Bimodal-grain structure enables superior strength-ductility synergy of pure Al

Developing materials with a strength-ductility synergy was eternally desirable in structural materials. Here, we prepared the bimodal grain structures through the designed powder assembly approach without introducing other elements, which utilized stable dislocations and substructures to regulate fine-grained structures. During the strain, geometrically necessary dislocations formed at fine/coarse grain boundaries to coordinate deformation induced by plastic incompatibility. The stress field induced by these previously accumulated geometrically necessary dislocations interacted with the subsequently formed dislocations. The dislocation movement was thus dynamically coordinated, which in return enlarged the work-hardening region of the materials. Compared with the cast-rolled pure Al, the ultimate tensile strength of the prepared pure aluminum was 212±2 MPa, which was increased by about 102 % and maintained the desirable elongation of 13.5±0.7 %.