Patent application title: METHOD OF MAKING POWDER METAL PARTS USING SHOCK LOADING
Yucong Wang (West Bloomfield, MI, US)
Yucong Wang (West Bloomfield, MI, US)
GM GLOBAL TECHNOLOGY OPERATIONS, INC.
IPC8 Class: AB22F702FI
Class name: Powder metallurgy processes with heating or sintering making composite or hollow article powder next to powder
Publication date: 2010-02-04
Patent application number: 20100028190
A method of preparing a titanium-based metal matrix composite component.
The method includes combining a titanium alloy-based matrix and a
titanium-based ceramic reinforcement to form one or more mixtures,
placing the mixture or mixtures into a mold, compacting the mixture or
mixtures by shock loading, and sintering the compacted mixture or
mixtures. In one form, the various mixtures may include differing levels
of reinforcement concentration. In this way, different portions of a
component produced by the present method may be made up of different
mixtures from other portions of the manufactured component, thereby
facilitating tailored mechanical or related structural properties.
1. A method of making a titanium-based metal matrix composite component,
said method comprising:combining a titanium alloy-based matrix and a
titanium-based ceramic reinforcement to form at least one mixture;placing
said at least one mixture into a mold;compacting said at least one
mixture by shock loading; andsintering said compacted at least one
2. The method of claim 1, wherein said titanium alloy-based matrix substantially comprises Ti-6Al-4V and said ceramic reinforcement substantially comprises TiB.sub.2.
3. The method of claim 1, wherein said component is an automotive component.
4. The method of claim 3, wherein said automotive component is an engine component.
5. The method of claim 4, wherein said engine component is a connecting rod.
6. The method of claim 1, wherein said at least one mixture comprises at least a first mixture comprising a first concentration of said titanium-based ceramic reinforcement, and a second mixture comprising a second concentration of said titanium-based ceramic reinforcement that is different from said first mixture.
7. The method of claim 6, wherein said placing said at least one mixture into a mold comprises:selectively placing one of said first and second mixtures into a first region within said mold; andselectively placing the other of said first and second mixtures into a second region within said mold such that upon said compacting, the portion of said component corresponding to said first region substantially comprises one of said first and second mixtures, while the portion of said component corresponding to said second region substantially comprises the other of said first and second mixtures.
8. The method of claim 1, wherein a source of said shock loading is selected from the group consisting of compressed spring, electrohydraulic, electromagnetic, piezoelectric and explosive means.
9. The method of claim 8, wherein said explosive means is selected from the group consisting of explosive shock loading and electric gun shock loading.
10. The method of claim 1, further comprising performing post-sintering machining on said component.
11. A method of making a titanium-based metal matrix composite component, said method comprising:defining a plurality of regions within a mold that is substantially shaped in the form of said component;arranging a plurality of mixtures comprising a titanium alloy-based matrix and a titanium-based ceramic reinforcement, each of said plurality of mixtures configured to comprise a different matrix-to-reinforcement ratio than the others;placing a first of said plurality of mixtures into a first of said plurality of regions;placing a second of said plurality of mixtures into a second of said plurality of regions;compacting said plurality of mixtures in said mold by shock loading such that upon said compacting, the portion of said component corresponding to said first region substantially comprises said first mixture, while the portion of said component corresponding to said second region substantially comprises said second mixture;removing said component from said mold; andsintering said component.
12. The method of claim 11, wherein said matrix is selected from the group consisting of beta titanium, alpha-2 titanium, gamma titanium and combinations thereof, and said reinforcement comprises a ceramic.
13. The method of claim 12, wherein said ceramic comprises TiB.sub.2.
14. The method of claim 11, further comprising performing post-sintering operations on said component.
15. The method of claim 14, wherein said post-sintering operations comprise machining.
16. The method of claim 11, wherein said component comprises a connecting rod, further wherein said first of said plurality of mixtures contains a lower concentration of reinforcing phase than said second mixture and the portion of said connecting rod that said first of said plurality of mixtures is placed in has a lower requirement of at least one of strength and stiffness than the portion of said connecting rod that said second of said plurality of mixtures is placed in.
17. A method of making a titanium-based metal matrix composite connection rod for an internal combustion engine, said method comprising:combining a titanium alloy-based matrix and a titanium-based ceramic reinforcement into a plurality of mixtures such that each of said plurality of mixtures comprises a different matrix-to-reinforcement ratio than the others;placing a first of said plurality of mixtures into a first region of a connecting rod mold;placing a second of said plurality of mixtures into a second region of said connecting rod mold;compacting said plurality of mixtures in said connecting rod mold by shock loading;removing said connecting rod from said mold; andsintering said compacted plurality of mixtures.
18. The method of claim 17, wherein said connecting rod substantially comprises a Ti-6Al-4V/TiB2 metal matrix composite.
19. The method of claim 17, wherein said shock loading is accomplished through movement of a compaction member in response to a shock source selected from the group consisting of a compressed spring, an electrohydraulic device, an electromagnetic device, a piezoelectric device, an explosive device and an electric gun.
20. The method of claim 17, wherein said compacting takes place in less than one second.
BACKGROUND OF THE INVENTION
The present invention relates generally to using powder metallurgy to produce reinforced titanium-based structures, and more particularly to making titanium alloy metal matrix composite-based components for automotive and other transportation applications.
Powder metallurgy (PM) is an important process used in the manufacture of automotive, marine and aviation components. PM typically involves mixing a metal powder with alloying materials that can be pressed into a near-net shape, then sintered in a controlled atmosphere to form a permanent metallurgical bond. Prior U.S. patent application Ser. No. 11/955,673 (hereinafter the '673 application) entitled METHOD OF MAKING TITANIUM ALLOY BASED AND TiB REINFORCED COMPOSITE PARTS BY POWDER METALLURGY PROCESS, the entirety of which is owned by the Assignee of the present invention and hereby incorporated by reference, discloses a method of making PM titanium ceramic composite parts (for example, engine connecting rods) by blending a titanium alloy matrix material with a ceramic-based reinforcing material to form a mixture, compacting the mixture, sintering the compacted mixture and closed die forging or phase-transformation densification.
Because titanium alloys have desirable structural properties, such as high specific strength and excellent corrosion resistance, they are particularly well-suited for automotive applications, including valves, retainers, valve springs, connecting rods in the engine and drivetrain and half shafts, bolts and fasteners, coil suspension springs and exhaust system in the body and chassis. Reinforcement, such as particle reinforcement, can be used to further their structural properties, such as elastic modulus (a measure of rigidity), wear resistance and heat resistance. Titanium diboride (TiB2) particles are commonly used as such particle reinforcement, and PM is one way to achieve particle reinforcement with TiB2 in a cost-effective way, although other ceramic reinforcing materials, such as titanium carbide (TiC) or titanium nitride (TiN) could also be used.
Nevertheless, there exists a desire for titanium-based MMC components with higher density. There further exists a desire to achieve such improved density components with shorter process cycle time and lower cost.
BRIEF SUMMARY OF THE INVENTION
These desires are met by the present invention, wherein a method and device that incorporates the features discussed below are disclosed. In accordance with a first aspect of the present invention, a method of making a powder metal component is disclosed where, in one form, the part is made from a Ti-6Al-4V/TiB MMC by powder metallurgy, and in a more particular form, the part is compacted by shock loading. In addition to shorter process times and costs, shock loading powder compaction (compared to conventional pressing methods) need not be limited to small scale applications. Furthermore, original powder properties can be maintained in the compact, alloys can be produced with unique compositions, and non-stoichiometry compositions and non-equilibrium structures can be fabricated. Moreover, densities of the finished parts approach that of theoretical densities, often exceeding ninety nine percent.
In addition to the mixing, compacting and sintering operations discussed above, other optional steps may be undertaken. The component may be a composite made from a titanium alloy matrix and TiB2 reinforcement particles dispersed within the matrix. The TiB2 reacts with the elemental titanium during sintering to produce TiB (the reinforcing particulate in the as-manufactured MMC), which is only thermodynamically stable in the titanium alloy. Sintering, which involves heating the material to a temperature slightly below its melting point such that the disparate particles of the precursor materials in the mixture adhere to one another by solid-state diffusion. The sintering may preferably be performed in a controlled atmosphere to avoid oxidation and related contamination.
While it will be appreciated by those skilled in the art that numerous titanium matrices may be used, there are certain alloys that have demonstrated particular suitability for structural components such as those encountered in aerospace and automotive applications. These include beta titanium, alpha-2 titanium, gamma titanium and combinations thereof. Examples of beta titanium which may be used in the present invention include titanium with approximately six weight percent aluminum and approximately four weight percent vanadium (i.e., referred to herein as Ti-6Al-4V, and elsewhere as Ti 6-4), and titanium with approximately six weight percent aluminum, approximately two weight percent tin, approximately four weight percent zirconium and approximately two percent molybdenum (i.e., Ti 6-2-4-2). The present inventors have found Ti-6Al-4V to be especially useful in the manufacture of composite-reinforced automotive components, based on its relative abundance, chemical compatibility and ease of processing. Furthermore, TiB2 is a particularly compatible reinforcement for Ti-6Al-4V based composites.
In another option, the component is a connecting rod used in aviation, marine, automotive and related internal combustion engines. In the present context, the term "automotive" is intended to refer to not only cars, but trucks, motorcycles, buses and related vehicular modes of transportation. In engine-related applications, high mechanical loading and high temperatures are both in existence. Other examples of automotive component where the present method and titanium-based MMC may find beneficial use includes valves, retainers, valve springs, bolts, fasteners, coil suspension springs and exhaust systems.
In another option, placing the one or more mixtures into a mold includes selectively placing one of the mixtures into a first region within the mold while selectively placing another of the mixtures into a second region within the mold. In this way, when the mixtures are compacted, the portion of the component corresponding to the first region is made up almost entirely of the first of the mixtures, while the portion of the component corresponding to the second region is made up almost entirely of the second mixtures of the mixtures, where it will be understood that in regions that bridge two disparate regions together generally correspond to a transition region made up of a blend of the mixtures from the adjoining regions. In another option, a source of the shock loading is selected from the group consisting of mechanical (for example, compressed spring), electrohydraulic, electromagnetic, piezoelectric and explosive means. More particularly, the explosive means is selected from the group consisting of explosive shock loading and electric gun shock loading. In yet another option, post-sintering machining may be performed on the component.
According to another aspect of the invention, a method of making a titanium-based MMC component is disclosed. The method includes defining numerous regions within a mold, arranging more than one mixture of a titanium alloy-based matrix and a titanium-based ceramic reinforcement so that each of the mixtures has a different matrix-to-reinforcement ratio than the other mixtures, placing a first of the mixtures into a first of the regions, placing a second of the mixtures into a second of the regions, compacting the various mixtures in the mold by shock loading, removing the component from the mold and sintering the component. In the method, the mold is substantially shaped in the form of the component. In the present context, the term "substantially" refers to an arrangement of elements or features that, while in theory would be expected to exhibit exact correspondence or behavior, may, in practice embody something slightly less than exact. As such, the term denotes the degree by which a quantitative value, measurement or other related representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. The shock loading functions in such a way that upon the compacting, the portion of the component corresponding to the first region substantially contains the first mixture, while the portion of the component corresponding to the second region substantially contains the second mixture.
Optionally, the matrix is one of beta titanium, alpha-2 titanium, gamma titanium and combinations thereof. Likewise, the reinforcement comprises a ceramic, a particular version of which is TiB2. In another option, post-sintering operations are performed on the component, such as machining. In a particular form of the method, the component being made is a connecting rod. In an even more detailed form, the first of the numerous mixtures contains a lower concentration of reinforcing phase than the second of the mixtures. Furthermore, the portion of the connecting rod that corresponds to the first of the mixtures has a lower structural or loading requirement than the portion of the connecting rod that corresponds to the second of the mixtures. Examples of such structural or loading requirement include strength, stiffness and related measure of a material's or component's load-bearing capability.
According to another aspect of the invention, a method of making a titanium-based MMC connection rod for an internal combustion engine is disclosed. The method includes combining a titanium alloy-based matrix and a titanium-based ceramic reinforcement into a plurality of mixtures such that each of the mixtures has a different matrix-to-reinforcement ratio than the others. The method further includes placing a first of the mixtures into a first region of a connecting rod mold, placing a second of the mixtures into a second region of the connecting rod mold, compacting the mixtures in the connecting rod mold by shock loading, removing the connecting rod from the mold than sintering the compacted plurality of mixtures in such a way as to form the connecting rod.
Optionally, the connecting rod substantially comprises a Ti-6Al-4V/TiB2 MMC. In another option, the shock loading is accomplished through movement of a compaction member (for example, a piston) in response to a shock source selected from the group consisting of a compressed spring, an electrohydraulic device, an electromagnetic device, a piezoelectric device, an explosive device and an electric gun. Preferably, the compacting takes place under high speed and high pressure shock waves in less than one second, more particularly in a fraction of a second, and more particularly, fewer than ten microseconds.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The following detailed description of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
FIG. 1 shows a process route flowpath for producing a titanium-based MMC component according to an aspect of the present invention;
FIG. 2 shows a shock wave generation device used to produce the shock loading according to an aspect of the present invention;
FIG. 3 shows a connecting rod made according to an aspect of the present invention, including various discreet regions where differing TiB2 concentration levels may be placed; and
FIGS. 4A through 4F show the impact of varying amounts of TiB2 additions to Ti-6Al-4V/TiB MMC microstructures.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring initially to FIG. 1, a process route flowpath for producing a titanium-based MMC component according to an aspect of the present invention is shown. The process includes blending 10 of various constituent powders 10A, 10B to 10N that correspond to the number of materials needed to make up the MMC. For example, if Ti-6Al-4V is the predominant matrix material, constituent powders 10A to 10N may include separate titanium, titanium hydride, aluminum-vanadium, TiB2 and other powders. It will be appreciated by those skilled in the art that additional constituents, such as binders, lubricants or the like may also be included into the mixture produced by blending 10, although such binders and lubricants are not necessary. The blending 10 may be followed by a milling and activation step 20, followed by close die compaction via shock loading 30 and then sintering 40 to produce the finished part. During sintering, it is advantageous to maintain a vacuum (for example, about 10-3 Pa for a period between two and eight hours, with a more specific range of three to six hours) in order to achieve ninety nine or more percent theoretical density. As will be understood by those skilled in the art, longer sintering times can further improve the sintered density. Additional post-sintering steps may also be employed, including machining 50. Numerous examples of such machining 50 and related operations are possible, including deburring, surface compressive peening, repressing or the like. Additionally, oxidation-prevention steps may be employed, such as through the addition of an oxide or related coating like Al2O3, SiO2 and B2O3 if hot forging is used after sintering.
Referring next to FIG. 2, a representative way to achieve shock loading (also called shock compaction or shock loading impaction) with a shock wave compaction device 300 is shown. The shock waves can be produced by electrohydraulic, electromagnetic, piezoelectric and explosive means. Electrohydraulic initiation of the shock waves produces higher energy flux density than the electromagnetic and piezoelectric variants. The explosion initiation includes explosive shock loading and electric gun shock loading; in the former, high explosives, such as trinitrotoluene (TNT), are used, while in the latter, a thin dielectric flyer is accelerated toward the powder assembly as a result of exploding, or vaporizing, a thin metallic foil. The electric gun uses the energy initially stored in a capacitor bank to ohmically heat and explode, or vaporize, a thin, metallic (e.g., aluminum) foil on a folded transmission line laminate.
Shock loading is used to produce a dense solid from precursor powders. In addition to the aforementioned Ti-6Al-4V metal powder and the TiB2 ceramic powders, shock loading can be used to compact polymeric powders or a combination of the above. The powders, which are generally at room temperature prior to initiation of the shock wave, are compacted by a shock front that travels through the encapsulated powders. Under high speed and high pressure shock waves in a very short time, a high-strain rate deformation is established, which tends to cause the material to deform plastically with a lot of localized heat generation. The heat may even melt the particle surface locally due to adiabatic effect, as there may not be enough time for heat dissipation through heat transfer. In shock loading, shock waves are used to produce high velocity impact (several to several hundred meters per second) at high pressure and in a very short time (for example, on the order of several microseconds). Unlike conventional PM approaches, no binder is necessary. As such, shock loading has the benefit of increasing the green part density (for example, to 99% or more).
Planar shock waves are preferred for their ability to provide controlled waves and concomitant maximum and uniform compaction through the part being compacted. The explosives are initiated at the top of the assembly by a detonator; this causes shock waves to run down the length of the powders. The shock front produced by detonating explosive compacts the encapsulated powders to a solid form. The pressure exerted by the shock front is usually several times greater than the shear stress of powders being compacted. This causes plastic deformation of the powders and the densification of the compact due to the plastic flow of the material and collapsing of voids. Particle-particle friction, deformational heat, and high velocity impact of individual particles caused by the shock front lead to the bonding of the particles to adjacent particles. Compacts with a high density, close to theoretical, can be fabricated using the explosive compaction method.
Advantages of explosive powder compaction (compared to conventional pressing methods) include that the process is not limited to small scale applications, original powder properties can be maintained in the compact, alloys can be produced with unique compositions, and non-stoichiometry compositions and non-equilibrium structures can be fabricated, densities approach that of theoretical densities.
Compaction device 300 includes a shock housing 310, where a compaction member (presently shown in the form of a piston 320, although capable of existing in another form) reciprocates up and down in a chamber 330 formed in the housing 310. An upper die 340A and a lower die 340B have shapes that cooperate so that when the dies 340A and 340B are brought into engagement with one another, a mixture containing one or more of the powders 10A, 10B . . . 10N is compacted into a shape dictated by the cooperating dies 340A and 340B. As stated above, explosive powder compaction (or one of the other shock loading approaches) can be used to impart enough energy to piston 320 to force compaction of the powder mixture resident between the dies 340A and 340B.
There are several ways to generate a shock wave to push the piston 320 and upper die 340A (which may be formed together as an assembly) to impact the powder 10A, 10B . . . 10N that is placed in the compaction shape between the dies 340A and 340B. The first is through a spring-piston gun (not shown), where by releasing a compressed coiled steel in the gun, the piston 320 is pushed forward. This takes place in a fraction of a second, during which the air between the assembly made up of the piston 320 and upper die 340A undergoes adiabatic heating to several hundred degrees during compression. The powders are compacted by a shock front that travels through the encapsulated powders. Under high speed and high pressure shock waves in a very short time, a material tends to deform plastically with a lot of heat generated locally. The heat may even melt the powder material locally due to the adiabatic effect, as there is not enough time for heat dissipation through heat transfer. Plastic deformation of the powder is caused by the high-strain rate deformation, and can even occur in ceramic materials. The shock waves produce high velocity impact (10-1000 m per second) at high pressure and in a very short time. Other methods to produce impact include electrohydraulic, electromagnetic and piezoelectric, as discussed above. The shock front produced by detonating explosive compacts the encapsulated powders to a solid form, and the pressure exerted by the shock front is usually several times greater than the shear stress of powders being compacted. This too causes plastic deformation of the powders and the densification of the compact which in the present case is due to the flow of the material and collapsing of voids. Particle-particle friction, deformational heat, and high velocity impact of individual particles caused by the shock front lead to the bonding of the particles to adjacent particles. Compaction with a density close to the theoretical maximum can be fabricated using the explosive compaction method. There is usually a layer of metal between the powder and the explosive, and this layer (which is sacrificial) can be a sheet made of steel or another metal. In another form, it can be a part of the die, depending on the part geometry.
The entire shock loading process uses one stroke, one die and produces one or multiple parts. However, multiple strokes are possible with means other than explosive shock loading. Once the component has gone through the shock loading, it can be sintered to further improve its density and strength. For a Ti-6Al-4V-based connecting rod with ten percent (by weight) TiB2, the part is heated at a rate of two to five degrees Celsius per minute, within a temperature range of between 1200 degrees Celsius and 1450 degrees Celsius for between two and eight hours. As such, an average sintering temperature is about 1300 degrees Celsius, with a typical sintering time of about three hours. Typical sintering vacuum is in the range of 10-3 Pascals. Longer sintering times can significantly improve the sintered density. During the sintering, diffusion causes a composition-gradient microstructure to be formed between the two different TiB2 composition regions. As with other forms of powder metallurgy processing, a cooling schedule may be used, where the sintered and compacted component is cooled over the course of numerous hours.
Referring next to FIG. 3, a connecting rod 100 made according to the present invention is shown. The rod 100 is used in automotive engines, acting as the joining element between a piston and a crankshaft (neither of which are shown) to transfer the rotary motion of the latter into a linear, reciprocating motion in the former. The top 110 of connecting rod 100 includes an exaggerated end 115 with a journal or bearing region 117 therein that houses wrist pin bushings (not shown), while the bottom 120 includes an even larger exaggerated end 125 with a journal or bearing region 127 therein that houses crankshaft bearings (not shown). Bolts 128 or related fasteners secure a bearing cap 129 to exaggerated end 125 that may include a small port (not shown) to allow the flow of motor oil or related pressurized lubricant to the piston. A neck region 130 extends between the ends 115 and 125, connecting the two together in a substantially unitary configuration. Connecting rod 100 is subject to extreme tensile, compression and bending stresses, and as such, has special requirements on its mechanical properties and machinability. The neck region 130 should have very high stiffness, tensile and compression yield strength, as well as fatigue resistance to ensure the high performance and durability, while the regions 117 and 127 within the respective housing ends 115 and 125 require precision machining.
To satisfy these myriad requirement, the concentration of the reinforcing TiB2 can be tailored to the particular regions within the connecting rod 100. In particular, the neck region 130 and at least the non-journalled part of the bottom region 120 can be made from a higher concentration of reinforcing phase material, for example, ten weight percent TiB2 particle reinforcement. These regions require higher stiffness, while generally involving only minimal machining. As such, they are good candidates for the harder, stiffer MMC produced by larger concentrations of TiB2 particles. The portion associated with cap 129, while made from the lower TiB2 particle concentration, can employ sacrificial metal rods in order to form the bolt holes therein. Sacrificial (either metallic or nonmetallic) mandrels can be used to make the necessary holes. The journal or bearing region 117 of the top housing end 115 and the journal or bearing region 127 of bottom housing 125 can be made from lower reinforcing phase material concentrations, for example, between five and seven weight percent TiB2 particle reinforcement. Typically, journals or bearings require a lot of machining, and the lower TiB2 content in the MMC makes it easier to machine, resulting in a much lower machining cost, as the machining productivity and related tool life are improved.
The filling of the blended powders with different TiB2 compositions into different die regions can be achieved through multiple sequences. In such an approach, while individual regions (such as regions 117, 127 and 130) are being filled with the powder, the other regions are blocked. In this way, different regions within a particular component can have differing levels of reinforcement placed to provide tailored properties. After the filling, the close die compaction is conducted at room temperature to make a compacted green (i.e., pre-sintered) part.
Such a tailored design made possible by placement of specific TiB2 concentrations in discreet component locations would provide great flexibility for the optimization of mechanical property and machining ability of connecting rod 100. In setting up the mold, die or related tooling with which the connecting rod 100 will be manufactured, the various regions 117, 127 and 130, because they employ a different concentration of reinforcing particles than other portions of the connecting rod 100, can be separately filled with the particle/matrix mixture. During the course of component manufacture, various transition regions will form between these discreet regions of differing particle concentration; these transition regions can have a gradient composition microstructure and gradient mechanical properties.
The typical sizes of the titanium powders used for making metal matrix composite (MMC) precursor powder (for example Ti-6Al-4V) can be in the range of two and one hundred and fifty micrometers, which is much wider than those in the conventional powder metal compaction. The typical TiB2 particle size and Al--V master-alloy powder are each in the range of five to seventy five micrometers. It will be appreciated by those skilled in the art that there are several possible methods for producing these powders. For example, the titanium powder can be made by the well-known hydride-dehydride process.
Referring next to FIGS. 4A through 4F, the sintered microstructures of the Ti-6Al-4V/TiB2 MMC with zero, three, seven, ten, fifteen and twenty weight percent TiB2 reinforcing phases are shown. As can be seen, the grain size in the microstructures becomes smaller with the increased TiB2 content. An increase in reinforcing phase TiB (where TiB2 becomes a TiB phase in the alloy) and reduced grain size explains the increased tensile and yield strength and stiffness. As shown in the following table, elongation decreases with the increased TiB2 content.
TABLE-US-00001 Young's UTS 0.2YS Modulus Type MPa MPa El % GPa Ti--6Al--4V 1047-1132 1019-1090 10-16 95-108 Ti--6Al--4V + 3 wt. % 1180-1230 1080-1120 11-13 118-129 TiB2 Ti--6Al--4V + 5 wt. % 1200-1250 1100-1135 7-9.5 120-137 TiB2 Ti--6Al--4V + 7 wt. % 1225-1287 1105-1125 6.5-7.8 128-138 TiB2 Ti--6Al--4V + 10 wt. % 1360-1390 1250-1320 1.5-2.5 155-170 TiB2
TiB2 is an excellent reinforcement for Ti-6Al-4V titanium alloy. As such, compared to an unreinforced Ti-6Al-4V alloy, the Ti-6Al-4V MMC has higher strength and elastic modulus. For example, the elastic modulus of the reinforced Ti-6Al-4V is over 140 GPa, with over 155 GPa in comparison with 100 GPa average for unreinforced Ti-6Al-4V. The ultimate tensile strength of over 1350 MPa (average 1450 MPa) is significantly greater than the 1100 MPa average for the unreinforced Ti-6Al-4V, with a 0.2% yield strength of over 1250 MPa (average 1300 MPa), in comparison with average of 1050 MPa for unreinforced Ti-6Al-4V. The Rockwell hardness is above forty three.
While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, which is defined in the appended claims.
Patent applications by Yucong Wang, West Bloomfield, MI US
Patent applications by GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Patent applications in class Powder next to powder
Patent applications in all subclasses Powder next to powder