Hao Shiming

Study on the phase equilibria of the Ti–Ni–Nb ternary system at 900°C

Abstract The phase equilibria of the Ti–Ni–Nb ternary at 900°C have been studied by means of the diffusion couple technique. The 900°C isothermal section of the Ti–Ni–Nb system was plotted based on the present experimental results. Four ternary compounds, X A , X B , X C and X D , have been observed, in which X B was discovered for the first time.

IMPROVEMENTS ON THE NATURAL ITERATION METHOD IN THE CLUSTER VARIATION METHOD

Abstract By examining the relationship between grand potential and various distribution variables, this paper combines the Natural Iteration Method (NIM) with the Step Speeded Method and Dichotomous method, respectively, and proposes two methods, Step Speeded- and Dichotomous-NIMs, for improving the conventional NIM by making use of the absolute convergence of the NIM. The calculated results indicate the numbers of iteration in the two methods obviously decreased, and they are still with absolute convergence.

Calculation of phase equilibria for the ternary system by the grand potential method

The relationships among the grand potential,G, the chemical potential, μi, and the effective chemical potential, μi, are geometrically demonstrated. An important equation concerning the relationship between the effective chemical potential, μi, and the molar free energy, Fm, was deduced. Use of the grand potential method enables calculation of the phase equilibria for the miscibility gap and different crystal structures in the ternary system.

Mechanism and kinetics of phase transformation in light heat-resisting alloys Ti-40~45at.%Al

The quenched and aged microstructures of Ti-40~45at.%Al were investigated. The results showed that the microstructure quenched from disordered α single phase is a supersaturated ordered single phase α882. When the supersaturated α882 phase is aged in α2+γ two phase field at 1273K and 1373K, it will transform into a α2+γ lamellar microstructure with semicontinuous or mixed semicontinuous and discontinuous decomposition mechanism. With the methods of quantitative metallograph examination and X-ray diffraction analysis, the relationship between the amount of γ phase precipitation and the time of isothermal transformation is agreed.