Sequence-Dependent Effects of Deep Cryogenic Treatment on the Strength-Damping Synergy of an M2052 Mn-Cu Alloy

Mn-Cu alloys have attracted considerable attention as structural damping materials because they combine excellent damping capacity with relatively good mechanical properties. However, realizing effective strength-damping synergy still constitutes a critical bottleneck restricting their widespread engineering deployment. In this study, the effects of solution treatment (ST), deep cryogenic treatment (DCT), aging treatment (AT), and their combined routes on the microstructure, mechanical properties, and damping behavior of the M2052 Mn-Cu alloy were systematically investigated. The results show that the ST + DCT + AT route (820 °C/0.5 h + − 196 °C/36 h + 435 °C/10 h) provides the optimum overall performance. Compared with the as-cast alloy, its tensile strength and hardness are enhanced by ~23.2% and ~36.7%, respectively. Meanwhile, high damping capacity with tanδ ≥ 0.01 can be maintained within a broad temperature window from − 100 °C to 200 °C. Microstructural characterization revealed that the ST + DCT + AT treatment generates refined α-Mn precipitates, maximized Mn-rich area fraction, abundant transformation-induced twins, and a relatively high dislocation density. The joint contributions from α-Mn particle refinement, abundant twin boundaries, and dislocation strengthening simultaneously improve mechanical strength and energy-dissipation capability. The results demonstrate that the insertion position of deep cryogenic treatment strongly modulates defect states, precipitate refinement and spinodal decomposition, and serves as a critical factor governing microstructural evolution and strength-damping synergy in Mn-Cu alloys.