Weldable metal article

1. An extruded or rolled clad metal article having a core metal layer and a cladding metal layer on at least one surface of the core layer, wherein said metals of said core metal layer and said cladding metal layer are each aluminium alloys having 3% to 8% Mg and Sc in a range of 0.05% to 1%, and wherein the Sc-content in the core metal layer is at least 0.02% lower than in said cladding metal layer.

2. A clad metal article according to claim 1 , wherein said metals of said core metal layer and said cladding metal layer are each aluminium alloys having, in wt. %,

Mg 3% to 8%

Mn up to 1.4%

Sc 0.05% to 1%

Ag up to 0.5%

Zn up to 2%

Cu up to 2%

Li up to 3%

optionally one or more elements selected from the group consisting of Zr 0.03 to 0.4%, Cr 0.03 to 0.4%, Hf 0.03 to 0.4%, and Ti 0.005 to 0.4%,

Fe up to 0.35%

Si up to 0.25%

inevitable impurities and balance aluminium.

3. A clad metal article according to claim 2 , wherein Mg of said core metal layer and said cladding metal layer are each 3.9% to 6%.

4. A clad metal article according to claim 2 , wherein Mg of said core metal layer and said cladding metal layer are each 3.8% to 4.7%.

5. A clad metal article according to claim 2 , consisting of said core metal layer and said cladding metal layer on at least one surface of the core layer, wherein Mn of said core metal layer and said cladding metal layer are each up to 0.25%.

6. A clad metal article according to claim 1 , wherein said metals of said core metal layer and said cladding metal layer are each aluminium alloys having, in wt. %,

Mg 3.8% to 5.1%

Mn up to 0.4%

Sc 0.05% to 1%

Zn up to 0.4%

Cu up to 0.25%

Cr up to 0.10%

Zr 0.05 to 0.20%

Ti up to 0.20%

Fe up to 0.35%

Si up to 0.25%

others and inevitable impurities each maximum 0.05%, total maximum 0.15, and balance aluminium.

7. A clad metal article according to claim 1 , wherein the core metal layer has a Sc-content in a range of 0.05% to 0.25% and the cladding metal layer has a Sc-content in a range of 0.2% to 1%.

8. A clad metal article according to claim 1 , wherein the core metal layer is made from an aluminium alloy having a composition within AA5024.

9. A clad metal article according to claim 1 , wherein said cladding metal layer has a thickness in a range of 1% to 70% of the thickness of the core metal layer.

10. A clad metal article according to claim 1 , wherein the clad metal article is a rolled article.

11. A clad metal article according to claim 1 , wherein the clad metal article is an extruded article.

12. Welded structure comprising a clad metal article according to claim 1 , and at least one aluminium alloy stiffening element joined to the cladding metal layer by welding.

13. Welded structural member of an aircraft comprising a rolled clad metal article according to claim 1 , and at least one aluminium alloy stiffening element, joined to the cladding metal layer by welding.

14. The welded structural member of claim 13 , wherein the at least one aluminium alloy stiffening element, comprises a stringer joined to the cladding metal layer welding.

15. A clad metal article according to claim 1 , wherein the Sc-content in the core metal layer is at least 0.04% lower than in said cladding metal layer.

16. A method of producing a rolled clad metal article according to claim 1 , the method comprises:

providing a cladding on at least one face of the core ingot by co-casting to form a clad ingot, and

rolling said clad ingot to produce a plate article or sheet article having a core layer and at least one cladding layer.

17. Method according to claim 16 , wherein the co-casting step comprises casting the core ingot onto the cladding layer at a point where the metal of the cladding layer is at a temperature between the solidus temperature and liquidus temperature of the metal of the cladding layer.

18. Method according to claim 16 , wherein the co-casting step comprises casting the cladding layer in molten form onto a solid core ingot.