Structures of Al-Ti Peritectic System Alloys Solidified under Microgravity Conditions

Abstract

In order to clarify the solidification mechanisms of Al-Ti and Al-Ti-B system alloys under microgravity conditions, experiments were performed using Sounding Rocket TR-lA No. 6. Different compositions of six samples were melted and solidified in the two isothermal fur­naces on board the rocket. In the higher temperature furnace (1400°C), observation of the peritectic composition of Al-1.3%Ti alloy revealed that the primary TiAl3 crystals distributed in the melt act as nucleation sites and then form granular crystals. A study of the hypoperitectic alloy revealed that the TiAl3 and TiB2 crystals in the Al-Ti and Al-Ti-B master al­loys melted completely then large crystals formed. In the lower temperature furnace (800°C), TiAl3 and TiB2 crystals in the master alloy remained and nucleated the granular crystals as if a peritectic reaction had occurred.