Hyperperitectic Alloy Research Articles

Cu-Sn合金における包晶β相の成長

The non-equilibrium peritectic transformation of Cu-Sn alloys was verified by experiment and calculation assuming a diffusion controlled thickening process of the peritectic β-phase. The unstable liquid and the α-solid solution remain in the hypo- and hyper-peritectic alloys respectively, when cooled down to just below the peritectic isotherm. The fact shows occurance of the non-equilibrium peritectic transformation. The rate of peritectic β-phase thickening by diffusion in the β-phase increases with undercooling from the peritectic isotherm 1072 K during holding at the temperature between two peritectic isotherms (1072 and 1029 K) and with the cooling rate during continuous cooling. If the peritectic β-phase to be formed is of large thickness or the cooling rate is great, solidification of Cu-Sn alloys completes with direct crystallization of secondary β-phase from super-cooled liquid at the later stage of solidification.