PECULIARITIES OF ALLOYING OF WELD METAL OF HIGH-STRENGTH ALUMINIUM ALLOY WELDED JOINTS WITH SCANDIUM

摘要

The problem of effect of solidification rate on structure of weld metal of scandium-containing aluminium alloys is considered. Peculiarities of scandium precipitation from melt in solidification of aluminium alloys under non-equilibrium conditions, simulating fusion welding, are investigated. Procedure of investigations has been developed and confirmed experimentally. Advantage of offered procedure over the existing ones consists in the fact that it allows simulate almost all the methods of fusion, from argon arc non-consumable electrode welding to electron beam welding. It is shown that the procedure satisfies the put aims completely. Microstructural investigations of ingots in height showed that within the interval of solidification rates from 10~(3.3) to 10~(2.5)℃/s the change of form of solidification occurs from dendritic to subdendritic ones. It was found that at rates of solidification, commensurable with solidification of weld metal, up to 0.41 % Sc can be contained in solid solution of alloys. When applying the highly concentrated power sources, such as electron beam, it is possible to reach the similar value also in welds. In arc methods of welding approximately 0.3 % Sc can be assimilated in solid solution of weld metal. It was found that it is necessary to provide its content in weld metal at the level of 0.35-0.40 wt.% to maximization of effect from alloying of welds with scandium. In this case the increase in mechanical properties of weld metal is provided both by refining of its crystalline structure, and also by hardening the solid solution by scandium.