Spinodal Decompositions in Undercooled Molten Pd-Ni-P Alloys
Abstract
Recently, Zhou et al. was able to determine the metastable liquid miscibility gap (MLMG) of a metal-metalloid alloy system, Pd-Ni-P, by a method that involves a morphological transition. More recently, it was found that Pd-Ni-P undergoes a liquid-liquid transition (LLT). More importantly, it was demonstrated that it is a first-order phase change. The experimental results enable us to establish that the short-range orders (SROs), arisen from different forms of the constituent clusters in the liquid state, are divided into groups. When one group changes into another group, it is a first-order phase transition. In terms of thermodynamics, it means that each of the characteristic SRO has its own Gibbs free energy, denoted by GSRO. In the experiments of Zhou et al., the MLMG is due to two different SROs, which are denoted by i,r-SRO and i,rl-SRO. In the experiments of the LLT, it was shown that the transition from i,r-SRO to i,rl-SRO is a first-order phase change. It can therefore be concluded from the experiments that we can define Gi,r-SRO and Gi,rl-SRO. The MLMG was therefore modeled by Gi,r-SRO and G i,rl-SRO in an earlier paper by us. In this thesis, we aim to study the behavior of Gi,r-SRO and Gi,rl-SRO as a function of T (temperature). The study can be divided into two parts. In the first, both Gi,r-SRO and Gi,rl -SRO are studied as a function of T. Experimental result shows that the MLMG arisen from Gi,r-SRO and Gi,r l-SRO is different from a conventional spinodal decomposition mechanism occurring in the crystalline state. The second part builds on the results of the first part. We attempt to study the reversible behaviors of Gi,r-SRO and Gi,rl -SRO with temperature. It turns out that the reversible behaviors comply with thermodynamics. But kinetics may stagger the observation.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 2018
- Bibcode:
- 2018PhDT........35N
- Keywords:
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- Materials science;Physics;Engineering