The self-designed semi-solid slurry equipment with uniform internal cooling stirring was adopted to prepare semi-solid slurry of AZ91 D magnesium alloy. The evolution law of semi-solid microstructure with various contents of Al-Ti intermediate alloy and heat preservation time were investigated. The results indicate that the solid particles of semi-solid slurry become fine

spherical

uniform

presenting good rheological properties with appropriate amounts of Al-Ti intermediate alloy and heat preservation time. When the addition of Al-Ti intermediate alloy is 0.1% and heat preservation time is 30 min

the average grain size and average shape factor of semi-solid slurry are 45.17 μm and 0.69

respectively

and the semi-solid slurry structure of AZ91 D magnesium alloy is fine and spherical

evenly distributed in the solution. However

the refining effect is weakened when the addition of Al-Ti intermediate alloy exceeds 0.1% and the heat preservation time exceeds 30 min. Moreover

the mechanism of semi-solid structure prepared by Al-Ti intermediate alloy and uniform internal cooling stirring was investigated.