Cryogenic- and ultrasonic-induced local martensite-like order in Cu47.5Zr45.5Al5Er2 bulk metallic glasses

This study analyzed the influence of low-temperature elastic ultrasonic stimulus on the local structural order of Cu47.5Zr45.5Al5Er2 amorphous alloy, using the ultrasonic pulse-echo technique with a longitudinal wave frequency of 10 MHz, between 100 K-300 K under consecutive cryogenic thermal cycles. Ultrasonic attenuation and wave velocity data of Cu47.5Zr45.5Al5Er2 sample revealed an evolution of the anomalies observed between cooling and heating cycles, being the progressive changes in the local amorphous structure related to the forming and grown of the locally ordered structures induced by the consecutive cryogenic and ultrasonic waves cycles. After the Cu47.5Zr45.5Al5Er2 sample maintained free of mechanical stress at RT for a week, their anelastic response exhibited the full recovery of the as-received condition ultrasonic behavior, denoting the metastable nature of the short- and medium-range order structures originated from the thermomechanical cycles. The amorphous sample ultrasonic response showed attenuation peaks compatible with those observed in a Cu36Zr59Al5 crystalline sample, ass-ociated with a typical reversible martensitic transformation between B2 CuZr to B19' and B33 CuZr phases.

Automated summary

The study found that the local amorphous structure of the Cu47.5Zr45.5Al5Er2 amorphous alloy gradually evolved into locally ordered structures during consecutive cryogenic thermal cycles and ultrasonic wave cycles. Additionally, after maintaining the sample stress-free at room temperature for a week, the ultrasonic response of the sample fully recovered to its initial state.