Precipitate strengthened nanostructured ferritic alloy and method of forming

Abstract

An alloy and method of forming the alloy are provided. The alloy includes a matrix phase, and a population of particulate phases dispersed within the matrix. The matrix includes iron and chromium; and the population includes a first subpopulation of particulate phases and a second subpopulation of particulate phases. The first subpopulation of particulate phases include a complex oxide, having a median size less than about 20 mu, and present in the alloy in a concentration from about 0. 1 volume percent to about 5 volume percent. The second subpopulation of particulate phases have a median size in a range from about 30 nm to about 10 microns, and present in the alloy in a concentration from about 1 volume percent to about 15 volume percent.

1 .- 20 . (canceled) 
     
     
         21 . A method of forming an alloy, comprising:
 melting starting materials comprising iron and chromium;   atomizing the melt to form an alloy powder;   milling the alloy powder in the presence of an oxide until the oxide is dissolved into the alloy powder, thus forming a milled alloy powder;   consolidating the milled alloy powder at a first temperature;   precipitating a first subpopulation of particulate phases comprising a complex oxide having a median size less than about 20 nm; and   establishing a second subpopulation of particulate phases having a median size in a range from about 30 nm to about 10 microns.   
     
     
         22 . The method of  claim 21 , wherein a concentration of the first subpopulation of particulate phases is in a range from about 0.1 volume percent to about 5 volume percent of the alloy. 
     
     
         23 . The method of  claim 21 , wherein a concentration of the second subpopulation of particulate phases is in a range from about 1 volume percent to about 15 volume percent of the alloy. 
     
     
         24 . The method of  claim 21 , wherein the precipitated particulate phases of the first subpopulation comprise at least two elements of the following group: yttrium, titanium, aluminum, zirconium, hafnium, and magnesium. 
     
     
         25 . The method of  claim 21 , wherein establishing the second subpopulation comprises an in-situ precipitation in the consolidated, milled alloy powder. 
     
     
         26 . The method of  claim 25 , wherein the particulate phases of the second subpopulation comprise a Laves phase. 
     
     
         27 . The method of  claim 25 , wherein the particulate phases of the second subpopulation comprise a mu phase. 
     
     
         28 . The method of  claim 25 , wherein the particulate phases of the second subpopulation comprise a carbide, nitride, or carbonitride phase. 
     
     
         29 . The method of  claim 25 , wherein the particulate phases of the second subpopulation comprise an intermetallic phase having a Ni 3 M structure, wherein M comprises titanium, aluminum, molybdenum, niobium, tantalum, or any combination of the foregoing. 
     
     
         30 . The method of  claim 21 , wherein establishing the second subpopulation comprises an in-situ precipitation by heat-treating the consolidated, milled alloy powder at a second temperature. 
     
     
         31 . The method of  claim 30 , wherein the consolidated, milled alloy powder is hot-worked before in-situ precipitation of the second subpopulation by heat-treating. 
     
     
         32 . The method of  claim 30 , wherein the second temperature is in a range from about 550° C. to about 850° C. 
     
     
         33 . The method of  claim 21 , wherein establishing the second subpopulation comprises mechanically mixing the milled alloy powder with an added particulate phase. 
     
     
         34 . The method of  claim 33 , wherein the added particulate phase comprises an oxide, boride, or a combination of oxide and boride. 
     
     
         35 . The method of  claim 21 , wherein establishing the second subpopulation comprises a combination of in-situ precipitating of the consolidated, milled alloy powder; and
 mechanically mixing an added particulate phase to the milled alloy powder.   
     
     
         36 . The method of  claim 21 , wherein establishing the starting materials comprises a vacuum induction melting process. 
     
     
         37 . A method of forming an alloy, comprising:
 melting starting materials comprising iron and chromium through a vacuum induction melting process;   atomizing the melt to form an alloy powder;   milling the alloy powder in the presence of an oxide until the oxide is dissolved into the alloy powder, thus forming a milled alloy powder;   consolidating the milled alloy powder at a first temperature precipitating a first subpopulation of particulate phases comprising a complex oxide comprising yttrium and titanium, having a median size less than about 20 nm, in a concentration from about 0. 1 volume percent to about 3 volume percent of the alloy;   hot-working the consolidated, milled alloy powder; and   heat-treating the hot-worked, consolidated, milled alloy powder at a second temperature and establishing a second subpopulation of particulate phases by an in-situ precipitation of a Laves phase having a median size in a range from about 30 nm to about 10 microns, in a concentration from about 1 volume percent to about 4 volume percent of the alloy.   
     
     
         38 . A method of forming an alloy, comprising:
 melting starting materials comprising iron and chromium through a vacuum induction melting process;   atomizing the melt to form an alloy powder;   milling the alloy powder in the presence of an oxide until the oxide is dissolved into the alloy powder, thus forming a milled alloy powder;   adding a particulate phase comprising an oxide, boride, or a combination of an oxide and boride to the milled alloy powder, and mixing;   consolidating the milled and mixed alloy powder at a first temperature precipitating a first subpopulation of particulate phases comprising a complex oxide comprising yttrium and titanium, having a median size less than about 20 nm, in a concentration from about 0.1 volume percent to about 3 volume percent of the alloy; and   establishing a second subpopulation of particulate phases resulting from the added particulate phase in the consolidated, milled, and mixed alloy powder, wherein the second subpopulation has a median size in a range from about 30 nm to about 10 microns, and present in the alloy in a concentration from about 1 volume percent to about 4 volume percent.