Effects of boron doping on the grain-growth kinetics and mechanical properties of gamma/gamma' nickel-aluminum alloys

The effects of 0.5 at. pet of boron doping on the microstructures and mecha nical properties of gamma/gamma ' nickel-aluminum alloys have been investig ated in the present study. A nickel-rich grain-boundary zone was observed i n the boron-doped alloy after homogenization at 1 100 degreesC and prolonge d annealing at 1200 degreesC. Boron doping also caused remarkable improveme nts in toughness and tensile elongation and caused the fracture mode to cha nge from completely intergranular to completely transgranular. The grain gr owth following recrystallization at 1200 OC was found to be retarded upon b oron doping. A sudden increase in tensile elongation and a sudden drop in h ardness were also observed upon prolonged heating during isothermal anneali ng at 1200 "C. The results are interpreted with reference to boron-nickel c osegregation at the grain boundaries.