Experimental investigations and thermodynamic descriptions of the Ni-Si and C-Ni-Si systems

Abstract

The binary Ni-Si phase diagram is reassessed and a consistent set of thermodynamic parameters is obtained based on literature data which we could verify experimentally (15 samples involving arc melting, annealing, water quenching, X-ray diffraction (XRD), and differential thermal analysis (DTA)). Applying this description of the Ni-Si system, as well as the descriptions of the Ni-C and Si-C systems available from the literature, preliminary calculations for the C-Ni-Si phase equilibria were made in order to provide guidance in selecting the compositions of decisive ternary alloys. These alloys were subjected to an experimental procedure similar to that employed for the Ni-Si alloys. The XRD and DTA measurements resulting from these ternary alloys provided accurate information on the invariant reaction temperatures in the C-Ni-Si system. Comprehensive comparisons between calculated and measured phase diagrams show that most of the experimental information is satisfactorily accounted for by the present description of the C-Ni-Si system. The liquidus projection and reaction scheme for the whole ternary system are presented.

A1-L12 interfacial free energies from data on coarsening in five binary Ni alloys, informed by thermodynamic phase diagram assessments

“…Equation 24, in which T is in°C, is somewhat awkward, but produces an excellent fit to the combined data of Ma and Ardell (unpublished research) and Ikeda et al [65]. The data on X c 0 e for Ni 3 Ga, Ni 3 Si, and Ni 3 Ti indicate that there is no change, or at best only a small variation, of concentration with temperature.…”

“…The model of Tokunaga et al [26], which has been used to calculate r in Table 7, overestimates the b 1 (c 0 -type) solvus, though it provides a better fit than the models of Lindholm and Sundman [25] or Du and Schuster [24]. The model of Miettinen [32] actually provides the best fit to the b 1 solvus.…”

“…Thermodynamic models of the Ni-rich solid solutions have been published for all five binary alloy systems: Ni-Al [19][20][21], Ni-Ga [22], Ni-Ge [23], Ni-Si [24][25][26], and Ni-Ti [27]. There are also thermodynamic models of ternary Ni-rich solid solutions involving Al, Ga, Ge, Si, and Ti that are helpful in selecting data on G m [28][29][30][31][32][33].…”

“…The capillary length, ' T , is also shown coarsening, the results are much smaller in magnitude. The results of calculations of r using the thermodynamic models of Du and Schuster [24] and Miettinen [32] are shown in Table 8. It is evident that the values of G 00 m are much smaller than those obtained from the model of Tokunaga et al [26] (see Table 4), yielding values of r that are about 1/2 to 2/3 those shown in Fig.…”

Non-integer temporal exponents in trans-interface diffusion-controlled coarsening

“…The L1 2 crystal structure of Ni 3 Ti is metastable, so diffusion in it cannot be measured. The L1 2 crystal structure of Ni 3 Si is stable only below *1130°C [77], thereby rendering measurement of diffusion of Si in Ni 3 Si by conventional methods very difficult; no such measurements exist. There have been measurements of diffusion as a function of concentration in ternary Ni 3 (Al,Cr) alloys, but there are not enough data to extrapolate to the low temperatures and c 0 concentrations in the coarsening regimes.…”