Method of refining aluminum alloy

Abstract

The invention provides a method of refining aluminum alloy, which is characterized in that aluminum-based nanometer quasicrystal alloy is used as an aluminum alloy refiner to refine the aluminum alloy; the aluminum-based nanometer quasicrystal alloy does not comprise Si, Fe or Cr; the aluminum-based nanometer quasicrystal alloy consists of (1) Al; (2) Mn and (3) La and/or Ce. The refiner selected in the invention is rare earth-containing alloy which has a strong refinement ability on the aluminum alloy, and is nanometer quasicrystal; after adding the rare earth-containing alloy to melt, the element distribution of the rare earth-containing alloy is more uniform than that of traditional alloy; and nanometer quasicrystal particles substantially increase the number of heterogeneous nucleation particles and improve the grain refinement effect of the aluminum alloy.

Claims

1. A method of refining an aluminum alloy, comprising: melting the aluminum alloy to be processed; adding 0.30%-0.60% of aluminum alloy refiner, by weight of the aluminum alloy to be processed, to the aluminum alloy as melted; mechanically stirring the aluminum alloy as melted; and after mechanically stirring the aluminum alloy as melted, deslagging the aluminum alloy, wherein the aluminum alloy refiner is an aluminum-based nanometer quasicrystal alloy; and the aluminum-based nanometer quasicrystal alloy consists of (1) Al; (2) Mn, and (3) La and/or Ce, and the aluminum alloy is A356.2 aluminum alloy.

2. The method of claim 1, wherein the aluminum-based nanometer quasicrystal alloy comprises 92 parts of the Al, 6 parts of the Mn and 2 parts of the La and/or Ce by atomic ratio.

3. The method of claim 1, wherein the aluminum alloy refiner is pressed columnar test blocks.

4. The method of claim 1, wherein a melting temperature of the aluminum alloy is 20 to 40 degrees Celsius higher than temperature of the aluminum-based nanometer quasicrystal alloy.

5. The method of claim 1, wherein the aluminum alloy refiner is added in an amount of 0.45% by weight of the aluminum alloy refiner to be processed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereinafter, the embodiments of the invention are described in details below with reference to the accompanying drawings, wherein:

(2) FIG. 1 is a transmission electron micrograph of Al.sub.92Mn.sub.6Ce.sub.2 nanometer quasicrystal alloy in embodiment 1;

(3) FIG. 2 is a differential scanning calorimetric curve of Al.sub.92Mn.sub.6Ce.sub.2 nanometer quasicrystal alloy in the embodiment 1;

(4) FIG. 3 is an as-cast microstructure of A356.2 alloy;

(5) FIG. 4 is an as-cast microstructure of A356.2 alloy treated by the traditional AlTiB refiner; and

(6) FIG. 5 is an as-cast microstructure of A356.2 alloy treated by Al.sub.92Mn.sub.6Ce.sub.2 nanometer quasicrystal alloy.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1 Al92Mn6Ce2 Nanometer Quasicrystal Alloy is Used as the Refiner

(7) Step one, selecting aluminum-based nanometer quasicrystal alloy composition.

(8) The selected aluminum-based nanometer quasicrystal alloy should not contain elements such as Si, Fe and Cr which are harmful to properties of A356.2 alloy. This embodiment selects the Al.sub.92Mn.sub.6Ce.sub.2 nanometer quasicrystal alloy composition.

(9) Step two, preparing a refiner of the aluminum-based nanometer quasicrystal alloy.

(10) According to the above composition selection principle, a kind of commercial nanometer quasicrystal alloy ribbon (purchased from Advance Technology & Materials Co., Ltd.) having a purity of not less than 99.99%, a thickness of 20 micrometers and a width of 1.5 mm is selected, and this alloy shown in FIG. 1 contains a large number of AlMnCe nanometer quasicrystal particle phases. The briquetting machine is used for pressing the ribbon for 5 seconds at the pressure of 500 MPa to form columnar test blocks having a size of 20 mm*5 mm, thus preventing the ribbon from floating upward in melting process, and the columnar test blocks are for later use.

(11) Step three, determining melting temperature of aluminum alloy and carrying out the melting process.

(12) According to detection results of the aluminum-based nanometer quasicrystal alloy obtained by the differential scanning calorimeter (DSC), the melting temperature of the aluminum-based nanometer quasicrystal alloy is analyzed to be approximately 748 degrees Celsius, and the melting temperature of the A356.2 alloy is so determined that it is at least 20 degrees Celsius higher than the melting temperature of the aluminum-based nanometer quasicrystal alloy, but is not lower than 720 degrees Celsius (i.e., the usual melting temperature of the A356.2 alloy), ultimately the melting temperature of the aluminum alloy is determined to be 770 degrees Celsius, ensuring the successful melting of the A356.2 aluminum alloy after being added to the aluminum-based nanometer quasicrystal alloy. After the A356.2 alloy is melted, add 0.45% (the first group of tests) by mass fraction of aluminum-based nanometer quasicrystal alloy columnar test blocks to A356.2 aluminum alloy melt, mechanically stir for 120 seconds so as to fully melt and uniformly disperse the test blocks, keep the alloy melt still for 10 minutes, deslag and cast. At the same time, 0.30% of refiner and 0.60% of refiner, respectively recorded as the second group of tests and the third group of tests, are also used for testing.

(13) FIG. 3 is an as-cast metallographic microstructure of A356.2 alloy (which contains 6.83% of Si, 0.33% of Mg, 0.07% of Fe, 0.08% of Ti, 0.023% of Sr, 0.0008% of B and the balance Al and is purchased from Binzhou Mengwei Lianxin New Material Co., Ltd.). As shown in FIG. 3, alpha-Al grains in the as-cast microstructure of the A356.2 aluminum alloy are relatively coarse, and the average grain size is 127.3 m.

(14) FIG. 4 is an as-cast microstructure of the alloy obtained by adding 0.25% by mass fraction of traditional as-cast Al-5Ti-1B refiner to the A356.2 aluminum alloy. As shown in FIG. 4, alpha-Al grains after such treatment are refined, and the average grain size is 71.8 m.

(15) The result of the first group of tests is shown in FIG. 5 which is an as-cast microstructure of the alloy obtained by adding 0.45% by mass fraction of Al.sub.92Mn.sub.6Ce.sub.2 nanometer quasicrystal alloy columnar test blocks to the A356.2 aluminum alloy. As shown in FIG. 5, alpha-Al grains after such treatment are further refined, and the average grain size is 28.7 m. It can be seen that the refinement effect prepared in this embodiment by adding the aluminum-based nanometer quasicrystal alloy ribbon columnar test blocks to the A356.2 alloy is better than the refinement effect achieved by adopting the traditional as-cast refiner.

(16) Test samples obtained by the second group of tests and the third group of tests are also subjected to alloy as-cast microstructure test. The results show that alpha-Al grains after treatment are further refined, and the average grain size is respectively 31.5 m and 28.2 m, which also shows that the aluminum alloy refiner of the invention is more effective than the traditional as-cast refiner.

Embodiment 2 Al92Mn6La2 Nanometer Quasicrystal Alloy is Used as the Refiner

(17) Step one, selecting aluminum-based nanometer quasicrystal alloy composition.

(18) The selected aluminum-based nanometer quasicrystal alloy should not contain elements such as Si, Fe and Cr which are harmful to properties of A356.2 alloy. This embodiment selects Al.sub.92Mn.sub.6La.sub.2 nanometer quasicrystal alloy composition.

(19) Step two, preparing aluminum-based nanometer quasicrystal alloy refiner.

(20) According to the above mentioned composition selection principle, a kind of commercial nanometer quasicrystal alloy ribbon (purchased from Advance Technology & Materials Co., Ltd.) having a purity of not less than 99.99%, a thickness of 20 micrometers and a width of 1.5 mm is selected, and the alloy contains a large number of AlMnLa nanometer quasicrystal particle phases. The briquetting machine is used for pressing the ribbon for 5 seconds at the pressure of 500 MPa to form columnar test blocks having a size of 20 mm*5 mm, thus preventing the ribbon from floating upward in melting process, and the columnar test blocks are for later use.

(21) Step three, determining melting temperature of aluminum alloy and carrying out the melting process.

(22) According to detection results of the aluminum-based nanometer quasicrystal alloy obtained by the differential scanning calorimeter (DSC), melting temperature of the aluminum-based nanometer quasicrystal alloy is analyzed to be approximately 770 degrees Celsius, and the melting temperature of the A356.2 alloy is so determined that it is at least 20 degrees Celsius higher than the melting temperature of the aluminum-based nanometer quasicrystal alloy, but is not lower than 720 degrees Celsius (i.e., the usual melting temperature of the A356.2 alloy), ultimately the melting temperature of the aluminum alloy is determined to be 790 degrees Celsius, ensuring the successful melting of the A356.2 aluminum alloy after being added to the aluminum-based nanometer quasicrystal alloy. After the A356.2 alloy is melted, adding 0.45% (the fourth group of tests) by mass fraction of aluminum-based nanometer quasicrystal alloy columnar test blocks to the A356.2 aluminum alloy melt, mechanically stir for 120 seconds so as to fully melt and uniformly disperse the test blocks, keep the alloy melt still for 10 minutes, deslag and cast. At the same time, 0.30% of refiner and 0.60% of refiner, respectively recorded as the fifth group of tests and the sixth group of tests, are also used for testing.

(23) Test samples in the fourth group to the sixth group are subjected to alloy as-cast microstructure testing. The results show that alpha-Al grains after treatment are further refined, and the average grain sizes are respectively 31.8 m, 33.2 m and 29.9 m, which also shows that the aluminum alloy refiner of the invention is more effective than the traditional as-cast refiner.

(24) Raw materials and devices used in the above mentioned embodiments are obtained by known approaches, and the adopted operation technology can be mastered by those skilled in the art.