Development of high-temperature structural material with an Al_3Ti base

点击翻译按钮获取中文摘要

Al_3Ti is a potential candidate for a high-temperature structural material of high strength/density ration because of its low density and excellent oxidation resistance.The major mode of deformation of Al_3Ti is the orderd twinning of the type {111}<11^^-] which does not disturb the DO_<22>-type symmetry of the lattice. At high temperatures, not only ordered twinning but also slip along<110] and <100] become operative. Polycrystalline Al_3Ti shows yielding ecen at room temperature ; however, its francture strain is much less than 1%. The stress-strain behavior and yield stress of single crystals of Al_3Ti shows a strong orientaltion dependence. This can be explained in view of the orientation and loading mode dependence of ordered-twinning.Alloying additions of hafnium, zirconium lithium and boron improve ductility of Al_3Ti. Additions of some rate-earth elements may also increase the activity of ordered twinning and improve ductility of Al_3Ti. Ductility of Al_3V, which is isostructural to Al_3Ti, is improved substantially by the partial replacement of vanadium by titanium. This is because the activity of ordered twinning in Al_3V is increased by the partial replacement of vanadium by titanium.Investigations on the effect of alloying elements which substitute for al on ductility of Al_3Ti are now in progress.