Effects of boron on the mechanical behaviour of a Ni-rich NiAl alloy

Abstract

The NiAl based intermetallic alloys are currently of considerable interest as new structural materials because of their relatively low density, comparatively high melting temperature and excellent high temperature oxidation resistance. It has also been found that the Ni-rich (62-65 at % Ni) NiAl alloys with the [beta] (B2) structure undergo a thermoelastic martensitic transformation and exhibit the shape memory effect (SME). Unfortunately, the binary NiAl alloys are extremely brittle at ambient temperature and, therefore, are restricted in practical application. The micro-alloying and macro-alloying methods are commonly used to overcome the brittleness of the alloys. It is reported that boron is the most effective microalloying element in improving the ductility and suppressing the intergranular fracture of the Ni[sub 3]Al intermetallic compound containing aluminium less than 25 at %. However, whether boron has a beneficial effect on the binary NiAl alloy with the B2 structure is not clear. The present paper reports the effect of boron on the mechanical 1 and martensitic transformation in a NiAl alloy containing 37.5 at % Al with the B2 structure.