Abstract:
A magnesium Mg--Al--RE magnesium alloy wherein an amount of a rare earth component may be reduced while optimial tensile strength and durability are obtained. The Alloy further includes a small calcium component. A high degree of creep resistance is obtained. Further, additional copper and/or zinc components may be introduced together, or singly for providing favorable tensile characteristics to the alloy material.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of The Invention 
     The present invention relates generally to a magnesium alloy for industrial use. 
     2. Description of The Related Art 
     Metallic alloys utilizing magnesium are widely used for automotive, electronic, aerospace and various industrial applications. Particularly, such alloys are favorable which have a high temperature `creep` strength and which may be utilized in high-temperature environments. 
     Various magnesium alloys have been developed and registered such as JIS H 5203 (MC1-MC10) or JIS H 5303 magnesium alloys (MDC1A, MDC1B). For high temperature environments, AE42 having Mg-4%Al-2%RE developed by Dow Chemical is well known. 
     Such a heat-resistant magnesium alloy, it is difficult to utilize in die casting where fast cooling is employed after molding of a metal article. 
     Further, a rare earth (hereinbelow: RE) component included in such alloys increases costs and high temperature creep resistance is reduced. 
     SUMMARY OF THE INVENTION 
     It is therefore a principal object of the present invention to overcome the drawbacks of the related art. 
     It is a further object of the present invention to provide a Mg--Al--RE magnesium alloy wherein RE is reduced while a small Ca component is introduced, while retaining a high degree of creep resistance and favorable bending characteristics. 
     In order to accomplish the aforementioned and other objects, there is provided a magnesium containing metallic alloy material, comrpising: an aluminium (Al) component contained in a range of 1.5-10% by weight; a rare earth (RE) component contained in a range of less than 2% by weight; a calcium (Ca) component contained in a range of 0.25-5.54 by weight; and wherein the remainder of the alloy is comprised of magnesium (Mg). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a stress graph showing ultimate tensile strength, yield strength and elongation in relation to Al--RE content; 
     FIG. 2 is a graph illustrating minimum creep rate in relation to Al content for alloys having various levels of RE content; 
     FIG. 3 is a graph comparing stress and Ca content in relation to various characteristics in alloys containing RE in a given range; and 
     FIG. 4 is a graph showing minimum creep rate characteristics in Ca containing alloys in relation to a given amount of RE contained in the alloy. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the accompanying drawings, a preferred embodiment of the invention will be described hereinbelow in detail. 
     The present invention seeks to provide a Mg--Al--RE magnesium alloy wherein RE is reduced while a small Ca component is introduced, while retaining a high degree of creep resistance. According to the inention, additional Cu, Zn components may be introduced together, or singly for providing favorable bending characteristics to the alloy material. 
     Various alloys have been formed according to generally known melting technique in a steel crucible having a nickel (Ni) component removed therefrom in an ambient atmosphere comprised of a gas such as SF 6 , CO 2  or air. 
     Referring to Table 1, thirty-eight alloys have been utilized including nineteen embodiments of the alloy of the invention developed by the inventors through experimentation, and nineteen samples for comparision, including the above mentioned conventional alloy. The pieces were tested for various characteristics such as ultimate tensile strength, yield strength, elongation and minimum creep rate. Table 2 shows the effects of the various alloy compositions: 
     
                       TABLE 1______________________________________SAMPLE  CHEMICAL COMPONENTS BY WEIGHT %                            COM-TYPE    Al    Mn     RE   Ca   Cu  Zn  Mg      MENTS______________________________________COMPAR- 2.0   0.39   --   --   --  --  RE-ISON 1                                 MAINDERCOMPAR- 4.1   0.29   --   --   --  --  RE-ISON 2                                 MAINDERCOMPAR- 9.5   0.25   --   --   --  --  RE-ISON 3                                 MAINDERCOMPAR- 2.1   0.38   0.49 --   --  --  RE-ISON 4                                 MAINDERCOMPAR- 3.9   0.28   0.51 --   --  --  RE-ISON 5                                 MAINDERCOMPAR- 1.9   0.41   1.1  --   --  --  RE-ISON 6                                 MAINDERCOMPAR- 4.1   0.31   1.2  --   --  --  RE-ISON 7                                 MAINDERCOMPAR- 2.0   0.41   2.1  --   --  --  RE-ISON 8                                 MAINDEREMBODI- 2.0   0.38   0.90 0.32 --  --  RE-MENT 1                                 MAINDEREMBODI- 4.1   0.29   1.1  0.31 --  --  RE-MENT 2                                 MAINDEREMBODI- 5.9   0.32   1.2  0.30 --  --  RE-MENT 3                                 MAINDEREMBODI- 9.4   0.25   1.0  0.29 --  --  RE-MENT 4                                 MAINDEREMBODI- 1.9   0.39   0.90 1.0  --  --  RE-MENT 5                                 MAINDEREBMODI- 4.0   0.35   1.1  0.90 --  --  RE-MENT 6                                 MAINDEREMBODI- 6.1   0.32   1.2  1.1  --  --  RE-MENT 7                                 MAINDEREMBODI- 9.5   0.26   1.1  1.0  --  --  RE-MENT 8                                 MAINDEREMBODI- 2.0   0.42   0.90 3.0  --  --  RE-MENT 9                                 MAINDEREMBODI- 4.2   0.35   0.90 3.1  --  --  RE-MENT 10                                MAINDEREMBODI- 5.9   0.31   1.1  3.2  --  --  RE-MENT 11                                MAINDEREMBODI- 9.3   0.28   1.0  3.0  --  --  RE-MENT 12                                MAINDERCOMPAR- 0.5   0.40   --   --   --  --  RE-ISON 9                                 MAINDERCOMPAR- 1.1   0.42   --   --   --  --  RE-ISON 10                                MAINDERCOMPAR- 0.4   0.42   1.0  0.25 --  --  RE-ISON 11                                MAINDERCOMPAR- 0.5   0.42   1.1  1.1  --  --  RE-ISON 12                                MAINDERCOMPAR- 0.5   0.38   1.0  3.1  --  --  RE-ISON 13                                MAINDERCOMPAR- 0.4   0.39   1.2  5.1  --  --  RE-ISON 14                                MAINDEREMBODI- 1.9   0.36   0.90 5.0  --  --  RE-MENT 13                                MAINDEREMBODI- 4.0   0.38   1.1  4.9  --  --  RE-MENT 14                                MAINDEREMBODI- 5.8   0.29   1.2  5.1  --  --  RE-MENT 15                                MAINDEREMBODI- 9.5   0.27   1.0  5.0  --  --  RE-MENT 16                                MAINDERCOMPAR- 4.0   0.33   1.9  --   --  --  RE-     AE42ISON 15                                MAINDER AlloyCOMPAR- 3.9   0.34   2.3  0.25 --  --  RE-ISON 16                                MAINDERCOMPAR- 4.0   0.35   2.4  1.1  --  --  RE-ISON 17                                MAINDERCOMPAR- 4.1   0.32   2.3  3.1  --  --  RE-ISON 18                                MAINDERCOMPAR- 4.0   0.33   2.3  5.1  --  --  RE-ISON 19                                MAINDEREMBODI- 4.0   0.34   1.1  0.2  0.5 --  RE-MENT 17                                MAINDEREMBODI- 4.0   0.34   1.1  0.5  --  2.0 RE-MENT 18                                MAINDEREMBODI- 4.1   0.32   1.2  0.2  0.5 0.5 RE-MENT 19                                MINDER______________________________________ 
    
     
                       TABLE 2______________________________________                                SMALLEST      BENDING   DURA-           CREEPSAMPLE     STRENGTH  BILITY  STRETCH SPEEDTYPE       (MPa)     (MPa)   (%)     (10.sup.4 % hr.)______________________________________COMPARISON 1      75        38      9.2     5.95COMPARISON 2      90        56      12.3    5.85COMPARISON 3      115       72      10.5    5.82COMPARISON 4      123       58      8.5     4.76COMPARISON 5      143       85      11.3    4.63COMPARISON 6      121       81      12.0    4.42COMPARISON 7      125       92      11.6    4.15COMPARISON 8      110       80      8.5     2.3EMBODIMENT 1      160       65      13.1    1.63EMBODIMENT 2      169       110     12.3    1.55EMBODIMENT 3      195       84      13.2    1.95EMBODIMENT 4      168       108     15.0    2.36EMBODIMENT 5      135       65      8.5     2.26EMBODIMENT 6      171       68      9.9     1.62EMBODIMENT 7      162       59      10.5    1.79EMBODIMENT 8      123       48      11.2    1.89EMBODIMENT 9      128       116     4.2     1.75EMBODIMENT 10      159       81      5.9     1.89EMBODIMENT 11      156       92      4.5     1.72EMBODIMENT 12      150       110     2.9     1.94COMPARISON 9      83        41      18.0    6.57COMPARISON 10      92        47      17.2    6.42COMPARISON 11      110       105     1.2     4.95COMPARISON 12      113       107     1.1     4.83COMPARISON 13      124       111     &lt;1.0    4.80COMPARISON 14      131       115     &lt;1.0    4.72EMBODIMENT 13      135       111     3.4     1.95EMBODIMENT 14      146       91      5.2     2.03EMBODIMENT 15      129       92      4.4     1.67EMBODIMENT 16      160       112     3.0     1.94COMPARISON 15      165       75      14.0    2.51COMPARISON 16      167       79      13.7    2.49COMPARISON 17      169       85      11.0    2.45COMPARISON 18      171       86      7.5     2.32COMPARISON 19      171       86      4.2     2.21EMBODIMENT 17      190       76      11.9    2.19EMBODIMENT 18      205       86      12.9    2.05EMBODIMENT 19      195       78      11.4    2.13______________________________________ 
    
     As may be seen from the Tables, embodiments 1-12 have favorable mechanical characteristics while RE is reduced compared with AE42 or the like, and high temperature creep strength is advantageously retained. Moreover, embodiments 13-15 include a Cu and/or Zn component having ultimate tensile strength of about 200 MPa and yeild strength of about 80 MPa. Also, a minimum creep rate of 2.0×10 -4  %/hr is obtained, while uniform temperature tensile characteristics are highly favorable. 
     It will be noted that high temperature creep strength is improved in comparison with AE42 and the other comparative examples, as shown in the tables. 
     While the present invention has been disclosed in terms of the preferred embodiment in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments which can be embodied without departing from the principle of the invention as set forth in the appended claims.