By means of sampling methods, we have determined the solubility of nitrogen in liquid Ni, Ni–Nb, Ni–Cr–Nb, Ni–Fe–Nb, and Ni-18Cr-17Fe-5.2Nb systems within the temperature range from 1773 K to 1873 K and with the niobium content from 5 to 20 mass%. It has been found that Sieverts’ formalism successfully describes the solubility of nitrogen in all these liquid alloys up to 7 atm of the nitrogen partial pressure. Niobium addition increases the nitrogen solubility and its effect to increase nitrogen solubility is only second to chromium. Furthermore, we have derived the enthalpy and entropy of dissolution of nitrogen in these liquid alloys, determining the first order interaction parameter, = –0.0785, up to 20 mass% Nb in nickel between nitrogen and niobium. In addition, the effects of alloying elements on the activity coefficient of nitrogen have been further investigated and the second order cross-interaction parameters between nitrogen and chromium or iron with niobium at 1873 K have been determined as = 0.0256 and = 0.0115.

The phase transformation behavior of Ti-42Al-5Mn (at.%) alloy from different phase regions with various cooling rates was investigated based on electron probe micro analyzer-backscattered electrons (EPMA-BSE). It is shown that β→α₂′ takes place when this alloy is cooled at a high rate, such as water quenching (WQ), oil cooling (OC), from β single phase. With the decreasing cooling rate to air cooling (AC), β→α₂′ is restrained and β→γ is promoted by forming γ platelets. The room-temperature microstructure is β_o + α₂ when alloy cooled (WQ and OC) from (β + α) dual-phase. However, under AC, β→γ occurs and γ platelets form. It should be noted that α₂→γ happens when this alloy cooled from 1180 °C (>T_eut) by OC and AC, forming an incomplete lamellae (α₂/γ) structure in the α₂ phase. However, when the alloy cooled from 1100 °C (<T_eut), α₂/γ→β_o,sec occurs and complete lamellae generates in α₂ phase.

An investigation has been made concerning the solubility of nitrogen in liquid binary alloys (Ni-V and Ni-Ta) and ternary alloys (Ni-Cr-V and Ni-Cr-Ta) by sampling method. The experiments were carried out in the temperature range from 1773 K to 1873 K and under the nitrogen partial pressure up to 1.0 bar. A technique involving induction melting and a rapid quench device has been used in this study. It has been found that Sieverts’ law successfully describes the nitrogen dissolution in all these liquid alloys up to 1.0 bar of nitrogen gas partial pressure. The additions of vanadium, tantalum and chromium significantly increase the nitrogen solubility, especially vanadium-alloying addition. Furthermore, we have determined the interaction parameters, enthalpies and entropies of nitrogen dissolution in these liquid alloys.