Magnesium alloy sheet

Patent metadata

Field	Value
Publication number	US-9334554-B2
Application number	US-201013382826-A
Country	US
Kind code	B2
Filing date	Jun 8, 2010
Priority date	Jul 7, 2009
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A magnesium alloy sheet having good press formability, a magnesium alloy structural member produced by pressing the sheet, and a method for producing a magnesium alloy sheet are provided. The magnesium alloy sheet is composed of a magnesium alloy containing Al and Mn. When a region from a surface of the alloy sheet to 30% of the thickness of the alloy sheet in a thickness direction of the magnesium alloy sheet is defined as a surface region and when a 200 μm 2 sub-region is arbitrarily selected from this surface region, the number precipitated impurity grains containing both Al and Mg and having a maximum diameter of 0.5 to 5 μm is 5 or less. When a 50 μm 2 sub-region is arbitrarily selected from the surface region, the number of crystallized impurity grains containing both Al and Mn and having a maximum diameter of 0.1 to 1 μm is 15 or less. In the grains of the crystallized phases, the mass ratio Al/Mn of Al to Mn is 2 to 5. The magnesium alloy sheet has good press formability since the crystallized phases and precipitates that cause breaking are small in amounts contained and in size.

First claim

The invention claimed is:

1. A magnesium alloy structural member produced by press-forming a magnesium alloy sheet, wherein the press-forming is conducted at a temperature in a range from 200° C. to 280° C., a heat treatment or an anti-corrosion treatment is conducted after the press-forming, and the magnesium alloy is in a temperature range of 150° C. to 250° C. for 60 minutes or less, including the heat treatment,
the magnesium alloy sheet comprising:
a magnesium alloy containing Al and Mn, wherein:
when a region from a surface of the alloy sheet to 30% of the thickness of the alloy sheet in a thickness direction of the magnesium alloy sheet is defined as a surface region and when a 200 μm 2 sub-region is arbitrarily selected from this surface region, the number of grains that are precipitates containing both Al and Mg and having a maximum diameter of 0.5 to 5 μm is 5 or less,
when a 50 μm 2 sub-region is arbitrarily selected from the surface region, the number of grains that are crystallized phases containing both Al and Mn and having a maximum diameter of 0.1 to 1 μm is 15 or less,
in the grains of the crystallized phases, the mass ratio Al/Mn of Al to Mn is 2 to 5, the magnesium alloy contains 5% by mass to 12% by mass of Al and 0.1% by mass to 2.0% by mass of Mn,
the magnesium alloy contains at least one element selected from the group consisting of Zn, Si, Ca, Sr, Y, Cu, Ag, Ce, Zr, and rare earth elements, excluding Y and Ce, and the magnesium alloy includes precipitates consisting of Mg 17 Al 12 .

2. The magnesium alloy structural member according to claim 1 , wherein in a tensile test (specimen: JIS 13B) of the magnesium alloy sheet at ordinary temperature, the tensile strength is 300 MPa or more and the 0.2% proof stress is 250 MPa or more, and
the elongation in a notch tensile test at 250° C. is 20% or more.

3. The magnesium alloy structural member according to claim 1 , wherein the magnesium alloy sheet has a structure in which the region is substantially free of precipitates having a maximum diameter of more than 5 μm.

4. The magnesium alloy structural member according to claim 1 , wherein the magnesium alloy further contains one or more of 0.2 to 7.0% by mass of Zn, 0.2 to 1.0% by mass of Si, 0.2 to 6.0% by mass of Ca, 0.2 to 7.0% by mass of Sr, 1.0 to 6.0% by mass of Y, 0.2 to 3.0% by mass of Cu, 0.5 to 3.0% by mass of Ag, 0.05 to 1.0% by mass of Ce, and 0.1 to 1.0% by mass of Zr.

5. The magnesium alloy structural member according to claim 1 , wherein the magnesium alloy further contains 1.0 to 3.5% by mass of rare earth elements, excluding Y and Ce.

6. A method for producing a magnesium alloy sheet, the method comprising the steps of:
casting a magnesium alloy containing Al and Mn into a cast sheet;
rolling the cast sheet obtained by the casting step; and
heat treating the cast sheet after the rolling step, wherein:
the casting is conducted by a twin-roll continuous casting process at a roll temperature of 100° C. or less and the thickness of the cast sheet is 5 mm or less, and
the rolling and heat treating are conducted while heating the cast sheet and the total length of time the cast sheet being retained in a temperature range of 150° C. to 250° C. during rolling and heating treating is 60 minutes or less.

7. The method for producing the magnesium alloy sheet according to claim 6 , wherein the casting is conducted at the roll temperature of 60° C. or less.

8. The method for producing the magnesium alloy sheet according to claim 6 , wherein the rolling step is conducted with a temperature of the sheet being in a range from 200° C. to 400° C.

9. The method for producing the magnesium alloy sheet according to claim 8 , wherein the rolling step is conducted with the temperature of the sheet being in a range from 230° C. to 360° C.

10. The method for producing the magnesium alloy sheet according to claim 8 , wherein the rolling step is conducted with rollers at a temperature being in a range from 150° C. to 300° C.

11. The method for producing the magnesium alloy sheet according to claim 6 , wherein, in the rolling step, the total length of time the material is retained in the temperature range of 150° C. to 250° C. is 45 minutes or less and the total length of time is adjusted based on an amount of the Al in the sheet.

12. The method for producing the magnesium alloy sheet according to claim 6 , wherein the casting is conducted in an inert gas atmosphere.

13. The method for producing the magnesium alloy sheet according to claim 6 , wherein the thickness of the cast sheet is 4 mm or less.

14. The method for producing the magnesium alloy sheet according to claim 6 , wherein, in the rolling step, a reduction ratio per pass is 5 to 50% and a temperature of rollers is in a range from 150° C. to 300° C.

Assignees

• Kitamura Takahiko
• Oishi Yukihiro
• Kawabe Nozomu
• Sumitomo Electric Industries

Inventors

• Kitamura Takahiko
• Oishi Yukihiro
• Kawabe Nozomu

Classifications

• C22F1/00

  Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working (apparatus for mechanical working of metal B21, B23, B24) · CPC title

• C22F1/06 Primary

  of magnesium or alloys based thereon · CPC title

• C22C23/02 Primary

  with aluminium as the next major constituent · CPC title