EFFECT OF BORON IN NI3AL - STRUCTURAL-TRANSFORMATION-INDUCED DUCTILIZATION

The Ni3Al(L1(2)) intermetallic compound after boron doping becomes duc tile. It is argued that grain-boundary segregation is not the only cau se of the increase in ductility. It is pointed out that the L1(2) stru cture undergoes transformation to D0(22) during deformation, and durin g the deformation of this D0(22) structure the material fails. With th e addition of boron, the stability of the L1(2) structure is enhanced with respect to D0(22) and slows the transformation rate. Therefore th e nucleation and propagation of cracks become inhibited. Numerous expe rimental observations have been explained with the proposed mechanism.