Effect of boron on the ductility of ordered Ni-Ni₄Mo alloys

Boron was identified to have a beneficial effect on the room temperature ductility of ordered Ni-Ni₄Mo alloys. An addition of 0.01 to 0.03 wt % boron to hypostoichiometric alloys was found to increase the tensile ductility from about 5% to 30% in the ordered state produced by exposure at 600 to 800 °C, of the annealed material. The boron effect was, however, found to diminish with exposure time at a given temperature and not to be maintained at elevated temperatures. The beneficial effect of boron on room temperature ductility was also found to be considerably less pronounced in stoichiometric Ni₄Mo alloy. Both electron energy loss spectroscopy and Auger electron spectroscopy techniques revealed no preferential segregation of boron to grain boundaries. Experimental results suggested that boron decelerates the kinetics of heterogeneous grain boundary ordering which leads to an improvement in ductility.