Medical alloys with a non-alloyed dispersion and methods of making same

Abstract

An article made of a medical alloy having two or more alloying elements, and a uniform dispersion of discrete particles, which are substantially free of the two or more alloying elements. A method of making the article includes melting a composition having two or more alloying elements to form an alloy and dispersing a discrete particle in the alloy to form an ingot. The melting and dispersing are performed at a temperature above the alloying temperature of the composition and below the melting temperature of the discrete particle. The ingot is hot worked to form a processed ingot. The processed ingot is cold worked and annealed to form the article.

1 . An article comprising: 
 a medical alloy comprising at least two alloying elements; and    a uniform dispersion of discrete particles in the article, wherein the discrete particles are substantially free of the at least two alloying elements.    
   
   
       2 . An article according to  claim 1 , wherein the medical alloy comprises a nickel-titanium alloy.  
   
   
       3 . An article according to  claim 2 , wherein the nickel-titanium alloy is nitinol.  
   
   
       4 . An article according to  claim 1 , wherein the discrete particles are selected from the group consisting of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       5 . An article according to  claim 1 , wherein the discrete particles comprise at least one element substantially free of the at least two alloying elements.  
   
   
       6 . An article according to  claim 5 , wherein the at least one element comprises at least one of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       7 . An article according to  claim 1 , wherein the discrete particles comprise at least one alloy substantially free of the at least two alloying elements.  
   
   
       8 . An article according to  claim 7 , wherein the at least one alloy comprises at least two of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       9 . An article according to  claim 1 , wherein the discrete particles are aligned perpendicular to the likely direction of fatigue crack propagation.  
   
   
       10 . An article according to  claim 1 , wherein the medical alloy comprises a binary alloy.  
   
   
       11 . An article according to  claim 1 , wherein the medical alloy comprises a ternary or higher alloy.  
   
   
       12 . An article according to  claim 1 , wherein the article is an implantable medical component or device.  
   
   
       13 . A method of making an article, the method comprising: 
 melting a composition comprising at least two alloying elements to form an alloy and dispersing at least one type of discrete particle in the alloy to form a cast ingot, wherein the melting and dispersing are performed at a temperature above the alloying temperature of the composition and below the melting temperature of the discrete particles;    hot working the cast ingot to form a processed ingot; and    cold working and annealing the processed ingot to form the article.    
   
   
       14 . A method according to  claim 13 , wherein the composition comprises a substantially equiatomic amount of nickel and titanium.  
   
   
       15 . A method of making an article, the method comprising: 
 vacuum melting a composition comprising at least two alloying elements to form a cast ingot, wherein the melting is performed at or above an alloying temperature for the composition;    pour stream injecting particles into the cast ingot during vacuum induction melting at a temperature below the melting point of the particles;    hot working the cast ingot to form a processed ingot; and    cold working and annealing the processed ingot to form the article, the article comprising a medical alloy comprising at least two alloying elements and a uniform dispersion of discrete particles substantially free of the at least two alloying elements.    
   
   
       16 . A method according to  claim 15 , wherein the composition comprises a substantially equiatomic amount of nickel and titanium and the article comprises a nickel titanium alloy and a uniform dispersion of discrete particles substantially free of nickel and titanium.  
   
   
       17 . A method according to  claim 16 , wherein the composition has a nickel: titanium atomic ratio of about 50:50.  
   
   
       18 . A method according to  claim 15  wherein the particles are selected from the group consisting of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       19 . A method according to  claim 15 , wherein the particles comprise an alloy comprising at least one of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       20 . A method according to  claim 15 , wherein the vacuum melting comprises vacuum induction melting.  
   
   
       21 . A method according to  claim 15 , wherein the vacuum melting comprises vacuum skull melting.  
   
   
       22 . A method of making an article, the method comprising: 
 preparing an electrode having a hollow center, the electrode comprising a composition comprising at least two alloying elements;    introducing particles into the hollow center;    vacuum arc melting the electrode and the particles at a temperature above the alloying temperature of the composition and below the melting point of the particles to form a cast ingot;    hot working the cast ingot to form a processed ingot; and    cold working and annealing the processed ingot to form the article, the article comprising a nickel-titanium alloy and a uniform dispersion of discrete particles substantially free of the at least two alloying elements.    
   
   
       23 . A method according to  claim 22 , wherein the composition comprises a substantially equiatomic amount of nickel and titanium.  
   
   
       24 . A method according to  claim 22 , wherein the particles are selected from the group consisting of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       25 . A method according to  claim 22 , wherein the particles comprise an alloy comprising at least one of iridium, platinum, gold, rhenium, tungsten, palladium, rhodium, tantalum, silver, ruthenium, and hafnium.  
   
   
       26 . A method according to  claim 22 , wherein the particles are introduced by injecting the particle into the hollow center.  
   
   
       27 . A method according to  claim 22 , wherein the particles are introduced by packing a powdered particle into the hollow center.