Metallographic and structural observations in the pseudo-binary section Ni₃Si-Ni₃Ti of the Ni-Si-Ti system

The metallographic and structural features of the alloys in the pseudo-binary section between Ni₃Si (L1₂) and Ni₃Ti (D0₂₄) were investigated. The L1₂ phase (γ′) extended along a pseudo-binary line between the two phases with Ti solubility of about 11 at.%. Also, the L1₂ phase expanded up to about 80 at.% Ni at high Ti concentration. Consistent with previous observations, the addition of the Ti elements into the Ni₃Si alloy led to congruent melting of L1₂ phase. Based on the observations of X-ray diffraction and an electron channeling technique aided with EDX (Energy Dispersive X-ray spectrometer), it was shown that the alloying element, Ti, substituted for the component element of Si the ternary alloy Ni₃(Si, Ti) was highly ordered. The solubility limit of boron in Ni₃(Si, Ti) was shown to be very low, i.e. less than 50 ppm.