Study of the growth of AlFe primary phases in Al alloys and of intermetallic layers in Sn-Bi-X/copper joints

Abstract

During recycling of Al alloys, the accumulation of residual impurities, Fe in particular, often leads to the formation of coarse intermetallic compounds during solidification that degrade the mechanical properties of the final product. Knowing the high cost associated with reducing the Fe content and/or using thermomechanical processing to reduce the intermetallics, it is preferable to manipulate the morphology, size and distribution during solidification. Therefore, advances related to the faceted growth of primary phases in Al-Fe alloys modified with Si, Ni and Mn are essential in refining the control of size, morphology and degree of anisotropy (aspect ratio) in different solidification conditions. The results obtained may be useful in the sense of generating morphologies that favor superior properties in Al alloys, enabling the production of alloys that are more tolerant to contamination with Fe, favoring recycling. Another challenge to be addressed in this project involves the growth of reaction layers in reflowed Sn-Bi alloys in copper pas, an increasingly important topic in the microelectronics industrial sector due to the trend towards miniaturization of soldered joints. Intermetallic layers produced under different exposure conditions and using different levels of Bi and alloying elements, In and Zn, will be examined in relation to their morphology, nature, growth direction and nanohardness. Solidification analyzes of the Sn-Bi-In and Sn-Bi-In-Zn alloys will be carried out through directional solidification experiments. The combination of characterization techniques such as SEM, XRD, EBSD, nanohardness and x-ray microtomography will allow understanding not only the formation and layer properties but also the solidification of these Sn-Bi alloys. The aim is to produce more stable, uniform, resistant layers with less Bi segregation. These same techniques will also be used in the mapping of AlFe intermetallics for the case of solidification of Al alloys with high Fe content. The development of these two research topics can result either in improvement of properties of alloys contaminated with Fe or in the improvement of the control of reaction layers in Sn-Bi-x/Cu joints. (AU)