MECHANICAL-PROPERTIES OF NI3AL CONTAINING C, B AND BE

Flow strength, ductility and fracture in polycrystals containing C, B and Be were investigated by tension and compression tests. Strengthening by the dopant was significant at ambient temperatures as well as at temperatures showing the anomalous temperature dependence of the yield stress while it was almost negligible at temperatures above the peak. The activation energy for the thermal stress term producing the anomalous positive temperature dependence was enhanced in the just-stoichiometric (25 at. percent Al) alloys while reduced in the off-stoichiometric (24 at. percent Al) alloys. The yield stress at 77 K implying the athermal term (solid solution strengthening) increased linearly with increasing concentration of each ternary atom, the slope of which was very remarkable for the addition of C and B atoms. The correlation between the increment of the yield stress DELTA sigma //y/ DELTA C and the increment of lattice strain DELTA epsilon / DELTA C, per atom portion of the ternary addition indicated that the solid solution strengthening by C, B and Be atoms is not fully explained by the size effect in the elastic interaction between solute atoms and dislocations.