銅-鉛合金の偏晶反応凝固

Abstract

Principles of monotectic solidification of the binary copper-lead alloy are introduced from the observation of crystallizing courses of direction-free and unidirectional solidification in the monotectic and hyper-monotectic alloys. In the direction-free solidification the α-solid of a monotectic product grows in volume spherically unlike dendritic growth in the hypo-monotectic alloy. The released L2 liquid accompanied by generation of the α-solid lies in the α-solid sphere radiately, while the initial L2 does in the boundaries. Columnar growth of the α-solid of a monotectic product occurs in an opposite direction of heat flow during unidirectional solidification. The monotectic cell is produced in which the α-solid of a monotectic product grows in an opposite direction of heat flow surrounding the released rod-like L2 liquid. In the unidirectional solidification at temperature gradient 50°C/cm and freezing rate 60 mm/min abnormal condensation of the L2 in the liquid in advance of the monotectic cell results in the bell-shape aggregation in the hyper-monotectic copper-50% lead alloy. At temperature gradient 10° to 30°C/cm and freezing rate 0.5 to 4.0 mm/min widening the (L1+L2) layer causes arrangement of coarse and rod-like L2 liquid within the monotectic cell. The inter-rod spacing is in inverse proportion to the square root of freezing rate and is reduced with temperature gradient in the liquid. Both copper and lead in the monotectic cell grow preferentially in the 〈110〉 direction at high rate of freezing and in 〈111〉 at slow rate.