An investigation of thermal aging effects on the mechanical properties of a Ni3Al-based alloy by nanoindentation

Ni3Al-based intermetallic alloys are composed of a gamma network and gamma' domains. In general, through precipitation, the gamma' phase is used as a hardening source for this alloy. This study examined how gamma' acts as a hardening material in a cast Ni3Al-based intermetallic alloy. Specimens cut from a centrifugally cast tube were aged in At at elevated temperatures for up to 1600 h. Hardness tests were then performed in air at room temperature. Vickers microhardness and nanoindentation tests were carried out on specimens aged at 900 degrees C and 1100 degrees C. The microstructures were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The microhardness of bulk Ni3Al decreased dramatically with increasing thermal aging time at 900 degrees C, but the nanohardness measured by the nanoindenter did not significantly decrease. The nanohardness data suggested that the hardening effects were caused by the precipitation of the gamma' phase on the gamma and gamma' cells. (C) 2009 Elsevier B.V. All rights reserved.