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Effect of Y_2O_3 on cracking susceptibility of Laser-Clad Ti-Based Composites Coatings

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Journal of Wuhan University of Technology(Materials Science) 2014年第5期29卷 1011-1018页

作者：李军 LI Guangjie LUO Xing School of Materials Engineering Shanghai University of Engineering Science

Ti-based composite coatings reinforced by in situ synthesized TiB and TiC were deposited on Ti6AlaV substrates by laser cladding. The effects of Y2O3 on the microstructure and cracking susceptibility of the coatings were investigated in details. It is shown that a small amount of Y2O3 addition can significantly refine the microstructure of the coatings by hastening spheroidization of the primary phase structure. The maximum refinement in microstructure was obtained with the optimum （2 wt%） addition of Y2O3. Moreover, it can increase the volume fraction of TiC and reduce the residual stress of the coatings due to the decrease in lattice distortion of the α（Ti） matrix. All of these factors lead to the reduction in cracking susceptibility of the coatings containing Y2O3 on the premise that the hardness of the coatings is improved. The fracture toughness of the coatings without and with Y2O3 （2 wt%） is 8.32 and 17.36 MPa.m1/2, respectively. Scanning electron microscope examination reveals a transition of the fractured surfaces from cleavage fracture to quasi-cleavage fracture resulting from the Y2O3 addition.

关键词： laser cladding coating microstructure cracking susceptibility

Evaluation of the cracking and aging susceptibility of asphalt mixtures using viscoelastic properties and master curve parameters

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Journal of Traffic and Transportation Engineering(English Edition) 2022年第1期9卷 106-119页

作者： Runhua Zhang Jo E.Sias Eshan V.Dave Department of Civil and Environmental Engineering University of New HampshireDurhamNH 03824USA

Aging can significantly affect the performance of asphalt mixtures, causing increase in stiffness, reduction in relaxation capability and increase in cracking susceptibility. It is also well known that fundamental viscoelastic properties are used for design and modelling of asphalt mixtures and pavement structures to addressing rutting, fatigue and thermal cracking concerns. The objective of this paper is to study how the viscoelastic properties of asphalt mixture change over time, and evaluate and identify the cracking and aging susceptibility of asphalt mixtures with different mix variables during material selection and mixture design. Ten mixtures are evaluated using different laboratory conditioning protocols to simulate a range of aging levels in the field. The complex modulus test is then conducted on the lab aged mixtures to measure the viscoelastic properties in order to construct the dynamic modulus and phase angle master curves. The mixture Glover-Rowe(G-Rm) parameter and the shape parameters of the dynamic modulus and phase angle master curves, including inflection point frequency(-β/γ), difference between the glassy modulus and the inflection point modulus(γ), peak value of phase angle(a) and the horizontal position(frequency) of the peak phase angle value(c), are determined and evaluated for the mixtures with different aging conditions and mix variables. The study indicates the ability of the G-Rmparameter and all the master curve shape parameters to capture the effect of different aging conditions on linear viscoelastic mixture properties, as well as the cracking and aging susceptibility of asphalt mixtures.

关键词： Asphalt mixture Viscoelastic properties Complex modulus and phase angle master curve Master curve shape parameters Aging susceptibility cracking susceptibility

Residual stress distribution in different depths of TiNi/Ti_2Ni-based laser clad coating prepared at different environmental temperatures

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Transactions of Nonferrous Metals Society of China 2017年第9期27卷 2043-2054页

作者： Yang-feng TAO Jun LI Ying-hao Lü Lie-feng HU School of Materials Engineering Shanghai University of Engineering Science Shanghai 201620 China

This study aimed to effectively reduce the cracking susceptibility of the laser clad coating by enhancing the environmental temperature during laser cladding,and reveal the residual stress distribution in different depths of the *** TiNi/Ti2Ni-based coatings were prepared on Ti6Al4V by laser cladding at different environmental temperatures of25,400,600and800°*** changes in residual stress along the depth of the coatings were investigated in detail by the nanoindentation *** showed that the average residual stress of2.90GPa in the coating prepared at25°C was *** the increase in environmental temperature,the average residual stress was reduced to1.34GPa(400°C),0.70GPa(600°C)and0GPa(800°C).For all the coatings,the residual stress was increased with increasing the distance from the coating *** the environmental temperature can effectively reduce the cracking susceptibility of the coatings.

关键词： laser cladding coating microstructure environmental temperature cracking susceptibility residual stress nanoindentation