Improvement of Thermoplastic Forming Ability of Ti–Zr–Ni–Cu Metallic Glass by Addition of Sn

Abstract

Ti–Zr–Ni–Cu metallic glass attracts an attention as a precursor of superelastic alloy that can be deformed into nm scale complex shapes. However, since the thermal stability of Ti–Zr–Ni–Cu metallic glass in the supercooled liquid region is quite low, application of thermoplastic forming is limited. Therefore, in the present study, the effect of Sn addition on thermoplastic forming ability of Ti–Zr–Ni–Cu metallic glass has been investigated. Sn containing (Ti35Zr15Ni35Cu15)99Sn1 metallic glass exhibits longer incubation time before onset of crystallization than Ti35Zr15Ni35Cu15 metallic glass, resulting in significant improvement of thermoplastic forming ability. The crystallization behavior changes from three-dimensional growth of saturated nuclei to three-dimensional growth with constant nucleation rate with the addition of Sn. The overall activation energy for crystallization of (Ti35Zr15Ni35Cu15)99Sn1 metallic glass is higher than that of Ti35Zr15Ni35Cu15 metallic glass, indicating that the thermal stability of metallic glass is improved by addition of Sn. Because nuclei are continuously generated during the crystallization in (Ti35Zr15Ni35Cu15)99Sn1, the average grain size is much smaller than that in Ti35Zr15Ni35Cu15.