Plastic cocrni-based medium-entropy alloy with 2.0 gpa-level ultra-high yield strength and preparation method thereof

Abstract

The present disclosure belongs to the field of preparation of high-performance alloy materials, and specifically relates to a plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength and a preparation method thereof. The alloy is prepared by melting and casting, homogenization treatment, solution heat treatment, cold deformation and aging heat treatment. After cold deformation and aging heat treatment, the prepared alloy has a dual heterogeneous microstructure due to the discontinuous precipitation of the strengthening phase and the incomplete recrystallization composition. The CoCrNi-based medium-entropy alloy of the present disclosure has ultra-high yield strength (2.0 GPa) and sufficient safety in use (uniform elongation of more than 8%), which can be processed into various forms of products, and has a wide range of applications in the production of fasteners used in the fields of aerospace, navigation, oil and gas, food processing, springs, non-magnetic components, and instrument parts.

1 . A plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength, wherein comprising the following components in atomic percentage: Cr: 14-25%, Ni: 25-35%, Al: 4-7%, Ti: 4-7%, Mo: 0-5%, and the balance is Co. 
     
     
         2 . The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 1 , wherein comprising the following components in atomic percentage: Cr: 17-22%, Ni: 28-30%, Al: 5-6%, Ti: 5-6%, Mo: 0-2%, and the balance is Co. 
     
     
         3 . The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength of  claim 1  with a composition selected from (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.995 Mo 0.5  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6  (at. %), (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.985 Mo 1.5  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6 ) 0.995 Mo 0.5  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6 ) 0.99 Mo 1  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6 ) 0.985 Mo 1.5  (at. %), (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.99 Mo 1  (at. %), (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.98 Mo 2  (at. %) and (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.98 Mo 2  (at. %). 
     
     
         4 . The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength of  claim 1  having a uniform elongation of more than 8%. 
     
     
         5 . The plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength of  claim 1  formed into a fastener. 
     
     
         6 . A method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 1 , comprising the following steps:
 (1) Preparing an alloy according to the atomic percentage of  claim 1  and melting into an ingot;   (2) Homogenizing the ingot to form a homogenized casting;   (3) Performing solution heat treatment on the homogenized casting to obtain an alloy casting with FCC single phase;   (4) Performing cold deformation with a deformation of 70-90% on the casting after solution heat treatment;   (5) Performing aging heat treatment on the cold deformed material to obtain the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength.   
     
     
         7 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 6 , wherein in step (2), the homogenization treatment is performing heat preservation at 1000-1200° C. for 12-24 h, after the completion of the heat preservation, quenching to room temperature. 
     
     
         8 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 6 , wherein in step (3), the solution heat treatment is performing heat preservation at 1150-1200° C. for 2-8 h, after the completion of the heat preservation, quenching to room temperature. 
     
     
         9 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 6 , wherein in step (4), the cold deformation is cold rolling, or rotary swaging and/or drawing at room temperature. 
     
     
         10 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 6 , wherein the temperature of the aging heat treatment is 600-800° C., and the time is 4-28 h. 
     
     
         11 . A method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength, comprising the following steps:
 (1) Preparing an alloy according to the atomic percentage of  claim 1  and melting into an ingot;   (2) Homogenizing the ingot to form a homogenized casting;   (3) Performing solution heat treatment on the homogenized casting to obtain an alloy casting with FCC single phase;   (4) Performing cold deformation with a deformation of 70-90% on the casting after solution heat treatment;   (5) Performing aging heat treatment on the cold deformed material to obtain the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength.   
     
     
         12 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein in step (2), the homogenization treatment is performing heat preservation at 1000-1200° C. for 12-24 h, after the completion of the heat preservation, quenching to room temperature. 
     
     
         13 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein in step (3), the solution heat treatment is performing heat preservation at 1150-1200° C. for 2-8 h, after the completion of the heat preservation, quenching to room temperature. 
     
     
         14 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein in step (4), the cold deformation is cold rolling, or rotary swaging and/or drawing at room temperature. 
     
     
         15 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein the temperature of the aging heat treatment is 600-800° C., and the time is 4-28 h. 
     
     
         16 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein the deformation is 80%. 
     
     
         17 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein the alloy has a composition of (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.995 Mo 0.5  (at. %) and wherein the ingot was homogenized at 1200° C. for 12 h, the homogenized casting was subjected to solution heat treatment at 1200° C. for 12 h and quenched at room temperature, and the cold-deformed part was subjected to aging heat treatment at 650 C for 24 h. 
     
     
         18 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11 , wherein the alloy has a composition selected from (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.995 Mo 0.5  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6  (at. %), (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.985 Mo 1.5  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6 ) 0.995 Mo 0.5  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6 ) 0.99 Mo 1  (at. %), (Co 43 Ni 30 Cr 15 Al 6 Ti 6 ) 0.985 Mo 1.5  (at. %), (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.99 Mo 1  (at. %), (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.98 Mo 2  (at. %) and (Co 40 Ni 30 Cr 20 Al 5 Ti 5 ) 0.98 Mo 2  (at. %). 
     
     
         19 . The method for preparing the plastic CoCrNi-based medium-entropy alloy with 2.0 GPa-level ultra-high yield strength according to  claim 11  further comprising forming a fastener from said plastic CoCrNi-based medium-entropy alloy.