Wrought product made of a magnesium-lithium-aluminum alloy

Abstract

The invention relates to a wrought product made of an aluminum alloy having the composition in % by weight, Mg: 4.0-5.0; Li: 1.0-1.8; Mn: 0.3-0.5; Zr: 0.05-0.15; Ag: ≦0.5; Fe: ≦0.1; Ti: <0.15; Si: ≦0.05; other elements ≦0.05 each and ≦0.15 in association; the remainder is aluminum. The invention further relates to a method for manufacturing a wrought product wherein an unprocessed form of aluminum alloy is cast, which has the composition, in % by weight: Mg: 4.0-5.0; Li: 1.0-1.8; Mn: 0.3-0.5; Zr: 0.05-0.15; Ag: ≦0.5; Fe: ≦0.1; Ti: <0.15; Si: ≦0.05; other elements ≦0.05 each and ≦0.15 in combination; the remainder is aluminum; optionally, said unprocessed form is homogenized; said unprocessed form is hot worked to obtain a hot-worked product; optionally, said hot-worked product is solution heat treated at a temperature from 360° C. to 460° C., preferably from 380° C. to 420° C., for 15 minutes to 8 hours; said hot-worked product is quenched; optionally, said worked and quenched product is straightened; optionally, the worked product is cold worked under controlled conditions to obtain permanent cold working set from 1 to 10%, preferably from 2 to 6%, most preferably from 3 to 5%; said worked and quenched product is aged. The invention further relates to the use of said wrought product to produce aircraft structural elements.

1 . Wrought product made of an aluminum alloy comprising in % by weight, Mg: 4.0-5.0; Li: 1.0-1.8; Mn: 0.3-0.5; Zr: 0.05-0.15; Ag: ≦0.5; Fe: ≦0.1; Ti: <0.15; Si: ≦0.05; other elements ≦0.05 each and ≦0.15 in combination; the remainder is aluminum. 
     
     
         2 . Wrought product according to  claim 1  having a Mn content, in % by weight, of 0.35 to 0.45. 
     
     
         3 . Wrought product according to  claim 1  having a Zn content, in % by weight, less than 0.04%, optionally less than or equal to 0.03%. 
     
     
         4 . Wrought product according to  claim 1  having an Fe content, in % by weight, less than 0.08%, optionally less than or equal to 0.07%, optionally less than or equal to 0.06%. 
     
     
         5 . Wrought product according to  claim 1  having an Li content, in % by weight, less than 1.6%, optionally less than or equal to 1.5%, optionally less than or equal to 1.4%. 
     
     
         6 . Wrought product according to  claim 1 , having less delamination on the rupture surfaces of the K1c specimens obtained according to standard ASTM E399 than an identical wrought product, having for a difference in its Mn content, in % by weight, less than 0.3%. 
     
     
         7 . Wrought product according to  claim 1 , having at mid-thickness, for a thickness between 0.5 and 15 mm, an ultimate tensile strength Rm (L) greater than that of an identical wrought product, having a difference in its Mn content, in % by weight. 
     
     
         8 . Wrought product according to  claim 1 , having at mid-thickness, for a thickness between 0.5 and 15 mm, a tensile yield strength Rp0.2 (L) greater than that of an identical wrought product, having for a difference in its Mn content, in % by weight. 
     
     
         9 . Method for manufacturing a wrought product comprising:
 (a) casting an unprocessed form of aluminum alloy, which comprises, in % by weight: Mg: 4.0-5.0; Li: 1.0-1.8; Mn: 0.3-0.5; Zr: 0.05-0.15; Ag: ≦0.5; Fe: ≦0.1; Ti: <0.15; Si: ≦0.05; other elements ≦0.05 each and ≦0.15 in combination; the remainder is aluminum;   (b) optionally, homogenizing said unprocessed form;   (c) hot working said unprocessed form to obtain a hot-worked product;   (d) optionally, solution heat treating said hot-worked product at a temperature from 360° C. to 460° C., optionally from 380° C. to 420° C. for 15 minutes to 8 hours;   (e) quenching said hot-worked product;   (f) optionally, straightening/flattening said worked and quenched product;   (g) optionally, cold working the worked and quenched product in a controlled manner in order to obtain a permanent cold working set from 1 to 10%, optionally from 2 to 6%, optionally from 3 to 5%;   (h) artificially aging said hot-worked and quenched product.   
     
     
         10 . Method according to  claim 9  wherein said aging (h) is carried out before cold working in a controlled manner (g). 
     
     
         11 . Method according to  claim 9  wherein the hot working of (c) is a working by extruding an unprocessed form. 
     
     
         12 . Method according to  claim 9  wherein the quenching of (e) is a press quenching. 
     
     
         13 . A wrought product according to  claim 1  used for an aircraft structural element, optionally a fuselage skin, a circumferential frame, a fuselage stiffener or stringer or a rib. 
     
     
         14 . A wrought product obtained according to  claim 9  used for an aircraft structural element, optionally a fuselage skin, a circumferential frame, a fuselage stiffener or stringer or a rib.