Crystal grain refiner for magnesium alloy, containing aluminum, a method for preparing magnesium alloy, and magnesium alloy manufactured by same method
A grain refiner for a magnesium alloy according to the present invention contains aluminum (Al) and manganese (Mn), and contains a compound of aluminum (Al) and manganese (Mn) in the microstructure thereof, wherein the grain refiner is composed of a structure in which, in the compound of aluminum (Al) and manganese (Mn), the area of the compound having an Al/Mn compositional (atomic) ratio of 4-4.5 is larger than the area of the compound having an Al/Mn compositional (atomic) ratio of 5.5-6.5. When the grain refiner is added to molten magnesium, crystal grains can be refined to 50-100 μm.
1. A refiner for a magnesium alloy, the refiner comprising:
5 wt % to 15 wt % of manganese (Mn), and aluminum (Al) as well as unavoidable impurities as a remainder;
wherein the refiner comprises:
an aluminum-based matrix; and
a second phase consisting of a compound of aluminum (Al) and manganese (Mn) inside the aluminum-based matrix,
wherein, in the second phase, an area of a compound having an Al/Mn compositional atomic ratio of 4 to 4.5 is greater than an area of a compound having an Al/Mn compositional atomic ratio of 5.5 to 6.5.
2. The refiner of claim 1 , wherein, in the compound of Al and Mn, the area fraction of the compound having an Al/Mn compositional atomic ratio of 4 to 4.5 is 50% or more.
3. The refiner of claim 1 , wherein, in the compound of Al and Mn, the area fraction of the compound having an Al/Mn compositional atomic ratio of 4 to 4.5 is 70% or more, and wherein the area fraction of the compound having an Al/Mn compositional atomic ratio of 5.5 to 6.5 is 30% or less.
4. The refiner of claim 1 , wherein at least one of a flat interface and an acicular interface is formed between the second phase and the aluminum-based matrix.
5. The refiner of claim 1 , further comprising 1 wt % or less of carbon (C).
6. The refiner of claim 1 , wherein an area fraction occupied by the second phase in the aluminum-based matrix is 5% or more.
7. A method of manufacturing a magnesium alloy, the method comprising:
preparing a molten magnesium alloy by applying a protective gas to a magnesium alloy and heating the magnesium alloy to a melting temperature of the magnesium alloy to melt the magnesium alloy;
adding the refiner of claim 1 to the molten magnesium alloy and maintaining and stirring for 5 minutes to 2 hours; and
casting the molten magnesium alloy having the refiner added thereto to manufacture a magnesium alloy casting material.
8. The method of claim 7 , wherein the refiner is added as a solid phase or a liquid phase.