High entropy alloy structure and a method of preparing the same

Abstract

A method for preparing a high entropy alloy (HEA) structure includes the steps of: preparing an alloy by arc melting raw materials comprising five or more elements; drop casting the melted alloy into a cooled mold to form a bulk alloy; applying an external force against the bulk alloy to reshape the bulk alloy; and heat-treating the reshaped bulk alloy, wherein the bulk alloy is reshaped and/or heat-treated for manipulating the distribution of the microstructure therein. The present invention also relates to a high entropy alloy structure prepared by the method.

1 . A method of preparing a high entropy alloy structure comprising the steps of:
 A. preparing an alloy by arc melting raw materials comprising five or more elements;   B. drop casting the melted alloy into a cooled mold to form a bulk alloy;   C. applying an external force against the bulk alloy to reshape the bulk alloy; and   D. heat-treating the reshaped bulk alloy;   wherein the bulk alloy is reshaped and/or heat-treated for manipulating the distribution of the microstructure therein.   
     
     
         2 . The method according to  claim 1 , wherein step C includes step C 1  of rolling the bulk alloy along a first direction to reduce the thickness of the bulk alloy. 
     
     
         3 . The method according to  claim 2 , wherein step C 1  of rolling is carried out along a longitudinal direction of the bulk alloy. 
     
     
         4 . The method according to  claim 2 , wherein the thickness of the rolled bulk alloy is reduced by 70%. 
     
     
         5 . The method according to  claim 1 , wherein formed bulk alloy includes a homogenous structure within which the microstructures are uniformly dispersed. 
     
     
         6 . The method according to  claim 1 , wherein heat-treated bulk alloy includes a heterogeneous structure within which the microstructures are non-uniformly dispersed. 
     
     
         7 . The method according to  claim 1 , wherein the crystals in the microstructure are deformed during the heat treatment in step D to form a plurality of twins. 
     
     
         8 . The method according to  claim 1 , wherein step D includes step D 1  of heating the bulk alloy to facilitate the movement of the microstructures. 
     
     
         9 . The method according to  claim 8 , wherein step D includes step D 2 , after step D 1 , of water quenching the heat-treated alloy. 
     
     
         10 . The method according to  claim 1 , wherein each of the elements is provided in an atomic percentage of 10% to 30%. 
     
     
         11 . The method according to  claim 1 , wherein the elements are Cobalt, Nickel, Chromium, Iron and Aluminum. 
     
     
         12 . The method according to  claim 11 , wherein Cobalt, Nickel, Chromium, Iron and Aluminum are provided in an atomic ratio of 30:30:20-0.5x:20-0.5x:x, with X being an integer of 14 to 20. 
     
     
         13 . The method according to  claim 1 , wherein the raw materials have a high purity of >99.90%. 
     
     
         14 . The method according to  claim 1 , wherein step A includes step A 1  of flipping and re-melting the raw materials in a repetitive manner. 
     
     
         15 . The method according to  claim 1 , wherein the mold is made of copper. 
     
     
         16 . The method according to  claim 1 , wherein the alloy is arc melted within a Ti-gettered argon atmosphere with a pressure below 8×10 −4  Pa. 
     
     
         17 . The method according to  claim 8 , wherein the rolled bulk alloy is annealed at a temperature of at least 800° C. for 6 hours. 
     
     
         18 . A high entropy alloy structure prepared by the method according to  claim 1 . 
     
     
         19 . The high entropy alloy structure according to  claim 18 , wherein the alloy structure includes lamellar structures. 
     
     
         20 . The high entropy alloy structure according to  claim 19 , wherein the size of the lamellar structures is provided in submicron range. 
     
     
         21 . The high entropy alloy structure according to  claim 18 , wherein the alloy structure possesses a hardness of 330 to 404 HV. 
     
     
         22 . The high entropy alloy structure according to  claim 18 , wherein the yield stress of the alloy structure is around 850 to 1000 MPa. 
     
     
         23 . The high entropy alloy structure according to  claim 18 , wherein the Young's modulus of the alloy structure is around 230 GPa. 
     
     
         24 . The high entropy alloy structure according to  claim 18 , wherein the alloy structure is thermal stable up to a predetermined temperature of 900° C. 
     
     
         25 . The high entropy alloy structure according to  claim 18 , wherein the structure is a dual phase eutectic structure. 
     
     
         26 . The high entropy alloy structure according to  claim 25 , wherein the dual phase includes ordered face center cubic (FCC) phase and body center cubic (BCC) phase.