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

초록

The strongly ordered intermetallic compound NiAl has been considered as a promising structural material at high temperature due to high melting point, low density, good electrical and thermal conductivity and excellent environmental resistance. However, inherent low room temperature ductility and poor creep strength at elevated temperature are drawbacks for being applied. Lotus NiAl whose long cylindrical pores are aligned in one direction was fabricated by unidirectional solidification in a pressurized hydrogen atmosphere. Compression tests were carried out at 673K and 873K with lotus and nonporous NiAl specimens. After compression at 673K, lotus specimens showed ductile behavior but nonporous specimens showed still brittle behavior. But in the case of 873K, all specimens showed ductile behavior. Compressive stress and yield stress of lotus and nonporous NiAl was decreased with increasing temperature. Furthermore, anisotropic compressive properties were presented with different compressive direction to the solidification direction. Crystallographic orientation of each direction was confirmed by electron backscattered diffraction. Microstructure was observed with optical and scanning electron microscope.