Abstract:Porous CoCrNi medium-entropy alloy (MEA) with porosity of 60.6%–78.1% and pore size of 1.8–2.4 mm were prepared by powder sintering-dissolution method. Results show that the pore distribution is uniform, and the metallurgical bonding is good. The dynamic compression test results show that the material has a significant strain rate strengthening effect, and the impact resistance is the best at strain rate of 500 s–1. The yield strength increases by 52.8% (from 22.9 MPa to 35.0 MPa) with the increase in strain rate from 200 s–1 to 800 s–1. The dynamic yield strength increases by 25% compared with the quasi-static yield strength. The energy absorption value reaches 35.4–14.5 MJ/m3 (6.6%–14.0% higher than the quasi-static result), and the maximum ideal energy absorption efficiency is close to 0.9. At the same time, under the condition of low temperature (–100 ℃), the elastic modulus and platform stress are increased by 2.4%–10.5% and 2.5%–9.8%, respectively, compared with those at room temperature. The energy absorption value is 41.3–15.2 MJ/m3, which is twice that of magnesium alloy foam, and the maximum ideal energy absorption efficiency is 0.8. In summary, the porous CoCrNi MEA has both dynamic strengthening and low-temperature strengthening characteristics, and it has good energy absorption capacity and high ideal energy absorption efficiency, showing significant application potential in the field of actual working conditions and extreme environments.