GB2369625A

GB2369625A - Magnesium alloy

Info

Publication number: GB2369625A
Application number: GB0122030A
Authority: GB
Inventors: Tsutomu Murai; Susumu Miyamoto; Yanao Aso; Yoshinari Oki; Hideo Sano; Seiichi Nagao; Shinichi Matsuoka
Original assignee: Sankyo Aluminium Industry Co Ltd
Current assignee: Sankyo Aluminium Industry Co Ltd
Priority date: 2000-12-01
Filing date: 2001-09-12
Publication date: 2002-06-05
Also published as: GB0122030D0; CN1357643A; TW530094B; JP2002173730A; KR20020043157A; DE10148573A1; AU6877701A; US20020102179A1

Abstract

A magnesium alloy comprising the following (in % by weight): 0.1-1.0 % aluminium, 0.1-2.0 % zinc, 0.1-1.0 % manganese, not more than 0.04 % copper, not more than 0.05 % silicon, not more than 0.005 % iron and not more than 0.005 % nickel. A preferable composition is as follows: (in % by weight): 0.2-0.8 % aluminium, 0.2-1.0 % zinc, 0.3 % manganese, 0.02-0.04 % copper, 0.02-0.03 % silicon, 0.004 % iron and 0.001 % nickel. The alloy may also comprise 0.3-1.0 weight % calcium and/or one or more rare earth elements, each up to 100 ppm by weight.

Description

- 1 MALLEABLE MAGNESIUM ALLOY

BACKGROUND OF THE INVENTION

Field of the Invention

5 The present invention relates to a malleable magnesium alloy, for example, to such an alloy material subjected to flattening such as extrusion or rolling and a structural material for buildings obtained by flattening the alloy material. 10 Description of the Related Art

The term "flattening" mentioned herein denotes a process of subjecting a material to pressure or hammering, such as extrusion molding, rolling, press molding or forging, to work the material into a predetermined shape.

15 Malleable magnesium alloys conventionally used for building structural materials include M1, which is an aluminium-zinc alloy prescribed by JIS (Japanese Industrial Standard). The M1 alloy contains, besides magnesium, 3.0% by weight of aluminium and 1.0% by weight of zinc.

20 In the case of the conventional malleable magnesium alloy, however, cracking can occur if the extrusion molding speed is increased, making the molding itself impossible.

Also, the resulting molded article often oxidizes at its surface and, in some cases, catches fire, so that the 25 surface properties are deteriorated.

On the other hand, there has been a demand for a magnesium alloy that can be extruded at an increased molding speed.

30 SUMMARY OF THE INVENTION

The present invention was created in view of the above circumstances, and an object thereof is to provide a malleable magnesium alloy which can be extruded at a higher

- 2 molding speed than in the case of conventional magnesium al oys and which has satisfactory mechanical properties and corrosion resistance suitable for use as structural materials. 5 To achieve the object, the present invention provides a magnesium alloy containing aluminium in a range of 0.1 wt% to 1.0 wt%, zinc in a range of 0.1 wt% to 2.0 wt% and manganese in a range of 0.1 wt% to 1.0 wt%, and if present there should be 0.04 wt% or less copper, 0.05 wt% or less lo silicon, 0.005 wt% or less iron, and 0.005 wt% or less nickel. In each case the content of each metal is given as a percentage of the total alloy.

A billet of the malleable magnesium alloy according to 15 the present invention was actually subjected to extrusion molding. The molded article obtained had no cracks even when it was extruded at an extrusion speed about ten times as high as the conventional speed and also no ignition attributable to surface oxidation occurred. Thus, a 20 structural material of the magnesium alloy could be extrusion molded at a higher extrusion speed than the conventional speed.

Also, the extrusion molded article produced using the malleable magnesium alloy of the present invention is 25 superior to conventional molded articles in physical properties, such as tensile strength, yield strength, elongation percentage and corrosion resistance, as well as in mechanical properties as a lightweight material.

The aluminium content is set to fall within the range 30 of 0.1 wt% to 1. 0 wt% for the following reasons: If the aluminium content is lower than 0. 1 wt%, the resulting molded article fails to show satisfactory mechanical properties as a structural material, and if the aluminium

3 - content is higher than 1.0 wt%, it is difficult to extrude the alloy at a higher extrusion speed than the conventional speed. Zinc is contained in the range of 0.1 wt% to 2.0 wt%, 5 because if the zinc content is lower than 0.1 wt%, the corrosion resistance lowers, and if the zinc content is higher than 2.0 wt%, it is difficult to extrude the alloy at a higher extrusion speed than the conventional speed.

Also, manganese is contained in the range of 0.1 wt% 10 to 1.0 wt%, because manganese contained in this range serves to enhance the corrosion resistance. If the manganese content is lower than 0.1 wt%, the corrosion resistance greatly lowers, and if the manganese content is higher than 1. 0 wt%, it is difficult to extrude the alloy 15 at a higher extrusion speed than the conventional speed.

Copper, silicon, iron and nickel are impurity elements and generally unavoidable. The content of copper may be from O to 0.04 wt%, silicon may be from 0 to 0.05 wt%, iron may be from O to 0.005 wt% and nickel may be from 0 to 20 0.005 wt%.

Preferably, the alloy contains at least 0.2 wt% of aluminium, and preferably there is no more than 0.8 wt% aluminium. Preferably, the alloy contains at least 0.2 wt% of zinc, and preferably there is no more than 1. 0 wt% zinc.

25 Preferably, the alloy contains substantially 0.3% manganese. Copper may be, for example, from 0.02 to 0.04 wt% of the alloy. Silicon may be, for example, no more than 0.03 wt% of the alloy and is, for example, from 0.02 to 30 0.03 wt%. Iron is, for example, no more than 0.004 wt% of the alloy, and is, for example, substantially 0.004 wt% of the alloy. Nickel is, for example, no more than 0.001 wt% of the alloy, and is, for example, substantially 0.001 wt%

of the alloy.

Preferably, the malleable magnesium alloy according to the present invention contains aluminium in a range of 0.2 wti to 0.8 wt%, zinc in a range of 0.2 wt% to 1.0 wt%, 5 0.3 wt% manganese, copper in a range of 0. 02 wt% to 0.04 wt%, silicon in a range of 0.02 wt% to 0.03 wt%, 0.004 wt% iron, and 0.001 wt% nickel, the balance being magnesium. These elements are contained in the respective ranges lo mentioned, because as a result of experiments, it was found that the extrusion speed could be increased to a level about ten times as high as the conventional speed and that the resulting extrusion molded article was superior to conventional molded articles in mechanical properties such 15 as tensile strength.

Calcium may further be added to enhance flame retardancy. In this case, calcium is preferably added in an amount of at least 0.3 we%, and preferably is added in an amount of no more than 1.0 who.

20 Also, for example, rare earth elements such as yttrium, neodymium and/or cerium may be present each in an amount of 100 ppm or less by weight, in order to improve the mechanical properties at high temperatures.

25 BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an extrusion molded shape; and FIG. 2 is a sectional view of another extrusion molded shape with a sectional form different from that shown in 30 FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples

As Examples 1 to 3, billets of malleable magnesium alloy were prepared which contained aluminium, zinc, manganese, silicon, iron, copper and nickel in respective amounts shown in Table 1 below, the balance (Bal.) being 5 magnesium. The figures shown in Table 1 are in the unit wt%. Comparative Examples Also, billets having the respective compositions shown in Table 1 were prepared as Comparative Examples 1 to 3.

Table 1

Al Zn Mn Si Fe Cu Ni Mg Example 1 0.5 0.25 0.3 0.03 0.004 0.03 0.001 Ball Example 2 0.8 0.2 0.3 0.02 0.004 0.02 0.001 Ball Example 3 0.2 1.0 0.3 0. 03 0.004 0.04 0.001 Ball Comparative 3.0 1.0 0.3 0.02 0.005 0.04 0.002 Ball Example 1

Comparative 0.8 2.5 0.3 0.03 0.004 0.03 0.001 Ball Example 2

Comparative 0.8 0.5 1.2 0.03 0.004 0.03 0.001 Ball Example 3

The billets of Examples l to 3 and Comparative Examples 1 to 3 were each extrusion molded into a shape having a sectional form shown in FIG. 1. For experimental 15 purposes, the extrusion molding was performed at different extrusion speeds, that is, at 5 m/min., 10 m/min., 15 m/min., 30 m/min., 50 m/mint and 70 m/mint The results are shown in Table 2 below. The dimensions of the shape shown in FIG. 1 were: W = 50 mm, S = 15 mm, and t 20 (thickness) = 1.2 mm. The extrusion conditions for the individual examples and comparative examples were as follows: billet temperature = 400 C, and extrusion load = 3 to 5 MN (meganewtons).

Table 2

Extrusion speed (m/min.) 5 10 15 30 50 70

Example 1 O O O O O O Example 2 O O O O O x Example 3 O O O O O x Comparative O x x _ Example 1

Comparative O x x Example 2

Comparative O x x _ Example 3

In Table 2, the mark "O" indicates that the extrusion molding could be carried out satisfactorily, "x" indicates 5 that the surface properties deteriorated due to cracks, and "-" indicates that the extrusion molding failed because of cracks. Also, the billets of Example 1 and Comparative Example 1 were each extrusion molded into a shape having a 10 sectional form shown in FIG. 2. The results are shown in Table 3 below. The dimensions of the shape shown in FIG. 2 were: W = 40 mm, S = 20 mm, V = 15 mm, and t (thickness) = 2.0 mm. The other conditions were identical with those for the extrusion molded articles shown in Table 2. In Table 15 3, the respective marks have the same meanings as explained above with reference to Table 2.

Table 3

Extrusion speed (m/min.) 1 2 5 10 15 20

Example 1 O O O O O O Comparative Example 1 O x

Further, with respect to the shapes of Examples 1 to 3 and Comparative Examples 1 to 3 extrusion molded at the respective extrusion speeds shown in Table 2, the tensile 5 strength was measured, the results being shown in Table 4 below. The tensile strength was measured with a universal testing machine. The numbers shown in Table 4 are in the unit MPa (megapascals). In Table 4, Comparative Examples 1 to 3 extrusion molded at an extrusion speed of 10 m/mint 10 had poor surface properties as indicated by the mark "x,' in Table 2, but their tensile strengths were measured for the sake of comparison.

Table 4

Extrusion speed (m/min.) 5 10 30 70

Example 1 240 240 240 240 Example 2 250 250 250 240 Example 3 240 240 240 230 Comparative 280 200 not not Example 1 extrudable extrudable Comparative 260 180 not not Example 2 extrudable extrudable Comparative 270 200 not not Example 3 extrudable extrudable As is clear from Table 2, Examples 1 to 3 could be extruded satisfactorily at each of the extrusion speeds 15 (molding speeds) S m/min., 10 m/min., 15 m/min., 30 m/mint and 50 m/mint Also, the external appearance was visually inspected and no deterioration in surface properties was observed. Example 1 in particular could be extruded even at a speed of 70 m/min., without entailing deterioration in 20 surface properties. Comparative Examples 1 to 3, by contrast, could be extruded at a speed of 10 m/mint but their surface properties were deteriorated, and at a speed of 15 m/mint or above, the extrusion molding itself could

- 8 not be carried out because of cracking. Namely, Examples 1 to 3 could be extrusion molded at an extrusion speed more than ten times as high as that of Comparative Examples 1 to 5 With regard to the extrusion molding of shapes having the sectional form shown in FIG. 2, Example 1 could be extruded even at a speed of 20 m/min., as seen from Table 3, but Comparative Example l cracked at a speed of 5 m/mint and could not be extruded. Also, as seen from the results 10 shown in Tables 2 and 3, it is apparent that in the case of extrusion molding shapes with an identical sectional form, the examples according to the present invention can be extruded at an increased speed more than ten times as high as that of the comparative examples, though the extrusion 15 speed can vary depending upon the sectional form of shapes to be extruded.

As regards the tensile strength of the shapes of the examples and the comparative examples, the tensile strengths of Comparative Examples 1 to 3 greatly lowered 20 with increase in the extrusion speed, as seen from Table 4, but in the case of the examples according to the present invention, the shapes extruded at increased speeds showed tensile strengths nearly equal to those of the shapes extruded at low extrusion speeds. Especially, Examples 1 25 to 3 extruded at the extrusion speed 10 m/mint all had higher tensile strengths than Comparative Examples 1 to 3 extruded at the same speed. A typical tensile strength of A6063 (JIS), which is a malleable aluminium alloy generally used, is 220 MPa, and thus the examples of the present 30 invention are superior to this malleable aluminium alloy in the tensile strength.

Also, Examples 1 to 3 were measured as to the 0.2%-

yield strength and the elongation percentage, and as a

- - result, the examples had a 0.2%-yield strength of 110 to 130 MPa and showed an elongation percentage of 8 to 12.

Further, to measure the corrosion resistance, the examples were sprayed with salt water containing 5% NaC1 for 24 5 hours, and the reduction in weight due to corrosion was found to be 2 mg/cm2/day. These values show that the magnesium alloy according to the present invention has mechanical properties equivalent to or superior to those of the malleable aluminium alloy A6063 (JIS) generally used 10 and can be suitably used as a lightweight structural material. Further, using billets of Examples 1 to 3 with 0.3 to 1.0 wit calcium added, shapes were obtained by extrusion molding. The shapes could be extruded at speeds equivalent 15 to those of Examples 1 to 3 and also had equivalent mechanical properties. Compared with the shapes containing no calcium, the shapes admixed with calcium were less liable to ignition attributable to surface oxidation and showed higher flame retardancy.

20 Also, using billets of Examples 1 to 3 additionally containing rare earth elements, such as yttrium, neodymium and cerium, each in an amount of 100 ppm or less by weight, shapes were prepared by extrusion molding. The shapes could be extrusion molded at speeds equivalent to those of 25 Examples 1 to 3 and also had mechanical properties superior to those of the examples at high temperatures (200 C to 300 C).

The molding process to be employed for the malleable magnesium alloy according to the present invention is not 30 limited to extrusion molding, and the magnesium alloy may alternatively be subjected to rolling, press molding or forging. Molded articles obtained by such molding processes also have advantages similar to those of the

- 10 aforementioned extrusion molded articles.

As described above, the magnesium alloy of the present invention can be extrusion molded at an extrusion speed higher than the conventional speed. In addition, the 5 extrusion molded article is not deteriorated in its surface properties due to cracking or ignition attributable to surface oxidation.

Claims

Claims:

1. A magnesium alloy, wherein the magnesium alloy contains aluminium in a range of 0.1 wt% to 1.0 wt%, zinc in a range of 0.1 wt% to 2.0 wt%, manganese in a range of 5 o.1 wt% to 1.0 wt%, no more than 0.04 wt% copper, no more than 0.05 wt% silicon, no more than 0.005 wt% iron, and no more than 0.005 wt% nickel.

2. A magnesium alloy according to claim 1, wherein the aluminium is present in an amount of at least 0.2 wt%.

10 3. A magnesium alloy according to claim 1 or claim 2, wherein the aluminium is present in an amount up to 0.8 wt%.

4. A magnesium alloy according to any one of claims 1 to 3, wherein the zinc is present in an amount of at 15 least 0.2 wt%.

5. A magnesium alloy according to any one of claims 1 to 4, wherein the zinc is present in an amount of up to 1.0 wt%.

6. A magnesium alloy according to any one of claims 20 1 to 5, wherein the manganese is present in an amount of substantially 0.3 wt%.

7. A magnesium alloy according to any one of claims 1 to 6, which contains 0.02 to 0.04 wt% copper.

8. A magnesium alloy according to any one of claims 25 1 to 7, which contains 0.02 to 0.03 wt% silicon.

9. A magnesium alloy according to any one of claims 1 to 8, which contains substantially 0.004 wt% iron.

10. A magnesium alloy according to any one of claims 1 to 9, which contains substantially 0.001 wt% nickel.

30 11. A magnesium alloy according to claim 1, which contains aluminium in a range of 0.2 wt% to 0.8 wt%, zinc in a range of 0.2 wt% to 1.0 wt%, 0.3 wt% manganese, copper in a range of 0.02 wt% to 0.04 wt%, silicon in a range of

- 12 0.02 wt% to 0.03 wt%, 0.004 wt% iron, and 0.001 wt% nickel 12. A magnesium alloy according to any one of claims 1 to 11, which contains calcium in an amount of at least 0.3 wt%.

5 13. A magnesium alloy according to any one of claims 1 to 12, which contains calcium in an amount of up to 1.0 wt%.

14. A magnesium alloy according to any one of claims 1 to 13, which contains one or more rare earth elements.

lo 15. A magnesium alloy according to any one of claims 1 to 14, wherein each rare earth element is present in an amount of no more than 100 ppm by weight.

16. A magnesium alloy according to claim 1, having a composition substantially as described in any one of 15 Examples 1 to 3 herein.

17. A magnesium alloy according to any one of claims 1 to 16, which has been subjected to flattening.

18. A magnesium alloy according to any one of claims 1 to 17, which has been subjected to extrusion.

20 19. A magnesium alloy according to any one of claims 1 to 17, which has been subjected to rolling.

19. A magnesium alloy according to any one of claims 1 to 16, which has been worked into a predetermined shape.

21. A building structural material produced from an 25 alloy according to any one of claims 1 to 16.