Recrystallization behavior of boron-doped Ni76Al24

Considerable hardness recovery and almost complete restoration of order wer e observed during annealing of 85 pet cold-rolled boron-doped Ni76Al24 prio r to recrystallization. Recrystallization kinetics were investigated over a wide range of temperatures at small intervals of transformed volume fracti on. The variation of transformed volume fraction with time showed two unusu al distinct regions characterized by separate Avrami exponents and activati on energies. The exponent decreased from 2.2 at 800 degrees C to 0.7 at 950 degrees C for X > 0.6 and had a temperature-insensitive value of 3 for X > 0.6. The activation energy below 900 degrees C was 145 kJ/g atom for X < 0 .6 and 110 kJ/g atom for X > 0.6, and that above 900 degrees C was about 43 5 kJ/g atom. Equations for the kinetics have been derived based on concurre nt recovery in the untransformed regions during recrystallization. The pred ictions of the equations agree exceedingly well with the experimental resul ts and yield separate values of the activation energies for interface migra tion and recovery.