Interaction of dislocation/compensated precipitates and mechanical property optimization of electron beam welded aluminum-lithium alloy with scandium addition

Abstract

In view of the precipitate deficiency and mechanical property deterioration, Sc was added into the weld of aluminum-lithium alloy electron beam welded joint to achieve precipitate compensation and the consequent mechanical property optimization. Quantities of intragranular angular Al3Sc precipitated inside the weld after adding Sc, corresponding to the grain refinement effect and dispersoid strengthening effect. The continuous brittle T2 (Al6CuLi3) quasi-crystal at grain boundaries of weld was transformed into intermittent state. The tensile strength of the joint was optimized from 335 MPa (61% of base metal) to 426 MPa (78% of base metal) as Sc was added into the weld, which was mainly due to the dispersoid strengthening effect of Al3Sc and morphology transformation of brittle T2 (Al6CuLi3) quasi-crystal. Dislocation clusters interacted with Al3Sc, indicating a pronounced inhibitory effect on dislocation movement. The novel phenomena of four-chain-shaped dislocations and dislocation loops were found at Al3Sc corners deriving from the attraction to dislocations. The formation model was proposed for the two kinds interaction between Al3Sc/α-Al interface and dislocations.