Strain-induced age strengthening in dilute magnesium alloy sheets

Patent metadata

Field	Value
Publication number	US-10570490-B2
Application number	US-201515565093-A
Country	US
Kind code	B2
Filing date	Apr 8, 2015
Priority date	Apr 8, 2015
Publication date	Feb 25, 2020
Grant date	Feb 25, 2020

Abstract

A method of strengthening a dilute magnesium alloy sheet includes providing a dilute magnesium alloy sheet, which includes a magnesium alloy consisting essentially of (wt %): >0 to 3.0 of Zn; >0 to 1.5 of Ca; 0 to 1.0 of Zr; 0 to 1.3 of a rare earth element or mixture of the same; 0 to 0.3 of Sr; 0 to 0.7 of Al, the balance of Mg and other unavoidable impurities, wherein the total weight % of alloying elements is less than 3%; subjecting the dilute magnesium alloy sheet to plastic deformation, in which the tensile plastic strain should exceed 0.5%, but be less than 8% to form a pre-deformed magnesium alloy sheets; and subjecting the pre-deformed magnesium alloy sheets to an ageing treatment in a temperature range of 80 to 250° C. for at least 1 minute, thereby forming a strengthened magnesium alloy sheet.

First claim

What is claimed is:

1. A method of strengthening a dilute magnesium alloy sheet comprising:
providing a dilute magnesium alloy sheet comprising a magnesium alloy selected from the group consisting of Mg-1Zn-0.4Gd-0.2Ca, Mg-1Zn-0.5Ca, Mg-2Zn-0.4Gd-0.2Ca, and Mg-2Zn-0.5Ca;
subjecting the dilute magnesium alloy sheet to plastic deformation, in which the tensile plastic strain should exceed 0.5%, but less than 8% to form a pre-deformed magnesium alloy sheets; and
subjecting the pre-deformed magnesium alloy sheets to an ageing treatment in a temperature range of 80 to 250° C. for at least 1 minute,
thereby forming a strengthened magnesium alloy sheet.

2. The method of claim 1 , wherein tensile plastic strain is controlled in the range of 0.5 to 6%.

3. The method of claim 1 , wherein plastic deformation is achieved by at least one of tensile stretching or cold rolling.

4. The method of claim 3 , wherein said tensile stretching is conducted at room temperature.

5. The method of claim 3 , wherein the reduction in thickness of the magnesium alloy sheet resulting from cold rolling does not exceed 10%.

6. The method of claim 1 , wherein the temperature range of the ageing treatment is between 100 and 250° C.

7. The method of claim 1 , wherein the ageing treatment is conducted in air or oil.

8. The method of claim 1 , wherein the ageing treatment is no more than 24 hours.

9. The method of claim 1 , wherein the ageing treatment is at least 1 minute.

10. The method of claim 1 , wherein the ageing treatment is between 5 minutes and 12 hours.

11. The method of claim 1 , wherein the strength increase of the strengthened magnesium alloy sheet relative to the dilute magnesium alloy sheet is at least 10%.

12. The method of claim 1 , wherein the strength increase of the strengthened magnesium alloy sheet relative to the dilute magnesium alloy sheet is between 20% and 100%.

13. The method of claim 1 , wherein the strength increase of the strengthened magnesium alloy sheet relative to the dilute magnesium alloy sheet is at least 20 MPa.

14. The method of claim 1 , wherein the strength increase of the strengthened magnesium alloy sheet relative to the dilute magnesium alloy sheet is between 33 MPa and 139 MPa.

15. The method of claim 1 , wherein the step of forming the dilute magnesium alloy sheet comprises:
providing a magnesium alloy melt from the magnesium-based alloy;
casting said magnesium alloy melt into a slab or a strip according to a predetermined thickness;
homogenising or preheating said cast slab or strip;
successively hot rolling said homogenised or preheated slab or strip at a suitable temperature to reduce said thickness of said homogenised slab or strip to produce an alloy sheet product of a predetermined thickness; and
annealing said alloy sheet product at a suitable temperature for a period of time.

16. A magnesium alloy sheet formed from a method according to claim 1 .

17. The method of claim 1 , wherein tensile plastic strain is controlled in the range of 1 to 4%.

18. The method of claim 1 , wherein the temperature range of the ageing treatment is between 100 and 200° C.

19. The method of claim 1 , wherein the ageing treatment is conducted in oil baths.

20. The method of claim 1 , wherein the ageing treatment is no more than 12 hours.

21. The method of claim 1 , wherein the strength increase of the strengthened magnesium alloy sheet relative to the dilute magnesium alloy sheet is at least 20%.

22. The method of claim 1 , wherein the strength increase of the strengthened magnesium alloy sheet relative to the dilute magnesium alloy sheet is at least 33 MPa.

Assignees

• Baoshan Iron & Steel

Inventors

• Nie jian-feng
• Zeng Zhuoran
• Bian Mingzhe
• Davies Christopher Huw John
• Birbilis Nick
• Xu Shiwei
• Zhang Pijun

Classifications

• C22C23/04

  with zinc or cadmium as the next major constituent · CPC title

• C22C23/00 Primary

  Alloys based on magnesium · CPC title

• C22C23/02

  with aluminium as the next major constituent · CPC title

• C22F1/06 Primary

  of magnesium or alloys based thereon · CPC title

• C22C23/06

  with a rare earth metal as the next major constituent · CPC title