Relationship between Microstructure and Tensile Strength in the Directionally Solidified (23-27) at. % Al-Ni Alloys
Directional or single crystal technique was applied to enhance the ductility, and two phases of γ (Ni) phase or β (NiAl) phase in γ‘(Ni3Al) matrix were also considered to increase the strength and ductility. In this study, directionally solidified rods were prepared at the solidification rate of 50µm/s in 23-27 at.% Al-Ni alloys, and tensile strengths of these rods were analyzed at room temperature. Directionally solidified samples showed the γ dendrite fibers formed in the Ni3Al matrix in the hypo eutectic composition of 23 at.% Al, the γ‘ single phase in the eutectic composition of 24.5 at. % Al, and the β dendrite fibers in the γ‘ matrix in the hyper eutectic compositions of 25, 26, 27 at.% Al. The hypoeutectic alloy including γ dendrites with γ‘ matrix exhibited a large elongation of over 70% with ductile transgranular fracture at room temperature. With increasing Al contents, the γ dendritic microstructure changed to the β dendrite in the γ‘ matrix, which resulted in decreasing the elongation by increasing the volume fraction of the brittle β dendrites in the ductile γ’ matrix.
Hyung Sun Kim, Yu Bao Li and Soo Wohn Lee
Y. Lu et al., "Relationship between Microstructure and Tensile Strength in the Directionally Solidified (23-27) at. % Al-Ni Alloys", Materials Science Forum, Vols. 510-511, pp. 458-461, 2006