GMNA GM6412M PDF

Material Description. The specification covers the requirements for wrought aluminum alloy sheet for use as automotive body and closures panels. Typical applications include hoods and lift-gates. This specification is applicable to two types of wrought aluminum alloys; age hardenable and non-age hardenable. Age hardenable (e.g., 6000 series) aluminum alloys can be used for exposed and unexposed applications. Due to surface characteristics, non-age hardenable (e.g., 5000 series) alloys may not be suitable for exposed applications.

Note: Exposing work hardened 5000 series aluminum alloys containing more than about 3% magnesium to temperatures above 66°C (150°F) may result in susceptibility to Stress Corrosion Cracking. Therefore, non-age hardenable, 5000 series aluminum alloy grades in this specification may not be suitable for panels that are exposed to above ambient temperatures.

Age hardenable aluminum alloys attain an increase in strength due to strain hardening and accelerated aging (precipitation hardening) when subjected to the assembly plant paint bake cycle. Non-age hardenable aluminum alloys increase in strength due to strain hardening only, and will show some decrease in strength following the paint bake cycle.

Material Identification. The following nomenclature shall be used to designate age hardenable and non-age hardenable aluminum alloy sheet approved to this specification on engineering part drawings and Material Parts Specification (MPS) sheets. The callout shall consist of the material specification number, GM6412M, followed by the grade designation. The grade designation shall consist of the capital letters "AL" designating aluminum, the minimum as-received yield strength in megapascals (MPa), a capital letter H or N designating whether the alloy is age hardenable or non-hardenable respectively, a number (i.e., 1, 2, 3 etc.) indicating which Aluminum Association (AA) chemical composition limit the grade is associated with, and the capital letters E or U to designate the surface quality as either exposed or unexposed, respectively. The capital letter H designates an age hardenable grade. The capital letter N designates a non-age hardenable (strain-hardening only) grade. Grades designated with the letter H are required to attain a minimum paint bake response of 70 MPa following 2% pre-strain and baking @ 175°C (350°F) for 30 minutes. The paint bake response is defined as the minimum increase in yield strength due to age hardening from a simulated E-coat paint bake cycle following 2% pre-strain. Grades designated with the letter N are strain hardenable only and therefore do not have a paint bake response requirement. The grade composition number (1, 2, 3, 4 or 5) designates the Aluminum Association (AA) composition limit that the grade is associated with as follows:

For example, GM6412M AL115H2E specifies an aluminum (AL) sheet grade with a 115 MPa asreceived minimum yield strength, that is age hardenable (H) and capable of attaining a minimum of 70 MPa increase in yield strength following 2% strain and baking @ 175°C (350°F) for 30 minutes, a chemical composition that falls within the AA6111 composition limit (2), with an exposed (E) surface quality.