Articles written in Bulletin of Materials Science
Volume 23 Issue 3 June 2000 pp 185-188
Volume 23 Issue 3 June 2000 pp 215-219
Volume 32 Issue 5 October 2009 pp 527-529 Alloys
The Fe-based multicomponent amorphous alloys (also referred to as metallic glasses) are known to exhibit soft magnetic properties and, it makes them important for many technological applications. However, metallic glasses are in a thermodynamically metastable state and in case of high temperature operating conditions, the thermally activated crystallization would be detrimental to their magnetic properties. The study of crystallization kinetics of metallic glasses gives useful insight about its thermal stability. In the present work, crystallization study of Fe67Co18B14Si1 (2605CO) metallic glass has been carried out using differential scanning calorimetry (DSC) technique. Mössbauer study has also been undertaken to know the phases formed during the crystallization process. The alloy shows two-stage crystallization. The activation energy has been derived using the Kissinger method. It is found to be equal to 220 kJ/mol and 349 kJ/mol for the first and second crystallization peaks, respectively. The Mössbauer study indicates the formation of 𝛼-(Fe, Co) and (Fe, Co)3B phases in the alloy.
Volume 38 Issue 7 December 2015 pp 1693-1698
A quantitative measure of the stability of a glass as compared to its corresponding crystalline state can be obtained by calculating the thermodynamic parameters, such as the Gibbs free energy difference (𝛥𝐺), entropy difference (𝛥𝑆) and the enthalpy difference (𝛥𝐻) between the super-cooled liquid and the corresponding crystalline phase. 𝛥𝐺 is known as the driving force of crystallization. The driving force of crystallization (𝛥𝐺) provides very important information about the glass-forming ability (GFA) of metallic glasses (MGs). Lesser the driving force of crystallization more is the GFA. The 𝛥𝐺 varies linearly with the critical size (𝑑𝑐). According to Battezzati and Garonne the parameter 𝛾 ( = (1−(𝛥𝐻𝑥/𝛥𝐻𝑚))/(1−(𝑇 𝑥/𝑇 𝑚))) in the expression for 𝛥𝐺 should be a constant (i.e., 0.8), but its uniqueness is not observed for all MGs. The thermal stability of various alloy compositions is studied by their undercooled liquid region (𝛥𝑇 = 𝑇 𝑥 − 𝑇 𝑔). Large 𝛥𝑇 𝑥 implies greater stability against crystallization of the amorphous structure. Other GFA parameters are also calculated and correlated with critical size (𝑑𝑐).
Volume 42 | Issue 6
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