Effects of Nb and Zr addition on introduction of misfit dislocations onto alpha(2)/gamma lamellar boundaries and change of lattice misfit in fully lamellar TiAl alloy

作者：Toriyama Yasunari^*; Yoshimi Kyosuke; Maruyama Kouichi

来源：Journal of the Japan Institute of Metals, 2007, 71(1): 96-102.

DOI：10.2320/jinstmet.71.96

• titanium aluminides
• interface
• lattice misfit
• misfit dislocation
• lamellar structure

Changes in microstructures of alpha(2)/gamma lamellar boundaries was studied on fully lamellar Ti-38Al-xM (at%, x = 0, 3, M = Zr, Nb) alloys over a wide range of average lamellar thickness from 290 to 20 nm. The lamellar structure was formed by isothermal aging and lamellar thickness was controlled by changing aging temperature. The addition of Nb or Zr alters the lattice mismatch between alpha(2) and gamma phases. At lamellar boundaries the mismatch is accommodated by elastic deformation and/or by introducing misfit dislocations. The elastic deformation totally accommodates the lattice mismatch (coherent boundary) when gamma lamellae are thin enough. Misfit dislocations are introduced to accommodate partly the mismatch when gamma lamellar thickness exceeds a critical value lambda(c). Density of the misfit dislocations saturates to an upper limit d(s) in thick lamellar structures.

• 出版日期2007-1