Study On Microstructures And Properties Of AlCrCuFeNiTi_x High-Etropy Alloys

High-entropy alloy,unlike traditional alloy,is a kind of alloy in which multiple metal elements are mixed in equimolar or near-equimolar proportions.Studies have shown that a variety of principal elements tend to be disorderly arranged to form a simple crystalline phase,meanwhile,nanocrystalline and amorphous phases often appear in the structure too.In generalm,high-entropy alloys have excellent properties such as high strength,high ductility,high wear resistance.In this paper,AlCrCuFeNiTi_x?x=0,0.5,1.0,1.5?high-entropy alloys were prepared by vacuum arc melting then subjected to three different conditions?600?/12h,800?/12h,1000?/12h?for heat treatment.The microstructures and properties of the alloys were studied.Characteristics of change in compressive properties,hardness,and wear resistance.The results are as follows:AlCrCuFeNi and AlCrCuFeNiTi_0.5 high-entropy alloys consist of simple body centered?BCC?,face centered?FCC?and NiAlintermetallic compound phases;AlCrCuFeNiTi alloy is composed of FCC,BCC,Laves and NiAl intermetallic compound phases,and chrysanthemum-like eutectic micro structure appears in the alloy.AlCrCuFeNiTi_1.5 alloy consists of FCC,BCC,NiAl and Ni3Ti type intermetallic compound phases.AlCrCuFeNi alloy has the highest strength and strain,which are 1624 MPa and 21%,whereas the strength and strain of AlCrCuFeNiTi_1.5 alloy are the lowest,which are 679 MPa and 8%,respectively.With the increase of Ti content,the hardness of AlCrCuFeNiTi_x high-entropy alloys increased,the wear rate decreased.When the AlCrCuFeNi high entropy alloy was heat-treated at 600? for 12 hours,the phase composition did not change with respec to the as-cast state,but the morphology changed greatly.After heat treatment,the plasticity of the alloys was improved,but the strength was decreased.The best plasticity after treatment at 800? is 28%,the lowest after treatment at 600 ? is 1420 MPa.The hardness and wear resistance of the alloys after heat treatment are all lower than those of as-cast state.For AlCrCuFeNiTi_0.5 high-entropy alloy,the phase composition did not change after heat treatment under different conditions.When the heat treatment temperature rose to 1000?,spherical particles were formed in the dendritic matrix,and some stripe-like structures appeared in the inter-dendrites.After heat treatment at 800?,the strength and strain of the alloy reach the highest value of 1525MPa and 21%respectively.The hardness and wear resistance of the alloy reached the best and worst after treatment at 600 ? and 1000?,respectively.The phase composition of AlCrCuFeNiTi high-entropy alloy remains unchanged after heat treated.When heating at 600? for 12 hours,the compressive property,hardness and wear resistance of AlCrCuFeNiTi high-entropy alloy are the best.The strength,strain and hardness values are 1536MPa,15%and 532HV,respectively.With the increase of heat treatment temperature,the strength,ductility,hardness and wear resistance of the alloy decreased.After heat treatment,the phase composition of the AlCrCuFeNiTi 1.5 high-entropy alloy changed to FCC,Laves phase and NiAl intermetallic compound.The morphology of the alloy changed greatly too.After heat treatment,though the strength and plasticity of AlCrCuFeNiTi_1.5 high-entropy alloy deteriorated obviously,the hardness and wear resistance were both higher than that of the as-cast state.