TiAl 일방향응고합금의 β응고법을 이용한 미세조직제어

Abstract

Ti-47A1-2W alloys, which have been reported as having alloy composition of β-solidification, were directionally solidified by using Bridgman and floating zone type directional solidification(DS) apparatuses. Mechanical properties of DS ingots were evaluated by room temperature and high temperature (800℃) tensile tests. In the results of DS by the floating zone type apparatus at a growth rate of 30 ㎜/h, the lamellar microstructure was well-aligned parallel to the growth direction. Ingots having lamellar orientation parallel to the growth direction showed excellent room temperature tensile ductility. High temperature tensile yield strength was maintained similarly to the yield strength at room temperature. The texture of γ lamellar laths was identified from the results of electron back scattered diffraction pattern (EBSD) analysis of the lamellar orientation of DS ingots, which were manufactured by a floating zone furnace. On the basis of the EBSD results, it was estimated that the preferred growth directions of bcc-β dendrite grown at high temperature near the melting point was in the [001]_β direction at a growth rate of 30 ㎜/h and the [111]_β direction at a growth rate of 90 ㎜/h.