Mechanical alloying of NiAl-based composites and cold sintering phenomenon

Abstract

Various approaches have recently been employed to improve mechanical properties of NiAl intermetallics at room temperature (RT) and high temperature (HT) respectively. However, some methods, such as refining grain size to improve RT brittleness and adding ceramic particles to enhance HT creep strength of the NiAl, may lead to contradictory results. It was pointed out that combining those two types of attempts or keeping the balance between the properties at RT and HT is very important for developing the NiAl as a new, high temperature structural material. Mechanical alloying (MA) can produce NiAl-based composites with a small grain size containing fine and homogeneously distributed oxides or other dispersions. This method can improve the toughness at RT and strength at HT of the NiAl at the same time if the following consolidation processing is adequately controlled so that the grain size, dispersion distribution and bonding with the matrix are appropriate. In this paper, the morphology, size and microstructures of MA NiAl-based composite powders, NiAl-TiB[sub 2] and NiAl-TiB[sub 2]-Y[sub 2]O[sub 3] are studied. The special cold sintering behavior of the NiAl-TiB[sub 2] powders during MA is reported.