Effects of ultrasonic vibration on microstructures and thermal properties of nickel-titanium shape memory alloy fabricated by directed energy deposition

Abstract

Directed energy deposition (DED) has been previously utilized to fabricate nickel-titanium alloys; however, the inhomogeneity of microstructures and the formation of precipitates are still two major problems encountered in current DED processes. In this study, an ultrasonic vibration-assisted strategy is proposed and integrated into a DED process. The influences of ultrasonic power on deposition area, microstructures, and thermal behaviors of fabricated NiTi alloys are investigated. The results show that ultrasonic vibration can effectively improve deposition area and ameliorate the shape memory effect. The reported ultrasonic vibration-assisted strategy is expected to reduce the microstructure heterogeneity and secondary phase formation in nickel-titanium alloy fabrication.