Effect of driving force of crystallization on critical cooling rate for Pd-based metallic glasses

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• 作者：Sonal R. Prajapati ; Supriya Kasyap…
• 关键词：Bulk metallic glasses (BMG) ; Glass forming ability (GFA) ; Critical cooling rate (Rc) ; Gibbs free energy difference ; Time ; temperature transformation (TTT) curves
• 刊名：Journal of Thermal Analysis and Calorimetry
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：127
• 期：3
• 页码：2083-2091
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Physical Chemistry; Analytical Chemistry; Polymer Sciences; Inorganic Chemistry; Measurement Science and Instrumentation;
• 出版者：Springer Netherlands
• ISSN：1588-2926
• 卷排序：127

文摘

The advent of bulk metallic glasses (BMG) has opened lot of scope of wide range of applications for this class of amorphous materials. Thermodynamics plays a very important role in glass formation in multicomponent metallic alloys. BMG’s can be synthesized with relatively lower cooling rate with ease now. However, the glass formation in these systems seems to depend on quite a few parameters like enthalpy of melting, reduced glass transition temperature, under cooling. In present paper, we have studied the glass forming ability of Pd-based metallic glasses using theoretically determined Gibbs free energy difference (ΔG), between the supercooled liquid and the corresponding crystalline phase, and the critical cooling rate (R_c). Time–temperature-transformation (TTT) diagrams were constructed to calculate R_c using Uhlmann and Davies formulation. Different theoretical expressions of ΔG are incorporated in nucleation and growth equations to find R_c from TTT diagram. The results obtained theoretically by Dhurandhar et al. expression of ΔG, assuming hyperbolic variation of specific heat difference (ΔC_p), were found to be in excellent agreement with experimental data for different Pd-based systems.