Damage tolerant aluminum alloy product and method of its manufacture

Abstract

The invention relates to a product comprising an aluminum base alloy consisting of (in weight %): Cu 3.8 - 4.9, Mg 1.2 - 1.8, Mn 0.1 - 0.9, Fe max. 0.12, Si max. 0.10, Ti max. 0.15, Zn max. 0.20, Cr max. 0.10, impurities each max. 0.05, total max. 0.15, balance aluminum. The product having a minimum L-0.2% yield strength of 300 MPa or more, a minimum LT-0.2% yield strength of 270 MPa, a minimum T-L fracture toughness K C(ao) of 100 MPa.{square root}m or more for a 700 mm wide CCT-panel, and has in both L/ST- and LT/ST-sections an average grain size of at least 6 according to ASTM E-112. Further the invention relates to a method for the manufacturing of such a product.

1 . A damage tolerant alloy product comprising an aluminum base alloy consisting essentially of (in weight %):  
                                           Cu   3.8-4.9         Mg   1.2-1.8         Mn   0.1-0.9         Fe   max. 0.12         Si   max. 0.10         Ti   max. 0.15         Zn   max. 0.20         Cr   max. 0.10                           impurities   each   max. 0.05             total   max. 0.15                                                         
       balance aluminum, 
 said product having a minimum L-0.2% yield strength of 300 MPa or more, a minimum LT-0.2% yield strength of 270 MPa, a minimum T-L fracture toughness K C(ao)  of 100 MPa.{square root}m or more for a 700 mm wide CCT-panel, and having in both L/ST- and LT/ST-sections an average grain size of at least 6 according to ASTM E-112.  
 
     
     
         2 . The product in accordance with    claim 1   , wherein the Cu content is in a range of 3.8 to 4.7%.  
     
     
         3 . The product in accordance with    claim 1   , wherein the Cu content is in a range of 3.9 to 4.6%.  
     
     
         4 . The product in accordance with    claim 1   , wherein the Mg content is in a range of 1.2 to 1.7%.  
     
     
         5 . The product in accordance with    claim 1   , wherein the Mn content is in a range of 0.1 to 0.8%.  
     
     
         6 . The product in accordance with    claim 1   , wherein the product has minimum longitudinal (L)-0.2% yield strength of 360 MPa or more, the minimum 0.2% yield strength in the TL-direction (transverse direction) is 300 MPa.  
     
     
         7 . The product in accordance with    claim 1   , wherein the product has minimum transverse (TL)-tensile strength of 440 MPa or more and a minimum longitudinal (L)-tensile strength of 475 MPa or more.  
     
     
         8 . The product in accordance with    claim 1   , wherein the product has minimum L-T fracture toughness K C(ao)  of 105 MPa.{square root}m for 700 mm wide CCT-panels.  
     
     
         9 . The product in accordance with    claim 1   , wherein the minimum T-L fracture toughness K C(ao)  is 170 MPa.{square root}m or more for 2000 mm wide CCT-panels.  
     
     
         10 . The product in accordance with    claim 1   , wherein the minimum T-L fracture toughness K C(ao)  is 175 MPa.{square root}m or more for 2000 mm wide CCT-panels.  
     
     
         11 . The product in accordance with    claim 1   , wherein the grain aspect ratio in both L/ST- and LT/ST-sections is 1:4 or less.  
     
     
         12 . The product in accordance with    claim 1   , wherein the grain aspect ratio in both L/ST- and LT/ST-sections is 1:3 or less.  
     
     
         13 . The product in accordance with    claim 1   , wherein the grain aspect ratio in both L/ST- and LT/ST-sections is 1:2 or less.  
     
     
         14 . The product in accordance with    claim 1   , wherein the product is a sheet product.  
     
     
         15 . The product in accordance with any one of    claim 1   , wherein the product is a plate product.  
     
     
         16 . A composite comprising the product in accordance with    claim 1   , and a cladding on the product, the cladding comprising a higher purity aluminum alloy than said product.  
     
     
         17 . A composite comprising the product in accordance with    claim 1   , and a cladding on the product, the cladding comprising a member of the group consisting of: 
 (i) an alloy of the Aluminum Association AA1000 series;    (ii) an alloy of the Aluminum Association AA6000 series; and    (iii) an alloy of the Aluminum Association AA7000 series.    
     
     
         18 . A method for manufacturing a damage tolerant alloy product, comprising the steps of: 
 (a) casting an ingot or a slab comprising an aluminum alloy consisting of (in wt. %):  
                                           Cu   3.8-4.9         Mg   1.2-1.8         Mn   0.1-0.9         Fe   max. 0.12         Si   max. 0.10         Ti   max. 0.15         Zn   max. 0.20         Cr   max. 0.10         impurities   each max. 0.05             total max. 0.15                                                  
   balance aluminum;    (b) hot rolling the ingot to form an intermediate product;    (c) cold rolling the intermediate product to form a rolled product in both the length and in the width direction with a total cold deformation of more than 60%;    (d) solution heat treating the intermediate product after cold rolling in at least one direction;    (e) cooling the solution heat treated intermediate product; and    (f) ageing the cooled intermediate product;    said damage tolerant product having a minimum L-0.2% yield strength of 300 MPa or more, a minimum LT-0.2% yield strength of 270 MPa, a minimum T-L fracture toughness K C(ao)  of 100 MPa.{square root}m or more for a 700 mm wide CCT-panel, and having in both L/ST- and LT/ST-sections an average grain size of at least 6 according to ASTM E-112.    
     
     
         19 . The method in accordance with    claim 18   , wherein during step (b) the ingot is hot rolled in both the length and in the width direction.  
     
     
         20 . The method in accordance with    claim 18   , wherein during step (c) the intermediate product is first cold rolled in the one direction with a total cold deformation in the range of 20 to 55% and then further cold rolled in the other direction to a rolled product with a total cold deformation of 60% or more.  
     
     
         21 . The method in accordance with    claim 20   , wherein the process step (c) comprises the sequential steps of: 
 (c-i) first cold rolling the intermediate product in one direction with a total cold deformation in the range of 20 to 55%;    (c-ii) solution heat treating the intermediate product after cold rolling;    (c-iii) tempering the solution heat treated intermediate product to a T3 or a T351-temper;    (c-iv) soft annealing the tempered intermediate product; and    (c-v) cold rolling of the soft annealed intermediate product in at least another direction to a final gauge thickness with a total cold deformation of more than 60%.    
     
     
         22 . The method in accordance with    claim 21   , wherein during process step (c-v) the soft annealed intermediate product is being cold rolled in both the length and in the width direction.  
     
     
         23 . The method in accordance with    claim 21   , wherein the hot rolling of the ingot to the intermediate product occurs after homogenization at a temperature of 400 to 505° C.  
     
     
         24 . The method in accordance with    claim 21   , wherein solution heat treating of the intermediate product after cold rolling in at least one direction occurs at a temperature of 460 to 505° C. for 5 to 120 minutes.  
     
     
         24 . The method in accordance with    claim 21   , wherein the solution heat treated intermediate product is cooled to a temperature of 175° C. or lower.  
     
     
         25 . The method in accordance with    claim 21   , wherein soft annealing of the cooled intermediate product occurs at a temperature of 300 to 430° C. for 0.5 to 12 hours.  
     
     
         26 . The method in accordance with    claim 21   , wherein between cold rolling passes, the intermediate product is inter-annealed at a temperature of 300 to 430° C. for 0.5 to 12 hours.  
     
     
         27 . An aircraft skin comprising a sheet or plate of the damage tolerant alloy product of    claim 1   .  
     
     
         28 . An aircraft skin comprising a sheet or plate of the damage tolerant alloy product made by the method of    claim 18   .  
     
     
         29 . A damage tolerant alloy product comprising an aluminum base alloy consisting of (in weight %):  
                                           Cu   3.8-4.9         Mg   1.2-1.8         Mn   0.1-0.9         Fe   max. 0.12         Si   max. 0.10         Ti   max. 0.15         Zn   max. 0.20         Cr   max. 0.10         impurities   each max. 0.05             total max. 0.15                                                    
       balance aluminum, 
 said product having a minimum L-0.2% yield strength of 300 MPa or more, a minimum LT-0.2% yield strength of 270 MPa, a minimum T-L fracture toughness K C(ao)  of 100 MPa.{square root}m or more for a 700 mm wide CCT-panel, and having in both L/ST- and LT/ST-sections an average grain size of at least 6 according to ASTM E-112.