多孔CoCrNi中熵合金的动态力学行为及其低温力学性能

Dynamic Mechanical Behavior and Low-Temperature Mechanical Properties of Porous CoCrNi Medium-Entropy Alloy

摘要:

通过粉末烧结-溶解法制备了孔隙率60.6%~78.1%、孔径1.8~2.4 mm的多孔CoCrNi中熵合金，其孔隙分布均匀且冶金结合良好。动态压缩试验结果表明，该材料具有显著应变率强化效应，且500 s^–1应变率下抗冲击性能最优；屈服强度随应变率从200 s^–1增加到800 s^–1而提升了52.8%（22.9 MPa到35.0 MPa），动态屈服强度较准静态屈服强度提高25%，能量吸收值达35.4~14.5 MJ/m³（较准静态提升6.6%~14.0%），最大理想吸能效率接近0.9。同时，在低温（–100 ℃）条件下，弹性模量和平台应力较室温分别提升2.4%~10.5%和2.5%~9.8%，能量吸收值达41.3~15.2 MJ/m³，为泡沫镁合金的2倍，最大理想吸能效率保持0.8。综上可知，多孔CoCrNi中熵合金兼具动态强化与低温强化特性，具有良好的能量吸收能力与高理想吸能效率，在实际工况与极端环境领域展现出显著的应用潜力。

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.