Biodegradable magnesium alloy implant

Abstract

A biodegradable implant is formed of a magnesium alloy having 3 to 7% by weight Zn, 0.001 to 0.5% by weight Ca, the remainder being magnesium containing total impurities, which promote electrochemical potential differences and/or the formation of intermetallic phases, in a total amount of no more than 0.0048% by weight, wherein the total impurity contains elements selected from a first group of Fe, Si, Mn, Co, Ni, Cu, Al, Zr and P and elements selected from a second group of rare earths having the ordinal numbers 21, 39, 57 to 71 and 89 to 103.

1 . A biodegradable implant comprising a magnesium alloy having 3 to 7% by weight Zn, 0.001 to 0.5% by weight Ca, the remainder being magnesium containing total impurities, which promote electrochemical potential differences and/or the formation of intermetallic phases, in a total amount of no more than 0.0048% by weight, wherein the total impurity contains elements selected from a first group of Fe, Si, Mn, Co, Ni, Cu, Al, Zr and P and elements selected from a second group of rare earths having the ordinal numbers 21, 39, 57 to 71 and 89 to 103. 
     
     
         2 . The biodegradable implant of  claim 1 , comprising a total amount of no more than 0.0038% of the first group. 
     
     
         3 . The biodegradable implant of  claim 1 , comprising a total amount of no more than 0.001% of the second group. 
     
     
         4 . The biodegradable implant of  claim 1 , wherein the content of Zn is 3 to 5% by weight and that of Ca is at least 0.2 to 0.4% by weight. 
     
     
         5 . The biodegradable implant of  claim 1 , wherein the alloy contains an intermetallic Ca 2 Mg 6 Zn 3  phase in a volume content of greater than 0 to 2%. 
     
     
         6 . The biodegradable implant of  claim 1 , comprising total impurities limited in % by weight: Fe<0.0005; Si<0.0005; Mn<0.0005; Co<0.0005; Ni<0.0005; Cu<0.0005; Al<0.0003; Zr<0.0003; P<0.0002. 
     
     
         7 . The biodegradable implant of  claim 1 , wherein the impurity elements Fe, Si, Mn, Co, Ni, Cu and Al total no more than 0.0033% by weight, the content of Al is no more than 0.0003% by weight, and the content of Zr is no more than 0.0001% by weight 
     
     
         8 . A method for producing a magnesium alloy implant 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 high-purity Zn and Ca in a composition of 3 to 7% by weight Zn, 0.001 to 0.5% by weight Ca, the remainder being magnesium containing total impurities, which promote electrochemical potential differences and/or the formation of intermetallic phases, in a total amount of no more than 0.0048% by weight, wherein the total impurity contains elements selected from a first group of Fe, Si, Mn, Co, Ni, Cu, Al, Zr and P and elements selected from a second group of rare earths having the ordinal numbers 21, 39, 57 to 71 and 89 to 103;   c) homogenizing the alloy by annealing at a temperature between 350° C. and 450° C. with a holding period of 4 to 40 hours; and   d) forming of the homogenized alloy in the temperature range between 250° C. and 350° C.   
     
     
         9 . The method according to  claim 8 , further comprising heat treating the homogenized alloy in the temperature range between 100° C. and 300° C. with a holding period of 1 minute to 3 hours.