Curie temperature behaviour at relaxation and nanocrystallization of Finemet alloys

• Published in: Journal of alloys and compounds 2011-06, Vol.509, p.S400-S403
• Main Authors: Kaloshkin, Sergey, Churyukanova, Margarita, Zadorozhnyi, Vladislav, Shchetinin, Igor, Roy, Rajat Kumar
• Format: Article
• Language: English
• Subjects: Activation energy; Alloys; Amorphous materials; Amorphous structure; Annealing; Calorimetry; Curie temperature; Differential scanning calorimetry; Ferrous alloys; Nanocrystals; Nanostructure; Nanostructures
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2011.01.090

► Relaxation and nanocrystallization of Finemet-type amorphous alloys is studied. ► DSC is used for control heat capacity in the Curie point (Tc). ► Tc is very sensitive to relaxation and crystallization processes. ► Nanocrystallization results in degradation of Tc heat capacity peak. ► Activation energies of relaxation and nanocrystallization are estimated. Dependence of Curie temperature (Tc) on time and temperature of annealing for Finemet-type amorphous alloys is studied by DSC. Structural relaxation of an amorphous phase at annealing is accompanied by increase of Tc. The σ-shaped time dependencies, however, are not characterized by the definite final value of Tc: long-term annealing of amorphous phase results in continuation of slow increase of Tc for every temperature. Apparent values of activation energy of relaxation were evaluated from the Tc time–temperature dependencies. It is found that the average value of activation energy increases with progress of the relaxation process. Correlation of the Tc data with structural alterations reflects redistribution of components in amorphous phase during annealing. Further increase of the annealing temperature results in precipitation of α-Fe(Si) nanograins in an amorphous matrix, that accompanied by gradual degradation of corresponding to Tc heat capacity peak. DSC measurements of Tc allow to detect the starting moment of amorphous phase crystallization.