Aluminum alloys and process for making aluminum alloy sheet

An aluminum alloy sheet containing amounts of Mg, Si and Cu falling within area INAFEM of FIG. 2 of the accompanying drawings contained within the following equations:

• Mg=0.4% (Line IM)
• Mg=1.375% -0.75.times.%Si (Line EM)
• Si=0.5% (Line EF)
• Mg=1.4% (Line AF)
• Si=0.2% (Line AN)
• Mg=1.567% -2.333.times.%Si (Line IN)
• and has Cu.ltoreq.2.5%
• said sheet having been heat treated to have a T4 temper strength, after cold rolling, solution heat treating, cooling to room temperature, natural aging and levelling or flattening, in the range 90-175 MPa and a potential T8X temper strength of at least 170 MPa when Simulated by deformation in tension by 2% followed by heat treatment selected from the group consisting of heat treatment at 170.degree. C. for 20 minutes or 177.degree. C. for 30 minutes;
• said sheet having been heat treated by a treatment selected from (a) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, (b) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, coiling said sheet and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, and (c) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then forced cooling said sheet using a means of cooling selected from water, water mist or forced air, and coiling said sheet at a temperature of between 50.degree. and 100.degree. C., then allowing said coil to cool at a rate of less than about 10.degree. C./hour.

An aluminum alloy sheet containing amounts of Mg, Si and Cu falling within area IJKLM of FIG. 4 of the accompanying drawings contained within the following equations:

• Si=0.5% (Line IJ)
• Mg=0.8% (Line JK)
• Mg=1.4% -%Si (Line KL)
• Si=0.8% (Line LM)
• Mg=0.4% (Line IM)
• and has Cu.ltoreq.2.5%
• said sheet having been treated to have a T4 temper strength, after cold rolling, solution heat treating, cooling to room temperature, natural aging and levelling or flattening, in the range 90-175 MPa and a potential T8X temper strength of at least 170 MPa when simulated by deformation in tension by 2% followed by a heat treatment selected from the group consisting of heat treatment at 170.degree. C. for 20 minutes or 177.degree. C. for 30 minutes;
• said sheet having been heat treated by a treatment selected from (a) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, (b) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, coiling said sheet and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, and (c) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then forced cooling said sheet using a means of cooling selected from water, water mist or forced air, and coiling said sheet at a temperature of between 50.degree. and 100.degree. C., then allowing said coil to cool at a rate of less than about 10.degree. C./hour.

A process of preparing aluminum alloy sheet material suitable in particular for automotive applications, comprising;

• in a belt casting machine, producing alloy slab by casting an alloy of aluminum containing magnesium, silicon, optionally copper, and optionally manganese, in amounts in percent by weight falling a range selected from the group consisting of;
• (1) 0.4.ltoreq.Mg.ltoreq.0.8, 0.2.ltoreq.Si.ltoreq.0.5, 0.3.ltoreq.Cu.ltoreq.3.5, Mn.ltoreq.0.4
• (2) 0.8.ltoreq.Mg.ltoreq.1.4, 0.2.ltoreq.Si.ltoreq.0.5, Cu.ltoreq.2.5, Mn.ltoreq.0.4, and
• (3) 0.4.ltoreq.Mg.ltoreq.1.0, 0.2.ltoreq.Si.ltoreq.1.4, Cu.ltoreq.2.0, Mn.ltoreq.0.4 while extracting heat from said alloy at a rate, falling within a shaded band defined in FIG. 3 of the accompanying drawings corresponding to a freezing range of said alloy, that avoids both shell distortion of said sheet and excessive surface segregation, at least until said alloy freezes;
• hot rolling and cold rolling said slab to form a sheet;
• solution heat treating said sheet to re-dissolve precipitated particles;
• and
• cooling said sheet at a rate that produces a T4 temper and a potential T8X temper suitable for automotive applications.

A process of imparting T4 and T8X temper suitable for automotive applications to a sheet of an aluminum alloy, comprising:

• solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour;
• wherein said aluminum alloy contains magnesium, silicon and optionally copper in amounts in percent by weight falling within a range selected from the group consisting of:
• (1) 0.4.ltoreq.Mg.ltoreq.0.8, 0.2 .ltoreq.Si.ltoreq.0.5, 0.3.ltoreq.Cu.ltoreq.3.5;
• (2) 0.8.ltoreq.Mg.ltoreq.1.4, 0.2 .ltoreq.Si.ltoreq.0.5, Cu.ltoreq.2.5;
• and
• (3) 0.4.ltoreq.Mg.ltoreq.1.0, 0.2 .ltoreq.Si.ltoreq.1.4, Cu.ltoreq.2.0.

A process of imparting T4 and T8X temper suitable for automotive panels to a sheet of an aluminum alloy, comprising:

• solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then force cooling said sheet by a method selected from the group consisting of water cooling, water mist cooling and forced air cooling, and coiling the sheet at a temperature of 50.degree. to 100.degree. C., and then allowing the sheet to cool at a rate of less than about 10.degree. C./hour;
• wherein said aluminum alloy contains magnesium, silicon and optionally copper in amounts in percent by weight falling within a range selected from the group consisting of:
• (1) 0.4.ltoreq.Mg.ltoreq.0.8, 0.2.ltoreq.Si.ltoreq.0.5, 0.3.ltoreq.Cu.ltoreq.3.5;
• (2) 0.8.ltoreq.Mg.ltoreq.1.4, 0.2.ltoreq.Si.ltoreq.0.5, Cu.ltoreq.2.5;
• and
• (3) 0.4.ltoreq.Mg.ltoreq.1.0, 0.2.ltoreq.Si.ltoreq.1.4, Cu.ltoreq.2.0.

Aluminum alloy sheet material produced by a process comprising:

• in a belt casting machine, producing alloy sheet by casting an alloy of aluminum containing magnesium, silicon optionally copper, and optionally manganes in amounts in percent by weight falling with a range selected from the group consisting of:
• (1) 0.4.ltoreq.Mg.ltoreq.0.8, 0.2.ltoreq.Si.ltoreq.0.5, 0.3.ltoreq.Cu.ltoreq.3.5, Mn.ltoreq.0.4
• (2) 0.8.ltoreq.Mg.ltoreq.1.4, 0.2.ltoreq.Si.ltoreq.0.5Cu.ltoreq.2.5, Mn.ltoreq.0.4, and
• (3) 0.4.ltoreq.Mg.ltoreq.1.0, 0.2.ltoreq.Si.ltoreq.1.4, Cu.ltoreq.2.0, Mn.ltoreq.0.4 while extracting heat from said alloy at a rate, falling within a shaded band defined in FIG. 3 of the accompanying drawings corresponding to a freezing range of said alloy, that avoids both shell distortion of said sheet and excessive surface segregation, at least until said alloy freezes;
• solution heat treating said sheet to re-dissolve precipitated particles;
• and
• cooling said sheet at a rate that produces a T4 temper and a potential T8X temperature suitable for automotive panels.

An alloy of aluminum containing magnesium silicon and optionally copper in amounts in percent by weight falling within a range selected from the group consisting of:

• (1) 0.4.ltoreq.Mg.ltoreq.0.8, 0.2.ltoreq.Si.ltoreq.0.5, 0.3.ltoreq.Cu.ltoreq.3.5;
• (2) 0.8.ltoreq.Mg.ltoreq.1.4, 0.2.ltoreq.Si.ltoreq.0.5, Cu.ltoreq.2.5;
• and
• (3) 0.4.ltoreq.Mg.ltoreq.1.0, 0.2.ltoreq.Si.ltoreq.1.4, Cu.ltoreq.2.0
• wherein the alloy has a T4 temper strength in the range 90-175 MPa and a potential T8X temper strength of at least 170 MPa and has been produced in the form of a sheet by a twin belt casting process and a hot and cold rolling process, said twin belt casting process having been carried out with a heat extraction rate within the range defined by the following equations:
• Lower bound heat flux (MW/m.sup.2)=2.25+0.0183.DELTA.T.sub.f
• Upper bound heat flux (MW/m.sup.2)=2.8+0.0222.DELTA.T.sub.f
• Lower bound of alloy freezing range=360.degree. C.
• Upper bound of alloy freezing range=90.degree. C.
• where .DELTA.T.sub.f is given in degree Celsius;
• said alloy being in the form of a sheet which has been heat treated by a heat treatment selected from the group consisting of (a) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, (b) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C., and 220.degree. C. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, coiling said sheet and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, and (c) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then forced cooling said sheet using a means of cooling selected from water, water mist or forced air, and coiling said sheet at a temperature of between 50.degree. and 100.degree. C., then allowing said coil to cool at a rate of less than about 10.degree. C./hour.

A process of preparing aluminum alloy sheet material suitable in particular for automotive applications comprising:

• in a belt casting machine, producing alloy slab by casting an alloy of aluminum containing magnesium, silicon and optionally copper in amounts in percent by weight falling within a range selected from the group consisting of:
• (1) 0.4.ltoreq.Mg.ltoreq.0.8, 0.2.ltoreq.Si.ltoreq.0.5, 0.3.ltoreq.cu.ltoreq.3.5
• (2) 0.8.ltoreq.Mg.ltoreq.1.4, 0.2.ltoreq.Si.ltoreq.0.5, Cu.ltoreq.2.5, and
• (3) 0.4.ltoreq.Mg.ltoreq.1.0, 0.2.ltoreq.Si.ltoreq.1.4, Cu.ltoreq.2.0 while extracting heat from said alloy at a rate, falling within a shaded band defined in FIG. 3 of the accompanying drawings corresponding to a freezing range of said alloy, that avoids both shell distortion of said sheet and excessive surface segregation, at least until said alloy freezes;
• hot rolling and cold rolling said slab to form a sheet;
• solution heat treating said sheet to re-dissolve precipitated particles;
• and
• cooling said sheet at a rate that produces a T4 temper and a potential T8X temper suitable for automotive applications;
• said sheet having been subjected to a treatment selected from the group of consisting of;
• (a) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. at a rate greater than about 10.degree. C./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec. but not faster than 50.degree. C./sec. then cooling to between 120.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour,
• (b) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then cooling said sheet according to a scheme comprising cooling to between 350.degree. C. and 220.degree. C. at a rate greater than about 10.degree. c./sec but not more than about 2000.degree. C./sec, then cooling to a temperature in the range of 270.degree. C. and 140.degree. C. at a rate greater than 1.degree. C./sec but not faster than 50.degree. C./sec, then cooling to between 120.degree. C. and 50.degree. C. and 50.degree. C. at a rate greater than 5.degree. C./min, but less than 20.degree. C./sec, cooling said sheet and then cooling to ambient temperature at a rate of less than about 10.degree. C./hour, and
• (c) solution heat treating said sheet at a temperature in the range of 500.degree. to 570.degree. C. and then forced cooling said sheet using a means of cooling selected from water, water mist or forced air, and cooling said sheet at a temperature of between 50.degree. and 100.degree. C. then allowing said coil to cool at a rate of less than about 10.degree. C./hour.