γ-TiAl 금속간화합물의 결정학적 인자와 기계적 특성에 미치는 Al 함량과 합금원소 첨가의 영향

Abstract

The effects of Al content and alloying elements on the crystallographic factors and the mechanical Properties of Ti-(47-54)Al and Ti-48Al-(1-3)M (M=Cr, Mn) intermetallic compounds have been investigated using optical microscopy, scanning electron microscopy, X-ray diffractometry, and compression testing. The γ grain size of heat-treated cast structure decreases with the decrease of Al content and the addition of Cr(or Mn). This is primarily due to the refinement of as-cast structure. In the heat-treated cast structure, the inhomogeneity of γ grain size is also related to the second phase particles, which are located within the dendrite core region. The variation of lattice parameters and tetragonality of γ phase as, a function of Al content shows a larger slope for the Ti-rich side than that for the Al-rich side in reference to the stoichiometric composition. This is believed to be primarily due to the difference of anti-site defect type. The hardness of Y phase is enhanced with the increase of the degree of non-stoichiometry. The variation of hardness is insensitive to the type of anti-site defect. The yield stresses of alloys containing Cr(or Mn) are mainly strengthened by the refinement of γ grain size. The ductility of γ-TiAl base intermetallic compounds depends primarily on the tetragonality rather than the unit cell volume change of γ phase.