CREEP RESISTANT CU-BASED CuCrNbZr ALLOY WITH HIGH THERMAL CONDUCTIVITY

Abstract

A Cu-based alloy according to the present invention comprises 1.0-2.0 wt % Cr, 0.5-1.5 wt % Nb, 0.1-0.5 wt % Zr, and balance Cu. The alloy has a matrix and grain boundaries, and has Cr 2 Nb precipitates within the grain boundaries and at least one selected from the group consisting of CuZr and Cr precipitates in the grain matrix. The CuZr precipitates can be at least one selected from the group consisting of Cu 5 Zr and Cu 51 Zr 14 precipitates. A method of making a CuCrNbZr alloy is also disclosed.

We claim: 
     
         1 . A Cu-based alloy, comprising:
 1.0-2.0 wt % Cr   0.5-1.5 wt % Nb   0.1-0.5 wt % Zr   balance Cu, the alloy having a matrix and grain boundaries, and comprising Cr 2 Nb precipitates within the grain boundaries and at least one selected from the group consisting of CuZr and Cr precipitates in the grain matrix.   
     
     
         2 . The alloy of  claim 1 , wherein the mole fraction, based on the total number of moles in the alloy, of the matrix Cr precipitates is from 0.005 to 0.02. 
     
     
         3 . The alloy of  claim 1 , wherein the mole fraction, based on the total number of moles in the alloy, of the matrix CuZr precipitates is from 0.005 to 0.02. 
     
     
         4 . The alloy of  claim 1 , wherein the CuZr precipitates comprise at least one selected from the group consisting of Cu 5 Zr and Cu 51 Zr 14 . 
     
     
         5 . The alloy of  claim 1 , wherein the mole fraction of Cr 2 Nb based on the total mole composition of the alloy at 500° C. is from 0.01 to 0.04. 
     
     
         6 . The alloy of  claim 1 , wherein the mole fraction of Cr 2 Nb based on the total mole composition of the alloy at 500° C. is from 0.02 to 0.03. 
     
     
         7 . The alloy of  claim 1 , wherein the combined mole fraction of Cr and CuZr precipitates based on the total mole composition of the alloy at 500° C. is from 0.01 to 0.04. 
     
     
         8 . The alloy of  claim 1 , wherein the combined mole fraction of Cr and CuZr precipitates based on the total mole composition of the alloy at 500° C. is from 0.01 to 0.02. 
     
     
         9 . The Cu-based alloy of  claim 1 , wherein the alloy is first solution annealed at from 950 to 980° C., and then aged at from 460 to 490° C. 
     
     
         10 . The alloy of  claim 1 , wherein the alloy consists essentially of Cr, Nb, Zr and Cu. 
     
     
         11 . The alloy of  claim 1 , wherein the alloy consists of Cr, Nb, Zr and Cu. 
     
     
         12 . The alloy of  claim 1 , wherein the alloy comprises impurities, and the impurities are limited to:
 O<0.025 wt %;   N<0.01 wt %;   C<0.01 wt %;   Sn<0.12 wt %; and,   Fe<0.1 wt %.   
     
     
         13 . The alloy of  claim 1 , wherein the Cr 2 Nb grain boundary precipitates are from 2 to 20 μm in diameter, the Cr matrix precipitates are from 1 to 10 nm in diameter, and the CuZr matrix precipitates are from 10 to 50 nm in diameter. 
     
     
         14 . The alloy of  claim 1 , wherein the mole fraction, based on the total number of moles in the alloy, for the Cr 2 Nb precipitates is from 0.01 to 0.04, the mole fraction for the Cr precipitates is from 0.01 to 0.02, and the mole fraction of the CuZr precipitates is from 0.01 to 0.03. 
     
     
         15 . The alloy of  claim 1 , wherein a mole ratio of Cr to Nb is from 2.5 to 4.0. 
     
     
         16 . The alloy of  claim 1 , wherein a mole ratio of Zr to Nb is from 0.2 to 1. 
     
     
         17 . The alloy of  claim 1 , wherein the creep performance as measured by the Larsen-Miller (L-M) parameters is, for an operational stress level of from 90 to 125 Mpa, an L-M parameter of from 17 to 18. 
     
     
         18 . The alloy of  claim 1 , wherein the alloy has an electrical resistivity of from 2.0043×10 −8  to 2.157×10 −8  Ω·m. 
     
     
         19 . The alloy of  claim 1 , wherein the alloy has a thermal conductivity as measured against pure copper according to International Annealed Copper Standard (IACS) at 20° C. of from 70 to 90% IACs. 
     
     
         20 . The alloy of  claim 1 , wherein the alloy has a thermal conductivity of from 4.06×10 7  to 5.22×10 7  S/m. 
     
     
         21 . The alloy of  claim 1 , wherein the alloy has a neutron irradiation resistance such that, when subjected to neutron irradiation at temperature range of from 275 to 325° C. with an irradiation dose of 5 dpa, and compared to the alloy without irradiation there is a change in yield strength of from −20 to 10%. 
     
     
         22 . The alloy of  claim 1 , wherein the alloy has a neutron irradiation resistance such that, when subjected to neutron irradiation at temperature range of from 275 to 325° C. with an irradiation dose of 5 dpa, and compared to the alloy without irradiation there is a change in ultimate tensile strength of from −20 to 10%. 
     
     
         23 . The alloy of  claim 1 , wherein the alloy has a neutron irradiation resistance such that, when subjected to neutron irradiation at temperature range of from 275 to 325° C. with an irradiation dose of 5 dpa, and compared to the alloy without irradiation there is a change in uniform elongation of from −50 and 10%. 
     
     
         24 . The alloy of  claim 1  wherein the alloy has a neutron irradiation resistance such that, when subjected to neutron irradiation at temperature range of from 275 to 325° C. with an irradiation dose of 5 dpa, and compared to the alloy without irradiation there is a change in total elongation of from −50 and 10%. 
     
     
         25 . The alloy of  claim 1 , wherein the alloy has a neutron irradiation resistance such that, when subjected to neutron irradiation at temperature range of from 275 to 325° C. with an irradiation dose of 5 dpa, and compared to the alloy without irradiation there is an increase in electrical resistivity of from 50 and 90%. 
     
     
         26 . The alloy of  claim 1 , wherein the crystal structure of the matrix is face centered cubic. 
     
     
         27 . A method of making a Cu-based alloy, comprising the steps of:
 providing starting materials comprising from 1.0 to 2.0 wt % Cr, from 0.5 to 1.5 wt % Nb, from 0.1 to 0.5 wt % Zr, and balance Cu;   melt-casting the starting materials into ingots;   cold rolling the as-cast ingots to a cold rolled plate with a thickness reduction of from 60 to 80% of the thickness of the plate before cold rolling;   solution annealing the cold-rolled plate at from 950 to 980° C. for from 15 to 30 minutes to form a solution annealed alloy with grain boundaries and Cr 2 Nb precipitates having a diameter of from 2 to 20 μm, wherein the Cr 2 Nb precipitates are within the grain boundaries;   performing a water quench on the solution annealed alloy at a temperature of 20 to 25° C. to form a quenched alloy;   aging the quenched alloy at a temperature of from 460 to 490° C. for from 150 to 210 minutes to form a CuCrNbZr alloy comprising at least one selected from the group consisting of matrix Cr and matrix CuZr precipitates, the Cr matrix precipitates being from 1 to 10 nm in diameter, and the CuZr matrix precipitates being from 10 to 50 nm in diameter.   
     
     
         28 . The method of  claim 27 , wherein the alloy comprises both Cr and CuZr matrix precipitates.