NEW 6XXX ALUMINUM ALLOYS

Abstract

New 6xxx aluminum alloy products are disclosed. The new 6xxx aluminum alloy products may include tin and may realize an improved combination of properties, such as an improved combination of two or more of strength, ductility (elongation), extrudability, extrusion temperature, extrusion speed, and the absence of visually apparent surface defects.

Claims

1. A 6xxx aluminum alloy product comprising: from 0.5 to 1.5 wt. % Sn; from 0.4 to 1.6 wt. % Si; from 0.6 to 1.2 wt. % Mg; wherein a weight ratio of (wt. % Si) to (wt. % Mg) is at least 0.75:1; from 0.5 to 1.1 wt. % Cu; from 0.15 to 1.5 wt. % Mn; from 0.10 to 0.80 wt. % Fe; wherein (wt. % Si)+(wt. % Mn)+(wt. % Fe) is at least 0.95 wt. %; up to 1.2 wt. % Bi; up to 1.2 wt. % In; up to 1.0 wt. % Zn; up to 0.35 wt. % Cr; up to 0.25 wt. % V; up to 0.25 wt. % Zr; up to 0.15 wt. % Ti; up to 0.04 wt. % Pb; the balance being aluminum, optional incidental elements and impurities; wherein the 6xxx aluminum alloy product comprises a dispersoid area fraction (f) of at least 0.30%, wherein the dispersoids comprise FeMn.sub.3Si.sub.2 dispersoids.

2. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product includes from 0.80 wt. % Sn to 1.30 wt. % Sn.

3. The 6xxx aluminum alloy product of claim 1, wherein (wt. % Si)+(wt. % Mn)+(wt. % Fe) is at least 1.0 wt. %.

4. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product includes not greater than 0.20 wt. % Bi.

5. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product includes not greater than 0.20 wt. % In.

6. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product includes not greater than 0.005 wt. % Pb.

7. The 6xxx aluminum alloy product of claim 1, wherein a mean (average) dispersoid size is from 0.05 to 0.20 micrometers.

8. The 6xxx aluminum alloy product of claim 1, wherein a D90 of the dispersoids is not greater than 0.30 micrometers, or not greater than 0.27 micrometers, or not greater than 0.24 micrometers, or not greater than 0.21 micrometers, or not greater than 0.19 micrometers, or not greater than 0.18 micrometers.

9. The 6xxx aluminum alloy product of claim 1, wherein a D10 of the dispersoids is at least 0.02 micrometers, or at least 0.03 micrometers, or at least 0.04 micrometers.

10. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product comprises at least 3 vol. % <111> microtexture.

11. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product is a sheet, plate, extrusion or forging.

12. The 6xxx aluminum alloy product of claim 1, wherein the 6xxx aluminum alloy product is an extrusion.

13. The 6xxx aluminum alloy product of claim 12, wherein the extrusion is a rod.

14. A method comprising: (a) casting a billet of the 6xxx aluminum alloy, wherein the 6xxx aluminum alloy comprises: from 0.5 to 1.5 wt. % Sn; from 0.4 to 1.6 wt. % Si; from 0.6 to 1.2 wt. % Mg; wherein a weight ratio of (wt. % Si) to (wt. % Mg) is at least 0.75:1; from 0.5 to 1.1 wt. % Cu; from 0.15 to 1.5 wt. % Mn; from 0.10 to 0.80 wt. % Fe; wherein (wt. % Si)+(wt. % Mn)+(wt. % Fe) is at least 0.95 wt. %; up to 1.2 wt. % Bi; up to 1.2 wt. % In; up to 1.0 wt. % Zn; up to 0.35 wt. % Cr; up to 0.25 wt. % V; up to 0.25 wt. % Zr; up to 0.15 wt. % Ti; up to 0.04 wt. % Pb; the balance being aluminum, optional incidental elements and impurities; (b) pre-heating the billet to an extrusion temperature, wherein the extrusion temperature is from 810 F. to 960 F.; and (c) extruding the billet into an extruded product.

15. The method of claim 14, comprising quenching the extruded product during the extruding step.

16. The method of claim 14, comprising, after the extruding step, solution heat treating and then quenching the extruded product.

17. The method of claim 16, comprising, after the quenching, artificially aging the extruded product.

18. The method of claim 1, wherein the extrusion speed is from 40 to 70 feet per minute.

19. The method of claim 1, wherein the extruded product is devoid of visually apparent surface defects.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0083] FIG. 1A is an SEM image of a representative one of Alloys 4-6 of Example 1.

[0084] FIG. 1B is a processed version of the SEM image of FIG. 1A used for particle (dispersoid) size analysis.

[0085] FIG. 2 is a graph showing dispersoid particle size distributions of the Example 1 alloys.

[0086] FIG. 3A is a representative microstructure of a standard 6020 alloy from Example 1 taken across the entire width of the extruded rod and centered at D/2; the microstructure is a <111> crystal direction map generated by EBSD data for points aligned within 10 of the extrusion axis.

[0087] FIG. 3B is a representative microstructure of Alloys 1-3 from Example 1 taken across the entire width of the extruded rod and centered at D/2; the microstructure is a <111> crystal direction map generated by EBSD data for points aligned within 10 of the extrusion axis.

[0088] FIG. 3C is a representative microstructure of Alloys 4-6 from Example 1 taken across the entire width of the extruded rod and centered at D/2; the microstructure is a <111> crystal direction map generated by EBSD data for points aligned within 10 of the extrusion axis.

DETAILED DESCRIPTION

Example 1

[0089] Six industrial-scale billets (11-inch (D)40-inch (L); 27.9 cm (D)101.6 cm (L)) of the new aluminum alloys shown in Table 1 were cast. Three conventional 6020 billets of the same size were also cast, the average composition of which is provided in Table 1, below.

TABLE-US-00001 TABLE 1 Composition of Ex. 1 Alloys (in wt. %)* Alloy Si Fe Cu Mn Mg Cr Zn Ti Sn 1 0.66 0.41 0.67 0.18 0.80 0.05 0.03 1.19 2 0.67 0.42 0.64 0.18 0.76 0.06 0.03 1.08 3 0.66 0.42 0.63 0.18 0.72 0.06 0.03 1.09 4 0.81 0.44 0.63 0.33 0.73 0.06 0.04 1.05 5 0.80 0.45 0.63 0.30 0.76 0.05 0.03 1.11 6 0.80 0.46 0.64 0.32 0.86 0.06 0.03 1.09 6020 0.55 0.33 0.70 0.02 0.75 0.06 0.02 1.05 *The balance of the alloy was incidental elements and impurities, where the alloy contained not greater than 0.03 wt. % of any one impurity, and where the alloy contained not greater than 0.10 wt. %, in total, of all impurities.

[0090] After casting, the billets were homogenized, and then extruded to coiled rods of 0.637 inch (16.17 mm) diameter at a nominal temperature of 940 F. (504 C.) (furnace set-point) and at an extrusion speed of 38.5 ft/min (11.58 m/min.) and then water quenched. The extruded rods were then drawn with 28.4% ROA (reduction of area) to a final diameter of 0.539 inch (13.7 mm) and then aged for 8 hours at 355 F. (179.4 C.), thereby producing T8 temper rods. The mechanical properties of the rods were then measured by obtaining tensile samples from the front and rear of every rod. The mechanical property results are summarized in Table 2, below. (Values are the average of duplicate specimens.)

TABLE-US-00002 TABLE 2 Mechanical Properties of Ex. 1 Alloys Alloy UTS (ksi) TYS (ksi) Elong. (%) 1 43.3 40 14.0 2 44.9 41.8 13.0 3 44.5 41.2 13.5 4 49.5 47.6 11.0 5 50.2 48.7 12.5 6 48.4 46.3 13.0 6020-1 42 38.5 15.0 6020-2 42.1 38.3 14.5 6020-3 41.8 38.2 15.0

[0091] As shown, the new alloys realize significantly higher strengths than the conventional 6020 alloys and with generally similar ductility. Alloys 4-6 with higher silicon (0.8 wt. %) and manganese (>0.3 wt. %) realize significantly higher strength than the conventional 6020 alloys.

[0092] Particle counts were also conducted on SEM images and in accordance with the Microstructure Assessment Procedure, above. The particle count results are shown in Table 3, below. FIG. 2 shows the particle size distribution. The mean and D10-D90 values provided below are in micrometers.

TABLE-US-00003 TABLE 3 Dispersoid Analysis - Example 1 Alloys Representative Representative Representative One of Alloys One of Alloys Property One of 6020 1-3 4-6 Area/(Vol.) % 0.27 0.59 0.97 Mean particle size 0.088 0.096 0.108 D10 (10%) 0.054 0.057 0.067 D25 (25%) 0.067 0.070 0.083 D50 (50%) 0.085 0.089 0.103 D75 (75%) 0.107 0.116 0.128 D90 (90%) 0.127 0.145 0.157

[0093] The particle counts are representative of the volume of dispersoids in the alloy product, including the volume of FeMn.sub.3Si.sub.2 dispersoids. As shown, the new alloys contain significantly more dispersoids than the conventional 6020 alloys but at generally similar dispersoid sizes. It is believed that the higher manganese, iron and/or silicon content at least partially contributes to the high volume fraction of dispersoids in the new aluminum alloy products. Such high dispersoid amounts may facilitate, among other things, the production of wrought aluminum alloy products in partially unrecrystallized or fully unrecrystallized form. Improved properties may accordingly be realized.

[0094] A microstructure analysis of the produced rods was also conducted. Specifically, one rod from Alloy 1-3, one rod from Alloys 4-6, and one rod of the 6020 alloys were subjected to EBSD imaging per the Microstructure Assessment Procedure, above. As shown in FIGS. 3A-3C, the standard 6020 alloys contained very little <111> microtexture having less than 3 vol. % of <111> microtexture, which is consistent with a fully recrystallized microstructure. Conversely, the new alloys having at least 0.15 wt. % Mn and 0.40 wt. % Fe realized significantly more <111> microtexture. Alloys 1-3 having about 0.66 wt. % Si, 0.42 wt. % Fe, and 0.18 wt. % Mn contained about 20 vol. % <111> microtexture, which is consistent with a partially unrecrystallized microstructure. Alloys 4-6 having about 0.81 wt. % Si, 0.45 wt. % Fe, and 0.32 wt. % Mn contained about 40 vol. % <111> microtexture, which is consistent with a fully unrecrystallized microstructure.

Example 2

[0095] Additional industrial scale billets were cast and homogenized as per Example 1, the composition of which is shown below in Table 4.

TABLE-US-00004 TABLE 4 Composition of Ex. 2 Alloys (in wt. %)* Alloy Si Fe Cu Mn Mg Cr Zn Ti Sn 7 0.86 0.46 0.67 0.31 0.86 0.12 0.05 0.06 1.08 *The balance of the alloy was incidental elements and impurities, where the alloy contained not greater than 0.03 wt. % of any one impurity, and where the alloy contained not greater than 0.10 wt. %, in total, of all impurities.

[0096] A first set of the homogenized billets were preheated from room temperature to 940 F. (504 C.) and then extruded to a diameter of 1.031 inch (26.2 mm) at an extrusion speed of 50 ft/min (15.24 m/min), and then water quenched. The extruded rods were then drawn with a 14.6% ROA (reduction of area) to a final diameter of 0.952 inch (24.2 mm) and then aged at 355 F. (179.4 C.) for 8 hours thereby producing a first set of T8 temper rods (Alloys 7A).

[0097] A second set of the homogenized billets were preheated from room temperature to 870 F. (465.6 C.) and then extruded to a diameter of 1.077 inch (27.3 mm) at an extrusion speed of 50 ft/min (15.24 m/min), and then water quenched. The extruded rods were then drawn with a 21.7% ROA (reduction of area) to a final diameter of 0.953 inch (24.2 mm) and then aged at 355 F. (179.4 C.) for 8 hours thereby producing T8 temper rods (Alloys 7B).

[0098] The mechanical properties of the rods were then measured by obtaining tensile samples from the front and rear of every rod. The mechanical property results are summarized in Table 5, below. (Values are the average of at least triplicate specimens.)

TABLE-US-00005 TABLE 5 Mechanical Properties of Ex. 2 Alloys Alloy UTS (ksi) TYS (ksi) Elong. (%) 7A 54.4 52.9 10.5 7B 53.1 51.7 10.0

[0099] It is believed that the high amount of dispersoids facilitated, among other things, the production of partially unrecrystallized or fully unrecrystallized rods, resulting in the improved mechanical properties. For instance, Alloy 7 contained 0.12 wt. % Cr as compared to the 0.05-0.06 wt. % Cr of Alloys 1-6. The increased amount of chromium in Alloy 7 may be at least partially responsible for its significantly higher strength properties.

[0100] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.