A comprehensive study on the microstructure and cryogenic mechanical properties of Er73Pr27 regenerator material

The performance of deep cryogenic refrigerators strongly depends on the specific heat (C _p) of the regenerator materials. Er-Pr alloys are promising cryogenic regenerator materials due to their high C _p, good mechanical properties and nontoxic feature. However, the practical cooling performance of Er ₇₃Pr ₂₇ in refrigeration machines and its cryogenic mechanical properties remain less explored. In this work, the heat capacity behavior of Er ₇₃Pr ₂₇ was investigated in the range of 10–20 K, and its cooling power for a Gifford-McMahon (GM) cryocooler was further evaluated. The results demonstrate that upon filling 1/3 Er ₇₃Pr ₂₇ + 2/3 Pb spherical powders, the cooling power is notably enhanced by 17.6 % at 12 K compared with the fully packed Pb. At 10 K, the values of tension and compression strength in Er ₇₃Pr ₂₇ alloys are 385 and 1008 MPa, and the deformation ratios are 4.2 % and 23.6 %, respectively. The high compression strength can be attributed to the formation of a large amount of stacking faults and deformation twins. Also, the deformation twinning contributes to the plasticity, maintaining high ductility at 10 K. This study indicates that Er-Pr alloys possesses both excellent mechanical properties and considerable cooling performance, making it a potential regenerator candidate material for cryocooler applications.