Effect of Cu and Co addition on non-isothermal crystallization kinetics of rapidly quenched Fe-Sn-B based alloys

Crystallization kinetics of rapidly quenched Fe-Sn-B alloys under non-isothermal conditions were studied using differential scanning calorimetry. Formation of crystalline phases was analyzed by X-ray diffraction. Nominal chemical compositions were Fe81Sn7B12, (Fe3Co1)81Sn7B12 and (Fe81Sn7B12)99Cu1. Alloys were prepared by planar flow casting in the form of ribbons approximately 20 mu m thick and 6 mm wide. Mechanism of crystal-lization was studied under framework of the Johnson-Mehl-Avrami-Kolmogorov model. Alloys exhibit two stages of crystallization. Results show decrease in activation energy of the first stage of crystallization with addition of Cu and increase with addition of Co. Crystallization mechanism of the first stage of crystallization for Fe81Sn7B12 and (Fe81Sn7B12)99Cu1 alloy starts as growth with increasing nucleation rate and continues as growth with decreasing nucleation rate. Addition of Co changes mechanism of crystallization. Which in case of (Fe3Co1)81Sn7B12 alloy starts as a growth with increasing nucleation rate. Then changes to growth with decreasing nucleation rate. After which nucleation rate decreases to zero. Rest of crystallization stage is governed by growth of pre-existing nuclei. In the first stage of crystallization alpha-Fe phase with bcc structure crystallizes from amorphous matrix. In the second stage of crystallization the remaining amorphous matrix crystalizes into tetragonal Fe2B phase and hexagonal FeSn phase. After the first stage of crystallization, 50 % to 55 % volume of studied alloys were crystalized. Addition of Cu decreases crystalline size of alpha-Fe crystallites by 60 % and de-creases concentration of Sn in alpha-Fe phase by 0.8 at. %. Addition of Co doesn't affect the size of alpha-Fe crystallites and decreases the concentration of Sn in alpha-Fe phase by 1.7 at. %.

Automated summary

The crystallization kinetics of rapidly quenched Fe-Sn-B alloys under non-isothermal conditions were studied in this research. Two stages of crystallization were observed in the alloys. The addition of Cu decreased the activation energy of the first stage, while the addition of Co increased it. The crystallization mechanism of Fe81Sn7B12 and (Fe81Sn7B12)99Cu1 alloys involved an increase and subsequent decrease in nucleation rate, whereas the mechanism of (Fe3Co1)81Sn7B12 alloy initially showed an increase in nucleation rate and then a decrease, followed by a decrease to zero. The first stage of crystallization resulted in the formation of alpha-Fe phase with bcc structure from the amorphous matrix, while the second stage led to the crystallization of tetragonal Fe2B phase and hexagonal FeSn phase. The addition of Cu reduced the size of alpha-Fe crystallites by 60% and the concentration of Sn in alpha-Fe phase by 0.8 at. %, while the addition of Co had no effect on the size of alpha-Fe crystallites but decreased the concentration of Sn in alpha-Fe phase by 1.7 at. %.