Ductile refractory alloys with high strength

Abstract

Alloy castings are provided and comprise Nb, Ta, V, Ti, and optional Hf in controlled proportions to impart unprecedented and unexpected high ductility in refractory based alloys. Certain alloys are extremely ductile (able to sustain >50% cold roll reduction without fracture) while have high hardness (about 400HV). The combination of high thermodynamic phase stability, low-temperature ductility, and strength at room temperature makes the disclosed alloy family likely candidates as next-generation high temperature structural alloys.

We claim: 
     
         1 . A ductile RMPEA alloy having a composition comprising Nb, Ta, V, Ti, and optional Hf in controlled proportions to impart high ductility to the alloy at room temperature. 
     
     
         2 . The alloy of  claim 1  having such high ductility that the alloy is able to sustain >50% cold roll reduction in thickness without fracture. 
     
     
         3 . The alloy of  claim 1  having a minimum room-temperature ductility (total plastic strain)>10%. 
     
     
         4 . The alloy of  claim 3  having a high fracture toughness >30 MPa/m 1/2 . 
     
     
         5 . The alloy of  claim 4  having a room-temperature hardness >3.0 GPa. 
     
     
         6 . The alloy of  claim 5  having a room-temperature uniaxial tensile strength >1.0 GPa. 
     
     
         7 . An alloy having a composition, in atomic percent (%):
 25 to 45% Nb, 0.9 to 45% Ta, 0.9 to 33% V, and 0.9 to 15% Ti.   
     
     
         8 . An alloy having a composition, in atomic percent (%):
 25 to 45% Nb, 0.9 to 45% Ta, 0.9 to 33% V, 0.9 to 15% Ti, and 0.9 to 15% Hf.   
     
     
         9 . An alloy having a composition of 32.5% Nb, 35.1% Ta, 24.3% V, 8.1% Ti, in atomic %, or variants of that composition where the content of one or more of Nb, Ta, V, and/or Ti is/are so varied as to provide a BCC phase microstructure. 
     
     
         10 . An alloy having a composition of 25.1% Nb, 25.3% Ta, 24.6% V, 12.6% Ti, 12.4% Hf, in atomic %, or variants of that composition where the content of one or more of Nb, Ta, V, Ti and/or Hf is/are so varied as to provide a BCC phase microstructure. 
     
     
         11 . A solidified alloy body comprising the alloy of  claim 7 . 
     
     
         12 . The solidified body of  claim 11  which is cast and annealed to provide a single BCC phase microstructure. 
     
     
         13 . A solidified alloy body comprising the alloy of  claim 8 . 
     
     
         14 . The solidified body of  claim 13  which is cast and annealed to provide a single BCC phase microstructure. 
     
     
         15 . A method of casting, comprising providing a melt of an alloy having the composition of  claim 7  and solidifying the melt in a manner to provide a BCC phase microstructure. 
     
     
         16 . A method of casting, comprising providing a melt of an alloy having the composition of  claim 8  and solidifying the melt in a manner to provide a BCC phase microstructure.