TiFe금속간 화합물의 Zr과 Ce첨가와 냉각속도에 따른 응고 조직 변화 및 기계적 특성

Microstructure and Mechanical Property of TiFe Compounds with Zr or Ce Prepared at Different Solidification Rates

Abstract

Microstructural and corresponding hardness changes of TiFe compounds with Zr (0~6 at%) or Ce (0~3 at%) were studied using samples prepared at different solidification rates. In arc-melted (TiFe)-Zr samples, the $Fe_{23}$ $Zr_6$ and $(Ti,\;Zr)_2Fe$ phases formed in the TiFe matrix, while in the (TiFe)-Ce sample, the $CeO_2$ phase formed along the grain boundary of the TiFe matrix. As the Zr content was increased, the volume fractions of the $Fe_{23}$ $Zr_6$ and $(Ti,\;Zr)_2Fe$ phases increased, forming a network structure. Accordingly, the hardness values of the samples also increased. With a small addition of Ce of approximately 0.1 at%, the as-cast microstructure could be effectively refined, reducing the average grain boundary diameter from ${\sim}100{\mu}m$ to ${\sim}14{\mu}m$. In the rapidly solidified sample prepared through a melt-spinning method, the constituent phases were identical to those of the arc-melted samples while the grains were refined. The microstructural changes of TiFe alloys can affect the hydrogen storage ability as well as the mobility of the hydrogen atoms in the alloys.

Fig. 1. XRD results of TiFe with various (a) Zr or (b) Ce contents, (c) EDS results of (TiFe)₉₆Zr₄ (as-cast), (d) EDS results of (TiFe)₉₇Ce₃ (as-cast).

Fig. 2. Ti-Fe, Fe-Zr and Ti-Zr phase diagrams presented by L. Zeng et al. [9].

Fig. 3. SEM micrographs of as-cast (TiFe)-Zr and (TiFe)-Ce alloys.

Fig. 4. Optical micrographs of as-cast (TiFe)-Zr and (TiFe)-Ce alloys.

Fig. 5. Vicker’s hardness values of TiFe alloys with different Zr or Ce additions.

Fig. 6. Optical micrographs of (TiFe)₉₆Zr₄ and (TiFe)₉₇Ce₃ alloys prepared at different solidification rates.

Table. 1. Experimental conditions for melt spinning process.