Development of AlBeMet® Extruded ProductsFigure 2 is a pictorial comparison between a solid billet and the four quarter segments extruded in Phase I. Metallography was performed on

Development of AlBeMet® Extruded Products Charles Pokross & Adam Carr, Materion Beryllium & Composites

ABSTRACT

Materion Beryllium & Composites has developed new powder metallurgy extrusion technology which resulted in successful extrusion of a 10-in. (25-cm) diameter x 240-in. (610-cm) long AlBeMet® 162 circular cylinder. AlBeMet® is a family of aluminum-beryllium compositions which contain 20-75 weight percent Be in an aluminum matrix. Input powder for the 10-in (25-cm) diameter extrusion was inert-gas atomized Al-62wt. % Be, AM162. The powder was cold isostatically pressed (CIP) into 4 quarter round segments, encapsulated in a copper can, sealed and extruded to a solid final shape. Extrusion was performed on a 35,000-ton (311-MN) vertical extrusion press. The results of micro-structural analysis and mechanical property testing of the extrusion are included. Following discussion of the 10-in (25-cm) diameter extrusion, a summary of a project to extrude more complex shapes from AlBeMet® metal matrix composites is presented.

INTRODUCTION

AlBeMet® is family of aluminum-beryllium compositions manufactured by Materion Beryllium & Composites which contain 20-75 weight percent Be in an aluminum matrix. AlBeMet® combines the high modulus and low density attributes of beryllium with the ease of fabrication offered by aluminum. The AM162 grade of AlBeMet® is primarily used for avionic applications; other grades of AlBeMet® are used in a wide variety of components such as computer hard drive actuator arms and high performance sporting goods.

The objective of extruding a 10-in. (25-cm) diameter round was to provide customers with a large cross section product exhibiting mechanical properties superior to hot isostatically pressed (HIP) powder. Although shapes of this size could be manufactured by HIP, the resulting mechanical properties are inferior to extruded product. The challenges were to utilize existing equipment and facilities to manufacture a large diameter extrusion billet; and to extrude a round which met the physical and mechanical property values of production extrusions.

For a majority of extruded products, the AlBeMet® powder process is comprised of the following steps: consolidate powder billet to 85% theoretical density by CIP; encapsulate in copper; and extrude with at least a 4:1 reduction ratio. A flow chart of the powder extrusion process is shown in Figure 1. Input powder for the 10-in (25-cm) diameter extruded round was AM162; a typical chemistry is presented in Table 1.

Figure 1. Process diagram for extruded AM162.

Atomization

Testing Heat Treat Decanning Extrusion

CanningCIPBlending

MAAB-010

MATERION BERYLLIUM & COMPOSITES `` MATERION CORPORATION 14710 W Portage River South Rd www.materion.com/beryllium Elmore, OH 43416-9502 p: +1 419.862.4533 or +1 419.862.4171 Intl: +1 419.862.4127 e: [email protected] © Materion Corporation MAAB-009

mailto:[email protected]

Table 1. Typical AM162 Chemistry

Be (%) O2 (%) C (%) Al Fe (ppm) Si (ppm) Cu (ppm) Ti (ppm)

61.25 0.19 0.059 Bal. 1090 410 115 1010

Extruding a 10-in. (25-cm) diameter bar which met or exceeded the minimum reduction ratio required a CIP billet 27-in (69-cm) in diameter. Encapsulating the billet in copper resulted in a total assembly diameter close to 30-in (76-cm). AM162 extrusion data was used to estimate a force of approximately 22,000 tons (196 MN) to extrude the assembly. A 35,000 ton (311 MN) vertical extrusion press which met the load and size requirements was located at Wyman-Gordon Forgings Inc., (WGF) Houston, Texas.

The CIP unit at Materion Beryllium & Composites’ Elmore, Ohio facility is capable of consolidating a maximum 19-in (48cm) diameter billet; therefore, an unconventional processing method was developed: CIPing four quarter round segments to form the 27-in (69-cm) diameter billet. A three-phase program was initiated to prove feasibility for this billet preparation method, and to confirm that WGF's tooling and lubrication systems did not substantially affect the extrusion characteristics of AM162.The objectives of the program were three-fold; Phase I: prove that four CIP'd segments could be extruded to a 100% dense and integral shape; Phase II: prove the extruder's tooling configuration and lubrication; Phase III: prove that a 30-in (76-cm) segmented billet could be successfully extruded to a 10-in (25-cm) diameter round and meet typical AM 162 extruded and annealed properties.

The large cross section extrusion offers designers of bulk components the advantages of AlBeMet®'s high specific strength and specific modulus, but these properties are equally important to designers of small, complex extruded shapes. The intricate design features which maximize the mechanical and physical properties of AlBeMet® often require costly post-extrusion machining or forming operations to complete. The objective of the complex extrusion program is to reduce or eliminate post-extrusion operations by directly extruding net- or near-net shapes. AlBeMet®, Materion Beryllium & Composites' trademark for aluminum/beryllium metal matrix composites, like many industrial materials poses a health risk only if mishandled. In its usual solid form, as well as for finished parts, and in most manufacturing operations, it is completely safe. However, breathing very fine particles may cause a serious lung condition in a small percentage of individuals. Risk can be minimized with simple, proven, and readily available engineering controls such as ventilation of operations producing fine dust. Information on safe handling procedures is available from Materion Beryllium & Composites.

RESULTS AND DISCUSSION Phase I was performed entirely at Materion Corporation’s Elmore Ohio manufacturing facility. AM162 was vibratory loaded into a CIP bag representing one quarter of a typical 8.1in (21-cm) inside diameter polyurethane bag. The bags were sealed & de-aired. CIP consolidation resulted in a powder compact approximately 85% of theoretical density.

Table 2. Phase I CIPd Billet Dimensions

Billet # Radium, in (cm) Length, in (cm) Weight, in (Kg) Diameter, in (cm)

Top Bottom Top Bottom

1440 3.837 (9.75) 3.721 (9.45) 27.125 (68.90) 19.6 (8.89)

1444 3.833 (9.74) 3.707 (9.41) 27.062 (68.74) 19.5 (8.85)

1445 3.818 (9.70) 3.743 (9.50) 27.140 (68.94) 19.7 (8.94

1446 3.843 (9.76) 3.743 (9.50) 27.190 (69.00) 19.8 (8.98)

Composite

Billet

7.670 (19.48) 7.450 (19.48)

BERYLLIUM & COMPOSITES MATERION CORPORATION 14710 W Portage River South Rd www.materion.com Elmore, OH 43416-9502 P: +1 419.862.4533 or +1 419.862.4171 Intl: +1 419.862.4127 e: [email protected] © Materion Corporation


The CIP'd segments were assembled in an 8-in (20-cm) diameter copper can and sealed. The sealed, segmented billet was pre-heated at 850°F (454°C) and extruded successfully to a 2.65-in (6.7cm) diameter round; a reduction ratio of 11:1. Extrusion of the 8-in (20-cm) diameter segmented billet required a force of 2622-tons (23 MN), and resulted in an extrusion constant K of 21; typical of solid AM162 CIP'd billet extrusion.

Figure 2 is a pictorial comparison between a solid billet and the four quarter segments extruded in Phase I.

Metallography was performed on the as-extruded cylinder. Figure 3 is a photomacrograph showing the etched cross section of the extruded rod. After etching, the interfaces or bond lines of the four segments can be seen by the naked eye. Radiographic and optical microscopic analysis of the bond interfaces revealed no porosity or segregation of Be or Al. Figure 4 shows the microstructure through the center line of the cylinder.

Figure 3. Etched cross section of extrusion showing bond lines

Centerline of Extrusion



Figure 4. Microstructure of Extruded Cylinder

300X

Centerline of Extrusion

A section of the cylinder was leached in a dilute nitric acid solution to remove the copper jacket. The section was annealed at 1100°F (593°C) prior to tensile specimen removal. Tensile specimens were removed from the center where the four segments formed a continuous longitudinal bond; a location where any segment-to-segment bond weakness would be most evident. Longitudinal specimens were removed with the bond line parallel to, and running the length of, the long axis of the tensile bar. Transverse radial specimens were removed from the rod. In these specimens, the bond line traversed the gauge length. Test results from both directions indicated no substantial deviation from typical AM162 tensile properties. Table 3 summarizes the tensile results. Density measurements on a section of the as-extruded and annealed cylinder revealed a change after anneal of <0.03%.Phase II was carried out at Materion Beryllium & Composites and the WGF facility. Using the same AM162 powder lot and manufacturing process as Phase I, a solid, right cylindrical CIP billet, 8-in (20-cm) in diameter and 9-in (23-cm) long, was prepared for trial extrusion. The billet was preheated at 950°F (510°C) and successfully extruded at a reduction ratio of 11:1 on Wyman-Gordon’s' 2500-ton (22-MN) press. The extrusion required a force of 2070-tons (18 MN), which resulted in an extrusion constant K of 16.5, closely matching the predicted value for AM162 at that temperature.

The copper jacket was removed by leaching in a dilute nitric acid solution, and the rod was annealed at 1100°F (593°C) prior to tensile specimen removal. Longitudinal and transverse tensile specimens were removed for comparison with the segmented billet and typical AM162 extruded and annealed properties. Tensile properties of the extruded rod compared favorably with the segmented billet in Phase I and typical extruded and annealed AM162 properties. Table 3 is a summary of mechanical properties. The results of Phase I and II proved feasibility for extrusion of a CIP'd, segmented AM162 billet, and confirmed extrusion process compatibility between the extruder and Materion Beryllium and Composites.

Table 3. Comparison of Extruded/Annealed Tensile Properties Type Orientation UTS ksi (MPa) 0.2% YS ksi (MPa) Elongation % Billet Preheat Temp oF (oC)

Segment L 64.8 (447) 51.2 (353) 9.8 850 (454) Segment L 64.8 (447) 50.1 (346) 7.3 850 (454) Segment T 53.8 (371) 49.2 (339) 2.5 850 (454) Segment T 54 (372) 49.3 (340) 3.1 850 (454)

Solid L 63 (434) 46.6 (321) 10.4 950 (510) Solid L 63.7 (439) 46.1 (318) 8.9 950 (510)

Solid T 49.3 (340) 44.4 (306) 1.1 950 (510) Solid T 51.9 (358) 47.8 (330) 3.3 950 (510)



Typical Annealed Properties

Typical L 61.9 (426) 47.0 (323) 10.2 Typical

Typical T 54.5 (375) 46.7 (322) 4.2 Typical Phase III was completed at Materion Beryllium & Composites and WGF. The same CIP billet preparation method used in Phases I and II was applied to manufacture a 27.750-in (70.5-cm) diameter billet. The four segments of the billet are shown in Figure 5; the tooling used to CIP the segments is shown in Figure 5; the tooling used to CIP the segments is shown in Figure 6. Table 4 summarizes dimensions of the CIPd segments.

Table 4. Phase III CIP’d Billet Dimensions

Billet # Radius inches (cm) Length inches (cm) Weight inches (kg) Diameter inches (cm)

Top Bottom

1 13.400 (34.0) 13.355 (33.92) 30.875 (78.42) 274 (124.3)

2 13.600 (34.54) 13.475 (34.23) 31.062 (78.90) 281 (127.5)

3 13.500 (34.29) 13.460 (34.200 31.000 (78.74) 279 (126.6)

4 13.500 (34.29) 13.400 (34.0) 31.00 (78.74) 278.6 (126.4)

Composite Billet 27.2 (69.1) Fig 6. CIPing

Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

The four segments were loaded into an extrusion capsule The copper canned segmented billet was sealed, pre-heated at 950°F (510°C) and successfully extruded from a 30-in (76-cm) liner to a 10-in (25-cm) round. The extrusion required a force of 24,408-tons (215 MN), resulting in an extrusion constant K of 15.75. This agreed with the predicted force of 25,500-tons (227 MN) for AM162 extrusion at 950°F (510°C). Figure 11 shows the actual extrusion force vs. time graph. Figure 12 shows the as-extruded cylinder.



Figure 11. Extrusion Force versus Time Plot (Wyman-Gordon Forgings (35K Ton Press load/Position/Velocity Data)

Prior to annealing, the extruded rod was leached in dilute nitric acid to remove the copper jacket. Following the anneal, mechanical test specimens were removed from the centerline where the four segments formed a continuous longitudinal bond, and from random areas near the outside edge of the cylinder. Room temperature tensile, compression, and fracture toughness tests were completed; Table 5 summarizes the results. A full cross-section of the cylinder was etched in a dilute acid solution to reveal segment bond lines visible to the naked eye as observed in the 8-in (20-cm) diameter segmented extrusion. No bond lines were observed in the 10-in (25-cm) round. Figure 13A and 13B show transverse and longitudinal microstructures. Density measurements before and after anneal showed a similarly small change in density, <0.02%, as measured on the segmented extrusion in Phase I.

Figure 12. Extruded Cylinder



Direction Location UTS ksi (MPa) 0.2% Y Elongation %

Long-1 Center 60.6 (418) 44 (303) 8.9

Long-2 Center 61.4 (423) 42.4 (292) 11.1

Trans-2 Center 52.6 (363) 44.7 (308) 3.3

Trans-2 Center 50.8 (350) 40,4 (279) 1.7

Long-3 180o 60.6 (418) 43.8 (302) 7.7

Trans-3 180o 52.7 (363) 43.2 (298) 3.3

Long-4 0o 61.4 (423) 42.4 (292) 10.3

Trans-4 0o 51.2 (353) 44.1 (304) 2.3

Fracture Toughness

Direction Location Ksi in (MPa √m)

LT Center 17.6 (19) LT Edge 17.8 (20)

TL Center 9.0 (10)

TL Edge 8.9 (10)

Room Temperature Compression Testing

Location Compression Strength ksi (MPa)

Compression Yield ksi (MPa) Compression % Expand %

Center 100.8 (695) 39.5 92727) 22.5 29.6

Edge-0o 101.5 (700) 39.5 (272) 24.8 34.1

Edge-180o 102.8 (709) 38.0 (2 28.5 39.6 COMPLEX SHAPE EXTRUSION EFFORT Criteria for process feasibility was successful extrusion of an Al-20wt. % (27vol. %) Be (AlBeMet® 120) tube 2-in (51-mm) diameter with 0.187-in (4.75-mm) wall. Extrusion of non-Be containing aluminum alloy 6061 was completed first to prove general process compatibility with Materion Beryllium & Composites’ 3000-ton (27-MN) Farrell extrusion press in Elmore, Ohio. Successful extrusion of the aluminum alloy was followed by A1-10% Be, designated AlBeMet® 110, and finally® AlBeMet® 120. All extrusions were performed using the 127-mm (5-in) inside diameter liner. Proprietary tooling for the extrusions was fabricated from standard die steel. The A16061 was purchased and extruded in as-cast/homogenized condition. The fully dense AlBeMet 110 and AlBeMet® 120 extrusion billets were prepared from pre-alloyed inert-gas atomized, screened and blended powder. Table 6 is the AlBeMet® 120 chemistry.

Table 6. AlBeMet® 120 Chemistry Be (%) O2 (%) C (%) Al Fe (ppm) Si (ppm) Cu (ppm)

22.07 0.12 0.024 Bal 1215 935 315 BERYLLIUM & COMPOSITES MATERION CORPORATION 14710 W Portage River South Rd www.materion.com Elmore, OH 43416-9502 P: +1 419.862.4533 or +1 419.862.4171 Intl: +1 419.862.4127 e: [email protected] © Materion Corporation


Two A16061 extrusions were required to prove process and tooling feasibility on the Elmore press. Examination of the extrusion seam was conducted using optical macro-and microscopy along with scanning electron microscopy (SEM). Figure 14 is a macrograph of the extrusion seam area. No seam discontinuities were observed in optical microscopic or SEM examination. Figure 15 is a 1000X magnification of a seam showing an integral Al-Be structure. No qualitative or quantitative testing has been performed to evaluate the mechanical properties of the seams. This project was performed at Materion Beryllium & Composites’ Research and Development lab in Cleveland, Ohio, and at the production facility in Elmore, Ohio. Future efforts are directed at extrusion seam characterization and process feasibility for AlBeMet® compositions with >20wt. % (27vol. %) Be.

Figure 14. Micrograph of extrusion seam area. 22X

Figure 15. Seam area showing integral AlBe structure 1000X

CONCLUSIONS 1) AM 162 can be extruded to a 10-in (25-cm) diameter cylinder which exhibits typical extruded and annealed mechanical

properties. 2) CIP tooling can be manufactured to produce quarter segments of a solid cylinder. 3) No substantial change in extrusion force is required to extrude a segmented billet. 4) The segments welded together during extrusion. Mechanical properties along the seams meet the typical extruded and

annealed AM162 mechanical property goals. 5) Bond lines may be seen after a heavy etch. These are innocuous with respect to properties. 6) The bond lines cannot be resolved by optical metallographic analysis. 7) Existing extrusion technology for aluminum alloys may be modified to successfully extrude a simple hollow shape from a

solid AlBeMet® 120 billet. The mechanical integrity of the resulting extrusion seams is unknown at this time. Note: Handling Aluminum-Beryllium Metal matrix composites in solid form poses no special health risk. Like many industrial materials, beryllium-containing materials may pose a health risk if recommended safe handling practices are not followed. Inhalation of airborne beryllium may cause a serious lung disorder in susceptible individuals. The Occupational Safety and Health Administration (OSHA) has set mandatory limits on occupational respiratory exposures. Read and follow the guidance in the Material Safety Data Sheet (MSDS) before working with this material. For additional information on safe handling practices or technical data on Aluminum Beryllium Metal matrix composites, contact Materion Beryllium & Composites. MAAB-010-0



Documents

Development of AlBeMet® Extruded ProductsFigure 2 is a pictorial comparison between a solid billet and the four quarter segments extruded in Phase I. Metallography was performed on