Ll₂型金属間化合物Ni₃Alのホウ素添加による常温延性の改善

抄録

The room temperature ductility of the L1₂ type intermetallic compound Ni₃Al which has been accepted to be brittle so far was improved considerably by a small addition of boron. Binary Ni₃Al poly-crystals without boron did not exhibit any ductility at room temperature in agreement with previous reports, while those to which boron was added showed considerable ductility as determined from the bending, cold-rolling and tensile tests. Improvement of the room temperature ductility by boron addition did not bring about lowering of the yield strength of Ni₃Al. Fracture mode changes trom the intergranular one which is typical for the alloy without boron to the transgranular type in the alloys containing a small amount of boron. Boron appeared to be the effective element which suppress the intergranular fracture. The mechanism of the improvement of the room temperature ductility was discussed based on impurity segregation to grain boundaries or the peculiarity of the grain boundary structure.