The limited creep resistance of wrought Mg–Al alloys restricts their lightweight applications at intermediate temperatures due to the softening effect of discontinuous precipitation (DP) on the dislocation-controlled creep. Here, we developed a creep-resistant wrought Mg–Al alloy through microalloying of Y and Ca. The resulting alloy exhibited an order of magnitude enhancement in the creep resistance at 125 ℃/50–100 MPa. In contrast to the grain boundary instabilities by DP in the previously reported wrought Mg–Al alloys, we show that the addition of 0.21Y+0.15Ca wt% produces a (Zn+Ca) co-segregation at the grain boundaries as a result of their segregation energy and the activation energy of grain boundary migration, thereby stabilizing the grain boundaries. The (Zn+Ca) co-segregation inhibits the dynamic DP and promotes the formation of intragranular Al-enriched clusters, which favorthe formation of Al₂Y, Mg₁₇Al₁₂ nano precipitates, thereby impeding intragranular dislocation motion during creep. Furthermore, the addition of 0.21Y+0.15Ca wt% facilitates the formation of a fine and uniform recrystallization structure in the microalloyed alloys compared to AZ80 due to the high activation energy of mobility for the (Zn+Ca) segregated grain boundary. Therefore, the microalloyed alloys exhibit good tensile properties with 380 MPa tensile strength and 18% elongation. Our constitutive analysis revealed that the (Y+Ca) microalloying decreased the creep stress exponent by 29% and increased the creep resistance in the medium to high-stress range. Microalloying provides a promising way to develop low-cost creep-resistant wrought Mg–Al alloys.

Vanadium dioxide (VO₂) has emerged as a promising micro-actuator material for its large amplitude and high work density across the transition between the insulating (M1 and M2) and metallic (R) phase. Even though M2–R transition offers about 70% higher transformation stress than M1–R structural phase transition, the application of the M2 phase in the micro-actuators is hindered by the fact that previously, M2 phase can only stay stable under tensile stress. In this work, we propose and verify that by synthesizing the VO₂ nanowires under optimized oxygen-rich conditions, stoichiometry change can be introduced into the nanowires (NWs) which in turn yield a large number free-standing single-crystalline M2-phase NWs stable at room temperature. In addition, we demonstrate that the output stress of the M2-phase NWs is about 65% higher than that of the M1-phase NWs during their transition to R phase, quite close to the theoretical prediction. Our findings open new avenues towards enhancing the performance of VO₂-based actuators by using M2–R transition.

Using nanoscale electrical-discharge-induced rapid Joule heating, we developed a method for ultrafast shape change and joining of small-volume materials. Shape change is dominated by surface-tension-driven convection in the transient liquid melt, giving an extremely high strain rate of ~10⁶ s^–1. In addition, the heat can be dissipated in small volumes within a few microseconds through thermal conduction, quenching the melt back to the solid state with cooling rates up to 10⁸ K·s^-1. We demonstrate that this approach can be utilized for the ultrafast welding of small-volume crystalline Mo (a refractory metal) and amorphous Cu₄₉Zr₅₁ without introducing obvious microstructural changes, distinguishing the process from bulk welding.