Fabrication and compression behavior of heat storage macrocapsules based on lead–bismuth eutectic and electroplated iron

Metal-based phase change materials (MPCMs) exhibit excellent thermophysical properties, making them highly advantageous for applications in thermal energy storage and thermal management systems. Meanwhile, barrel plating provides a low-cost and thickness-controllable approach for encapsulating MPCMs, yet relevant studies remain scarce. In this study, lead and bismuth eutectic (LBE) was employed as the MPCM, while electroplated iron prepared via barrel plating was used as the shell material. The microstructure and growth behavior of the electroplated iron were characterized. Compression tests were conducted under both solid and liquid states of LBE to investigate the fracture behavior of the shells. The results demonstrated that a shell thickness of 147 μm provided reliable sealing performance for LBE pellets with a diameter of 1 mm. The electroplated iron exhibited a heterogeneous microstructure composed of clustered submicron grains and coarse grains. The mechanical rolling during barrel plating significantly refined the grain size and suppressed the formation of fiber texture of <110>//growth direction. When the LBE core was in solid, external cracks initiated at Σ3 <111> 60°grain boundaries within the coarse grains, but were strongly inhibited during inward propagation. In contrast, when the LBE core was in liquid, the increased driving force on the cracks, combined with the lack of suppression of hydrogen embrittlement, led to the rapid penetration of internal cracks through the shell. Compression testing under liquid-phase LBE conditions provided a more realistic evaluation of the sealing performance of the shell. This study could promote the application of barrel plating in the fabrication of macrocapsules.