Strain-induced age strengthening in dilute magnesium alloy sheets

Patent metadata

Field	Value
Publication number	US-2018105910-A1
Application number	US-201515565093-A
Country	US
Kind code	A1
Filing date	Apr 8, 2015
Priority date	Apr 8, 2015
Publication date	Apr 19, 2018
Grant date	—

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 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 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 2 , 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, preferably at most 12 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 magnesium alloy includes 0.1 to 3.0 wt % Zn.

16 . The method of claim 1 , wherein the magnesium alloy includes 0.05 to 1.5 wt % Ca.

17 . The method of claim 1 , wherein the magnesium alloy comprises a Mg—(Zn)—RE based alloy consisting essentially of (wt %):
>0 to 3.0 of Zn;
>0 to 1.0 of Ca;
0.05 to 1.0 of a rare earth element or mixture of the same;
0 to 0.3 of Sr, and
the balance of Mg and other unavoidable impurities.

18 . The method of claim 1 , wherein the rare earth element mixture comprises gadolinium or yttrium and a rare earth element of the lanthanide series

19 . The method of claim 1 , wherein the rare earth element mixture comprises gadolinium or yttrium and La.

20 . The method of claim 1 , wherein the rare earth element consists essentially of gadolinium.

21 . The method of claim 1 , wherein the magnesium alloy consists essentially of (wt %):
Zn: >0 to 3.0; Ca: >0 to 1.5; Zr: 0 to 1.0; Gd: 0 to 1.0; Sr: 0 to 0.3; La: 0 to 0.3; Al: 0 to 0.7; and the balance of Mg and other unavoidable impurities.

22 . The method of claim 1 , wherein the magnesium alloy comprises a Mg—Zn—(Gd)—Ca—(Zr) based alloy consisting essentially of (wt %):
Zn: 0.5 to 2.0;
Ca: 0.05 to 1.0;
Zr: 0 to 1.0;
Gd: 0 to 1.0;
Sr: 0 to 0.3;
La: 0 to 0.3; and
the balance of Mg and other unavoidable impurities.

23 . The method of claim 1 , wherein the magnesium alloy comprises a Mg—Ca—Zn—(Zr) based alloy consisting essentially of (wt %):
Ca: 0.5 to 1.5;
Zn: 0.1 to 0.8;
Zr: 0 to 1.0;
Gd: 0 to 1.0;
Al: 0 to 0.7;
Sr: 0 to 0.3; and
the balance of Mg and other unavoidable impurities.

24 . The method of claim 1 , wherein the magnesium alloy further comprises (wt %): 0.05 to 0.7 Mn.

25 . The method of claim 1 , wherein the magnesium alloy is selected from the group consisting of Mg-1Zn-0.4Gd-0.2Ca, Mg-1.3Gd, Mg-1Zn-0.5Ca, Mg-2Zn-0.4Gd-0.2Ca, Mg-2Zn-0.5Ca, Mg-0.8Ca-0.4Zn-0.1Sr-0.5Zr, Mg-0.8Ca-0.4Zn-0.4Gd-0.5Zr, and Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr.

26 . 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.

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

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

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

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

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

32 . 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%.

33 . 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.

34 . The method of claim 1 , wherein the magnesium alloy includes 0.5 to 2.0 wt % Zn.

35 . The method of claim 1 , wherein the magnesium alloy includes 0.1 to 1.0 wt % Ca.

36 . The method of claim 1 , wherein the magnesium alloy further comprises (wt %): 0.1 to 0.5 Mn.

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

• C22F1/06 Primary

  of magnesium or alloys based thereon · CPC title

• C22C23/02

  with aluminium as the next major constituent · CPC title

• C22C23/06

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