Production method for AZ91D alloy with ultra-fine grain solidification structure

The invention discloses a production method for AZ91D alloy with the ultra-fine grain solidification structure. The method includes the steps of 1, preprocessing and 2, high-pressure solidifying of samples. In the step 1, diffusion annealing is carried out on an AZ91D alloy ingot and the AZ91D alloy ingot is cut into the samples; and in the step 2, the samples in the step 1 are placed into a CS-1B type high-pressure cubic press for high-pressure solidification and then products are obtained. According to the production method for the AZ91D alloy with the ultra-fine grain solidification structure, the obtained products are high in strength and plasticity. In the AZ91D alloy obtained through the method, the grain size of a Mg substrate is reduced to 10 micrometers from 350 micrometers of virgin alloy, the dendritic structure is obviously refined, and the mode of distributing a beta-Mg17Al12 phase among dendritic crystals in a skeleton shape in a netted form of the virgin alloy is changed into the mode of distri