TIZR-BASED METALLIC ALLOYS: CONTROLLABLE COMPOSITE PHASE STRUCTURES AND RELATED PROPERTIES

摘要

Composite phase structure of early transition metal-based metallic alloys, including those of crystalline, quasicrystalline and amorphous phases, can be obtained in a controllable way upon direct (in-situ) cooling (solidification) of the alloy, realized either by adjusting the alloy compositions at a fixed cooling rate or by changing the cooling rates for a given alloy composition. Some embodiments are based on the addition of later transition metals, mainly of Cu with Ni or Fe with Co in early transition metal based (mainly Ti and Zr or Hf and Nb) metallic alloys. If cooling rate is on the scale of 10³ °C/s, a wholly amorphous structure is obtained for most of the compositions. At reduced cooling rates, composite structures with different kinds of phases can be achieved, as illustrated graphically in Figure 1. Nickel addition promotes the formation of quasicrystalline phases, especially for Ti-rich alloy compositions with beryllium. A critical percentage of Ni exists below which no quasicrystalline phases will be formed.