Influence of Rotating Magnetic Field (RMF) on Dendrite Growth, Mechanical and Elastic Properties of Sn-Cu-Co Lead-Free Solder Alloy

Abstract

Dendritic microstructures are a common issue in casting applications, leading to subpar mechanical properties. A new and innovative approach for combating this problem is through the application of mechanical stirring using an RMF. The solidification microstructures, mechanical and elastic characteristics of Sn-0.7wt%Cu-xCo (where x = 0.05 and 0.5) alloys were analyzed with and without the application of an RMF. The results revealed that, in the absence of an RMF, both solder alloys displayed extensive and undesirable columnar formations of the dendritic β-Sn phase. However, the application of an RMF led to a significant modification of the solidification microstructure, transforming the dendritic β-Sn phase from columnar to equiaxed, resulting in fragmentation of the dendrites. As well, the average size of (Cu,Co) 6 Sn 5 IMCs was reduced, resulting in successful suppression of the growth rate of IMCs with the use of RMF. Tensile testing showed that the Sn-0.7wt%Cu-0.05Co alloy with RMF exhibited the highest strength across a range of temperatures and strain rates. Additionally, the ultimate tensile strength, yield strength, yield modulus, and elongation percentage of the Sn-Cu-0.05Co alloy with RMF were approximately 29.2%, 31.8%, 29.2% and 7.1% at 25°C higher compared to that of the RMF-free Sn-Cu-0.05Co alloy. By evaluating the Poisson's ratio, Young's modulus, shear modulus, and bulk modulus, it was determined with a high level of confidence that the application of RMF during solidification made the Sn-7Cu-0.5Co alloy more ductile, while the Sn-7Cu-0.05Co alloy demonstrated increased strength compared to their counterparts without RMF.