Improving the damping capacity of NiTiHf alloys with nanoscale spherical Nb phases

Abstract

Shape memory alloys (SMAs) are well-suited for vibration and noise reduction due to their outstanding mechanical and damping properties. However, their damping capacity is limited due to low-temperature stabilized thermoelastic martensite and constrained twin migration. This work designs nanoscale Nb phases to enhance the damping capacity and maintain a wide working temperature range of NiTiHf-based SMAs. The NiTiHf/Nb alloys containing spherical Nb phases demonstrate a 125% improvement in internal friction (IF) and remain stable up to 400 K. Alloys with spherical Nb phases exhibit high migration ability for martensitic twinning, resulting in a relatively high intrinsic IF. High-resolution transmission electron microscopy images and IF spectra suggest spherical Nb phase introduces additional dislocation damping effects and interface damping effects by inducing multiple types of dislocations near the multi-directional phase interfaces. These findings provide insights into the role of second-phase shape effects in damping properties and offer valuable guidance for designing ultra-high damping alloys.