Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability, which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries. However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.

Generally, edge crack of rolled magnesium alloy sheets initiates in the RD (rolling direction)-ND (normal direction) plane and then propagate in the RD-TD (transverse direction) plane. Hence, the Mg-2Zn-1.5Mn (ZM21) alloy sheets with and without crack notch were designed to carry out in-situ tensile experiments under 150 ℃ (the same temperature of rolling), with the aim to understand their crack propagation mechanism. The scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) techniques were utilized to reveal microstructural evolution in real time at designated displacements. The results show that the prismatic slip, basal slip, and extension twining play synergistic role in coordinating strain during the tensile process in ZM21 alloy sheet at 150 ℃. In both tensile samples with and without crack notch, localized strain is mainly concentrated at relatively fine grain area and the grain boundaries or triple junctions of the grains with large basal Schmid factor (SF) difference, which eventually leads to severe surface roughening and subsequent crack initiation. Compared with the sample without crack notch, the pre-cracked sample exhibits severer deformation at the crack tip due to strain concentration. Strain gradient distribution is observed at the crack tip region in the pre-cracked sample. The crack propagation path of the sample with pre-crack is identified and the underlying mechanism is also discussed.