Mechanical properties of Ni₃Al containing C, B and Be

The mechanical properties of the flow strength, ductility and fracturing in the Ni₃Al polycrystals containing C, B and Be were extensively investigated by tension and compression tests. The strengthening by the dopant was very significant at ambient temperatures as well as at temperatures showing the anomalous temperature dependence of the yield stress while was almost negligible at temperatures above the peak for every ternary alloy. The activation energy for the thermal stress term producing the anomalous positive temperature dependence was, by the addition of every dopant, enhanced in the just-stoichiometric (25 at.%Al) alloys while reduced in the off-stoichiometric (24 at.%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 evaluation in the correlation between the increment of the yield stress Δσ_y ΔC and the increment of lattice strain Δε{lunate} ΔC, per atom portion of the ternary addition indicated that the solid solution strengthening by C, B and Be atoms in Ni₃Al alloy was not fully expained only by the size effect in the elastic interaction between solute atoms and dislocations. The ductilization was found for the addition of B and Be atoms but not for the addition of C atom, and then disappeared above 1000 K for the addition of B atom and above 800 K for the addition of Be atoms. These ductilization behavior was discussed in terms of the species and concentration of the dopant, alloys stoichiometry and test environment.