Materials and Construction for High-Strength, Light-Weight Bicycle

Abstract

Systems and methods for fabricating a high-strength, low-weight material suitable for construction of a bicycle. A composition of powdered materials including magnesium, aluminum, copper, zinc, zirconia, and silicon carbide is combined and blended together. The mixture is vacuum hot pressed into a billet and then extruded. The resulting material is suitable for construction of a bicycle having excellent physical properties including strength, flexibility, comfort, and light-weight.

Claims

1. A method of fabricating a material for a bicycle, the method comprising: combining powdered aluminum (Al), powdered zinc (Zn), powdered copper (Cu), powdered zirconia (Zr), powdered silicon carbide (SiC), and powdered magnesium (Mg) in the following percentages by weight: Al (20-30%) Zn 6-10%, Cu (0.5-2.5%), Zr (0.1-0.9%), SiC 0.5-10%, and Mg (remainder); blending the powdered constituents in a manner to substantially eliminate segregation; vacuum hot pressing the mixture at 750 degrees F.; and extruding the resulting billet into a tube shape.

2. The method of claim 1 wherein vacuum hot pressing the mixture is performed between 725 degrees F. and 775 degrees F.

3. The method of claim 1 wherein extruding the resulting billet is performed with the billet at 750 degrees F.

4. The method of claim 1 wherein extruding the resulting billet is performed using a mandrel and a die with the mandrel at 800 degrees F., the die at 700 degrees F., the mandrel ad 800 degrees F.

5. The method of claim 4 wherein the mandrel is between 790 and 810 degrees F., the die is between 690 and 710 degrees F., and the billet is between 740 and 760 degrees F.

6. The method of claim 4 wherein extruding the resulting billet comprises forming fins on an interior surface of a tube.

7. The method of claim 6 wherein the fins are approximately twice as thick as the walls of the tube.

8. The method of claim 4 wherein forming fins on the interior surface of the tube comprises forming four generally-equally spaced fins at approximately 90 degrees from one another.

9. The method of claim 1 wherein extruding the resulting billet into a tube shape comprises forming a tube with walls of approximately 1 mm thickness.

10. The method of claim 1 wherein blending the powdered constituents comprises V-blending the powdered constituents.

11. The method of claim 1 wherein extruding the resulting billet comprises extruding at an extrusion ratio of 30:1.

12. The method of claim 12 wherein after extrusion the tube shape has a specific gravity of between 2 and 2.6 and a strength of between 40 and 80 ksi.

13. A bicycle, comprising: a frame having hollow tube sections, the hollow tube sections having interior fins being approximately twice as thick as walls of the tube sections, the fins running substantially the length of the tube sections, wherein the frame is extruded from a combination of 20-25% aluminum, 6-10% zinc, 0.5-2.5% copper 0.1-0.9% zirconia, 0.5-10% silicon carbide, and the remainder magnesium.

14. The bicycle of claim 13 wherein the aluminum, zinc, copper, zirconia, silicon carbide, and magnesium are combined in powdered form, blended, and vacuum hot pressed into a solid billet before extruding.

15. The bicycle of claim 13 wherein the frame comprises a top tube, a head tube, a down tube, a bottom bracket shell, and a seat tube, and wherein the top tube, head tube, down tube, bottom bracket shell, and seat tube are extruded according to claim X.

16. The bicycle of claim 13 wherein the frame is extruded at an extrusion ratio of 30:1.

17. A material, comprising a mix of constituents of 25% aluminum, 8% zinc, 1.5% copper, 0.5% zirconia, 5% silicon carbide, and 60% magnesium, wherein the constituents are mixed together in powdered form in a manner to substantially prevent segregation between the constituents, wherein the constituents are vacuum hot pressed at 750 degrees F.

18. The material of claim 17 wherein the material is extruded into a tube shape having interior fins extending along an interior surface of the tube, wherein the fins are approximately twice as thick as walls of the tube.

19. The material of claim 17 wherein the material has a specific gravity of between 2 and 2.6.

20. The material of claim 17 wherein the material has a strength of between 40 and 80 ksi.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0014] FIG. 1 is a graph of a binary AlMg phase diagram according to embodiments of the present disclosure.

[0015] FIG. 2 is a binary MgZn phase diagram according to embodiments of the present disclosure.

[0016] FIG. 3 is a binary AlZn phase diagram according to embodiments of the present disclosure.

[0017] FIG. 4 is a ternary AlMgZn phase diagram according to embodiments of the present disclosure.

[0018] FIG. 5 is a first-melting projection (FMP) of the phase diagram of the Zn+Mg+Al system shown in FIG. 4 according to embodiments of the present disclosure.

[0019] FIG. 6 is a flowchart diagram showing methods according to the present disclosure by which a material having the desired properties can be manufactured.

[0020] FIG. 7 is a Differential scanning calorimetry (DSC) scan on a cold pressed billet to predict temperature ranges for solid state reactions and incipient melting in blends from Exotherms and Endotherms to converge on consolidation temperatures according to embodiments of the present disclosure.

[0021] FIG. 8A is a front cross-sectional illustration of an extrusion process according to embodiments of the present disclosure.

[0022] FIG. 8B is a side cross-sectional view of the embodiments of FIG. 8A according to embodiments of the present disclosure.

[0023] FIG. 9 is a cross-sectional view of the resulting tube structure formed according to the fabrication and extrusion systems and methods of the present disclosure.

DETAILED DESCRIPTION

[0024] Below is a detailed description according to various embodiments of the present disclosure. FIG. 1 is a graph of a binary AlMg phase diagram according to embodiments of the present disclosure. FIG. 2 is a binary MgZn phase diagram according to embodiments of the present disclosure. FIG. 3 is a binary AlZn phase diagram according to embodiments of the present disclosure. FIG. 4 is a ternary AlMgZn phase diagram according to embodiments of the present disclosure. FIG. 5 is a first-melting projection (FMP) of the phase diagram of the Zn+Mg+Al system shown in FIG. 4 according to embodiments of the present disclosure.

[0025] The first-melting projections (FMP) from phase diagrams, be it a binary, ternary or a higher-order system, predicts the temperature at which there is the first emergence of a liquid phase upon heating at any given composition at thermodynamic equilibrium. Generally, FMP are identical to solidus projections. They are often observed to obey same established topological rules as isothermal sections of phase diagrams. Only in systems with metatectic (catatectic) invariants (partial melting during cooling) or retrograde solid solubility do exceptions to these rules occur. In these regions the FMP and solidus projections are not identical. Here we usually plot the FMP which is always single-valued at all compositions.

[0026] The liquid projection of the (Zn+Mg+Al) system is shown in FIG. 4. The phase diagrams of the (Mg+Al, Mg+Zn, and Al+Zn) binary sub-systems are shown in FIGS. 1, 2, and 3. These diagrams have been calculated by minimization of Gibbs energy minimization with a commercial software. The calculated FMP for the ternary system is shown in FIG. 5. For each ternary eutectic point (E), ternary peritectic point (P) and ternary quasi-peritectic point (PAT) on the liquid projection in FIG. 4, there is a corresponding isothermal tie-triangle on the FMP, each labeled with the temperature of the invariant reaction (FIG. 5). This ternary alloy will first melt isothermally (peritectically in this case) at 471 C. to form a liquid phase with a composition at the peritectic point labelled A in FIG. 4.

[0027] Initial phase behavior is determined by simulation and predictions after production of binary and ternary phase diagrams using simulation software, for example Thermocalc, FactSage etc. Eutectic and peritectic reactions in designed alloys dictates design by PM or IM processing. Simulation predicts temperature range to consolidate blended powders (PM route) or alternatively melting temperature (IM route).

[0028] FIG. 6 is a flowchart diagram showing methods according to the present disclosure by which a material having the desired properties can be manufactured. At 100 powdered materials are mixed together in a homogeneous manner to promote an even mix of the materials. According to embodiments the materials are:

TABLE-US-00001 Material % by weight Aluminum (Al) 25 5% Zinc (Zn) 8 2% Copper (Cu) 1.5 1% Zirconia (Zr) 0.5 0.4% Silicon Carbide (SiC) 0.5-10% Magnesium (Mg) Remainder

[0029] The portion of Mg of course is calculated after the other constituents have been chosen and will complete the 100%.

[0030] The materials are in powdered form which helps to promote an even blend. Each of these materials can be obtained in a powdered form using known techniques. At 102 the materials are blended together. In some embodiments the blending can be achieved by using a V-blending technique. The materials can be blended in such a way that segregation between the powders is minimized or eliminated. At 104 the mixture can be vacuum hot pressed at a temperature of 750 degrees F., 25 degrees F. The vacuum hot pressing causes the materials to melt and fuse together and when it cools it forms a solid alloy that can be extruded or otherwise machined. At 106 the material is extruded. In some embodiments the extrusion can be performed using a die-mandrel-container configuration with the billet at 800 degrees F., the die at 700 degrees F., the mandrel at 800 degrees F., and the liner/container at 800 degrees F. The shape of the die and mandrel can form the desired shape of the tubes which can be constructed into a bicycle frame.

[0031] FIG. 7 is a Differential scanning calorimetry (DSC) scan on a cold pressed billet to predict temperature ranges for solid state reactions and incipient melting in blends from Exotherms and Endotherms to converge on consolidation temperatures according to embodiments of the present disclosure.

[0032] FIG. 8A is a front cross-sectional illustration of an extrusion process according to embodiments of the present disclosure. FIG. 8B is a side cross-sectional view of the embodiments of FIG. 8A according to embodiments of the present disclosure. The material produced by the methods and systems discussed and described previously can be machined in a variety of ways including milling, welding, and cutting. The extrusion process shown and described in FIGS. 8A and 8B involve the use of a mandrel 110 and a die 112. The billet 114 is O-shaped and is placed on the mandrel 112 which urges the billet against the die 112. The die 112 has a shape that defines the resulting extruded shape of the material. In this case, the material will be extruded into hollow tubes suitable for use in manufacturing a bicycle or other similar activities. The extrusion process can be executed with the billet at 800 degrees F., with the die at 700 degrees F., the mandrel at 800 degrees F., and a liner/container also at 800 degrees F. All temperatures can be 10 degrees F. The liner/container is not shown but it can be configured and positioned to receive the extruded tube.

[0033] FIG. 9 is a cross-sectional view of a resulting tube structure 124 according to embodiments of the present disclosure. In some embodiments the die 112 has an interior profile that produces fins 118 on an interior surface of the tube. The thickness of the tube walls at 116 can be 40 mils ( 40/1000) or approximately 1 mm. The fins 118 can be approximately twice as thick as the walls at 80 mils (approximately 2 mm). Other dimensions are possible. In other embodiments the thickness is not uniform and the tube can be elliptical, square, rectangular, or polygonal. The fins extend along the length of the tube and give additional stiffness to the tubes especially when subject to bending loads similar to the loads experienced in a bicycle. In the embodiment shown there are four fins distributed around the perimeter of the tube in each cardinal direction. In other embodiments there may be more than four fins. The width of the fins can be approximately 2 mm but wider fins are also possible. The wider and thicker the fins, the stiffer the resulting tube will be. The stiffness of the tube can accordingly be tailored closely by manipulating the size of the fins.

[0034] The foregoing disclosure hereby enables a person of ordinary skill in the art to make and use the disclosed systems without undue experimentation. Certain examples are given to for purposes of explanation and are not given in a limiting manner.