Preparation Of Micro/nano Structure 2507 Duplex Stainless Steel And Regulation Of Mechanical Properties By Rolling

In this paper,based on the preparation of a small amount of nano/microcrystalline 2507 duplex stainless steel by the aluminothermic reaction method,the large size bulk micronanostructure 2507 duplex stainless steel was prepared by using a large furnace.The sample after the 1000? cogging was rolled with 30%,50% and 70% deformation at 600 and 800?,respectively.And then the effect of the rolling temperature and deformation on the mechanical properties was investigated.The XRD,SEM and EPMA were used to explore the optimum rolling process of nano/microcrystalline 2507 duplex stainless steel.1.The Cr element lost during the nano/microcrystalline 2507 duplex stainless steel prepared by a large furnace.This is mainly due to the high temperature of the reaction causing the Cr element to evaporate and deposit on the furnace wall.The 70% excess of Cr added in the reaction mass to offset the amount of evaporation,and the nano/microcrystalline 2507 duplex stainless steel that meets the composition and organization requirements can be obtained.The ratio of austenite to ferrite is basically 1:1,the volume fraction of nanocrystalline austenite is 41%,and the average grain size is 34 nm.2.At 1000? rolling with different deformations,the stainless steel consisted of austenite and ferrite the and the ratio of them is 1:1.After the 1000? rolling,the pores in the as-cast alloy have almost disappeared,the elements of the alloy are evenly distributed,and a small amount of carbide precipitated.The tensile strengths of the samples after rolling with 40,60,and 80% deformation were 533,577,and 582 MPa,respectively,and the elongations were 12.5,11.1,and 11.5%,respectively.Fracture analysis shows that the material is a mixture of ductile and brittle fractures.With the increase of deformation,the proportion of brittle fracture gradually increases.3.After rolling with 30%,50% and 70% at 800?,the strength,hardness and elongation increased first and then decreased.The fracture mainly consists of tough-brittle hybrid fractures,and the mechanical properties of the material after rolling with 50% rolling deformation are the best.The ? precipitated phase appeared after the rolling with 50% rolling deformation.After rolling at 600?,the strength,hardness and elongation of the material increase with the increase of the deformation amount,and the mechanical properties of the material after 70% rolling deformation are the best.4.When rolling at 600? with different deformation amounts,the longer the material stays at high temperatures as the amount of deformation increases,the more nanocrystals grow into submicron and micron crystals,and the grain size increases.According to the anti-Hall-Petch relationship,the larger the grain size,the higher the strength of the material.In addition,with the increase of rolling deformation,austenite and ferrite are elongated in the rolling direction,which also improves the mechanical properties in the rolling direction.5.When rolling at 50% deformation,as the rolling temperature decreases,the strength of the material decreases.When rolled at 600?,the crushing speed of the crystal grains is faster than that of the grain growth,so that the size of the nanocrystals decreases,and the strength decreases according to the anti-Hall-Petch relation.