JP4242807B2 - Magnesium alloy for die casting and magnesium die casting products - Google Patents

Description

  The present invention relates to a lightweight and high specific rigidity magnesium alloy, and more particularly to a magnesium alloy for die casting and a magnesium die casting product using the same.

  Among alloys used in large quantities, magnesium alloys are the lightest and have the highest specific rigidity. Most of the casting Mg alloys used in notebook PCs, mobile phones, and portable power tools are AZ91 alloys. is there. This AZ91 alloy is excellent in strength, corrosion resistance, formability, etc., and is widely used for die casting as a well-balanced casting alloy, but it requires automobiles and motorcycles that require high mechanical properties in terms of elongation, bending, and heat resistance. Not suitable for use. Therefore, for these applications, an AM60 alloy or an AM50 alloy whose elongation is improved by reducing the amount of Al is usually used.

  In recent years, demands for weight reduction of automobile parts have increased, and covers close to the engine are also made into Mg alloys, so that new alloys imparted with heat resistance have been actively developed (for example, see Patent Document 1). This prior art alloy is an improvement over AM50 alloy or AM60 alloy, based on Al: 2-9 wt%, Sr: 0.5-7 wt%, preferably Al: 4-6 wt% %, Al: 4.5 to 5.5% by weight and Zn: 0.35% by weight or less (AM alloy level). Further, for example, Non-Patent Document 1 describes a comparison between the above-described prior art alloy and an AZ-based alloy. FIG. 17 is a diagram showing the contents of comparison described in this document.

  Furthermore, Patent Document 2 shows an example in which characteristic improvement is attempted by Si, RE, etc. As an example, RE: 0.1 to 4% by weight, Si: 0.7 to 5% by weight, Mn: 1 It is shown that the components are composed of wt% or less, Zr: 1 wt% or less, Ca: 4 wt% or less, Al: 10 wt% or less, Zn: 5 wt% or less, Ag: 5 wt% or less.

Special table 2003-517098 gazette JP-A-9-316586 "Development of Creep Resistant Mg-Al-SrAlloys", co-authored by Pegrelewz and Baryl Magnet Technology 2001 (TMS)

  However, the above conventional alloys (improved AM50 alloy or AM60 alloy) have the following problems.

  In FIG. 17, the lower part represents an example of the above-described prior art alloy (hereinafter referred to as a conventional alloy as appropriate), but the tensile strength at room temperature (room temperature) is reduced by about 15% as compared with the AZ91 alloy. Yes. The tensile strength at 175 ° C. is improved by about 7%, but the elongation value at room temperature and 175 ° C. is lowered. Although the creep characteristic value and the like are certainly improved, when the material is actually used, it is exposed from room temperature to a high temperature of about 175 ° C., so the physical properties at room temperature cannot be ignored. In the above prior art, such a point is not taken into consideration, and a decrease in strength at room temperature cannot be prevented.

  An object of the present invention is to provide a magnesium alloy for die casting that can improve high-temperature creep performance without causing a decrease in room temperature strength, and a magnesium die-cast product using the same.

  In order to achieve the above object, the magnesium alloy for die casting according to the first aspect of the present invention comprises aluminum 6.0 to 11.0% by weight, zinc 0.1 to 2.5% by weight, manganese 0.1 to 0.5% by weight. % AZ91 alloy, at least one of antimony and calcium, and strontium are added as a crystal refining agent.

  In the first invention of the present application, the base alloy is an AZ91 alloy of 6.0 to 11.0% by weight of aluminum, 0.1 to 2.5% by weight of zinc, and 0.1 to 0.5% by weight of manganese, On the other hand, it is set as the composition which adds Sb, Ca, and Sr. By making the base AZ91 series, it is possible to prevent the strength characteristics at room temperature from being lowered as in the AM60 series alloy. Then, by adding Sb, Ca, Sr as a crystal refining agent to the AZ91 alloy, the alloy structure is improved to refine the crystal grain size, and the AS21 alloy known as a heat-resistant magnesium alloy with high-temperature creep performance. Excellent characteristics equivalent to the above can be obtained. As a result, an alloy with improved high temperature creep performance can be realized without causing a decrease in room temperature strength.

  In order to achieve the above object, the magnesium alloy for die casting according to the second aspect of the present invention comprises aluminum 6.0 to 11.0% by weight, zinc 0.1 to 2.5% by weight, manganese 0.1 to 0.5% by weight. % AZ91 alloy was added with at least one of 0.1 to 1.5 wt% silicon, 0.1 to 1.2 wt% rare earth, and 0.2 to 0.8 wt% zirconium. The alloy is further characterized by adding at least one of antimony and calcium and strontium as a crystal refining agent.

  In the second invention of the present application, so-called AZ91 containing 6.0 to 11.0% by weight of aluminum, 0.1 to 2.5% by weight of zinc, and 0.1 to 0.5% by weight of manganese, which are base alloys. At least one of silicon 0.1 to 1.5 wt%, rare earth 0.1 to 1.2 wt%, and zirconium 0.2 to 0.8 wt% is added to the alloy. The base alloy was completed, and elements were added to improve high temperature creep performance while maintaining formability and room temperature strength. By adding Sb, Ca, Sr as a crystal refining agent to the AZ91 alloy, the alloy structure can be improved and the crystal grain size can be refined.

  Unlike the first invention of the present application, any one of silicon, rare earth, and zirconium is added to the base alloy side, but these alloys are grain boundary products Mg17Al12 (β phase, which is a weakness of AZ91 series alloys. ), And when Ca is added, it enters the gaps of the Al2Ca crystals that are formed, and these phases are divided to improve the strength. However, if too much is added, detrimental effects such as deterioration of moldability are caused. Therefore, silicon is preferably 1.5% by weight, rare earth is 1.2% by weight, and zirconium is preferably up to 0.8% by weight. As a result, the formability, which is a feature of the alloy of the present invention, is reliably maintained, and the heat resistant creep characteristics can be further improved.

  According to a third invention, in the first or second invention, the crystal refining agent is at least one of antimony 0 to 1.5 wt% and calcium 0.2 to 3.5 wt%, and strontium 0 0.1 to 1.5% by weight, and other components are inevitably contained.

  In the third invention of the present application, in particular, the addition amount of antimony, calcium and strontium is 0 to 1.5% by weight of antimony, 0.2 to 3.5% by weight of calcium, and 0.1 to 1.5% by weight of strontium. By doing so, the crystal grain size can be reliably set to 20 μm or less, and excellent characteristics equivalent to those of the AS21 alloy known as a heat-resistant magnesium alloy can be obtained with high-temperature creep performance. As a result, an alloy with improved high-temperature creep performance can be reliably realized without causing a decrease in room temperature strength.

  In order to achieve the above object, the magnesium die-cast product according to the fourth aspect of the present invention comprises aluminum 6.0 to 11.0% by weight, zinc 0.1 to 2.5% by weight, manganese 0.1 to 0.5% by weight. The AZ91 alloy is characterized in that it is formed by die casting using a magnesium alloy for die casting to which at least one of antimony and calcium and strontium are added as a crystal refining agent.

  In the fourth invention of the present application, as an alloy used for a magnesium die-cast product, so-called containing 6.0 to 11.0% by weight of aluminum, 0.1 to 2.5% by weight of zinc, and 0.1 to 0.5% by weight of manganese. An alloy having a composition in which Sb, Ca, Sr is added to the AZ91 alloy is used. By making the base of the alloy AZ91 series, it is possible to prevent the strength characteristics at room temperature from being lowered like the AM60 series alloy. And, by adding Sb, Ca, Sr as a crystal refining agent that does not impair the effect even if remelted for die casting, the alloy structure can be obtained without impairing the hot metal flowability. As a result, the crystal grain size can be refined and excellent characteristics equivalent to those of the AS21 alloy known as a heat-resistant magnesium alloy can be obtained with high-temperature creep performance. As a result, a die-cast product can be manufactured with good moldability by using an alloy that does not cause a decrease in room temperature strength and has improved high-temperature creep performance.

  In order to achieve the above object, the magnesium die cast product according to the fifth aspect of the present invention comprises aluminum 6.0 to 11.0% by weight, zinc 0.1 to 2.5% by weight, manganese 0.1 to 0.5% by weight. An alloy obtained by adding at least one of 0.1 to 1.5% by weight of silicon, 0.1 to 1.2% by weight of rare earth, and 0.2 to 0.8% by weight of zirconium to AZ91 alloy of On the other hand, it is characterized in that it is formed by die casting using a magnesium alloy for die casting to which at least one of antimony and calcium and strontium are added as a crystal refining agent.

  As in the second aspect of the invention, by adding any one of silicon, rare earth, and zirconium to the base alloy side, these alloys have a grain boundary product Mg17Al12 (which is a weakness of the AZ91 alloy) (β phase) and when Ca is added, it enters the gaps of the Al 2 Ca crystals that are formed, and these phases are divided to improve the strength. However, if too much is added, detrimental effects such as deterioration of moldability are caused. Therefore, it is preferable that silicon is 1.5 wt%, rare earth is 1.2 wt%, and zirconium is 0.8 wt%. As a result, the formability, which is a feature of the alloy of the present invention, is reliably maintained, and the heat resistant creep characteristics can be further improved.

  6th invention is the said 4th invention or 5th invention. As said crystal refining agent, at least any one among 0-1.5 weight% of antimony and 0.2-3.5 weight% of calcium, and strontium It is characterized in that it is formed by die casting using the magnesium alloy for die casting in which 0.1 to 1.5% by weight is added and other components are inevitably contained.

  In the sixth invention of the present application, in particular, the addition amount of antimony, calcium and strontium is 0 to 1.5% by weight of antimony, 0.2 to 3.5% by weight of calcium, and 0.1 to 1.5% by weight of strontium. By doing so, the crystal grain size can be reliably set to 20 μm or less, and excellent characteristics equivalent to those of the AS21 alloy known as a heat-resistant magnesium alloy can be obtained with high-temperature creep performance. As a result, a die-cast product can be manufactured with good moldability by using an alloy that does not cause a decrease in room temperature strength and that reliably improves high-temperature creep performance.

  According to the first to sixth aspects of the present invention, the composition of adding Sb, Ca, Sr to the AZ91 alloy prevents the strength characteristics at room temperature from being lowered, and the addition of Sb, Ca, Sr The alloy structure can be improved to refine the crystal grain size and improve the high temperature creep performance.

  According to the second and fifth aspects of the present invention, since the base alloy is made by adding Si, RE, and Zr to such an extent that the formability of the AZ91 alloy does not change significantly, the strength characteristics at room temperature are reduced. And formability is maintained. Moreover, since these elements precipitate at the grain boundaries and precipitate in the gaps of the β phase, which causes weakness, and divide the β phase, the high temperature creep performance can be reliably improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As described above, the inventors of the present application have the high temperature creep characteristics while maintaining the excellent characteristics of the AZ91 alloy from the viewpoint of improving the high temperature creep performance without causing a decrease in the room temperature strength as in the conventional alloys. Various investigations were made on the improved magnesium alloy for die casting and die casting products. Hereinafter, the concept and the examination results will be described in order. In addition,% display in a sentence represents weight% altogether.

(1) Refinement of crystal grain size First, the inventors of the present application proceeded with a study aimed at improving the characteristics of the AZ91 alloy die-cast product. When AZ91 alloy is die-cast, the crystal grain size is approximately 40 μm, and the crystal grains are considerably finer than in the case of ordinary gravity casting of approximately 200 to 300 μm. For this reason, the crystal refiner conventionally used for gravity casting has been considered unnecessary for die casting. The inventors of the present application dared to add a micronizing agent to the die-cast alloy and tried to die-cast the alloy with an ingot.

  Among various refining agents, there are those that generate a chlorine gas at the time of addition, such as hexachloroethane, although they have a high refining effect, and those that are extremely dangerous in handling, such as metal Na. In the present invention, Sb, Ca, Sr was selected as a finer that does not lose its effect even if it is re-dissolved for die casting, and composite addition was studied.

  First, the melting point of the AZ91 alloy and the alloy to which AZ91 + Sb 0.5% + Ca 0.5% + Sr 0.5% was added was measured by a furnace cooling method. As a result, it was found that the alloy to which Sb, Ca, Sr was added had a slightly lower melting point than the AZ91 alloy (see FIG. 1). As for other elements, 1% each was added to the hot water of AZ91 alloy and the melting point was measured. As a result, it was found that when each element was small, the melting point was maintained or decreased (see FIG. 2). Each hot water was re-dissolved and poured into each mold, but in each case, it was confirmed that the hot water flowability (corresponding to die-casting formability when applied to a die-cast product) was absolutely satisfactory. did. In FIG. 2, MM (mixed rare earth metal) is used as the RE source.

  Next, in a steel crucible coated with alumina, 3 kg of the AZ91 alloy was melted and kept at 680 ° C., and then a predetermined amount of Ca and Sr were added and the pipe mold (wall thickness 3 mm, inner diameter 32 mmφ) heated to 100 ° C. , A depth of 53 mm) was quickly cast by 100 g with a ladle to prepare a sample. The sample was cut laterally at the middle part, and subjected to a solution treatment at 410 ° C. for 2 hours in order to sharpen the crystal grain boundary, polished to a mirror surface, etched with a 6% picric acid alcohol solution, and examined. The crystal grain size was determined by the intercept method of the crystal grain size measurement method of steel JIS.

  FIG. 3 shows the results of adding Sb and Ca to the AZ91 alloy. The effect of antimony is slightly smaller, but it can be seen that when antimony and calcium are added in combination, the effect is almost the same as calcium. FIG. 4 shows an example in which Sr is added to the hot water added in a composite manner, and the crystal grain size is reduced to 20 μm or less by adding 0.6% or more of Sr. A similar test was conducted on an alloy obtained by adding 0.5 to 1.0% of Si, RE, and Zr to the AZ91 alloy. The results were almost the same for the crystal grain size. Crystals unique to each of Si, RE, and Zr appeared in a dispersed manner, but there was no change in the overall crystal grain size.

  FIG. 5 shows an example of the results of examining the relationship between the crystal grain sizes with various levels of Sb, Ca, and Sr. The AZ alloy in this case refers to an AZ91 + 0.5% Si alloy, an AZ91 + 0.5% RE alloy, and an AZ91 + 0.5% Zr alloy in addition to the AZ91 alloy. As shown in FIG. 5, it can be seen that when a composite addition is made in the range of 0.5% Sb, 0.5% to 3.0% Ca, 0.1% to 1.5% Sr, it can be made 20 μm or less within the range surrounded by the dotted line. It was.

  In addition, the inventors of the present application have conducted a separate experiment, and at least Sb: 0 to 1.5% and Ca: 0.2 to 3.5% without adding both of the above Sb and Ca. It has been found that by adding either one of them, the same refinement effect as in the range surrounded by the dotted line can be obtained. Therefore, in order to obtain this refinement effect, at least one of Sb: 0 to 1.5% and Ca: 0.2 to 3.5%, and Sr: 0.1 to 1.5% May be added in combination.

  When an alloy obtained by adding Sb, Ca, and Sr to AZ91 alloy is die-cast and compared with AZ91 alloy, the crystal grain size of the die-cast product is the crystal grain size when cast into a pipe mold. On the other hand, it was found that the crystal grain size ratio of the AZ91SbCaSr alloy to the AZ91 alloy was refined to about 1/3 even under different casting and forming conditions (see FIG. 6). ). Conventionally, since the grain refiner has not been used for die-cast products, this is a new finding.

  Such refinement of the grain size increases the strength of the material because the grain boundary network becomes finer, and the thickness of the β phase that precipitates at the grain boundary decreases, which causes corrosion. Since it becomes difficult to produce a coarse intermetallic compound that is easily generated, corrosion resistance can be improved. The strength and corrosion resistance of an alloy obtained by adding Si, RE, and Zr to an AZ alloy are improved, and the β phase is prevented from becoming coarse due to intergranular intermetallic compounds, resulting in improved characteristics. This is a very similar mechanism of action.

(2) Room temperature strength and elongation characteristics and hot metal flowability Next, the inventors of the present application based on the result of (1) above, AZ91 system in which Si, RE, and Zr are added to AZ91 alloy and AZ91 alloy as described above. The room temperature strength characteristics and room temperature elongation characteristics of the base alloys and alloys obtained by further adding Sb, Ca, Sr thereto (hereinafter, simply referred to as “Sb, Ca, Sr added alloys”) were examined.

  Using an alloy ingot as shown in FIG. 7, a mold temperature (melting furnace temperature) of 650 ° C., 1.5 mm thickness, B5 size flat test die using a cold chamber die casting machine, a mold temperature of 200 ° C. Thus, 80 sheets were formed. 5 molded plates were cut equally into 3 parts in the horizontal direction and 2 parts in the vertical direction to make 6 pieces, and the density was measured by the water displacement method. The filling factor in the mold was calculated from the theoretical density obtained by integration from the density table of atoms. Further, room temperature tensile test pieces were cut out from 5 molded plates, and the tensile strength and elongation value at room temperature were measured with an Instron tensile tester.

  FIG. 8 shows the filling rate (average value of the composition of the present invention) of the above-mentioned test plate formed by die casting. It can be seen that when Sb, Ca, Sr is added, the filling rate is improved.

  FIG. 9 shows the room temperature tensile strength of the die cast product. In addition, the measurement results when the die cast test piece was subjected to solution treatment at 410 ° C. for 2 hours are also shown. As shown, in the case of as-cast, the Sb, Ca, Sr-added alloy shows a value about 7% higher than that of the AZ91 alloy. Further, the strength of the AZ91 alloy decreased when the solution treatment was performed, but as a result of observation of the test piece, bubbles were scattered, which is considered to be a cause of lowering the physical properties and lowering the filling rate. In the alloy according to the embodiment of the present invention to which Sb, Ca, Sr was added, no strength reduction was observed and no bubbles were observed even after solution treatment.

  Further, FIG. 10 shows elongation values, but the Sb, Ca, Sr-added alloys were almost the same as AZ91 alloys. It can be seen that when Sb, Ca, Sr is added to the AZ91 alloy, there is no entrainment of bubbles in the die casting, the filling rate is improved, and the tensile strength is improved, so that the die casting formability is improved.

  On the other hand, although it is an AZ91 alloy on the added side, the inventors of the present application have examined each component, and if Al is lower than 6%, the effect of improving the room temperature tensile strength described above cannot be obtained. I found out. Therefore, in order to improve the room temperature tensile strength, it was determined that the ratio of Al contained was 6% or more.

  About the addition effect of Si, RE, and Zr, the above-mentioned upper limit was determined by confirming the hot-water flow property visually as described above. When these upper limits were exceeded, it was confirmed that the viscosity increased and the hot water flowability was adversely affected. Further, the lower limit value was determined by taking the room temperature tensile strength of the added alloy into consideration and taking the amount of improved strength as the lower limit value. FIG. 11 shows the relationship between the addition amount at this time and the room temperature tensile strength. The average addition improvement effect was + 12%.

  As a result of the above, the inventors of the present application made Si, RE, Zr with respect to the AZ91 alloy of Al: 6 to 11.0%, Zn: 0.1 to 2.5%, and Mn: 0.1 to 0.5%. It was judged that it would be appropriate to use a base alloy with a predetermined amount added. These base alloys are collectively referred to as AZ91 alloys, and the respective graphs also show the average values of the whole.

(3) High-temperature creep characteristics Next, the inventors of the present application examined high-temperature creep characteristics of Sb, Ca, and Sr alloys based on the results of (1) and (2) above.

  Test pieces were cut out from five die-cast molded products, and creep data at 175 ° C. was obtained with a constant speed high temperature creep tester. For comparison, the same measurement was performed for a normal AZ91 alloy or another AZ alloy.

  12, 13, and 14 show the results of the constant rate method high temperature creep test at 175 ° C.

  FIG. 12 shows the relationship between strain rate and flow stress. The Sb, Ca, Sr-added alloy of this embodiment in which Sb, Ca, Sr is added to an AZ91 alloy has a 15-30% flow stress improvement at each strain rate and a high creep resistance compared to the AZ91 alloy. You can see that

  FIG. 13 shows the data of the creep elongation value. The AZ61 alloy and the AZ91 alloy have 25% or less depending on the creep rate, whereas the Sb, Ca, Sr-added alloy shows 35% or more at any strain rate.

For comparison with other alloys, FIG. 14 shows these results entered on a database graph of the Japan Magnesium Society. The association's measurement method is the constant stress method. In principle, both methods evaluate the same physical properties. Reference data of other alloys at 175 ° C. are also shown. In the figure, “Mercer” refers to the document “WEMercerII“ Magnesium Die ”.
Cast Alloys for Elevated Temperature Applications ", SAE Paper No.900788,
The data by SAEWarrendale, PA, USA, 1990. is shown. “Nagaoka University of Technology” is written by Yasuhiro Gokan, Shigeharu Kamado, Hideshi Takeda et al .: “Mg-Zn-Al-Ca-RE alloy die casting” The microstructure and high-temperature strength properties of the materials are shown in “Data Collection of the 103rd Autumn Meeting of Light Metal Society P-16, P.375”.

  FIG. 15 shows the measurement conditions of the creep test of the inventors of the present application shown in FIG. 14 and the creep test of the Japan Magnesium Association.

  In FIG. 14, the Nagaoka Institute of Technology ZACE05411 alloy crosses AS21 and stands up. The other data are data on Mercer's basic alloy, and can be obtained by looking at the level of creep resistance of AS41, AS21 and AS42 of heat-resistant magnesium alloys.

  The Sb, Ca, Sr-added alloy according to this embodiment is on the extension line of the creep characteristic curve of the AS21 alloy, and the creep resistance at 175 ° C. is considered to be equivalent to that of AS21. That is, it can be seen that by adding Sb, Ca, Sr to the AZ91 alloy, an alloy having a high temperature creep property equal to or higher than AS21 having a high temperature creep property can be obtained.

  In addition, the inventors of the present application separately examined the influence of the component of the added AZ91 alloy on the tensile strength at room temperature, not the addition amount of Sb, Ca, Sr, as described above, and included Al. If the ratio exceeds 11%, the deterioration of the elongation value exceeds 1%. Therefore, in order to improve the high temperature creep property, it was determined that the ratio of Al contained is 11% or more.

(4) Corrosion resistance AZ91 alloy is an alloy having excellent corrosion resistance among Mg alloys, but in the alloy of the present embodiment, Si, RE, Zr is used as a base alloy, and new elements Sb, Ca, Sr are used as a refinement agent. Is added. As a result, if the corrosion resistance is greatly deteriorated, it cannot be put into practical use. Therefore, the inventors of the present application confirmed the corrosion resistance of the AZ-based Sb, Ca, Sr-added alloy according to the present embodiment and a normal AZ91 alloy by a salt spray test.

  The outline of the salt spray test was performed as follows. First, as a raw material ingot, the composition shown in FIG. 15 was used. For die casting, match gold A and B were die-cast at respective molding temperatures (melting furnace temperatures) of 620 ° C., 650 ° C., and 680 ° C. to obtain a plate. Moreover, as a sample shape for a salt spray test, the thickness of the molded plate was 0.7 mm, and this was cut out to 95 mm × 130 mm. As pretreatment conditions, no chemical conversion treatment was performed, and the surface was wiped off with acetone.

As a test method, a CAS salt spray tester (manufactured by Suga Test Instruments) was used, the temperature in the test tank was 35 ° C., and the spray pressure was 0.098 MPa (1 kgf / cm ² ). After spraying continuously for 2 hours under these conditions, the sample was washed away with running water and allowed to stand for 16 hours, and the degree of corrosion was visually evaluated on a five-point scale: “almost no corrosion—5” “little corrosion + -4” “corrosion” Existence ++ to 3 "," corrosion on the entire surface +++ to 2 "," significant corrosion on the entire surface to 1 ".

  FIG. 16 shows the result. As shown in FIG. 16, in the 0.5% alloy of AZ91 series Sb, Ca, Sr according to this embodiment, the above-mentioned “corrosion occurred ++-3”. That is, it was found that there was no significant difference between the two alloys in terms of corrosion resistance, and that the Sb, Ca, Sr-added alloy of the present embodiment can ensure substantially the same corrosion resistance as that of a normal AZ alloy.

  As described above, according to the present embodiment, it is possible to obtain a magnesium alloy for die casting having room temperature tensile strength equivalent to that of AZ91 alloy and having high temperature creep properties while ensuring good die cast formability and corrosion resistance. it can. In particular, the alloy according to the present embodiment is a magnesium die casting that covers a room temperature range to a high temperature range in applications such as transmission covers and oil pans that can achieve a light weight effect, or car air conditioner piston housings, airbag covers, and engine covers. Useful for products.

It is a figure showing the melting | fusing point characteristic of the alloy which added Sb, Ca, and Sr to the AZ91 alloy. It is a figure showing melting | fusing point of the alloy which added 1 weight% of Ca, Si, RE, Sr, and Zr to AZ91 alloy respectively. It is a figure showing the fine agent addition effect to an AZ91 type alloy. It is a figure showing the addition effect of Sr to an AZ91SbCa alloy. It is a figure showing the range of the ratio which adds Sb, Ca, and Sr to the AZ91 type | system | group alloy in one Embodiment of this invention. It is a figure showing the change behavior of the crystal grain size ratio of AZ91 alloy and AZ91SbCaSr alloy. It is a figure showing the composition of an alloy ingot. It is a figure showing the filling rate behavior of an alloy. It is a figure showing the behavior of room temperature tensile strength of an alloy. It is a figure showing the behavior of the room temperature elongation characteristic of an alloy. It is a figure showing the behavior of the relationship between the high temperature strain rate and flow stress of an alloy. It is a figure showing the behavior of the relationship between the high temperature strain rate of an alloy, and a creep elongation value. It is a figure showing the relationship between the high temperature creep rate and stress in various magnesium alloys. It is a figure showing the test conditions of a creep test. It is a figure showing the composition of the raw material ingot used by the corrosion resistance test. It is a figure showing the result of a corrosion resistance test. It is a figure showing the comparison content of the alloy characteristic described in the well-known technical literature.

Claims (6)

Aluminum 6.0 to 11.0% by weight, zinc 0.1 to 2.5% by weight, manganese 0.1 to 0.5% by weight, antimony 1.5% by weight or less (excluding 0% by weight), calcium 0 A magnesium alloy for die casting, characterized in that it comprises 2 to 3.5% by weight and 0.1 to 1.5% by weight of strontium , the balance being magnesium and other components inevitably contained . Silicon 0.1 to 1.5 wt%, claims, characterized in that it further comprises rare earth 0.1 to 1.2 wt%, and at least any one of zirconium 0.2-0.8 wt% 2. The magnesium alloy for die castings according to 1 .   The magnesium alloy according to claim 1 or 2, wherein the crystal grain size is 20 µm or less. Aluminum 6.0 to 11.0% by weight, zinc 0.1 to 2.5% by weight, manganese 0.1 to 0.5% by weight, antimony 1.5% by weight or less (excluding 0% by weight), calcium 0 It was formed by die casting using a magnesium alloy for die casting comprising 2 to 3.5% by weight and 0.1 to 1.5% by weight of strontium , the balance being magnesium and other components inevitably contained . Magnesium die-cast product characterized by that. The die casting magnesium alloy further includes at least one of 0.1 to 1.5% by weight of silicon, 0.1 to 1.2% by weight of rare earth, and 0.2 to 0.8% by weight of zirconium. Magnesium die-cast product characterized by that. The magnesium die-cast product according to claim 4 or 5, wherein the crystal grain size is 20 µm or less.

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