Microstructures of Multiphase Al3Ti-8Mn-Based Alloys

The microstructures of the alloys near the Al3Ti-8Mn composition region of the Al-Ti-8Mn quaternary system change with variation of the Nb content. The microstructures have been investigated using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is determined that in Al67Mn8Ti22-based alloys modified with Nb the second phases can he DO22Al3(Ti, Nb), L1(0) TiAl or Ga2Hf type of Al2Ti. The microstructures of four typical experimental alloys, Al-67 Mn3Ti23Nb2, Al59Mn3Ti30Nb3, Al65Mn3Ti26.5Nb0.5 and Al65Mn3Ti23Nb4, are presented in this paper, The second phase Al-3 (Ti,Nb) particles con be dispersed blocky or dendritic,the L1(0) TiAl particles are ripple-like or needle-like, and L1(0) TiAl arrays alternately with L1(2) matrix. The netty Al2Ti phase is plate-like under TEM and distributes across the L1(3) matrix.