The effect of lamella thickness on the creep behaviour of Ti-48Al-2Nb-2Mn

摘要

There is now copious evidence that the mechanical properties of alloys based upon the TiAl phase are strongly dependent, upon both alloy chemistry and microstmcture [1, 2], Creep is no exception and it has been demonstrated that of the three possible niicrostructures: near γ, duplex and fully lamellar -which consists of colonies of discrete lamellae (platelets) of mainly γ-TiAl with a smaller number of γ2-Ti3Al lamellae - the latter is the most creep resistant [3 - 5], These studies have shown that the creep behaviour oflamellar structures is independent of colony size in the range 600 to 120Oμm, and that γ grains located on the colony boundaries degrade the creep resistance until their volume fraction exceeds 20% whereupon the γ grains dominate the creep behaviour.