High-entropy austenitic stainless steel and preparation method thereof

Abstract

A high-entropy austenitic stainless steel and a preparation method thereof are provided. The elemental composition of the stainless steels developed by the invention is as follows: Cr: 5-30%; Ni: 5-50%; Ti: 1-15%; Al: 1-15%; the rest are Fe and inevitable impurities; preferably, the composition is Cr: 5-19%; Ni: 5-29%; Ti: 6-15%; Al: 5-15%; the rest element is Fe. By adjusting the atomic ratio of each element, the nano-sized precipitates are generated as much as possible, and the strength is maximized while maintaining a high plasticity. The stainless steels provided by this invention have only five alloying components, a low manufacturing cost, and high-strength and high-plasticity. They can be widely used in many industrial fields such as aviation, aerospace, marine, and nuclear power with broad market prospects.

1 . A high-entropy austenitic stainless steel, comprising an elemental composition expressed with an atomic percentage content as follows:
 5-30% of Cr; 5-50% of Ni; 1-15% of Ti; 1-15% of Al; and a balance of Fe.   
     
     
         2 . The high-entropy austenitic stainless steel according to  claim 1 , wherein the elemental composition expressed with the atomic percentage content is as follows:
 5-19% of the Cr; 5-29% of the Ni; 6-15% of the Ti; 5-15% of the Al; and the balance of the Fe.   
     
     
         3 . The high-entropy austenitic stainless steel according to  claim 1 , wherein a size of each of nano-sized precipitates in the high-entropy austenitic stainless steel is ≤30 nm, and a number density of each of the nano-sized precipitates is ≥5.0×10 21  m −3 . 
     
     
         4 . A preparation method for a high-entropy austenitic stainless steel, comprising steps of: mixing raw materials according to atomic percentage content to obtain a resulting mixture; melting and casting the resulting mixture in a vacuum argon arc furnace to obtain an ingot; performing solution/homogenization treatment on the ingot to obtain a first resulting product; performing a first process by cold rolling and recrystallizing the first resulting product to obtain a second resulting product or performing a second process by hot rolling, cold rolling, and recrystallizing the first resulting product to obtain a second resulting product; carrying out an aging treatment on the second resulting product to obtain the high-entropy austenitic stainless steel. 
     
     
         5 . The preparation method according to  claim 4 , wherein the cold rolling in the first process is as follows: a reduction in thickness per pass is no more than 0.2 mm, and a total reduction in thickness is 60%-70%. 
     
     
         6 . The preparation method according to  claim 4 , wherein the hot rolling and the cold rolling in the second process is as follows: carrying out the hot rolling at a temperature of 800-1150° C., wherein a reduction in thickness per pass of the hot rolling is no more than 0.5 mm, and the temperature is guaranteed to be within a range of 800-1150° C. during the hot rolling; when the temperature decreases during the hot rolling, the first resulting product is put back into a furnace and remained within the range of 800-1150° C. for 5-15 min; after a total reduction in thickness during the hot rolling is 50%-60%, carrying out the cold rolling, wherein a reduction in thickness per pass during the cold rolling is no more than 0.2 mm, and a total reduction in thickness is 60%-70%. 
     
     
         7 . The preparation method according to  claim 4 , wherein an operation of the recrystallizing is as follows: remaining the first resulting product rolled by the first process or the second process at 1140-1160° C. for 1-3 min;
 a heating rate of the recrystallizing is 10-20° C./min. 
 
     
     
         8 . The preparation method according to  claim 4 , wherein vacuuming the vacuum argon arc furnace to a pressure better than 5.0×10 −3  Pa to obtain a first resulting furnace and then filling argon into the first resulting furnace to a pressure of 5.0×10 3  Pa to obtain a second resulting furnace, removing oxygen with pure Ti in the second resulting furnace, starting the melting when an oxygen content and a nitrogen content in the second resulting furnace are lower than 0.002% within 180 min;
 the melting is repeated at least four times. 
 
     
     
         9 . The preparation method according to  claim 4 , wherein an operation of the solution/homogenization treatment is as follows: heating the ingot to 1140-1160° C. under a vacuum with a pressure better than 1.0×10 −3  Pa to obtain a heated ingot, remaining the heated ingot at 1140-1160° C. for 1-2.5 h, and then quenching the heated ingot in water or cooling the heated ingot in air to obtain the first resulting product;
 a heating rate of the solution/homogenization treatment is 10-20° C./min. 
 
     
     
         10 . The preparation method according to  claim 4 , wherein an operation of the aging treatment is as follows: ageing the second resulting product at 500-600° C. for 0.5-1.5 h to obtain a third resulting product and then quenching the third resulting product in water or cooling the third resulting product in air to obtain the high-entropy austenitic stainless steel;
 a heating rate of the aging treatment is 5-15° C./min.