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

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 Al 3 Sc precipitated inside the weld after adding Sc, corresponding to the grain refinement effect and dispersoid strengthening effect. The continuous brittle T 2 (Al 6 CuLi 3) 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 Al 3 Sc and morphology transformation of brittle T 2 (Al 6 CuLi 3) quasi-crystal. Dislocation clusters interacted with Al 3 Sc, indicating a pronounced inhibitory effect on dislocation movement. The novel phenomena of four-chain-shaped dislocations and dislocation loops were found at Al 3 Sc corners deriving from the attraction to dislocations. The formation model was proposed for the two kinds interaction between Al 3 Sc/α-Al interface and dislocations. • Precipitate compensation is achieved for Al–Li alloy welded joint by adding Sc. • Mechanical properties of welded joint are considerably optimized after adding Sc. • The novel phenomenon of four-chain-shaped dislocations is found at Al 3 Sc corners. • Interaction between Al 3 Sc/α-Al interface and dislocations is analyzed in detail. [ABSTRACT FROM AUTHOR]