Elevated Temperature Compressive Properties of Porous NiAl Fabricated by Continuous Zone Melting Technique

초록

Ordered bcc intermetallic compound NiAl has been considered as high temperature structural materials because of its high melting point, low density, good electrical and thermal conductivity. Since only three independent slip system is available, NiAl exhibit poor low temperature ductility and fracture toughness. Recently, several studies have been reported to improve these drawbacks from directional solidifying. The purpose of this study was to investigate elevated temperature compressive properties of porous NiAl with directional pores when the material is fabricated by continuous zone melting technique under a pressurized hydrogen gas. Compressive specimens of porous NiAl were cut from the rods and carried out compression test at 298K, 673K and 873K. Also, nonporous specimens were tested for the comparison with porous specimens. After compression test at 673K, the compressive strain of porous NiAl showed much higher amount than nonporous specimens. The main reason for this behavior is that pores have significant effect on the brittle matrix in terms of ductility and fracture toughness. The yield strength of porous and nonporous NiAl decreased with increasing temperature. Anisotropic compressive properties between parallel and perpendicular solidification direction to the compressive direction were also shown. Crystallographic orientation of each solidifying direction was confirmed by electron backscattered diffraction (EBSD).