Fabrication of a NiAl–Cr(Mo) eutectic alloy with network microstructure for high-temperature strengthening

To improve the high temperature (up to 1100 °C) strength of NiAl-based alloy, a method of the microstructural optimization for achieving network Cr(Mo) reinforcements was proposed. A network Cr(Mo) microstructure was successfully obtained by evolution of the ultrafine lamellas in the sintering of rapid-solidified powders. As a result, the micro-sized Cr(Mo) networks are formed at the sintering necks and nano-sized Cr(Mo) networks exist inside the powders. Moreover, the Cr(Mo) phases are interconnected and their network morphology is characterized in 3D using micro-CT, as well as light optical tomography based on OM and SEM. Compared with other NiAl-based alloys, the sintered sample with network Cr(Mo) reinforcements has a considerably improved strength at high temperature. Based on detailed TEM analysis, the high temperature strengthening mechanism is discussed and the proposed network microstructure for NiAl-based alloy can provide synergetic strengthening effect, which is beneficial for achieving enhanced high temperature strength.