The present invention belongs to the field of amorphous metal alloys and especially concerns a Ce based amorphous metallic plastic.
Compared with metallic glasses, polymeric glasses have superior glass forming ability, low glass transition temperature (Tg) and wider supercooled liquid region (ΔT, defined as the difference between Tg and the onset crystallization temperature Tx), thus have a very wide range of applicability. The thermoplasticity nature of common glassy polymers is exploited in molding and imprinting. Since chemical scientists invented the thermoplastics in 1940's, they became the basic materials for the 2nd industrial revolution. Although their strength is only about one fiftieth of that of steels, thermoplastics products became very cheap because they could be prepared repeatedly using the same mold at a temperature near room temperature. Now thermoplastics are widely used in our daily lives.
In the early 1960's, non-crystalline alloys (so called metallic glasses) were firstly fabricated in laboratories. Compared with polymers, metallic glasses also have advantages in mechanical, electrical, magnetic and chemical properties. Amorphous metal alloys have a supercooled liquid region ΔT above Tg. When an amorphous metal alloy was heated into this region, it still keeps its glassy state and does not crystallized immediately. In general, the wider range of ΔT suggests better deformability of the supercooled state. Therefore, the stability against crystallization is crucial for deformation of an amorphous metal alloy in its supercoolied state. The stability during a heating process is closely related with the critical cooling rate necessary for forming a glass from its liquid. For a good glass former, it is expected that the time-temperature-transformation (TTT) curve will move toward the long time direction.
The conventional melt-spin glasses have a limited ΔT and could not be used to investigate the related properties of the supercooled liquid region. In the early 1990's, bulk metallic glasses (BMGs) with large size up to millimeters even centimeter scales in three dimensions were developed using conventional casting methods. For most of BMGs, their values of ΔT are larger than 45 K and even larger than 100 K in some case. The supercooled liquids of these BMGs show typical Newtonian flow characteristics at low strain rates or low stresses and the maximum elongation could reach about 15000%. For crystalline alloys, they are unable to deform as easily as the viscous supercooled liquids of BMGs, which are capable of remaining the glassy structure and original properties even after large plastic deformation. The unique combination of these superior properties and homogeneous microstructure makes BMGs a new type of engineering materials in applications such as manufacturing the micro-electro-mechanical components. Meanwhile, high strain rates and superplasticity are suitable for quality control, thus make it possible for the mass production.
For most of the known BMGs, however, their industrial applications are still impeded by the limitation of alloy size and the lack of workability and machinability. The polymerlike exploitation of the supercooled viscous flow of many BMGs was also postponed due to low Tg and low stability against crystallization. Additionally, some BMGs based on noble metals like Pd, Pt and Au can only be used in the experimental laboratory because of their high cost although they have good glass forming ability and superplasticity in the supercooled liquid region.
The present invention is aimed to overcome the problems in the known BMGs and thus to provide a new type of BMGs named Ce-based amorphous metallic plastics. These problems are the limitation of the small size, poor workability and merchantability, the limitation in exploitation of the viscous supercooled liquid due to high Tg and low crystallization resistance and the high cost in some BMGs containing the noble metals such as Pd, Pt and Au. The present amorphous metallic plastics have extremely low Tg, wide supercooled liquid region ΔT and low cost coming from the cheap raw materials having low purity.
The invention is realized using the following techniques and methods.
The invention provides amorphous metallic plastics based on Cerium which can be represented by the following formula:
CeaAlbMc
in which 55≦a≦75, 5≦b≦25, 10≦c≦25, and a+b+c=100.
The M can be one of three elements Co, Cu and Ni.
The purities of the said Ce, Al and M are no less than 99.5.wt. % (weight percent).
The present invention provides Ce-based amorphous metallic plastics which can be represented by the following formula:
CedAleCufZg
in which 55≦d≦75, 5≦e≦15, 15≦f≦25, 0.01≦g≦10, and d+e+f+g=100.
Z is one element selected from Co, Fe, Hf, Mg, Mo, Nb, Sc, Ta, Ti, W, Zn and Zr.
The purities of the said Ce, Al, Cu and Z are no less than 99.5.wt. % (weight percent).
Furthermore, the present invention provides Ce-based amorphous metallic plastics which can be represented by the following formula:
CehAliCujNik.
in which 55≦h≦75, 5≦i≦15, 15≦j≦25, 0.01≦k≦5, and h+i+j+k=100.
The purities of the Ce, Al, Cu and Ni are no less than 99.5.wt. % (weight percent).
The above-described Ce-based amorphous metallic plastics can be prepared using the conventional method known in the field of metallic glasses. Specifically, the preparation method includes the following steps:
1) Preparation of mother ingots: In a Ti-absorbed arc melting furnace under Argon atmosphere, a mixture of elements Ce, Al and M according to the above formula CeaAlbMc, or a mixture of Ce, Al, Cu and Z according to the above formula CedAleCufZg, or a mixture of Ce, Al, Cu and Ni according to the above formula CehAliCujNik is blended and melted until homogeneity, and then cooled to form a mother ingot.
2) Suction casting: In a Ti-absorbed arc melting furnace under Argon atmosphere, the mother ingot prepared in the first step is remelted and then suction casted into a copper mold with different cavities to form a sample in the form of rod or sheet.
It should be stressed that many modifications and changes can be made to the present invention without departing the spirit and scope thereof. Although what the instant invention illustrates is to produce Ce-based amorphous metallic plastics by forming an amorphous ingot in a way of suction casting, it is well-known to the person ordinarily skilled in the art that any suitable technique for fabricating non-crystalline alloys or any related casting method under a protective atmosphere such as spray casting, single- or twin-roll melt-spinning, planar flow casting and metal pulverization and so on can also be used to prepare Ce-based amorphous metallic plastics.
For the present Ce based amorphous metallic plastics, the amorphous nature and the volume fraction of the amorphous phase can be determined and evaluated using known techniques such as X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). In the examples of the present invention, XRD measurements were carried out on a MAC M03 XHF diffractometer with Cu Kα radiation and HRTEM measurements on a TECNAI-F20 instrument operated at 200 kV. The thin foils for the HRTEM measurements were prepared by mechanical thinning and chemical polishing.
Similarly, any suitable methods can also be used to examine the thermal properties of the Ce-based amorphous metallic alloys. By way of an example, the thermal properties of our samples were determined by differential scanning calorimetry (DSC) under a purified argon atmosphere in a Perkin-Elmer DSC-7, calibrated for temperature and energy with high-purity indium and zinc. Both isothermal and continuous heating (at a rate of 10 K min−1) were used
The mechanical properties and density data, etc of the present Ce based alloys can be measured using many universal instruments. In the present invention, the mechanical properties including yield strength and elastic strain were measured at room temperature and at 90° C. by an MTS 880 system. Compression tests were conducted at a strain rate of 1×10−3 s−1. Acoustic velocities were determined by a pulse echo overlap method on a MATEC 6600 ultrasonic system with a measuring sensitivity of 0.5 ns and a frequency of 10 MHz. Young's modulus E, bulk modulus B, Poisson's ratio v and shear modulus G were derived from the acoustic velocities. The density was determined by the Archimedean technique and the accuracy lies within 0.1%. Vickers hardness was measured with a Polyvar Met microhardness tester using a load of 1.96 N. The electrical resistance of the sample at room temperature was measured on a PPMS 6000 instrument (Quantum Design Instrument, Inc.).
The Ce based amorphous metallic plastics defined in the present invention should contain the amorphous phase with a volume fraction of at least 50%. In most cases, the Ce based amorphous metallic plastics prepared according to the present invention have a single amorphous phase, a wide supercooled liquid region ΔT of no less than 20 K and a low Tg of no more than 430 K. These thermal parameters (ΔT and Tg) can be examined using DSC method at a scanning rate of 10 K/min.
The Ce based amorphous metallic alloys in this invention have an extremely low Tg close to room temperature, a wide supercooled liquid region and high stability against crystallization, thus can be deformed homogeneously in their viscous supercooled liquid state in low temperatures like the near boiling point of water. This polymerlike superplasticity (homogenous deformation) of these Ce based amorphous metallic alloys makes them very easy to form or imprint a complex product with an amorphous structure. For example, in this invention, a precise shape or article can be imprinted on the surface of a Ce based amorphous metallic sample in near boiling water under a pressure of 30-300 MPa.
Generally, compared with the prior arts, the present Ce based amorphous metallic plastics contain Ce as a main component and also several addition elements like Al, Co, Cu, Fe, and Nb, and have advantages as follows:
The inset picture in the right corner in
The inset of
Ingots with nominal compositions of Ce70Al10Cu20 (at. %) were prepared by arc melting commercial-purity Ce (99.5 wt. %) with high-purity Al (99.99%), Cu (99.99%) and Nb (99.9%) under a purified argon atmosphere. The ingots were remelted and suction-cast into a Cu-mould with different cavities (cylinder or sheet) to obtain bulk form such as a sheet with dimension of 1.5×12×70 mm3 (see
The as-cast 2 mm diameter Ce70Al10Cu20 rod is fully glassy. As shown in
The XRD pattern of the 2 mm diameter Ce70Al10Cu20 rod is shown as curve A in
HRTEM is more sensitive than XRD to minitor volume fractions of dispersed crystals. As seen in
The DSC trace for the as-cast Ce70Al10Cu20 alloy at 10 K/min is shown in
The stability of the Ce70Al10Cu20 glassy alloy is examined by isothermal DSC method. As shown in the inset of
As seen in
The temperature required for this excellent deformability is approximately 100° C., which is normal for polymers but highly unusual for metallic alloys. The ease of thermoplastic forming can be demonstrated using near-boiling water (
Although showing thermoplastic behaviour like nylon or PVC, the Ce70Al10Cu20 metallic thermoplastics show mechanical and physical properties, which are very different from polymeric materials. Their density (6738 kg m−3), Vickers hardness (1.50 GPa), fracture toughness (10.0 MPa m1/2), E=29.91 GPa, K=29.18 GPa, G=11.25 GPa, Poisson's ratio (0.32) and tensile strength (490 MPa) are all much higher than those of typical polymers. The electrical resistivity of the BMG is ˜119 μΩ-cm; it is thus a metallic conductor, in contrast to the insulating properties of typical polymers.
The excellent imprintability and viscous deformability of the Ce70Al10Cu20 metallic thermoplastics can also be demonstrated by the impression of a UK five-pence coin made on the surface of its sheet held in near-boiling water by hand pressure.
It may also be very useful that this imprintability is combined with electrical conductivity.
Using the same preparation methods described in Example 1, Ce69.5Al10Cu20Co0.5 amorphous metallic plastic was developed. Compared with Ce70Al10Cu20, Ce69.5Al10Cu20CO0.5 shows larger glass forming ability with a critical diameter of 10 mm. The amorphous nature of Ce69.5Al10Cu20CO0.5 as-cast alloy was also demonstrated by the XRD method as shown in
For this composition, a glassy rod with at least 8 mm in diameter can be prepared using the same preparation methods described in Example 1. Its appearance picture is shown in
Five Ce based ternary CeaAlbMc amorphous metallic plastics of Examples 4 to 8 were prepared using the same method as that of Example 1, where M is one element selected from Co, Cu and Ni. The detailed composition for these five ternary alloys are listed in Table I. Their glass forming ability indicated by the critical diameter d, and thermal properties including Tg, Tc, ΔT, Tm (the melting temperature) and T, (the liquidus temperature) are all listed in Table I.
All the Ce-based amorphous metallic plastics of Examples 9 to 35 can be prepared using the same method described in Example 1. Their compositions all come from the formula CedAleCufZg and CehAliCujNik, where Z is one element selected from Co, Fe, Ni, Hf. Mg, Mo, Nb, Sc, Ta, Ti, W, Zn and Zr. Their XRD results are similar to those of Example 3. For the alloys of Examples 9 to 19, their compositions and thermal data detected by the DSC method are listed in Table I. For Examples 9-11, 13 and 14, their elastic constants (E, G and K) are also listed in Table I. For the alloys of Examples 20-35, the compositions and the minimum volume fraction of the glass phase in each alloy are shown in Table II. Compared with the ternary alloy Ce70Al10Cu20 (Example 1), the introduction of the fourth element like Z and Ni in these quaternary alloys can improve its glass forming ability more or less, but does not change its elastic properties very much.
Note:
1) dc is the smallest critical diameter for the fully glassy rod prepared under our own experimental conditions
2) Thermal parameters were measured by DSC at a constant heating rate of 10 K/min.
In general, in the present invention, most of the Ce based amorphous metallic plastics show extremely low Tg in the range of 341-364 K, very close to those of typical polymeric glasses like Nylon (˜316 K) and PVC (348-378 K). By introducing the additional element, the Tg of Ce based amorphous metallic plastics can be adjusted to meet the requirements of manufacturing and application. Therefore, the Ce-based amphous metallic plastics provided by the present invention can be deformed so as to form desired shapes, as with thermoplastic plastics.
Number | Date | Country | Kind |
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200510066113.2 | Apr 2005 | CN | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CN06/00617 | 4/7/2006 | WO | 10/20/2007 |