Plastic Deformation Behavior of Al5Ti3 Single-Phase Single Crystals

Abstract

ABSTRACTAl5Ti3 single-phase single crystals with the stoichiometric composition of Ti-62.5at.%Al were obtained by the floating zone method and subsequent heat treatment at 750°C for 48h. The crystals contain no L10 phase, but compose of anti-phase domains (APD) surrounded by the anti-phase boundary (APB) on the basis of the Al5Ti3 long-period superstructure.Orientation dependence of plastic deformation behavior and operative slip system were examined in compression in a wide temperature range between RT and 750°C using the single-phase single crystals in comparison with Al-rich TiAl single crystals with the L10 matrix and Al5Ti3 precipitates. In the wide crystal orientation area, {111)<110] ordinary slip appeared independent of the tested temperature, while {111)<101] superlattice slip was operative only at around [001] and [110] axes. This is because the critical resolved shear stress (CRSS) for the ordinary slip is lower than that for the superlattice slip and that for the ordinary slip in other Al-rich TiAl crystals containing L10. This implies that existence of the L10 matrix with the Al5Ti3 phase must be closely related to strengthening for the ordinary slip, similarity in Ni-base super-alloys consisting of the Ni-based matrix and L12 precipitates. The CRSS for both slips gradually decreased or was kept constant with temperature, showing no remarkable anomalous strengthening.In this paper, deformation mechanism in Al5Ti3 single-phase single crystals will be discussed focusing on condition of the Al5Ti3 superstructure.