Aluminium alloy and method for producing the alloy

Abstract

A rapidly-solidified and plastically consolidated aluminium alloy comprises between 3.00 and 10.00 wt. % of magnesium and between 1.00 and 6.00 wt. % of manganese and dispersoid forming transition elements that are selected from the group consisting of chromium, vanadium, titanium, zirconium, molybdenum, cobalt and niobium. The total amount of these transition elements is at least 0.50 wt. %. The maximum amounts of these elements is 1.50 wt. % for Cr, 1.50 wt. % for V, 1.00 wt. % for Ti, 1.00 wt. % for Zr, 1.50 wt. % for Mo, 1.50 wt. % for Co and 1.00 wt. % for Nb. The aluminium alloy is corrosion resistant and allows, due to its fine grained stabilized structure, to combine a high yield strength at room temperature with a good thermal resistance and with relatively low forming forces at high temperatures. The liquidus temperature of the alloy remains relatively low so that it can be produced easily on an industrial scale.

1 . An aluminium alloy which is rapidly solidified and plastically consolidated and which comprises aluminium (Al) and:
 between 3.00 and 10.00 wt. % of magnesium (Mg);   more than 1.00 and less than 6.00 wt. % of manganese (Mn); and   one or more transition elements which are selected from the group consisting of chromium (Cr), vanadium (V), titanium (Ti), zirconium (Zr), molybdenum (Mo), cobalt (Co) and niobium (Nb), a total amount of the one or more transition elements being at least equal to 0.50 wt. % and the maximum amounts of the transition elements being 1.50 wt. % for Cr, 1.50 wt. % for V, 1.00 wt. % for Ti, 1.00 wt. % for Zr, 1.50 wt. % for Mo, 1.50 wt. % for Co and 1.00 wt. % for Nb,   wherein the aluminium alloy comprises:   no or less than 2.00 wt. %, preferably less than 1.00 wt. % of zinc (Zn), no or less than 2.00 wt. %, preferably less than 1.00 wt. % of silicon (Si), no or less than 1.00 wt. % of scandium (Sc) and no or less than 1.00 wt. % of tungsten (W);   no other elements different from Al, Mg, Mn, Cr, V, Ti, Zr, Mo, Co, Nb, Zn, Si, Sc and W or in total less than 4.00 wt. %, preferably less than 2.0 wt. % and more preferably less than 1.00 wt. % of the other elements; and   aluminium as balance.   
     
     
         2 . The aluminium alloy according to  claim 1 , which comprises at most 1.20 wt. %, preferably at most 1.00 wt. % and more preferably at most 0.75 wt. % of V. 
     
     
         3 . The aluminium alloy according to  claim 1 , which comprises at most 1.40 wt. %, preferably at most 1.30 wt. % and more preferably at most 1.20 wt. % of Cr. 
     
     
         4 . The aluminium alloy according to  claim 1 , which comprises at least 0.10 wt. %, preferably at least 0.20 wt. %, more preferably at least 0.30 wt. % and most preferably at least 0.40 wt. % of Cr. 
     
     
         5 . The aluminium alloy according to  claim 1 , which comprises at least 0.10 wt. %, preferably at least 0.20 wt. %, more preferably at least 0.30 wt. % and most preferably at least 0.40 wt. % of V. 
     
     
         6 . The aluminium alloy according to  claim 1 , which comprises two or more, preferably three or more of the transition elements. 
     
     
         7 . The aluminium alloy according to  claim 1 , which comprises Cr and V in a total amount of at least 0.50 wt. %, preferably of at least 0.70 wt. % and more preferably of at least 0.90 wt. %. 
     
     
         8 . The aluminium alloy according to  claim 1 , which comprises Cr and/or V, and additionally at least 0.15 wt. %, preferably at least 0.20 wt. % of Ti, at least 0.15 wt. %, preferably at least 0.20 wt. % of Zr, at least 0.15 wt. %, preferably at least 0.20 wt. % of Mo, at least 0.15 wt. %, preferably at least 0.20 wt. % of Co and/or at least 0.15 wt. %, preferably at least 0.20 wt. % of Nb. 
     
     
         9 . The aluminium alloy according to  claim 1 , wherein the total amount of the one or more transition elements is larger than 0.70 wt. %, preferably larger than 0.80 wt. %, more preferably larger than 0.90 wt. % and most preferably larger than 1.00 wt. %. 
     
     
         10 . The aluminium alloy according to  claim 1 , wherein the total amount of the one or more transition elements is smaller than 3.00 wt. %, preferably smaller than 2.75 wt. %, more preferably smaller than 2.50 wt. % and most preferably smaller than 2.25 wt. %. 
     
     
         11 . The aluminium alloy according to  claim 1 , which comprises at least 1.10 wt. %, preferably at least 1.20 wt. %, more preferably at least 1.30 wt. % and most preferably at least 1.40 wt. % of Mn. 
     
     
         12 . The aluminium alloy according to  claim 1 , which comprises less than 5.00 wt. %, preferably less than 4.50 wt. % and more preferably less than 4.00 wt. % of Mn. 
     
     
         13 . The aluminium alloy according to  claim 1 , which comprises at least 4.00 wt. %, preferably at least 4.50 wt. %, more preferably at least 5.00 wt. %, most preferably at least 5.50 wt. % and even more preferably at least 6.00 wt. % of Mg. 
     
     
         14 . The aluminium alloy according to  claim 1 , which comprises less than 9.00 wt. %, preferably less than 8.00 wt. % and more preferably less than 7.00 wt. % of Mg. 
     
     
         15 . The aluminium alloy according to  claim 1 , which has a true yield strength (YS, R 0.2 ), measured at 20° C. in accordance with ASTM E8/E8M-13a, of at least 400 MPa, preferably of at least 450 MPa, more preferably of at least 500 MPa and most preferably of at least 550 MPa. 
     
     
         16 . The aluminium alloy according to  claim 1 , which has a maximum true stress during plastic deformation in a compression test at a true strain rate of 10 −2  per second, of less than 25 MPa, preferably less than 21 MPa and more preferably less than 18 MPa at 450° C., and/or of less than 20 MPa, preferably less than 17 MPa and more preferably less than 14 MPa at 500° C., and/or of less than 17 MPa, preferably less than 14 MPa and more preferably less than 8 MPa at 550° C. 
     
     
         17 . The aluminium alloy according to  claim 1 , which has a true yield strength (YS, R 0.2 ), measured at 20° C. in accordance with ASTM E8/E8M-13a, and a maximum true stress during plastic deformation in a compression test to 50% of an initial height at a temperature of 525° C. and at a true strain rate of 10 −2  per second, which maximum true stress, expressed in MPa, is smaller than 3.0%, preferably smaller than 2.0% and more preferably smaller than 1.5% of the true yield strength expressed in MPa. 
     
     
         18 . The aluminium alloy according to  claim 1 , which comprises between 1.50 and 3.50 wt. %, preferably between 2.00 and 3.00 wt. % of Mn and between 3.00 and 5.00 wt. %, preferably between 3.00 and 4.50 wt. % of Mg, with the total amount of the one or more transition elements being less than 1.00 wt. %, and with Cr being preferably either absent or present in an amount of at most 0.3 wt. % or preferably of at most 0.2 wt. %. 
     
     
         19 . The aluminium alloy according to  claim 18 , which has a percent elongation at fracture (el) of at least 15%, preferably of at least 18%, and a true yield strength (YS, R 0.2 ), of at least 320 MPa, preferably of at least 340 MPa, both measured at 20° C. in accordance with ASTM E8/E8M-13a, the true yield strength being preferably further defined by the following equation:
     YS> 525-10. el   (equation 1)
 
 
     
     
         20 . The aluminium alloy according to  claim 1 , which comprises no or less than 3.00 wt. % of Fe, preferably no or less than 2.00 wt. % of Fe, and more preferably no or less than 1.00% of Fe, and no or less than 2.00 wt. % of Cu, preferably no or less than 1.00 wt. % of Cu, and no or less than 0.40 wt. % of Ni, preferably no or less than 0.30 wt. % of Ni, and no or less than 0.40 wt. % of Bi, preferably no or less than 0.30 wt. % of Bi, and no or less than 0.40 wt. % of Sn, preferably no or less than 0.30 wt. % of Sn, and no or less than 0.40 wt. % of Pb, preferably no or less than 0.30 wt. % of Pb. 
     
     
         21 . The aluminium alloy according to  claim 1 , which has a liquidus temperature lower than 950° C., preferably lower than 900° C. and more preferably lower than 850° C. 
     
     
         22 . The aluminium alloy according to  claim 1 , which has, as plastically consolidated, an average grain size, measured in accordance with standard ASTM E2627-13 (2019), of less than 2000 nm, preferably of less than 1000 nm, more preferably of less than 800 nm and most preferably of less than 600 nm. 
     
     
         23 . The aluminium alloy according to  claim 1 , which is hot forged, in particular die forged, and which has an average grain size, measured in accordance with standard ASTM E2627-13 (2019), of less than 4000 nm, preferably of less than 2000 nm, more preferably of less than 1500 nm and most preferably of less than 1200 nm. 
     
     
         24 . The aluminium alloy according to  claim 1 , which is substantially free of primary intermetallic phases and preferably also of dendrites. 
     
     
         25 . A method for producing an aluminium alloy according to  claim 1 , which aluminium alloy has a liquidus and a solidus temperature and a predetermined difference between the liquidus and the solidus temperature, in which method a molten aluminium alloy composition is made having a composition as defined in any one of the  claims 1 to 24 , wherein the molten aluminium alloy composition is rapidly solidified in a form of pieces of rapidly solidified material, and wherein the pieces of the rapidly solidified material are plastically consolidated to produce the plastically consolidated aluminium alloy. 
     
     
         26 . The method according to  claim 25 , wherein the liquidus temperature is lower than 950° C., preferably lower than 900° C. and more preferably lower than 850° C. 
     
     
         27 . The method according to  claim 25 , wherein the molten aluminium alloy composition is ejected from at least one nozzle to be rapidly solidified, the molten aluminium alloy composition exiting the at least one nozzle having a predetermined temperature upon exiting the at least one nozzle and is rapidly solidified by being cooled down within a predetermined period of time to the solidus temperature of the aluminium alloy at an average cooling rate which is determined as a ratio of the difference between the predetermined temperature and the solidus temperature over the predetermined period of time and which is higher than 10 000° C./sec. 
     
     
         28 . The method according to  claim 27 , wherein the predetermined temperature is at least 75% of the liquidus/solidus temperature difference higher than the solidus temperature, the predetermined temperature being preferably equal to or higher than the liquidus temperature, and being more preferably at least 10° C. higher than the liquidus temperature. 
     
     
         29 . The method according to  claim 27 , wherein the molten aluminium alloy composition is supplied through a piping to the at least one nozzle and is additionally heated in the piping before being ejected out of the nozzle, the piping being preferably substantially completely filled with the aluminium alloy composition. 
     
     
         30 . The method according to  claim 25 , wherein the pieces of rapidly solidified material are plastically consolidated by plastic deformation under pressure at a temperature of at least 300° C., preferably of at least 400° C. and more preferably of at least 450° C. 
     
     
         31 . The method according to  claim 25 , wherein the pieces of the rapidly solidified material are plastically consolidated at a temperature which is lower than the solidus temperature of the alloy, preferably at least 10° C. lower than the solidus temperature, but higher than 350° C., preferably higher than 375° C. and more preferably higher than 400° C., the temperature being most preferably comprised between 400° C. and 550° C. 
     
     
         32 . The method according to  claim 25 , wherein the pieces of rapidly solidified material are consolidated by plastic deformation to reduce an average grain size of the consolidated aluminium alloy, measured in accordance with standard ASTM E2627-13 (2019) to a value of less than 2000 nm, preferably less than 1000 nm, more preferably less than 800 nm and most preferably less than 600 nm. 
     
     
         33 . The method according to  claim 25 , wherein the pieces of the rapidly solidified material are consolidated by extruding them with a cross section reduction λ of at least 3, preferably of at least 6, more preferably of at least 8 and most preferably of at least 10. 
     
     
         34 . The method according to  claim 25 , wherein the consolidated aluminium alloy is hot forged, in particular die forged. 
     
     
         35 . The method according to  claim 34 , wherein the consolidated aluminium alloy is hot forged at a temperature higher than 400° C., preferably higher than 450° C. and more preferably higher than 475° C. or higher than 500° C., but lower than the solidus temperature of the alloy, preferably at least 10° C. lower than the solidus temperature.