Adopting copper mould spray casting combining with isothermal heat treatment

the existing form of rare earth Ce in AZ91magnesium alloy with different cooling rate and its evolution behavior during solid solution treatment were analyzed.The influences of Ce on microstructure refinement and thermal stability of rapid cooled magnesium alloy were analyzed.The results show that Ce is enriched ahead of the solidification interface

which suppresses the grain growth and promotes nucleation.Consequently

grain refinement is achieved in magnesium alloy.However

accicular Al

11

Ce

3

phase can be generated in the higher Ce content alloy

which reduces constitutional undercooling and harmful to refinement.Due to the increase of undercooling and the relief of inhibition effect of nucleation by latent heat

the grain refinement of spray casted alloy presents remarkable

and formation of the accicular rare earth phase can be avoided effectively by formation of supersaturated solid solution.After solid solution treatment at 420℃

the precipitation of fine granular Mg

12

Ce compounds can inhibit the grain growth at high temperature

which improves the thermal stability of fine grain structure in rapidly cooled magnesium alloys.