Aluminum wheels and methods of manufacture

1. A wheel, comprising:

a rim; and

a disc having a mounting portion, the mounting portion including:

an inner mounting face and an outer mounting face; and

a coarse grain region and a fine grain region,

the coarse grain region being adjacent to, and at least partially forming, one of the inner mounting face or the outer mounting face;

the coarse grain region including aluminum alloy grains of a first average grain length, wherein the first average grain length is greater than 1 mm;

wherein the coarse grain region has a maximum depth of no less than 6.35 mm;

the fine grain region extending between the coarse grain region and the other of the inner mounting face or the outer mounting face; and

the fine grain region including aluminum alloy grains of a second average grain length, wherein the second average grain length is less than 0.5 mm.

2. The wheel according to claim 1 , wherein the disc further comprises a disc slope region between the mounting portion and the rim, and wherein the disc slope region includes aluminum alloy grains of the second average grain length.

3. The wheel according to claim 1 , wherein the first average grain length is greater than 1 mm and less than 25 mm.

4. The wheel according to claim 1 , wherein the rim and the disc are formed of an aluminum alloy including silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), and aluminum (Al).

5. The wheel according to claim 1 , wherein the coarse grain region is a first coarse grain region adjacent to, and at least partially forming, the outer mounting face, wherein the mounting portion further includes a second coarse grain region adjacent to, and at least partially forming, the inner mounting face,

wherein the second coarse grain region includes aluminum alloy grains having the first average grain length; and

wherein the fine grain region extends between the first coarse grain region and the second coarse grain region.

6. The wheel according to claim 5 , wherein the second coarse grain region has a maximum depth of no less than 6.35 mm.

7. A method for manufacturing a wheel having a rim and a disc, the disc having a mounting portion including an inner mounting face and an outer mounting face, the method comprising:

heating an aluminum alloy billet to a temperature of no less than 480° C. and no greater than 540° C.;

rotary forging the heated aluminum alloy billet; and

after rotary forging, removing a forging cover stock such that the mounting portion of the disc includes a coarse grain region and a fine grain region,

the coarse grain region being adjacent, and at least partially forming, one of the outer mounting face or the inner mounting face;

the coarse grain region including aluminum alloy grains of a first average grain length, wherein the first average grain length is greater than 1 mm;

wherein the coarse grain region has a maximum depth of no less than 6.35 mm;

the fine grain region extending between the coarse grain region and the other of the outer mounting face or the inner mounting face; and

the fine grain region including aluminum alloy grains of a second average grain length, wherein the second average grain length is less than 0.5 mm.

8. The method according to claim 7 , wherein heating the aluminum alloy billet includes heating the aluminum alloy billet to a temperature of no less than 495° C. and no greater than 540° C.

9. The method according to claim 8 , wherein heating the aluminum alloy billet includes heating the aluminum alloy billet to a temperature of no less than 495° C. and no greater than 520° C.

10. The method according to claim 7 , wherein rotary forging includes downward forging the heated aluminum alloy billet with a continuous stroke of a die.

11. The method according to claim 10 , wherein the single downward continuous stroke is performed at a strain rate of 0.01 seconds −1 to 0.3 seconds −1 .

12. The method according to claim 11 , further comprising:

flow forming a contour of the rim; and

performing solution heat treatment and aging after flow forming.

13. A wheel, comprising:

a rim; and

a disc connected to the rim, the disc having:

a mounting portion including an inner mounting face and an outer mounting face, the mounting portion including a coarse grain region and a fine grain region,

the coarse grain region being adjacent to, and at least partially forming, one of the inner mounting face or the outer mounting face;

the coarse grain region having a maximum depth of no less than 6.35 mm;

the coarse grain region including aluminum alloy grains of a first average grain length, wherein the first average grain length is greater than 1 mm and less than 25 mm;

the fine grain region extending between the coarse grain region and the other of the inner mounting face or the outer mounting face; and

the fine grain region including aluminum alloy grains of a second average grain length, wherein the second average grain length is less than 0.5 mm; and

a disc slope region between the mounting portion and the rim, and wherein the disc slope region includes aluminum alloy grains of the second average grain length.

14. The wheel according to claim 13 , wherein the coarse grain region is a first coarse grain region adjacent to, and at least partially forming, the outer mounting face, wherein the mounting portion further includes a second coarse grain region adjacent, and at least partially forming, the inner mounting face,

wherein the second coarse grain region includes aluminum alloy grains having the first average grain length;

wherein the fine grain region extends between the first coarse grain region and the second coarse grain region; and

wherein the wheel is formed of an aluminum alloy including silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), and aluminum (Al).

15. The wheel according to claim 14 ,

wherein the second coarse grain region has a second coarse grain region maximum depth of no less than 6.35 mm.

16. The wheel according to claim 15 , the aluminum alloy comprising, by weight percentage:

0.8% to 1.2% Si;

0.7% Fe;

0.10% to 0.7% Cu;

0.10% to 0.40% Mn;

0.7% to 1.2% Mg;

0.04% to 0.35% Cr;

0.25% Zn; and

0.10% Ti,

the balance of weight percent comprising aluminum and incidental elements and impurities,

wherein the aluminum alloy comprises dispersoids in a density sufficient to provide a disc slope region grain structure having aluminum alloy grains of the second average grain length.

17. The wheel according to claim 15 , the aluminum alloy comprising, by weight percentage:

0.40% to 0.8% Si;

0.7% Fe;

0.15% to 0.40% Cu;

0.15% Mn;

0.8% to 1.2% Mg;

0.04% to 0.35% Cr;

0.25% Zn; and

0.15% Ti,

the balance of weight percent comprising aluminum and incidental elements and impurities,

wherein the aluminum alloy comprises dispersoids in a density of no less than 20 dispersoids per μm 2 .