Microstructure and tensile properties of the bismuth-containing 2091 AlLi alloy

Studies show that the ductility and toughness of Al-Li alloys are lower than those of 2024 and 7075 commercial alloys, which are widely used in the aerospace industry. Therefore, it is very important to improve the ductility and toughness of Al-Li alloys for industrial applications. Among the many reported reasons for the low ductility and toughness of Al-Li alloys, grain boundary embrittlement resulting from the grain boundary segregation of trace impurity elements is a important reason. There are two approaches to reducing or eliminating the embrittlement, which resulted from the low melting point metals. One is to use high pure materials, containing lower amounts of Na, K and Ca impurities. The other way is to add some alloying elements to change the distribution of these impurities or to form compounds with them in order to reduce the grain boundary segregation of these harmful impurities. Previous work showed that a small addition of bismuth could neutralize the harmful effect of sodium, decrease the trend of cracking during hot rolling, and increase the ductility of Al-Mg alloys. The purpose of this paper is to study the influence of a small addition of bismuth on the microstructure and tensile behavior of a 2091 Al-Li alloy, containing higher sodium content, and to investigate the efficacy of bismuth in reducing the harmful influence of sodium.