Magnesium-aluminum-zinc alloy, method for the production thereof and use thereof

Abstract

A magnesium alloy and to a method for the production thereof and implants made thereof. The magnesium alloy includes up to 6.0% by weight Zn, and preferably 2.0 to 4.0% by weight Zn, 2.0 to 10.0% by weight Al, and preferably 3.0 to 6.0% by weight Al, where % by weight Al≧% by weight Zn shall apply, the remainder being magnesium containing impurities, which promote electrochemical potential differences and/or the formation of precipitations and/or intermetallic phases, in a total amount of no more than 0.0063% by weight of Fe, Si, Mn, Co, Ni, Cu, Zr, Y, Sc or rare earths having the ordinal numbers 21, 57 to 71 and 89 to 103, Be, Cd, In, Sn and/or Pb as well as P, and the matrix of the alloy is solid solution hardening due to Al and An and is also particle hardening due to the intermetallic phases formed of Mg and Al.

1 . A magnesium alloy having improved mechanical and electrochemical properties, comprising: less or equal 4.0% by weight Zn, 2.0 to 10.0% by weight Al, the alloy content of Al in % by weight being greater than or equal to the alloy content of Zn in % by weight, the remainder being magnesium containing impurities, which promote electrochemical potential differences and/or the formation of precipitations and/or intermetallic phases, in a total amount of no more than 0.0063% by weight of Fe, Si, Mn, Co, Ni, Cu, Zr, Y, Sc or rare earths having the ordinal numbers 21, 57 to 71 and 89 to 103, Be, Cd, In, Sn and/or Pb as well as P, wherein the matrix of the alloy is solid solution hardening due to Al and Zn and is also particle hardening due to the intermetallic phases formed of Mg and Al. 
     
     
         2 . The magnesium alloy according to  claim 1 , wherein the content of Zn less or equal 2.0% by weight, in particular preferably less or equal 1.0% by weight and/or the content of Al is 2.0 to 8.0% by weight, preferably 3.0 to 8.0% by weight and still more preferably 3.0 to 6.0% by weight. 
     
     
         3 . The magnesium alloy according to  claim 1 , wherein individual impurities in the total sum of impurities amount to the following in % by weight: Fe, Si, Mn, Ni, Co, Cu each with <0.0005; Zr; Y each with <0.0003; and P<0.0002. 
     
     
         4 . The magnesium alloy according to  claim 1 , wherein impurity elements Fe, Si, Mn, Co, Ni, and Cu together total no more than 0.003% by weight. 
     
     
         5 . The magnesium alloy according to  claim 1 , wherein the alloy has a fine-grained microstructure having a grain size of no more than 7.5 μm. 
     
     
         6 . The magnesium alloy according to  claim 1 , having a tensile strength of >275 MPa, a yield point of >200 MPa, and a yield ratio of <0.8, wherein the difference between the tensile strength and yield point is >50 MPa, and the mechanical asymmetry is <1.25. 
     
     
         7 . A method for producing a magnesium alloy having improved mechanical and electrochemical properties, comprising:
 a) generating a high-purity magnesium by vacuum distillation;   b) generating a billet of the alloy by synthesis of the high-purity magnesium with less or equal 4.0% by weight Zn, 2.0 to 10.0% by weight Al, wherein the alloy content of Al in % by weight is greater than or equal to the alloy content of Zn in % by weight, the remainder being magnesium containing impurities, which promote electrochemical potential differences and/or the formation of precipitations and/or intermetallic phases, in a total amount of no more than 0.0063% by weight of Fe, Si, Mn, Co, Ni, Cu, Zr, Y, Sc or rare earths having the ordinal numbers 21, 57 to 71 and 89 to 103, Be, Cd, In, Sn and/or Pb as well as P, wherein the matrix of the alloy is solid solution hardening due to Al and Zn and is also particle hardening due to the intermetallic phases formed of Mg and Al;   c) homogenizing the alloy by annealing at a temperature between 150° C. and 450° C. with a holding period of 4 to 40 hours;   d) forming of the homogenized alloy in the temperature range between 200° C. and 400° C.   
     
     
         8 . The method according to  claim 7 , wherein the billet content of Zn is less or equal 2.0% by weight, and/or the content of Al is 2.0 to 8.0% by weight. 
     
     
         9 . The method according to  claim 7 , wherein individual impurities in the total sum of impurities amount to the following in % by weight: Fe, Si, Mn, Ni, Co, Cu each with <0.0005; Zr, Y each with <0.0003; and P<0.0002. 
     
     
         10 . The method according to  claim 7 , wherein Fe, Si, Mn, Co, Ni, and Cu together total no more than 0.003% by weight. 
     
     
         11 . The method according to  claim 7 , wherein the forming process comprises extrusion, equal channel angular extrusion (EACE) and/or a multiple forging process. 
     
     
         12 . The method according to  claim 7 , wherein steps c) and d) are repeated at least once. 
     
     
         13 . The method according to  claim 7 , wherein step c) is performed at a temperature between 250° C. and 450° C. and/or step d) is performed at a temperature between 225° C. and 400° C. 
     
     
         14 . A biodegradable implant formed from the alloy of  claim 1 . 
     
     
         15 . A biodegradable implant according to  claim 14 , comprising one of a stent, an implant for fastening and temporarily fixing tissue implants and tissue transplantations, an orthopedic implant, a dental implant, and a neuroimplant. 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . The magnesium alloy according to  claim 1 , wherein the alloy has a fine-grained microstructure having a grain size of <5 μm. 
     
     
         19 . The magnesium alloy according to  claim 1 , wherein the alloy has a fine-grained microstructure having a grain size of <2.5 μm. 
     
     
         20 . The magnesium alloy according to  claim 1 , having a tensile strength of >300 MPa, a yield point of >225 MPa, and a yield ratio of <0.75, wherein the difference between the tensile strength and yield point is >100 MPa, and the mechanical asymmetry is <1.25. 
     
     
         21 . The method according to  claim 7 , wherein the billet content of Zn is less or equal 1.0% by weight and/or the content of Al is 3.0 to 6.0% by weight.