STRENGTHENING AND DUCTILIZATION OF NI3SI BY THE ADDITION OF TI ELEMENTS

The mechanical properties of Ni3Si polycrystals alloyed with Ti and doped with boron were investigated by compressive and tensile tests. The yield stress increased with increasing Ti concentration and with decreasing Ni concentration at all testing temperatures. The peak temperature in the yield stress increased with increasing Ti concentration. The activation energy for the thermal stress term producing the positive temperature dependence decreased with increasing Ti concentration and was correlated with the phase stability of L12(Ni3Si) relative to D024(Ni3Ti). Ductility was obtained by the addition of Ti. Higher elongation values were observed in the alloys consisting of higher Ti concentration and higher Ni concentration. Further improvement of the tensile elongation was found by the addition of a small amount of boron. The variation of the elongation with temperature showed a peak at intermediate temperature. The elongation behavior correlated well with the variation of the fracture patterns. The ductilization of the Ni3Si observed in this work verified the alloying method to improve the grain boundary cohesion of L12 type ordered alloys which has been proposed by the present authors. © 1990.