Microstructure and Deformation Behavior of Lamellar Ti-Rich TiAl Crystal with Lotus-Type Aligned Pores
A porous Ti-48.0at.%Al (Ti-rich TiAl) crystal, in which lotus-type long cylindrical pores were aligned and (γ/α2) two-phase lamellar structure was simultaneously developed, was fabricated by floating zone method under the pressure of hydrogen and helium mixed gas. Plastic deformation behavior and microstructure of the Ti-rich TiAl crystal with lotus-type aligned pores were investigated by focusing on the elongated pore direction. The as-grown and annealed crystals show a well-developed lamellar structure and no texture accompanied by 52% porosity and a mean pore diameter of 380 μm. Yield stress strongly depends on the loading direction against the elongated pore. When loading directions are parallel and perpendicular to the pore direction, yield stresses obey K=1 and 2.5, respectively, in equation of σ=σ0(1-p)K, where σ is the yield stress with pores, σ0 is the yield stress without pores and p is porosity. This reflects macroscopically homogeneous and locally heterogeneous plastic deformation between pores, respectively.
Young Won Chang, Nack J. Kim and Chong Soo Lee
T. Nakano et al., "Microstructure and Deformation Behavior of Lamellar Ti-Rich TiAl Crystal with Lotus-Type Aligned Pores", Materials Science Forum, Vols. 561-565, pp. 383-386, 2007