Phase transition and nano-mechanical properties of directionally solidified Sn–Co peritectic alloy

Abstract

In this work, directional solidification method was used to investigate the growth characteristics of intermetallic compounds whose solubilities are narrow during solidification of Sn-9at.%Co peritectic alloy (L+CoSn→CoSn2). In this work, the transition of the leading phase during solidification is observed in all samples. By the application of the Interface Response Function (IRF), the calculated velocity range for the transition of the primary phase by the peritectic phase ranges from 0.501 μm/s to 398 μm/s. Moreover, the phase transition of CoSn and CoSn2 intermetallic compounds does not initiate from the initial growth interface, and the distance required for the occurrence of the phase transition is found to increase with increasing growth velocity. The measurement of the hardness and Young's modulus was accomplished by nanoindentation with the continuous stiffness measurement (CSM) technique. The elastic modulus is nearly constant while the hardness increases with increasing growth velocity. In addition, the hardness of CoSn2 phase is lower than that of CoSn phase.

Keywords

• hardness
• intermetallics
• casting methods
• phase transformation