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Binary As–Se glasses with different amounts of As content have been prepared and scanned with different heating rates (3 ≤ ψ ≤ 48 K min−1) over temperatures ranging from 300 to 450 K. Both the glass transition temperature (Tgl) and the temperature peak of crystallization (Tpc) increase as a function of As and/or the ψ values. A good correlation between Tgl and Tpc has been investigated. The observed increase in Tgl and Tpc by increasing the ψ values or as a function of As is well discussed in accordance with Lasocka’s relationship and using the average coordination number Acn, the viscosity at glass transition μ(Tgl) and the overall mean bond energy E. The glass transition Egl and crystallization activation energies (Egl and Epc) were determined based on the changes in Tgl and Tpc values due to the heating rate (ψ). The increase in the values of Egl and Epc with increasing the As content is expected due to the increase in Tgl and Tpc values. The kinetic exponent n and the crystal dimensionality m have been determined.
相似文献The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α ? γ and γ ? α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.
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