Redetermination of the Eutectic Composition of the Co-Sn Binary Alloy

Abstract

A series of Co-Sn alloys was solidified. It was found that the as-cast microstructure of the Co-20.5at.%Sn alloy, which on the basis of literature reports has long been thought to be the eutectic composition, contains much primary phase besides lamellar eutectics. The cooling curve of this alloy contains two exothermic peaks. In contrast, when a Co-24.0at.%Sn alloy was solidified, an entire lamellar eutectic was obtained in the as-cast microstructure. Also, the thermal analyses indicate that there is only one solidification reaction in this alloy. It is suggested that the actual eutectic composition of the Co-Sn system is around Co-24.0at.%Sn, and the corresponding eutectic temperature is about 1385 K.

Anomalous eutectic formation in the solidification of undercooled Co–Sn alloys

“…The experimental materials were Co-20at%Sn hypo-eutectic alloy, Co-24at%Sn eutectic alloy [25] and Co-28at%Sn hypereutectic alloy. The alloy ingots were prepared by arc melting Co and Sn of 99.999 wt% and 99.99 wt% purities, respectively, in a Ti-gettered argon atmosphere.…”

“…2a). According to the Co-Sn binary phase diagram [25], the phases in the microstructure are rather complex as solid-state phase transformations may be involved in the post-solidification cooling process, especially at slow cooling rates. So the samples solidified at low and large undercoolings respectively were analyzed through XRD, and the results indicate that four phases, a-Co, b-Co 3 Sn 2 , e-Co and a-Co 3 Sn 2 coexist in the microstructure (Fig.…”

Structural studies of liquid Co–Sn alloys

“…Meanwhile according to the different works the melting temperatures for key compositions have dissimilar values such as Co 3 Sn 2 compound (∼1473 K [1] , ∼1443 K [2,3] , and ∼1453 K [4,5] ) as well as an eutectic point (∼1398 K [1] , ∼1385 K [2,3] , ∼1323 K [4] , and ∼1376 K [5] ). Moreover the composition of the eutectic point is also under discussion [6] . The mentioned above discrepancies in the data could be connected with experimental difficulties due to a high diffusion of the cobalt in tin [7] , meanwhile in [8] is mentioned the very small diffusion mobility of the Co atoms in the Co-based alloys.…”

Strong magnetic field effect on the nucleation of a highly undercooled Co-Sn melt

“…%), is shown to be hypereutectic in Co-Sn binary phase diagram 23 , but determined to be the eutectic point by Liu and Li et al . 24 . According to Fig.…”