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• A large number (10.0 vol.%) of galvanic couples were formed ((α-Mg-Li)-Mg 2 (Ni, Cu) in designed Mg-Li-Ni-Cu alloy, with a potential difference of ∼500 mV, which is significantly higher than that of most couples formed in comparative Mg alloys. • A superb degradation rate of 2404.3 ± 24.0 mm/y was obtained, 2.3 times higher than the reported highest degradation rate of comparative Mg alloys. • Adding Ni and Cu and the formation of the Mg 2 (Ni, Cu) phase can refine the grains (1.5 μm), leading to high strength and plasticity. • The designed alloy exhibits a combined superb degradation rate (2404.3 mm/y) high compressive strength (484.9 MPa), lower density (1.70 g/cm3) and high compressive strain (16.1%). Lightweight Mg alloys with high degradation rates and high strength are attractive for fracturing tools used in unconventional oil/gas extraction. The common design strategy for such alloys is to directly add Ni/Cu into existing high-strength Mg alloys, which meets the high-strength demand but the degradation rates are still insufficient for some extreme downhole environments, especially those with low temperature and low chloride ion concentrations. Here we designed an extruded lightweight Mg-Li-Ni-Cu alloy with superb degradation rate and high strength. The high degradation rate is attributed mainly to the formation of highly effective galvanic couples, Ni/Cu-containing second phases (cathode) and Mg-Li matrix (anode) with ultrahigh potential difference. The degradation rate achieved 2404.3 mm/y, ∼2.3 times higher than the reported highest rate of extruded Mg alloys for fracturing tools. The alloy also has a high compressive strength of 484.9 MPa, which can be attributed largely to grain refinement strengthening. [ABSTRACT FROM AUTHOR]

The corrosion behavior of WE43 alloy with different rolling reductions (0%, 25%, 45%, and 80%) at 500 °C was investigated in 3.5 wt.% NaCl solution. The microstructure evolution of the rolled WE43 alloy was characterized in detail by means of optical microscopy (OM), transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). The results show that with increasing reductions, basal texture is gradually enhanced and grain size gradually decreases. Only the alloy with 45% reduction exhibits dispersed dynamic precipitates. Immersion and electrochemical measurements demonstrate the decreasing order of the corrosion resistance of the rolled WE43 alloy: 45% reduction > 80% reduction > 25% reduction > 0 reduction. The best corrosion resistance of the WE43 alloy with 45% reduction is mainly related to a large number of finely dispersed precipitates, which are capable of promoting the formation of a compact corrosion product layer. The increased corrosion rate of the sample with 80% reduction is induced by the re-solution of the majority of precipitates into the matrix. The grain size, basal texture and deformation twins have a limited effect on the corrosion resistance of rolled WE43 alloy compared with the precipitates.