Microstructure and mechanical properties of NiAl-based hypereutectic alloy obtained by liquid metal cooling and zone melted liquid metal cooling directional solidification techniques

The microstructure, room temperature compressive property, and elevated temperature tensile property of directionally solidified NiAl–Cr(Mo)–(Hf,Dy) hypereutectic alloy were investigated. The directional solidifications of liquid metal cooling technique (LMC) and zone melted liquid metal cooling technique (ZMLMC) were adopted. In the LMC alloy, the well-aligned and fully eutectic lamellar structure parallel to the growth direction is obtained. The interlamellar spacing gradually decreases with increasing the withdrawal rate, and the compressive yield strength gradually increases. In the ZMLMC alloy, the eutectic lamellar structure is disordered and not parallel to the growth direction, and the quantities of Cr(Mo) primary phases are observed. Compared to the ZMLMC alloy, the LMC alloy has a better combination property because of the well-aligned lamellar structure. The observations of crack propagation and fracture surface are performed to better understand the fracture behavior.