Grain refiner for magnesium and magnesium alloys and method for producing the same

Abstract

The present invention pertains to the field of metal alloy, and relates a grain refiner for magnesium and magnesium alloys, which is an aluminum-zirconium-carbon (AlZrC) intermediate alloy, having a chemical composition of: 0.01%?10% Zr, 0.01%?0.3% C, and Al in balance, based on weight percentage. Also, the present invention discloses the method for preparing the grain refiner. The grain refiner according to the present invention is an intermediate alloy having great nucleation ability and in turn excellent grain refining performance for magnesium and magnesium alloys, and is industrially applicable in the casting and rolling of magnesium and magnesium alloy profiles, enabling the wide use of magnesium in industries.

Claims

1. A method of forming grain refiner comprising: melting commercially pure aluminum, heating to a temperature of 1000? C.-1300? C., and adding zirconium scrap and graphite powder thereto to be dissolved therein, and keeping the temperature under agitation for 15-120 minutes, and performing direct casting molding so as to form an AlZrC grain refiner having a grain size between 2 and 10 ?m and a chemical composition consisting of: 0.01%-10% Zr, 0.01%-0.3% C, Fe?0.5%, Si?0.3%, Cu?0.2%, Cr?0.2%, and Al in balance with contents of other impurity elements present ?0.2%, based on weight percentage.

2. The method of forming grain refiner according to claim 1, so as to form grain refiner having a chemical composition consisting of: 0.1%-10% Zr, 0.01%-0.3% C, Fe?0.5%, Si?0.3%, Cu?0.2%, Cr?0.2%, and Al in balance with contents of other impurity elements present 0.2%, based on weight percentage.

3. The method of forming grain refiner according to claim 2, so as to form grain refiner having a chemical composition consisting of: 1%-5% Zr, 0.1%-0.3% C, Fe?0.5%, Si?0.3%, Cu?0.2%, Cr?0.2%, and Al in balance with contents of other impurity elements present 0.2%, based on weight percentage.

4. The method of forming grain refiner of claim 1, further comprising adding the formed grain refiner at 1% to a Mg-5% Al alloy melted and heated at 740? C. under protection of a gas mixture of SF.sub.6 and CO.sub.2, held at 740? C. under mechanical agitation for 30 minutes, and cast into ingots, so as to provide Mg alloy grains having an average diameter of 50 ?m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the SEM calibration graph of AlZrC intermediate alloys magnified by 1000;

(2) FIG. 2 is the energy spectrum of point A in FIG. 1;

(3) FIG. 3 is the SEM calibration graph of Mg-5% Al alloy at 100 magnification; and

(4) FIG. 4 is the SEM calibration graph of Mg-5% Al alloy after adding AlZrC intermediate alloy at 100 magnification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) The present invention can be further clearly understood in combination with the particular examples given below, which, however, are not intended to limit the scope of the present invention.

Example 1

(6) 968.5 kg commercially pure aluminum (Al), 30 kg zirconium (Zr) scrap and 1.5 kg graphite powder were weighed. The aluminum was added to an induction furnace, melt therein, and heated to a temperature of 1050? C.?10? C., in which the zirconium scrap and graphite powder were then added and dissolved. The resultant mixture was kept at the temperature under mechanical agitation for 100 minutes, and directly cast into Waffle ingots, i.e., aluminum-zirconium-carbon (AlZrC) intermediate alloy. Analysis was made under scanning electron microscope (SEM). FIG. 1 shows the SEM photographs of AlZrC intermediate alloy at 1000 magnification, in which the particles size is calibrated. It can be seen that the size of the compound particle was between 2 and 10 ?m, mostly between 4 and 8 ?m. FIG. 2 is an energy spectrum of A in one particle in FIG. 1. The standard samples used in the test were C:CaCO.sub.3, Al:Al.sub.2O.sub.3, and Zr:Zr, and the calculated atom percentages were 61.05% C, 23.82% Al, and 15.13% Zr.

Example 2

(7) 952.3 kg commercially pure aluminum (Al), 45 kg zirconium (Zr) scrap and 2.7 kg graphite powder were weighed. The aluminum was added to an induction furnace, melt therein, and heated to a temperature of 1200? C.?10? C., in which the zirconium scrap and graphite powder were then added and dissolved. The resultant mixture was kept at the temperature under mechanical agitation for 30 minutes, and directly cast into Waffle ingots, i.e., aluminum-zirconium-carbon (AlZrC) intermediate alloy.

Example 3

(8) 989 kg commercially pure aluminum (Al), 10 kg zirconium (Zr) scrap and 1 kg graphite powder were weighed. The aluminum was added to an induction furnace, melt therein, and heated to a temperature of 1100? C.?10? C., in which the zirconium scrap and graphite powder were then added and dissolved. The resultant mixture was kept at the temperature under mechanical agitation for 45 minutes, and directly cast into Waffle ingots, i.e., aluminum-zirconium-carbon (AlZrC) intermediate alloy.

Example 4

(9) 974 kg commercially pure aluminum (Al), 25 kg zirconium (Zr) scrap and 1 kg graphite powder were weighed. The aluminum was added to an induction furnace, melt therein, and heated to a temperature of 1300? C.?10? C., in which the zirconium scrap and graphite powder were then added and dissolved. The resultant mixture was kept at the temperature under mechanical agitation for 25 minutes, and directly cast into Waffle ingots, i.e., aluminum-zirconium-carbon (AlZrC) intermediate alloy.

Example 5

(10) 900 kg commercially pure aluminum (Al), 97 kg zirconium (Zr) scrap and 3 kg graphite powder were weighed. The aluminum was added to an induction furnace, melt therein, and heated to a temperature of 1270? C.?10? C., in which the zirconium scrap and graphite powder were then added and dissolved. The resultant mixture was kept at the temperature under mechanical agitation for 80 minutes, and directly cast into Waffle ingots, i.e., aluminum-zirconium-carbon (AlZrC) intermediate alloy.

Example 6

(11) 998.7 kg commercially pure aluminum (Al), 1 kg zirconium (Zr) scrap and 0.3 kg graphite powder were weighed. The aluminum was added to an induction furnace, melt therein, and heated to a temperature of 1270? C.?10? C., in which the zirconium scrap and graphite powder were then added and dissolved. The resultant mixture was kept at the temperature under mechanical agitation for 120 minutes, and directly cast into Waffle ingots, i.e., aluminum-zirconium-carbon (AlZrC) intermediate alloy.

Example 7

(12) Mg-5% Al alloy was melt in an induction furnace under the protection of a mixture gas of SF.sub.6 and CO.sub.2, and heated to a temperature of 740? C., to which 1% AlZrC intermediate alloy prepared according to example 1 was added to perform grain refining. The resultant mixture was kept at the temperature under mechanical agitation for 30 minutes, and directly cast into ingots.

(13) The Mg-5% Al alloy before and after grain refining were analyzed and compared under scanning electron microscope. FIG. 3 is the SEM photographs of Mg-5% Al alloy at 100 magnification, from which measurement was made by cut-off point method under GB/T 6394-2002, providing an average diameter of grains of 150 nm. FIG. 4 is the SEM photographs of Mg-5% Al alloy subjected to grain refining of AlZrC intermediate alloy at 100 magnification, from which the measurement was made by the same method as above, providing an average diameter of grains of 50 nm. The test results indicate that the AlZrC intermediate alloy according to the present invention has very good grain refining effect for magnesium alloys.