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The quasiperitecticcoated transformation has the dual characteristics of eutectic transformation and peritectic transformation, and it exists in many industrial alloys. However, a relatively complete theoretical model of peritectic solidification has not been established so far, and there are few related studies on its solidification mechanism. Based on this, this article carried out directional solidification experiments at different drawing speeds (v=1, 3, 5, 15, 30, 70 μm/s) for the Nb42Ti21Co37 quasiperitectic alloy, aiming to study the alloy"s performance at different drawing speeds. Microstructure evolution law, and build the corresponding solidification mechanism. The research results show that the conventional as-cast and directional solidification structures of Nb42Ti21Co37 quasiperitectic alloy contain α-Nb,Co₆Nb₇ and TiCo+Co₆Nb₇ quasiperitectic phases. With the gradual increase of the drawing rate, the primary α-Nb phase undergoes a spherical shape →petal-like →cluster-like →dendrite-like transformation; along with the above process, the quenched interface has undergone the transformation from cellular interface to cellular dendrite-like interface, and at the pulling rate v=70 μm/s, solid/liquid The interface disappears; secondly, the quasiperitectic structure in the steady-state growth zone of directional solidification is gradually refined, and the interlayer spacing has an exponential linear relationship with the growth rate, that is, λ=1＋5×e^_2.5V;when the pulling rate is lower than 5μm/s the directional solidification process of the alloy is similar to equilibrium solidification; in addition, the growth mechanism of each phase in the stable growth zone is symbiotic growth. With the increase of the pulling rate, the directional arrangement of the quasiperitectic structure gradually deteriorates.