There exists a severe strength-crack tolerance trade-off in dilute magnesium (Mg) alloys. Herein, a heterogeneous Mg-0.6Al-0.6Mn-0.5Zn-0.2Ce-0.2Nd (A200-10) alloy with a high density of dislocations was obtained through low-temperature extrusion and short-term annealing. The microstructure consists of recrystallized (RXed) and unrecrystallized (unRXed) regions, with a precisely controlled volume fraction ratio of 3:1. The heterogeneous A200-10 alloy exhibits a high tensile yield strength (TYS) of ~306 MPa and a superior tensile elongation (TEL) of ~18.4%. Based on quasi-in-situ electron backscattered diffraction (EBSD) and scanning electron microscope (SEM)-digital image correlation (DIC) analysis, we find that plastic deformation occurs preferentially in the RXed regions, mediated by the mobile <a> dislocations. As strain increases, strain gradient gradually accumulates at the interface between RXed and unRXed regions, generating hetero-deformation induced (HDI) strengthening and hardening. Besides, there is significant intergranular slip transfer in RXed regions, which can coordinate partial strain incompatibility. Furthermore, heterogeneous interfaces play a crucial role in enhancing crack tolerance. The heterogeneous interface functions as a bridging ligament to withstand stresses, and activates non-basal slips in the unRXed grains near the crack tip. Such activation of extra dislocations not only alleviates stress concentration but also dissipates the energy essential for microcrack propagation, thus effectively blunting the crack tip. Accordingly, the heterogeneous A200-10 alloy obtains an excellent strength and elongation combination. This work is anticipated to provide a valuable avenue for the development of Mg alloys with outstanding performance by regulating the appropriate heterostructure.

Texture regulation is a prominent method to modify the mechanical properties and anisotropy of magnesium alloy. In this work, the Mg-1Al-0.3Ca-0.5Mn-0.2Gd (wt.%) alloy sheet with TD-tilted and circular texture was fabricated by unidirectional rolling (UR) and multidirectional rolling (MR) method, respectively. Unlike generating a strong in-plane mechanical anisotropy in conventional TD-tilted texture, the novel circular texture sample possessed a weak in-plane yield anisotropy. This can be rationalized by the similar proportion of soft grains with favorable orientation for basal <a> slip and {1012} tensile twinning during the uniaxial tension of circular-texture sample along different directions. Moreover, compared with the TD-tilted texture, the circular texture improved the elongation to failure both along the rolling direction (RD) and transverse direction (TD). By quasi-in-situ EBSD-assisted slip trace analysis, higher activation of basal slip was observed in the circular-texture sample during RD tension, contributing to its excellent ductility. When loading along the TD, the TD-tilted texture promoted the activation of {1012} tensile twins significantly, thus providing nucleation sites for cracks and deteriorating the ductility. This research may shed new insights into the development of formable and ductile Mg alloy sheets by texture modification.

It is a long-sought goal to achieve desired mechanical properties through tailoring phase formation in alloys, especially for complicated multi-phase alloys. In fact, unveiling nucleation of competitive crystalline phases during solidification hinges on the nature of liquid. Here we employ ab initio molecular dynamics simulations (AIMD) to reveal liquid configuration of the Mg-Al-Ca alloys and explore its effect on the transformation of Ca-containing Laves phase from Al₂Ca to Mg₂Ca with increasing Ca/Al ratio (r_Ca/Al). There is structural similarity between liquid and crystalline phase in terms of the local arrangement environment, and the connection schemes of polyhedras. The forming signature of Mg₂Ca, as hinted by the topological and chemical short-range order originating from liquid, ascends monotonically with increasing r_Ca/Al. However, Al₂Ca crystal-like order increase at first and then decrease at the crossover of r_Ca/Al = 0.74, corresponding to experimental composition of phase transition from Al₂Ca to Mg₂Ca. The origin of phase transformation across different compositions lies in the dense packing of atomic configurations and preferential bonding of chemical species in both liquid and solid. The present finding provides a feasible scenario for manipulating phase formation to achieve high performance alloys by tailoring the crystal-like order in liquid.