Effect of Catalyst on Heterogeneous Nucleation in Fe-Ni-Cr Alloys

In order to elucidate the nature of heterogeneous nucleation, a differential scanning calorimetry (DSC) thermal analysis of Fe–Ni–Cr alloys (Ni+Cr content=30 mass% (constant); Ni content: 7.5 to 29.3 mass%) containing TiN and Al2O3 was conducted. Then, special attention was paid to the difference in the phase of the primary crystal nucleated by the triggering effect of a catalyst (nucleating agent). The solidification and transformation mode appearing during cooling in these alloys is classified into three cases: F mode, FA mode, and A mode. The change of modes and the critical undercooling (ΔT) depend on the kind of catalyst used as well as on the chemical composition. In addition, in spite of the kind of primary crystal, the value of ΔT is always smaller in the order of TiN