The Microstructure,Oxidation Resistance And Electrochemical Properties Of Fecocrnimn(Al_0.3)High Entropy Alloys

Muti-principle element alloy named high entropy alloy?HEA?broke the design concept of the alloy with single element as the main element,which provides a broad development space for the development and application of new alloy.Recently,it has been widely absorbed in FeCoCrNiMn HEA with single FCC phase possessing excellent comprehensive mechanical properties,good abrasion resistance,oxidation resistance and corrosion resistance.In present work,0.3 mol Al element was added into a typical FeCoCrNiMn high entropy alloy?Al₀ HEA?system,which is Al_0.3FeCoCrNiMn high entropy slloy(Al_0.3 HEA),and severe cold rolling and subsequently annealing at different temperatures were conducted to obtain the ultra-fine grain high entropy alloy.The evolution rules,high temperature oxidation and electrochemical corrosion behavior of two high entropy alloys in different processing conditions were systematically studiedThe results show that,the addition of Al element with light weight made the microhardness and strength increased.After the severe cold rolling process,the microstructures of HEAs were refined significantly.And the grain size of Al₀ HEA is from 140?m at solution-treated state?STed state?to 130 nm at cold rolled state?CRed state?,and Al_0.3 HEA is from 164?m at STed state to 125 nm at CRed state.After annealing at 600,800 and 1000?for 1 h?annealing state?,the grain size of Al₀ HEA was 248 nm?4.57?m?22.37?m respectively.Compared with Al₀ HEA,the grain size of Al_0.3 HEA was refined more sevely after the deformation and annealing.The grain size of Al_0.3 HEA was smaller than 500 nm after annealing at 800?for 1 h,andbecame 4.56?m at 1000?.What's more,Al₀ HEA was single FCC phase at different states,and Al_0.3 HEA with BCC phase?rich in Al,Ni?and?phase?rich in Fe,Cr?at 600 and 800?,which inhibited the growth of recrystallized grains.It has been investigated the effects of Al addition on the high temperature oxidation resistance of FeCoCrNiMn high entropy alloy.The results show that the oxidation resistance of solution-treated Al_0.3 HEA was better than solution-treated Al₀ HEA at 800 and 1000?,but for 600?,Al₀HEA was the better one.Many oxide particles with Al element occurred possessing 5?m in diameter beneath Cr₂O₃ oxide layer while Al_0.3 HEA were treated at 1000?for 100 h.These oxide particles improved the oxidation resistance of Al_0.3 HEA by thickening the Cr₂O₃ oxide layer and inhibiting the the combination of internal metal with O element.The electrochemical properties of Al₀ and Al_0.3.3 HEAs in different processing conditions were studied.The addition of Al leads to the formation of precipitations and forms porous passive film on the surface of substract.Hence,the corrosion property of HEA was weakened by Al element and the corrosion resistance of Al₀ HEA was better.The dislocation cells and sub-boundaries introduced by severe cold rolling process interrupted the continuous distribution of the poor chromium and improved the corrosion resistance of the system.What's more,the corrosion resistance of Al₀ HEA in 0.5 M H₂SO₄+x NaCl?x=0,0.25?solution decreased with the increasing of the grain size.Finally,the formation of?and BCC phase in Al_0.3.3 HEA system weakened the corrosion resistance of the matrix.