Evolution of damping capacity and vacancy behavior with the environmental temperature in ductile Cu–Al–Mn–Ni alloys

To enhance the damping capacity at 350 K, the martensitic transformation temperatures must be increased. However, the increment in martensitic transformation temperatures can deteriorate the damping capacity. Whether good damping capacity can be obtained at elevated temperature is unknown to us. In this paper, we carefully investigated the evolution of damping capacity and vacancy behavior with the environmental temperature in ductile Cu–Al–Mn–Ni alloys with different M s temperatures. Our results showed that the damping capacity in Cu–Al–Mn–Ni alloys subjected to 15 min step-quenching all showed an obvious degradation tendency with the increment in environmental temperature to above 313 K. The reduction of martensite amount and mobility of martensite boundaries could rationalize the degradation of damping capacity with the environmental temperature. The original number of vacancies on the martensite boundaries ( N vmb ), which is positively dependent on the M s temperature, controls the degradation rate of damping capacity in martensitic Cu–Al–Mn–Ni alloys. Among the experimental Cu–Al–Mn–Ni alloys, the Cu-18.0Al-8.4Mn-2.5Ni alloy with M s = 360 K have the superior resistance to the degradation of damping capacity with the environmental temperature. In addition, we found that a critical temperature for vacancy diffusion exists at between 313 K and 333 K. With M s temperature below the critical temperature, the alloy has a far lower original N vmb than the one with M s above the critical temperature. These findings highlight the importance of lowering the original N vmb and increasing the critical temperature on improving the damping capacity at elevated temperatures.