiuAbstract:Abstract Macroscopic Grain sub-division in Columnar Grain A1 with {0 0 1}〈u v 0〉 orientations was studied. Significant differences, both between Columnar Grains of similar orientation, and between the Columnar Grains and equivalent single crystals were observed. These differences can be attributed to either differing initial orientations and/or Grain–Grain interactions during deformation.
Chih Chen - One of the best experts on this subject based on the ideXlab platform.
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deformation induced Columnar Grain rotation in nanotwinned metals
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: Chia Wei Hsu, Yi Hsin Ting, Nienti Tsou, Chih ChenAbstract:Abstract A significant Grain rotation in 111 >-oriented nanotwinned Cu film under tensile test at room temperature is reported. After rotation, the dislocation network in low angle tilt-type boundaries increases the strain energy, which provides the driving force for recrystallization in a subsequent annealing, resulting in the formation of millimeter size Grains.
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effect of reverse currents during electroplating on the oriented and nanotwinned Columnar Grain growth of copper films
Crystal Growth & Design, 2020Co-Authors: Kuanju Chen, Chih ChenAbstract:Nanotwinned copper (nt-Cu) has been attracting a great deal of attention in the past decades due to its excellent mechanical and electrical properties. In this study, a new approach, periodic-rever...
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Tensile Properties of -Oriented Nanotwinned Cu with Different Columnar Grain Structures
Materials, 2020Co-Authors: Chih ChenAbstract:We performed tensile tests on highly -oriented nanotwinned copper (nt-Cu) foils with different Columnar Grain structures. For a systematic study, we altered the microstructure of the foils by tuning the electroplating electrolyte and annealing temperatures under a nitrogen atmosphere. The results show that the yield strength ranges from 300 to 700 MPa, and elongation spans from 5% to 25%. Knowing the measured twin spacing and average Grain size, and combining the confined layer slip with the Hall–Petch equation, we calculated the theoretical yield strength of the nt-Cu with different microstructures, and the theoretic values match the experiment results. Owing to the unique crystal orientation properties of -oriented Columnar Grains, dislocations induced by slip are very limited. The Schmid factor of Grains along the tensile axis direction is highly identical, so the plastic deformation is much more suitably explained by the Schmid factor model. Thus, we replace the Taylor factor with the Schmid factor in the slip model of nt-Cu.