Prediction of the maximal recalescence temperature upon rapid solidification of bulk undercooled Cu70Ni30 alloy

Non-equilibrium transformation path for bulk undercooled hypereutectic Fe–B alloy

“…However, the above model predictions are still unsatisfactory as compared with our experimental results for bulk undercooled Cu-Ni alloy [18]. After an analysis of the solute distribution in the quenched grain and a quantitative thermodynamic calculation, we proposed T R for bulk undercooled melts should reach the thermodynamic T 0 point (with no L/S Gibbs energy difference) of the residual liquid [18]. This criterion is compatible with Hindmarsh et al's conclusion that T R should depend on the solute concentration in the remaining liquid [22].…”

“…Later, Vedovato et al reported recalescence in gas atomization should reach a temperature interval between the two cooling lines described by full diffusion and no diffusion in solid [21]. However, the above model predictions are still unsatisfactory as compared with our experimental results for bulk undercooled Cu-Ni alloy [18]. After an analysis of the solute distribution in the quenched grain and a quantitative thermodynamic calculation, we proposed T R for bulk undercooled melts should reach the thermodynamic T 0 point (with no L/S Gibbs energy difference) of the residual liquid [18].…”

“…As reported earlier, the recalescence time for undercooled Ni-Sn eutectic alloy is about 0.1 s [20]. Moreover, the cooling rate in the current experiment was measured as 14 K/s [18]. On this basis, the decrease of melts temperature due to heat extraction to the environment can be estimated as less than 2 K. This value is obviously within the experimental uncertainty and can be neglected in comparison with the temperature rise due to the release of latent heat.…”

“…The undercooling experiment was carried out in a quartz crucible under the protection of B2O3 glass slag so as to remove the impurities, and to prevent the alloy from oxidation. Preparation of the fluxing glass was described elsewhere [18]. The crucible was set in the mid position of a high-frequency induction coil.…”

“…Meanwhile, great progresses have also been made in the related theoretical investigations, such as homogeneous or heterogeneous nucleation theory [6][7][8], dendrite growth model [9][10][11][12][13] and metastable phase formation mechanism [14][15][16], in order to understand the physical essence underlying such rapid transformation process. Generally, solidification of undercooled melts consists of two distinctive regimes [17][18][19], i.e., rapid solidification accompanying recalescence, which can be experimentally observed as the abrupt rising of liquid temperature, and the subsequent near-equilibrium solidification controlled solely by external heat extraction to the environment. Up to now, it has been accepted from a thermodynamic view that the occurrence of non-equilibrium solidification is caused by the liquid/solid (L/S) Gibbs energy difference [2,8].…”