Aluminum-copper-lithium alloy having improved compressive strength and improved toughness

Abstract

The invention relates to a product based on an aluminium alloy comprising, as percentages by weight, 4.0 to 4.6% by weight of Cu, 0.7 to 1.2% by weight of Li, 0.5 to 0.65% by weight of Mg, 0.10 to 0.20% by weight of Zr, 0.15 to 0.30% by weight of Ag, 0.25 to 0.45% by weight of Zn, 0.05 to 0.35% by weight of Mn, at most 0.20% by weight of Fe+Si, at least one element selected from Cr, Sc, Hf, V and Ti, the amount of said element, if selected, being from 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and 0.01 to 0.15% by weight for Ti, the other elements being at most 0.05% by weight each and 0.15% by weight in total, the remainder being aluminium. The invention also relates to a method for obtaining such a product and to the use thereof as an aircraft structural element.

1 . A product based on an aluminum alloy comprising, in percentage by weight,
 4.0 to 4.6% by weight of Cu,   0.7 to 1.2% by weight of Li,   0.5 to 0.65% by weight of Mg,   0.10 to 0.20% by weight of Zr,   0.15 to 0.30% by weight of Ag,   0.25 to 0.45% by weight of Zn,   0.05 to 0.35% by weight of Mn,   at most 0.20% by weight of Fe+Si,   at least one element selected from Cr, Sc, Hf, V and Ti, the amount of said element, if selected, being from 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and from 0.01 to 0.15% by weight for Ti,   other elements at most 0.05% by weight each and 0.15% by weight in total, the remainder being aluminum.   
     
     
         2 . The product based on an aluminum alloy according to  claim 1  wherein the Cu content is comprised between 4.2 and 4.5% by weight, optionally between 4.2 and 4.4% by weight. 
     
     
         3 . The product based on an aluminum alloy according to  claim 1  wherein the Li content is comprised between 0.8 and 1.0% by weight, optionally preferably between 0.85 and 0.95% by weight. 
     
     
         4 . The product based on an aluminum alloy according to  claim 1  wherein the Zn content is comprised between 0.30 and 0.40% by weight. 
     
     
         5 . The product based on an aluminum alloy according to  claim 1  wherein the Mn content comprised between 0.10 and 0.35% by weight. 
     
     
         6 . The product based on an aluminum alloy according to  claim 1  wherein the sum of the Zn, Mg and Ag contents comprised between 0.95 and 1.35% by weight, optionally between 1.00 and 1.30% by weight, optionally between 1.15 and 1.25% by weight. 
     
     
         7 . The product based on an aluminum alloy according to  claim 1  wherein the Zr content is 0.10 to 0.15% by weight, optionally between 0.11 and 0.14% by weight. 
     
     
         8 . The product based on an aluminum alloy according to  claim 1  wherein the Ti content is comprised between 0.01 to 0.15% by weight for Ti, optionally between 0.01 and 0.08% by weight, optionally between 0.02 and 0.06% by weight. 
     
     
         9 . The product based on an aluminum alloy according to  claim 8  wherein the Ti is present in the form of particles of TiC. 
     
     
         10 . A method for manufacturing a product based on an aluminum alloy wherein, successively,
 a) a liquid metal bath based on aluminum is prepared comprising 4.0 to 4.6% by weight of Cu; 0.7 to 1.2% by weight of Li; 0.5 to 0.65% by weight of Mg; 0.10 to 0.20% by weight of Zr; 0.15 to 0.30% by weight of Ag; 0.25 to 0.45% by weight of Zn; 0.05 to 0.35% by weight of Mn; at most 0.20% by weight of Fe+Si; at least one element selected from Cr, Sc, Hf, V and Ti, the amount of said element, if selected, being from 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and for V and from 0.01 to 0.15% by weight for Ti; other elements at most 0.05% by weight each and 0.15% by weight in total and the remainder being aluminum;   b) a crude form is cast from said liquid metal bath;   c) said crude form is homogenized at a temperature comprised between 450° C. and 550° C. and optionally between 480° C. and 530° C. for a period comprised between 5 and 60 hours;   d) said homogenized crude form is hot-worked, optionally by rolling;   e) the hot-worked product is solution heat-treated between 490 and 530° C. for 15 min to 8 h and said solution heat-treated product is quenched;   f) said product is cold-worked with a working of 2 to 16%;   g) aging is carried out wherein said product reaches a temperature comprised between 130 and 170° C. and optionally between 140 and 160° C. for 5 to 100 hours and optionally 10 to 70 hours.   
     
     
         11 . The product according to  claim 1 , with a thickness comprised between 8 and 50 mm having, at mid-thickness:
 i) a compressive yield strength Rc p0.2 (L)≥590 MPa, optionally Rc p0.2 (L) 595 MPa;   ii) a toughness K app  (L−T)≥60 MPa√m, optionally K app  (L−T)≥75 MPa√m, with K app  (L−T) the value of the apparent stress intensity factor at rupture defined according to standard ASTM E561 (2015) measured on CCT test specimens of width W=406 mm and thickness B=6.35 mm;   iii) a difference between the tensile yield strength R p0.2 (L) and the compressive yield strength Rc p0.2 (L), R p0.2 (L)−Rc p0.2 (L), less than or equal to 10 MPa, optionally ≤5 MPa.   
     
     
         12 . An aircraft structure element, optionally an aircraft upper wing skin element, comprising a product according to  claim 1 .