<p>Cu-based shape memory alloys are an important class of smart materials whose multifunctional properties are closely related to their unique microstructure. Therefore, it is of great crucial to thoroughly elucidate the law of dynamic microstructure evolution of the alloys. Internal friction measurement was carried out to track dynamic microstructural changes and phase transformations of the as-cast Cu-12Al-5Mn (wt.%) shape memory alloy. Five typical internal friction peaks (labeled as P₁, P₂, P₃, P₄, and P₅, respectively) were observed during heating process. It is confirmed that the Peak P₁ is originated from reverse martensitic transformation. Peak P₂ is associated with an elastic relaxation of grain boundary with an activation energy of 1.41 eV. Peak P₃ is attributed to dissolution of the Al₂Cu precipitate phase. Peak P₄ stems from the order-disorder transition, specifically the transformation of a long-range ordered L2₁ (Cu₂AlMn) structure into a short-range ordered B2 structure. Peak P₅ should be related with the transition of ordered B2→disordered A2. It can be concluded that an in-depth analysis of the internal friction peaks can perfectly response the microstructural evolution law of the CuAlMn alloy.</p>