This study investigates microstructural evolution in Al-Cu-Li alloy resistance spot welds (RSW) under electric pulse treatment (EPT). Comparative analysis of conventional RSW (AW), immediate EPT (AW-P1), and delayed EPT (AW-P2) joints reveals that: (1) In AW specimens, dendritic boundaries are characterized by continuous blocky T 1 -Al 2 CuLi phases, while the inner-dendritic region contains predominantly dispersed T 1 -Al 2 CuLi platelets with minor δ'-Al 3 Li precipitates; (2) EPT transforms inter-dendritic region’s microstructure from continuous blocky T 1 -Al 2 CuLi phases to icosahedral short-range ordered clusters (ISROCs). Simultaneously, it promotes the formation of T 1 -Al 2 CuLi platelets within inner-dendritic regions while suppressing the precipitation of δ'-Al 3 Li phases. EPT treatment suppressed δ′-Al 3 Li precipitation while promoting T 1 -Al 2 CuLi formation, shifting the joint failure mode from interfacial (AW and AW-P1) to mixed interfacial/pull-out failure and significantly improving peak load and energy absorption (AW-P2).
Zhang et al. (Fri,) studied this question.