The use of rare earth elements for alloying of aluminum alloys is a promising direction nowadays — filler materials doped with rare earth metals (REM) improve the mechanical properties of welded joints of high-strength aluminum-lithium alloys compared to serial filler material. The results of studying the effect of the composition of alloyed filler materials Sv1209 and Sv1221 and heat treatment mode on the mechanical properties and structure of welded joints of high-strength aluminum-lithium alloys B-1461 and B-1469 are presented. It is shown that the use of filler materials alloyed with rare earth metals in combination with full heat treatment (quenching and artificial aging) carried out after welding provide an increase in the strength characteristics of the welded joint to the level of strength of the base material with sufficiently high ductility and toughness. Metallographic study of welded joints after heat treatment revealed a fine-grained structure in the center of welds attributed to alloying of the filler with REM. Transmission electron microscopy is used to study precipitated hardening phases in welded joints. The round-shaped phase Al3(Sc, Zr) and a fine δ’-phase precipitated upon cooling of the welded joint are present in weld adjacent zone of V-1469 alloy. At the same time, artificial aging after welding results in formation of copper-containing Ω’- and θ’-phases. Quenching and artificial aging of the welded joint resulted in an increase in the size of precipitated hardening T1’-, S’-, θ’-phases and density of their distribution in the grain volume in the heat-affected zone of V-1461 alloy. Thus, heating upon welding leads to uneven phase precipitation, whereas additional artificial aging aggravates the non-uniformity of decomposition through partial dissolution of some phases and coarsening of the other.
Characterization and Depth Profile of Lithium Depletion in Aluminum-Lithium Alloys by Ultrasound
