Patent Grant
8992705
1. Field of Invention
The present invention relates to a microcrystalline alloy, a method for the production of the alloy, an apparatus for the production of the alloy, and a method for the production of a casting of the alloy. The present invention is directed, in particular, to an Al—Si alloy.
2. Description of Related Art
It is widely known that when a liquid is irradiated with ultrasonic waves, an acoustic stream or ultrasonic cavitation is generated in the liquid. Many applications of ultrasonic waves to metal liquid-phase processes have also been reported, and, above all, refinement of a solidification structure by ultrasonic waves has been conventionally known. It is also said that a physical phenomenon such as ultrasonic cavitation closely relates to refinement of metal crystal grains, and applying ultrasonic vibration to a casting process has become common knowledge.
For example, Japanese Patent Application Publication No. 7-278692 (JP-A-7-278692) describes a method for the production of a hypereutectic Al alloy die-cast member that has an Si content of 20 to 40%. The production method achieves refinement of coarse acicular primary crystal Si by immersing an ultrasonic vibrator into a melt of a material and applying ultrasonic vibration to the melt through the ultrasonic vibrator to produce a die cast member that has high strength.
Japanese Patent Application Publication No. 2006-102807 (JP-A-2006-102807) describes a method for reforming a metal structure. In this method, ultrasonic vibration is applied to a molten metal in a mold from a horn located a specified distance away from the surface of the molten metal. Then, fine nuclei are formed in the molten metal and dendrites of the primary crystal are destroyed, resulting in a fine solidification structure.
Japanese Patent Application Publication No. 7-90459 (JP-A-7-90459) describes an abrasion-resistant aluminum alloy and a method for the production of the alloy. The machinability and hot workability of the alloy are improved by reducing the Si content to a value that is lower than those of conventional aluminum alloys and adding P instead, and by properly setting the contents of Mn, Ni, Cr, and Zr.
However, only the refinement of the primary crystal Si can be achieved by the technique that is described in JP-A-7-278692, and the refinement of primary crystal α-Al cannot be achieved by the technique. In addition, since the ultrasonic vibrator is immersed into the melt, the ultrasonic vibrator is deteriorated by adhesion of the melt.
Also, with the technique that is described in JP-A-2006-102807, microcrystalline grains cannot be refined while macrocrystalline grains can be refined.
Further, the technique that is described in JP-A-7-90459 is a method for refining the primary crystal Si by applying chemical means such as additives, and it is expected that various components that are added as additives cause various problems such as poor recyclability, increase in workload for preparation and control of the additives, segregation during casting, chipping during machining, and corrosion and diffusion during use. In addition, addition of such additives can achieve the refinement of the primary crystal Si but cannot achieve the refinement of the primary crystal α-Al.
In other words, with the above crystal refinement techniques that employ an ultrasonic vibration method, only the refinement of macrocrystalline grains can be achieved, and it is difficult to achieve the refinement of a microcrystalline structure. Specifically, in order to achieve the refinement of the microcrystalline structure, a technique is required by which the primary crystal α-Al can be crystallized.
The present invention provides an alloy that has a microcrystalline structure wherein a microcrystalline structure is refined by crystallization of a primary crystal, a method for the production of the alloy, an apparatus for the production of the alloy, and a method for the production of a casting of the alloy.
A first aspect of the present invention is an alloy that has a microcrystalline structure that is obtained by applying a pressure to an alloy melt during a process of cooling the melt and then by crystallizing a fine primary crystal. An Al—Si alloy is an example of the alloy. Meanwhile, the α-Al is an example of the primary crystal.
Since the primary crystal α-Al is crystallized by applying a pressure to an Al—Si alloy melt during a process of cooling the melt to obtain the microcrystalline structure, the crystallization range of Si becomes significantly narrower so that the Si is refined, resulting in an Al—Si alloy that has improved mechanical characteristics.
The pressure may be applied using ultrasonic cavitation that is generated in the melt by applying ultrasonic vibration to the melt.
Since the primary crystal α-Al is crystallized by applying a pressure to the melt using ultrasonic cavitation to obtain the microcrystalline structure, the crystallization range of Si becomes significantly narrower so that the Si is refined, resulting in an Al—Si alloy that has improved mechanical characteristics.
The Al—Si alloy may be hypereutectic.
A second aspect of the present invention is a method for the production of an alloy that has a microcrystalline structure, which includes a melting step in which an alloy is melted to obtain an alloy melt; a pressure applying step in which a pressure is applied to the melt in the cooling process the melt; and a cooling step in which the melt is quenched. As an example of the alloy, there may. be mentioned an Al—Si alloy.
Since primary crystal α-Al is crystallized by applying a pressure to an Al—Si alloy melt during a process of cooling the melt to obtain the microcrystalline structure, the crystallization range of Si becomes significantly narrower so that the Si is refined, resulting in an Al—Si alloy that has improved mechanical characteristics.
The Al—Si alloy may be hypereutectic.
In the pressure applying step, the pressure may be applied using ultrasonic cavitation that is generated in the melt by applying ultrasonic vibration to the melt.
Since the primary crystal α-Al is crystallized by applying a pressure to the melt using ultrasonic cavitation to obtain the microcrystalline structure, the crystallization range of Si becomes significantly narrower so that the Si is refined, resulting in an Al—Si alloy that has improved mechanical characteristics.
A third aspect of the present invention is directed to a production apparatus for the production of an alloy that has a microcrystalline structure wherein a fine primary crystal is crystallized by applying ultrasonic vibration to an alloy melt during a process of cooling the melt. The production apparatus includes: an ultrasonic transducer that generates the ultrasonic vibration; an ultrasonic transmitter that is connected to the ultrasonic transducer and transmits the ultrasonic vibration in a specified direction; a treatment vessel that holds the melt and is in contact with the ultrasonic transmitter; and a treatment vessel fixing device that fixes the treatment vessel by pressing the treatment vessel against the ultrasonic transmitter, in which the ultrasonic vibration is applied to the melt via the treatment vessel. As an example of the alloy, there may be mentioned an Al—Si alloy. As an example of the primary crystal, there may be mentioned α-Al.
Since the apparatus is configured to apply ultrasonic vibration to the melt in a non-contact manner without immersing the ultrasonic transmitter in the melt, contamination of the melt through the ultrasonic transmitter and deterioration of the ultrasonic transmitter by adhesion of melt can be prevented, and the yield and the service life of the apparatus can be improved.
A fourth aspect of the present invention includes: a melting step in which an alloy is melted to obtain an alloy melt; a pressure applying step in which a pressure is applied to the melt during a process of cooling the melt; and a casting step in which casting of the alloy casting is carried out using the melt in which a fine primary crystal has been formed during the cooling process. As an example of the alloy, there may be mentioned an Al—Si alloy. As an example of the primary crystal, there may be mentioned α-Al.
By forging the alloy in which the primary crystal α-Al has been formed, a casting that has a high strength, a high toughness, and an abrasion resistance can be obtained.
The foregoing and further objects, features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
An experimental apparatus to which a method for the production of a microcrystalline Al—Si alloy according to an embodiment of the present invention is applied is described with reference to
An experimental apparatus 10 (which is hereinafter referred to as “apparatus 10”) is an apparatus that is configured to solidify a metal melt in a cooling process while applying ultrasonic vibration thereto. As shown in
The ultrasonic generator 1 includes an ultrasonic horn 7 as an ultrasonic transmitter, and an ultrasonic transducer 8 that is coupled to a lower part of the ultrasonic horn 7.
The ultrasonic horn 7 is a resonator that is made of a metal (made of Ti-6 Al-4V (mass %) alloy) and is adapted to transmit vibration energy, which is generated by the ultrasonic transducer 8 in a specified direction (in a direction of the arrow shown in
The treatment vessel 2 is a cup-shaped crucible that is made of a metal (a vessel that is made of SUS304 and has an upper inside diameter of 40 mm, an inside bottom diameter of 30 mm, and an effective depth of 33 mm), and can hold a specified amount of a melt (Al—Si alloy melt in this embodiment). The expression “a specified amount of a melt,” in this case, means that the treatment vessel 2 contains the melt but is not full to the brim so that there is a specific distance between the melt surface and the upper end surface of the treatment vessel 2 when ultrasonic vibration is applied to the melt.
The treatment vessel fixing device 3 is an air cylinder that has a rod 3a which can extend and contract vertically, and a buffer 3b at an end of the rod 3a that holds the upper end of the treatment vessel 2 when the rod 3a extends downward (toward the treatment vessel 2). The treatment vessel fixing device 3 can fixedly hold the treatment vessel 2 by extending the rod 3a of the air cylinder downward until the lower side of the buffer 3b abuts against the upper end of the treatment vessel 2 and pressing the upper end of the treatment vessel 2 toward the ultrasonic horn 7 at a specified pressure.
The thermocouple 4 is a melt temperature meter, and can be immersed into the melt that is held in the treatment vessel 2 to measure the melt temperature at a specified position in the melt. The thermocouple 4 is connected to a measuring and recording device (which is not shown), and the measuring and recording device can monitor and record the measured melt temperature continuously. The crystalline state that is formed during a process of cooling the melt can be known based on the melt temperature that is measured by the thermocouple 4, and, as a result, a material that has a desired crystalline structure can be obtained.
The upper plate 5 fixedly supports the air cylinder as the treatment vessel fixing device 3. The lower plate 6 fixedly supports the ultrasonic horn 7 and the ultrasonic transducer 8. In addition, the upper and lower plates 5 and 6 are disposed with a specified distance maintained therebetween, and are placed such that the lower plate 6 is located at a resonant antinode of the ultrasonic transducer 8 when ultrasonic vibration is being applied.
The melt water-cooling device can quench the melt under specified conditions (temperature and time), and can solidify the melt into any desired crystalline structure by properly adjusting the conditions.
The timer measures the time that is taken to reach a cooling step in which the melt is quenched. The timer is used in time management to improve the reliability of the crystalline structure formation (reproducibility of the crystalline structure).
By constructing the apparatus 10 as described above, when the air cylinder is driven to cause the buffer 3b to fixedly hold the upper end of the treatment vessel 2 and the ultrasonic transducer 8 is vibrated under specified vibration conditions by the ultrasonic oscillator (which is not shown) after the treatment vessel 2 into which a specified amount of melt has been poured is placed on the upper end of the ultrasonic horn 7, ultrasonic vibration can be applied to the melt in a non-contact manner (in a state where the melt and the ultrasonic horn 7 are not in direct contact with each other) and ultrasonic cavitation (bubbles) and an acoustic stream can be generated in the melt in the treatment vessel 2. That is, the apparatus 10 can transmit ultrasonic vibration to the melt in the treatment vessel 2 by applying ultrasonic vibration to the bottom surface of the treatment vessel 2 that is pressed against the upper end surface of the ultrasonic horn 7. The apparatus 10 can therefore apply ultrasonic vibration to the melt in a non-contact manner. In other words, since the apparatus 10 applies ultrasonic vibration to the melt in a non-contact manner without directly immersing the ultrasonic horn 7 into the melt, contamination of the melt through the ultrasonic horn 7 and deterioration of the ultrasonic horn 7 by adhesion of melt can be prevented and the yield and the service life of the apparatus can be improved. In addition, the apparatus 10 is also a pressure applying apparatus that applies a specified pressure to the melt by using the ultrasonic cavitation, and can apply a localized pressure in the melt with high efficiency. It should be noted that, while the apparatus 10 uses ultrasonic cavitation that is induced by ultrasonic vibration as a pressure applying apparatus in this embodiment, the present invention is not particularly limited thereto and may employ a system in which the entire melt is integrally pressurized by a specified pressure device, for example. Experiments that were conducted, to obtain a microcrystalline Al—Si alloy using the above-described apparatus 10 as examples of the present invention are described below in detail.
Experimental Method:
The outline of the apparatus 10, which was used to apply ultrasonic vibration to the metal melt in this example, is shown in
The hypereutectic Al-18 Si alloy and the Al-25 Si were melted at 730° C. and 830° C., respectively, and teemed at 690° C. and 760° C., respectively. The hypoeutectic Al-7 Si alloy and the almost eutectic Al-12 Si alloy were melted at 730° C. and teemed at 640° C. No grain refiner was added to any of the Al—Si alloy melts, and Ar was blown from an end of an Al2O3 pipe for 0.9 ks as a degassing operation. In every case, approximately 65 g of the melt was teemed into the treatment vessel 2, and ultrasonic vibration started to be applied immediately after the teeming. When the melt reached a specified temperature, the melt, together with the treatment vessel 2, was quenched into water to preserve the microstructure. A type K thermocouple was used to continuously measure and record the temperature of the melt in the cooling process. The temperature measurement and structure observation were made at a point almost in the center of the sample, which is on the center line of the vessel and 8 mm away from the bottom of the vessel unless otherwise noted. Temperature measurement and structure observation were also made at a lower point (3 mm away from the bottom surface) and a higher point (13 mm) in some of the sono-solidification experiments.
To verify only the influence of the acoustic stream that was induced in the melt by ultrasonic vibration, a vortex flow was created in the melt by mechanical stirring and crystallization of α-Al during the process of solidification of the hypereutectic Al—Si alloy was observed. In the mechanical stirring experiments for the purpose, an vessel that is made of SUS304, the same vessel as the above mentioned one that was used for the sono-solidification was used, and a two-propeller stirrer (which is not shown) was rotated at 23 s−1 (1400 rpm) to create a stirring flow. Then, after mechanically stirring the melt until the melt underwent partial eutectic solidification, the melt, together with the vessel, was cooled with water. A line analysis with Electron Probe Micro Analyzer (EPMA) was conducted to compare the Si contents in a primary crystal α-Al phase that appears in a normally solidified hypoeutectic Al—Si alloy and in a nonequilibrium α-Al phase that is crystallized in the hypereutectic Al—Si alloy by sono-solidification. In preparing samples, the melts were quenched into water immediately after the completion of eutectic solidification to avoid a change in the Si concentration during the cooling process, and EPMA analysis was performed on the cross-sections of the samples. The microhardness (Vickers hardness) of the α-Al phases that were crystallized in the hypoeutectic and hypereutectic Al—Si alloys were also measured. The samples for hardness measurement were not quenched but air-cooled to room temperature, however.
The results and considerations of the experiments are described below.
Differences in solidification structure among the hypoeutectic Al-7 Si, eutectic Al-12 Si, and hypereutectic Al-18 Si alloys that depend on whether or not ultrasonic vibration was applied are shown in
Since the nonequilibrium α-Al phase, which is not crystallized in hypereutectic Al-18 Si alloys under normal circumstances, was formed by sono-solidification, an experiment to identify the exact time of crystallization of the nonequilibrium α-Al phase was first conducted. Sample melts that had been solidified to different solid phase rates under ultrasonic vibration were quenched into water. As a representative example, the microstructures in the central part of sono-solidified and quenched samples (8 mm away from the bottom surface) are shown in the order of the progress of solidification in
The number of nonequilibrium α-Al grains, which are not crystallized in hypereutectic Al—Si alloys under normal circumstances, increases with the progress of eutectic solidification. However, it was not clear from the observation of the structure in the central part of the sono-solidified sample whether the crystallization of nonequilibrium α-Al phase started before the eutectic temperature was reached. As a similar solidification phenomenon, a separated eutectic structure, which is formed when an almost eutectic Al—Si alloy melt is solidified under mechanical stirring and in which massive Si grains are present independently from the α-Al phase, has been reported. The explanation is that the α-Al phase and Si grains are separately present because eutectic Si is forcibly peeled off from the solidification interface where Si/α-Al coexist by a stirring flow during the process of eutectic solidification. Thus, to clarify the stirring effect of an acoustic stream, an experiment using mechanical stirring, which is considered to generate less ultrasonic cavitation, was conducted. Using the same experimental apparatus as shown in
In the microstructure at the bottom of the sample that was quenched from a temperature immediately above the eutectic temperature during the process of sono-solidification, crystallization of nonequilibrium α-Al grains was clearly found to have occurred in contrast to the microstructure in the central part thereof, which is shown in
The melt temperatures at points which were on the sample center line and 3 mm, 8 mm and 13 mm away from the bottom were continuously recorded during the process of sono-solidification. When ultrasonic vibration was not applied, the temperatures at the upper, lower and intermediate points reached the eutectic temperature. There was a difference between a time at which the temperature at the upper point reached the eutectic temperature and a time at which the temperature at the intermediate point reached the eutectic temperature, and the time difference was about 5 s. However, on the cooling curve during the process of sono-solidification, there was almost no difference in the time at which the eutectic temperature was reached between the upper, intermediate and lower points because of the stirring effect of the acoustic stream. It is, therefore, believed that, in sono-solidification, not only primary crystal Si grains but also the granular α-Al phase had been crystallized in the pre-eutectic liquid phase at the bottom of the vessel before the eutectic temperature was reached because there was no difference in the time at which the eutectic temperature was reached between the points. It can be seen from a comparison between
To investigate the effect of ultrasonic cavitation, a vibration experiment was conducted in which vibration was applied to a transparent glass vessel (wall thickness: 1 mm, not shown) with an inside diameter of 25 mm and a depth of 50 mm which was filled with pure water using the ultrasonic vibration system (the apparatus 10) that is shown in
dT/dP=Tm(Vliq−Vsol)/ΔHm (1)
where Tm represents the melting point, Vliq and Vsol represent the molar volumes of liquid and solid, respectively [(Vliq−Vsol)/Vsol=ΔVm], and ΔHm represents the molar latent heat of fusion. Physical properties of Al and Si are summarized in the table of
That is, in the region where ultrasonic cavitation bubbles are concentrated, a local high-pressure field with a pressure of 1 GPa or higher is generated in the melt and, as a result, refinement of the microstructure can be controlled by displacement of the eutectic point.
It is expected from the equilibrium diagram at high pressure in
As described above, a sono-solidification experiment was conducted in which sample melts were solidified under ultrasonic vibration using, primarily, a hypereutectic Al-18 mass % Si alloy, and the following conclusions were obtained. (1) When a hypereutectic Al—Si alloy is sono-solidified, not only the primary crystal Si is refined but also a large number of grains of a nonequilibrium α-Al phase are crystallized. Because of the crystallization of the granular α-Al phase, the eutectic regions that include Si/α-Al are significantly reduced. (2) Intense generation of cavitation was observed in the vicinity of the bottom surface of the vessel in which the alloy was sono-solidified. A local high-pressure field that is generated by the collapse of cavitation bubbles increases the liquidus temperature of the α-Al phase and raises the Si solubility limit in the α-Al phase. The generation of the local high-pressure field allows crystallization of the nonequilibrium α-Al phase even at a temperature equal to or higher than the eutectic temperature (577° C.). (3) As can be expected from the equilibrium diagram at high pressure, the Si content in the nonequilibrium α-Al phase that has been crystallized by sono-solidification is higher than that in the primary crystal α-Al phase of a normally solidified hypoeutectic Al—Si alloy. As described above, in the case of sono-solidification of a hypereutectic Al—Si alloy, since a nonequilibrium α-Al phase with a high Si content is crystallized at a temperature equal to or higher than the eutectic temperature, it is believed that the local high-pressure field that is generated by the collapse of ultrasonic cavitation bubbles plays a dominant role in the formation of the α-Al phase.
Based on the above experimental results, it is possible to form a microcrystalline structure in which granular α-Al has been crystallized and eutectic regions that include Si/α-Al have been significantly reduced (
As in the description of the above experiment, the method for the production of a microcrystalline Al—Si alloy according to this embodiment includes a melting step in which an Al—Si alloy is melted to obtain an Al—Si alloy melt, a pressure applying step in which a pressure is applied to the melt during a process of cooling, the melt, and a cooling step in which the melt is quenched. Since the primary crystal α-Al is crystallized by applying a pressure to the Al—Si alloy melt during a process of cooling the melt to obtain a microcrystalline structure, the crystallization range of Si becomes significantly narrower and the Si is refined, resulting in an Al—Si alloy with improved mechanical characteristics.
The method for the production of a microcrystalline Al—Si alloy that is described in the above example is applicable to casting and forging. Some specific application examples are described below.
First, a casting method is described in which casting is carried out utilizing the nonequilibrium α-Al grains that are formed (crystallized) in the Al—Si alloy melt during the process of sono-solidification of the melt as described before. While a microstructure as shown in
A main flow of the method for the production of a microcrystalline Al—Si alloy casting according to this embodiment includes a melting step in which an Al—Si alloy is melted to obtain an Al—Si alloy melt, a pressure applying step in which a pressure is applied to the melt during a process of cooling the melt, and a casting step in which casting of an Al—Si alloy casting is carried out using the melt in which primary crystal α-Al has been formed during the cooling process. The melting step and the pressure applying step in the flow are the same as those in the method for the production of a microcrystalline Al—Si alloy that has been described before. A melt purifying step in which degassing of the melt or removal of impurities (slag removal) is carried out may be provided between the melting step and the pressure applying step.
First, the apparatus to which the method for the production of an Al—Si alloy casting is applied is required to be equipped with the apparatus 10, which has been described before, or an ultrasonic vibration apparatus that has the same configuration as the apparatus 10, and a casting device for the intended purpose such as centrifugal casting or die casting or a forging device (casting/forging process). The ultrasonic vibration apparatus and the casting device may be integrally constituted so that the production of the casting can continuously be carried out.
In the casting step, the melt that has been through the sono-solidification process is teemed into a specified mold, and the mold is cooled under specified cooling conditions (such as a condition to quench (cool with water) the mold). Examples of the casting method for use in the casting step include die casting and centrifugal casting. That is, in the casting step, casting is carried out by teeming the melt that has been through the sono-solidification process by the ultrasonic vibration apparatus (melt in which nuclei of the primary crystal α-Al have been formed) into a mold.
Flows of some application examples are shown below. The steps in each flow primarily correspond to the steps that have been described before (melting step→melt purifying step→pressure applying step→casting step), and their description are not repeated.
Melting an Al-18 Mass % Si at 730° C.→Purifying the Melt (Degassing, Slag Removal)→Applying Ultrasonic Vibration (20 kHz, 20 μm)→Centrifugal Casting after 578° C. is Reached.
Melting an Al-18 Mass % Si at 730° C.→Purifying the Melt (Degassing, Slag Removal)→Applying Ultrasonic Vibration (20 kHz, 20 μm)→Die-Casting after the Temperature Reaches 578° C.
When Application Example 1 is employed, the crystallized primary crystal Si moves toward the center (inside) of the casting as shown in
Melting an Al-18 Mass % Si at 730° C.→Purifying the Melt (Degassing, Slag Removal)→Applying Ultrasonic Vibration (20 kHz, 20 μm)→Centrifugal Casting after 577° C. is Reached.
Melting an Al-18 Mass % Si at 730° C.→Purifying the Melt (Degassing, Slag Removal)→Applying Ultrasonic Vibration (20 kHz, 20 μm)→Die Casting after 577° C. is Reached.
When Application Example 3 is employed, the crystallized primary crystal Si moves toward the center (inside) of the casting as shown in
Melting an Al-18 Mass % Si at 730° C.→Purifying the Melt (Degassing, Slag Removal)→Applying Ultrasonic Vibration (20 kHz, 20 μm)→Waiting for 20 Seconds after 577° C. is Reached→Forging.
Melting an Al-18 Mass % Si at 730° C.→Purifying the Melt (Degassing, Slag Removal)→Applying Ultrasonic Vibration (20 kHz, 20 μm)→Waiting for 20 Seconds after 577° C. is Reached→Quenching.
When Application Example 5 is employed, a forging product that has a microstructure as shown in
As described in the above Application Examples, it is possible to provide a casting product or forging product with further improved mechanical characteristics by effectively utilizing the crystal in which primary crystal Si or the like has been crystallized.
When a metal melt in the cooling process is solidified under ultrasonic vibration (sono-solidified), the microstructure is refined and improvement of the mechanical properties can be expected. Since refinement of crystal grains is almost synonymous with increase in the number of solidification nuclei, stirring of the melt, in other words, ultrasonic acoustic stream, promotes separation of crystal nuclei from the mold wall surfaces, which contributes to the increase in the number of crystal nuclei. In addition, as described above, when a hypoeutectic or hypereutectic Al—Si alloy melt was sono-solidified, refinement of α-Al phase or Si grains in the primary crystal was observed. Moreover, in the microstructure obtained by sono-solidifying a hypereutectic Al—Si alloy melt, crystallization of the nonequilibrium α-Al phase, which cannot be predictable from the equilibrium diagram, was observed in addition to the refined primary crystal Si grains. Therefore, when a hypoeutectic or hypereutectic Al—Si alloy melt is sono-solidified, refinement of Si grains is achieved in either case, and the resulting alloy has improved mechanical characteristics, in particular, improved abrasion resistance. As the ingot that is used as the melt, a hypereutectic Al—Si alloy is more preferred than a hypoeutectic Al—Si alloy for better abrasion resistance in terms of Si content.
Based on the assumption that generation and collapse of ultrasonic cavitation bubbles plays a critical role in crystallization of the nonequilibrium α-Al phase, an experiment was conducted in which melts in the process of sono-solidification were quenched in water to find its crystallization mechanism. As a result, it was found possible to produce an alloy that has excellent mechanical characteristics by utilizing the crystallization mechanism.
The production method for obtaining a microcrystalline structure that has been described in this embodiment is not limited to the application to Al—Si alloys, and it is possible to create a microcrystalline structure in other alloys, such as Al—Mg and Mg—Zn binary and ternary alloys, by applying the production method according to the present invention. Note that, in a Mg—Zn alloy, a fine primary crystal is α-Mg. Examples of an Al—Mg alloy include not only a binary Al—Mg alloy but also a ternary alloy that contains Al, Mg and another metal. Examples of a Mg—Zn alloy include not only a binary Mg—Zn alloy but also a ternary alloy that contains Mg, Zn and another metal. In each of these alloys, a primary crystal is a generally spherical crystal.
A material that has improved abrasion resistance can be produced from a hypereutectic Al—Si (Si: 12% or higher) alloy melt. For example, members that requires less plating, surface coating or the like can be obtained by casting or forging.
Since an ultrasonic vibration apparatus is used as one example of the apparatus that applies pressure to the melt, a local pressure rise that is induced by the application of ultrasonic vibration occurs in the melt, and an eutectic point displacement effect (increase in eutectic temperature, increase in Si element saturation temperature) is obtained. As a result, primary crystal α-Al can be obtained easily, and the solidification structure can be controlled into any desired state.
When primary crystal α-Al or granular Si crystal which has been crystallized is solidified by a cooling step in which the melt is solidified by rapid quenching, a crystalline structure that has both abrasion resistance and high toughness (grain refining) can be obtained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-197167 | Aug 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2010/001891 | 8/2/2010 | WO | 00 | 2/27/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/024040 | 3/3/2011 | WO | A |
| Number | Date | Country |
|---|---|---|
| 51-092709 | Aug 1976 | JP |
| 06-002056 | Jan 1994 | JP |
| 07-090459 | Apr 1995 | JP |
| 07-278692 | Oct 1995 | JP |
| 11-090615 | Apr 1999 | JP |
| 2004-209487 | Jul 2004 | JP |
| 2006-037190 | Feb 2006 | JP |
| 2006-102807 | Apr 2006 | JP |
| 2008-200692 | Sep 2008 | JP |
| 2008-272819 | Nov 2008 | JP |
| Entry |
|---|
| Abramov V et al: “Solidification of aluminium alloys under ultrasonic irradiation using water-cooled resonator”, Materials Letters, North Holland Publishing Company, Amsterdam, NL, vol. 37, No. 1-2, Sep. 1, 1998, pp. 27-34, XP004255985, ISSN: 0167-577x, DOI:10.1016/S0167-577X(98)0064-0. |
| Eskin<1> G I: “Broad prospects for commercial applicationof the ultrasonic (cavitation) melt treatment of light alloys”, Ultrasonics: Sonochemistry, Butterworth-Heinemann, GB, vol. 8, No. 3, Jul. 1, 2001, pp. 319-325, XP004245625, ISSN: 1350-4177, DOI: DOI:10.1016/S1350-4177(00)00074-2. |
| Feng H K et al: “Effect of ultrasonic treatment on microstructures of hypereutectic Al—Si alloy”, Journal of Materials Processing Technology, Elsevier, NL, vol. 208, No. 1-3, Nov. 21, 2008, pp. 330-335, XP025469035, ISSN: 0924-0136, DOI: DOI:10.1016/J.JMATPROTEC.2007.12.121. |
| International Search Report and Written Opinion for corresponding International Patent Application No. PCT/IB2010/001891 mailed Jan. 28, 2011. |
| Japanese Office Action for corresponding JP Patent Application No. 2009-197167 drafted Nov. 18, 2011. |
| Journal of Japan Foundry Engineering Society: “Crystallization of Non-Equilibrium a-Aluminum Solid Solution in Al-18mass%Si alloy through Acoustic Cavitation”, vol. 81, No. 10 (2009), pp. 469-474, issued on Oct. 25, 2009. |
| Aluminium-Zentrale, Dusseldorf (Publisher); W. Hufnagel, Unter Mitarbeit Zahlreicher Fachkollegen (Responsible Editor); “Aluminium-Taschenbuch”; 14th Edition; Aluminium-Verlag Dusseldorf; 1983; pp. 421-427 and 435. |
| Jian, Xiaogang; “The Effect of Ultrasonic Vibration on the Solidification of Light Alloys”; Trace: Tennessee Research and Creative Exchange; Doctorial Dissertations; University of Tennessee, Knoxville; URL: http://trace.tennessee.edu/utk—graddiss/2144; Dec. 2005. |
| German Office Action dated May 11, 2014 issued in German Patent Application No. DE 11 2010 003 405.2. English Translation. |
| Number | Date | Country | |
|---|---|---|---|
| 20120168040 A1 | Jul 2012 | US |
