Abstract
This study introduces a novel (Al_0.8Si_0.2)_100−xBi_x (x = 1, 2, 3, 4, and 5 at.%) phase change energy storage alloy, showcasing high heat capacity for energy regulation and heat management applications. We investigated the influence of Bi content on the alloy's microstructure, thermal properties, high-temperature stability, and container compatibility using optical microscopy, DSC, XRD, SEM, and EDS. Adding 4 wt.% Bi significantly refines the microstructure, evidenced by reduced eutectic silicon size and increased grain boundaries. The (Al_0.8Si_0.2)₉₆Bi₄ alloy achieved a maximum enthalpy change of −397 J g⁻¹ and exhibited phase change temperatures of 500-600 °C, suitable for diverse high-temperature applications. The phase composition remained stable after 100 thermal cycles at high temperatures. Static corrosion tests at 560 °C for 240 h revealed enhanced compatibility with SS304 containers, attributed to a dense oxide layer formed by accelerated Cr and Ni atom diffusion through increased grain boundaries. This layer effectively prevents further diffusion of Al and Fe atoms, demonstrating the alloy's improved suitability for practical applications.

Key words
Al-Si-Bi alloys, energy storage materials, high-temperature thermal cycling, container compatibility

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