The non isothermal crystallization behavior of two model blends of immiscible polymers (an isotactic polypropylene and a polyamide-6) was examined by a quenching procedure within a range of cooling rates from 0.1 to above 1000 degrees C/s in order to emulate the solidification conditions arising during polymer processing. The final structure of the blend was analyzed by density and WAXD and the transition from stable to metastable phases in the blends and the pure homopolymers was compared examining their dependence on cooling rate. this shows that crystallization in the blends is always faster since the transitions move to larger cooling rates. Observation of morphological details suggests that this can be due to enhanced nucleation at the interface. The density variation in the case of the polyamide-6 rich blend is larger than expected from an additive volume contribution which maya be ascribed to development of microvoids at the interface. In the case of the isotactic polypropylene rich blend the additive volume contribution is consistent wit experimental observations.