Patent Application
20160273081
The present disclosure relates to fine particle reinforced aluminum alloys known as metal matrix composites which offer an enhancement in non-aggressive wear properties, providing a significant life increase and performance improvement in articles made therefrom. This particle reinforced aluminum matrix composite material uses fine particle sizes in the range of about 0.3 microns up to about 5 microns. These particle reinforced aluminum matrix composite materials provide high strength to avoid tooth deformation, sufficient ductility to deal with robust usage, lightweight characteristics (for weight-dependent applications), non-aggressive wear resistance, and an ability to manufacture the components using conventional machining processes.
Metal matrix composites are composite materials including a metal matrix and a reinforcing material (e.g., a ceramic material or an organic compound) dispersed in the metal matrix. The metal matrix phase is typically continuous whereas the reinforcing dispersed phase is typically discontinuous. The reinforcing material may serve a structural function and/or change one or more properties of the material. Metal matrix composites can provide combinations of mechanical and physical properties that cannot be achieved through conventional materials or process techniques. These property combinations have made metal matrix composites particularly useful in the aerospace and other transport industries.
Powder metallurgy is a process by which powdered materials are compacted into a desired shape and sintered to produce desired articles. Powder metallurgy allows faster quenching of the metal which typically results in smaller grain sized, increased solid solubility of most solute elements, and reduced segregation of intermetallic phases. These results may lead to beneficial properties in the produced articles, such as high strength at normal and elevated temperatures, high modulus values, good fracture toughness, low fatigue crack growth rate, good thermal conductivity, non-aggressive wear resistance and high resistance to stress corrosion cracking.
Aluminum alloys are typically used to make motorcycle and bicycle chain rings and sprockets. These sprockets suffer from wear against the drive chain, as well as wear attributable to the accumulation of grit, mud, dust, or the like, leading to abrasion-related degradation of the chain ring or sprocket. Limitations on the type of aluminum alloy to be used depend largely upon the application in which the sprocket is to be used. For example, bicycle and motorcycle components need to be lightweight, while retaining high strength for the drive train assemblies. Furthermore, advancements in brakes on small vehicles and bicycles have led toward the adaptation of disc braking systems to road bicycles, which are much more efficient and effective than the traditional cantilevered design. However, while disc brakes have increased performance over traditional cantilevered braking systems, widespread adoption on racing bicycles has not occurred as the weight of the disc is greater than that of the traditional designs. A lightweight disc is needed to render the disc light enough for use on lightweight bikes.
It would be desirable to provide compositions and methods for producing articles containing aluminum matrix composites having fine reinforcement particles that overcome the aforementioned deficiencies.
The present disclosure relates to metal matrix composite materials including a reinforcement phase dispersed in a matrix phase. The matrix phase includes aluminum or an aluminum alloy. The reinforcement phase may include a reinforcement material having an average particle size in the range of from about 0.3 μm to about 5 μm, and more particularly about 0.3 μm to about 3 μm. The present disclosure further relates to lightweight, strong and enhanced wear resistant articles made from such metal matrix composites, and in particular articles such as sprockets, chain rings, discs or rotors, which have relatively small cross-sections that must withstand heavy wear. The reinforced aluminum alloy materials disclosed herein use reinforcement particles of about 0.3 μm to 7 μm in size, representing a substantial reduction in size of currently available reinforced aluminum alloys.
Disclosed in various embodiments are discs, rotors, sprockets and chain rings machined from metal matrix composites. The metal matrix composite includes an aluminum or aluminum alloy matrix; and reinforcement particles dispersed in the matrix. The reinforcement particles have an average particle size in the range of about 0.3 μm to about 3 to 7 μm.
The reinforcement particles may include at least one ceramic material selected from the group consisting of carbides, oxides, silicides, borides, and nitrides.
In some embodiments, the reinforcement particles comprises at least one ceramic material selected from the group consisting of silicon carbide, titanium carbide, boron carbide, silicon nitride, titanium nitride, aluminum oxide, and zirconium oxide.
The aluminum alloy may include at least one element selected from the group consisting of chromium, copper, lithium, magnesium, manganese, nickel, zinc, iron, vanadium, scandium, silver, and silicon.
In some embodiments, the aluminum alloy includes from about 91.2 wt % to about 94.7 wt % aluminum, from about 3.8 wt % to about 4.9 wt % copper, from about 1.2 wt % to about 1.8 wt % magnesium, and from about 0.3 wt % to about 0.9 wt % manganese.
The aluminum alloy may include from about 95.8 wt % to about 98.6 wt % aluminum, from about 0.8 wt % to about 1.2 wt % magnesium, and from about 0.4 wt % to about 0.8 wt % silicon.
In some embodiments, the composite includes from about 15 vol % to about 40 vol % of the reinforcement particles.
Also disclosed are methods for producing an article from a metal matrix composite material, comprising: cold compacting the metal matrix composite material to form a preform; hot compacting the preform to produce a billet; and processing the billet to form the article; wherein the metal matrix composite material comprises an aluminum or aluminum alloy matrix material with reinforcement particles dispersed therein, the reinforcement particles having an average size of from about 0.3 μm to about 5 μm.
In some embodiments, the reinforcement particles include at least one ceramic material selected from the group consisting of carbides, oxides, silicides, borides, and nitrides.
The reinforcement particles may include at least one ceramic material selected from the group consisting of silicon carbide, titanium carbide, boron carbide, silicon nitride, titanium nitride, aluminum oxide, and zirconium oxide.
The aluminum alloy may include chromium, copper, lithium, magnesium, manganese, nickel, zinc, iron, vanadium, scandium, silver, or silicon.
The aluminum alloy may include from about 91.2 wt % to about 94.7 wt % aluminum, from about 3.8 wt % to about 4.9 wt % copper, from about 1.2 wt % to about 1.8 wt % magnesium, and from about 0.3 wt % to about 0.9 wt % manganese.
The aluminum alloy may include from about 91.2 wt % to about 94.7 wt % aluminum, from about 3.8 wt % to about 4.9 wt % copper, from about 1.2 wt % to about 1.8 wt % magnesium, and from about 0.3 wt % to about 0.9 wt % manganese.
The metal matrix composite formed according to the method may comprise from about 15 vol % to about 40 vol % of the reinforcement particles.
These and other non-limiting characteristics of the disclosure are more particularly disclosed below.
The following is a brief description of the drawings, which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same.
A more complete understanding of the components, processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments.
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.
The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
As used in the specification and in the claims, the term “comprising” may include the embodiments “consisting of” and “consisting essentially of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named components/steps and permit the presence of other components/steps. However, such description should be construed as also describing compositions or processes as “consisting of” and “consisting essentially of” the enumerated components/steps, which allows the presence of only the named components/steps, along with any impurities that might result therefrom, and excludes other components/steps.
Numerical values in the specification and claims of this application should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.
All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of “from 2 to 10” is inclusive of the endpoints, 2 and 10, and all the intermediate values).
The term “about” can be used to include any numerical value that can vary without changing the basic function of that value. When used with a range, “about” also discloses the range defined by the absolute values of the two endpoints, e.g. “about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” may refer to plus or minus 10% of the indicated number.
The present disclosure relates to materials having an average particle size. The average particle size is defined as the particle diameter at which a cumulative percentage of 50% (by volume) of the total volume of particles are attained. In other words, 50 vol % of the particles have a diameter above the average particle size, and 50 vol % of the particles have a diameter below the average particle size.
The use of particle reinforced aluminum alloys for brake discs is well known, but such alloys contain particles having large sizes of greater than 15 microns (μm). Such relatively large reinforcement particle sizes present difficulties in machining, particularly the speed with which such metal matrix composite materials can be machined, as well as the tolerances associated with the machined product. Certain articles have complex and difficult profiles to machine, especially when the ceramic reinforcement is coarse. It is considered to be almost impossible to machine compositions with reinforcement particle sizes of 15 microns (μm). Even at a particle size of 7 μm, tool wear issues make achieving a suitable surface finish very difficult, and not economical.
The present disclosure relates to articles machined or otherwise manufactured from metal matrix composite materials which include a reinforcement phase dispersed in a matrix phase. The matrix phase includes aluminum or an aluminum alloy. The reinforcement phase is formed from a reinforcement material having an average particle size in the range of from about 0.3 μm to about 5 μm. The disclosure also relates to methods for producing and using the composite materials. Because the reinforcement particles are finer, tool wear issues are reduced, making articles easier to machine.
Particle-reinforced aluminum alloys offer an increased elastic modulus as a function of the vol % or reinforcement material added. Existing materials offer medium strength levels. However, greater strength is desirable for many applications (particularly in space, defense, aerospace, and transportation applications). The refinement of reinforcement particles provides the potential for high-strength materials without negatively impacting secondary properties (e.g., ductility).
Reinforcement fibers having an average particle size in the range of from about 0.3 μm to about 5 μm offer enhanced strength over coarser grades. The finer reinforcement materials allow the production of composite materials that can be machined faster with conventional tools and with low tool wear. For example, the finer reinforcement materials offer advantages in forming processes (e.g., extrusion) to very close precision shapes without tool wear, thereby allowing use of conventional tools (e.g., steel H13 dies). That is, the finer reinforcement sizes allow machining capability using high speed techniques to make parts with fine finish and tolerances. The addition of the fine reinforcement particles offers a major increase in the wear resistance combined with a good balance of strength, stiffness, ductility and fatigue properties. This combines the mechanical properties needed for disc and rotor components with the ability to process and machine in a cost effective manner.
The finer reinforcement materials also allow high-strength to be achieved in heat treatments that allow low residual stress (high stability) conditions.
The finer reinforcement materials may also allow enhanced elevated temperature properties and/or strength stability after soaking at medium and high temperatures.
When low and medium strength 2xxx and 6xxx aluminum alloys are utilized as the matrix alloy, their strengths can be increased to levels equivalent to or greater than 7xxx aluminum alloys.
Good corrosion and stress corrosion performance can be achieved as a result of the lower solute content matrix alloys. This results in strength and modulus increases which are useful for designing lightweight structural components.
The composite material may include from about 15 vol % to about 45 vol % of the reinforcement particles, including from about 17 vol % to about 40 vol % and from about 20 vol % to about 25 vol %.
In some embodiments, the aluminum alloy includes from about 91.2 wt % to about 94.7 wt % aluminum, from about 3.8 wt % to about 4.9 wt % copper, from about 1.2 wt % to about 1.8 wt % magnesium, and from about 0.3 wt % to about 0.9 wt % manganese.
In other embodiments, the aluminum alloy includes from about 95.8 wt % to about 98.6 wt % aluminum, from about 0.8 wt % to about 1.2 wt % magnesium, and from about 0.4 wt % to about 0.8 wt % silicon.
The aluminum alloy may be 2124. The composition of 2124 aluminum alloy is as follows:
The reinforcement particles may include at least one material selected from carbides, oxides, silicides, borides, and nitrides. In some embodiments, the material is selected from silicon carbide, titanium carbide, boron carbide, silicon nitride, titanium nitride, aluminum oxide, and zirconium oxide. Again, the reinforcement particles have an average particle size of from about 0.3 microns to about 5 microns, including from about 0.3 microns to about 3 microns.
The metal and ceramic powders should be mixed with a high energy technique to distribute the ceramic reinforcement particles into the metal matrix. Suitable techniques for this mixing include ball milling, mechanical attritors, teamer mills, rotary mills and other methods to provide high energy mixing to the powder constituents. Mechanical alloying should be completed in an atmosphere to avoid excessive oxidation of powders preferable in an inert atmosphere using nitrogen or argon gas. The processing parameters should be selected to achieve an even distribution of the ceramic particles in the metallic matrix.
The powder from the high energy mixing stage 120 is compacted 130. Compaction 130 may include one, two, or more steps. In some embodiments, compaction 130 includes a cold (e.g., room temperature) compaction step which forms a preform a desired shape. The cold compacting coalesces the particles and increases density. However, the preform is not close to fully dense. In particular embodiments, the cold compacting is performed using a tool diameter of about 50 mm to about 70 mm, with a load of about 80 tons to about 90 tons. In other embodiments, the cold compacting is performed using a tool diameter of about 50 mm to about 70 mm, with an exerted pressure of about 250 MPa to about 330 MPa.
The powder from the high energy mixing stage is degassed to remove any retained moisture from the powder surface, this may be completed at between 120 to 500° C.
A hot compacting step may also be performed to increase density and produce a billet 140. The hot compacting may be performed at a temperature in the range of from about 400° C. to about 600° C., including from about 425° C. to about 550° C. and about 500° C. Hot compaction may include the use of hot die compaction, hot isostatic pressing or hot extrusion typically at pressures of between 30 to 150 MPa.
In particular, hot isostatic pressing is contemplated for making the billet. In the HIP process, the powder is exposed to both elevated temperature and high gas pressure in a high pressure containment vessel, to turn the powder into a compact solid, i.e. a billet. The isostatic pressure is omnidirectional. The HIP process eliminates voids and pores. The hot isostatic pressing may be performed at a temperature of 1000° C. to 1200° C. and a pressure of 30 to 150 MPa for a period of sufficient to allow the metal section to reach the required temperature, typically between 1 and 8 hours. The hot isostatic pressing may be performed on commercially available steel or nickel HIP systems.
The billet may be subsequently processed 150 into a final article. This processing may include rolling, extrusion, or machining, without hot working. In accordance with one embodiment, the billet is rolled or extruded into an intermediate article. Final machining, e.g., CNC, is performed on the intermediate article resulting in a final article such as a rotor, disc, chain ring, or sprocket.
The resulting articles have high wear resistance. It is particularly contemplated that the articles of the present disclosure have small cross-sections which must withstand high stresses for long periods of time. In embodiments, the articles have a thickness of about 1 millimeter (mm) to about 10 mm. Parts of the articles also have sections with a width of about 1.5 mm to about 5 mm. For example, toothed articles such as gears, sprockets, and chain rings have teeth with such widths and thicknesses. In particle, articles contemplated by the present disclosure include articles formed from an annular structural member having teeth pointing outwards radially and distributed about the outer circumference of the annular structural member. Also contemplated are discs that are formed from an annular structural member and having various holes and patterns punched through the annular structural member. Examples of such articles are seen in
The resulting articles may have a 0.2% offset yield strength of about 400 MPa to about 680 MPa; an elastic modulus of about 80 GPa to about 150 GPa; or about 3% to about 8% elongation to failure, as measured according to ASTM E8M. Combinations of these properties are also specifically contemplated. The articles have a balance of high strength and high elastic modulus with good ductility.
The following examples are provided to illustrate the compositions, articles, and methods of the present disclosure. The examples are merely illustrative and are not intended to limit the disclosure to the materials, conditions, or process parameters set forth therein.
A pin-on-disc wear test was conducted according to ASTM G99. The pins were ⅜-inch in diameter, and the disc was 1.5 inches in diameter. The conditions were 23° C., 36% relative humidity. The wear cycle frequency was 2 Hz, and the wear pattern was a 15 mm unidirectional path. The tests were performed at loads of 20 newtons (N), 35 N, 50 N, and 65 N. The test duration was 5000 cycles for the 65 N load, and 10,000 cycles for the 20 N, 35 N, and 50 N loads. The contact area between the pin and the disc was 71.26 mm2. The weight loss on the disc and the pin were measured.
The discs were made of 2124 aluminum containing 25 vol % SiC reinforcement particles. The SiC particles had particle sizes of either 3 microns or 0.7 microns. The discs were either heat treated to T4 or T6 specifications. For T4, the disc was solution treated at 505° C. followed by quenching using water or polymer glycol, then naturally aged at room temperature for more than 24 hours. For T6, the disc was solution treated at 505° C. followed by quenching using water or polymer glycol, then artificially aged at 150° C. for 1 hour. Results are shown in the following Tables A and B:
As seen in Tables A and B, the use of the metal matrix composites for the disc significantly reduced wear in both the disc and the pin, compared to the test where both materials were steel.
Although not shown, a further example is a motorcycle sprocket, which can suffer substantial wear against the drive chain, as well as from grit and mud causing abrasive wear on the sprockets. Aluminum matrix composite fine particle reinforced aluminum alloys by Materion® offer a significant enhancement in wear properties and provide significant life and sprocket performance improvement over conventional aluminum sprockets. This has to be combined with high strength to avoid tooth deformation, sufficient ductility to deal with robust usage, lightweight characteristics and an ability to manufacture the components. These characteristics will also apply to bicycle chain rings. There can also be some application for lightweight brake discs.
The manufacture of aluminum alloys with finer reinforcement sizes of 5 μm down to 0.3 μm in accordance with the methods and materials described herein, particularly the finer reinforcement sizes, allow machining capability using high speed techniques to make parts with fine finish and tolerances. The addition of the fine reinforcement offers a major increase in the wear resistance combined with a good balance of strength, stiffness, ductility and fatigue properties. This combines the mechanical properties needed for disc, rotor, chain ring, and sprocket components with the ability to process and machine in a cost effective manner.
The present disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
This application claims priority to U.S. Provisional Patent Application Ser. No. 62/134,185, filed on Mar. 17, 2015. The entirety of that application is hereby fully incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 62134185 | Mar 2015 | US |
