METHOD OF MANUFACTURING AN ALMGSC-SERIES ALLOY PRODUCT
The invention relates to a method of manufacturing an AIMgSc-series aluminium alloy product, the method comprising the step of cooling said AIMgSc-series aluminium alloy product from a final annealing temperature to below 150° C., wherein the cooling in a first temperature range of about 250° C. to about 200° C. is at an equivalent time of more than 4 hours, and wherein the cooling in a second temperature range from about 200° C. to about 150° C. is at an equivalent time of more than 0.2 hours, and wherein the equivalent time (t(eq)) is defined as (I) wherein T (in degrees Kelvin) indicates the temperature of the heat treatment, which changes over the time t (in hours) and T ref (in degrees Kelvin) is the reference temperature selected at 473K. t ( eq ) = ∫ exp ( - 16000 / T ) dt exp ( - 16000 / T ref ) ( I )
1 . A method of manufacturing an AlMgSc-series aluminium alloy product, the method comprising the step of cooling said AlMgSc-series aluminium alloy product from a final annealing temperature to below 150° C., wherein the cooling in a first temperature range of about 250° C. to about 200° C. is at an equivalent time of more than 4 hours, and wherein the cooling in a second temperature range from about 200° C. to about 150° C. is at an equivalent time of more than 0.2 hours, and wherein the equivalent time (t(eq)) is defined as
t
(
eq
)
=
∫
exp
(
-
16000
/
T
)
dt
exp
(
-
16000
/
T
ref
)
wherein T (in degrees Kelvin) indicates the temperature of the heat treatment, which changes over the time t (in hours) and T ref (in degrees Kelvin) is the reference temperature selected at 473K (200° C.).
2 . The method according to claim 1 , wherein the equivalent time in the first temperature range is longer than 6.5 hours.
3 . The method according to claim 1 , wherein the equivalent time in the second temperature range is longer than 0.4 hours.
4 . The method according to claim 1 , wherein the final annealing temperature is in a range of 250° C. to 400° C.
5 . The method according to claim 1 , wherein said AlMgSc-series aluminium alloy product is in a form selected from the group consisting of a rolled product, an extruded product, a forged product, a powder-metallurgy product.
6 . The method according to claim 1 , wherein said AlMgSc-series aluminium alloy product is a rolled product.
7 . The method according to claim 6 , wherein the rolled product has a thickness of up to 25.4 mm.
8 . The method according to claim 1 , wherein the method comprises the steps of casting an AlMgSc-series aluminium alloy ingot, rolling the ingot to final gauge into a rolled product, and heat-treating by annealing of the rolled product at the final annealing temperature, followed by cooling in accordance with claim 1 .
9 . The method according to claim 1 , wherein the method comprises the steps of a high temperature forming operation of an AlMgSc-series aluminium alloy product into a single- or double-curved shape product at the final annealing temperature followed by cooling in accordance with claim 1 .
10 . The method according to claim 9 , wherein the high temperature forming operation at the final annealing temperature is by a creep forming operation or a relaxation forming operation.
11 . The method according to claim 1 , wherein the AlMgSc-series aluminium alloy product has a composition comprising of, in wt. %:
Mg 3.0% to 6.0%,
Sc 0.02% to 0.5%,
Mn up to 1%,
Zr up to 0.3%,
impurities and balance aluminium.
12 . The method according to claim 1 , wherein the AlMgSc-series aluminium alloy product has a composition comprising of, in wt. %:
Mg 3.0% to 6.0%,
Sc 0.02% to 0.5%,
Mn up to 1%,
Zr up to 0.3%,
Cr up to 0.3%,
Ti up to 0.2%,
Cu up to 0.2%,
Zn up to 1.5%,
Fe up to 0.4%,
Si up to 0.3%,
impurities and balance aluminium.
13 . The method according to claim 1 , wherein the AlMgSc-series aluminium alloy product achieves a measured mass loss per ASTM G67-13 not greater than 15 mg/cm 2 , both before and after being sensitized.
14 . The method according to claim 13 , wherein the measured mass loss is not greater than 12 mg/cm 2 .
15 . The method according to claim 13 , wherein the measured mass loss is not greater than 9 mg/cm 2 .
16 . The method according to claim 12 , wherein the Mg content is from 3.2% to 4.8%.
17 . The method according to claim 12 , wherein the Sc content is from 0.02% to 0.40%.
18 . The method according to claim 12 , wherein the Mn content is from 0.3% to 1.0%.
19 . The method according to claim 12 , wherein the Zr content is from 0.05% to 0.3%.
20 . The method according to claim 12 , wherein the Ti content is from 0.01% to 0.2%.