The Research Of Lightweight High-Entropy Alloys

High-entropy alloys are a new class of alloys which attract a lot of attention in the fieldof research in resent years. Generally, high-entropy alloys are often composed of Co, Cr, Fe,Ni, Mn and other transition metal elements with high density. We prepared lightweighthigh-entropy alloys with high strength using Al, Mg, Ti, Ca, Li, etc. lightweight metalelements in the present work.Based on the existing solid solution formation criterion of high-entropy alloys, weprepared8kinds of alloys by vacuum metallurgy and cast them using a steel mold with itsdiameter of20mm and a copper mold with its diameter of5mm respectively to get sampleswith different cooling rates. XRD, SEM and EDS were used to analyze the phase compositionand the micro-structure of the alloys. Compressive mechanical properties of samples werecarried on materials testing machine. The densities of the alloys which were used to calculatethe specific strength of the alloys were measured by Archimedes’ method. And chemicalcomposition of the alloys were analyzed to verify the accuracy of the component designtheory.The results show that for Al-Mg-Zn-Sn-Cu based alloys, Mg and Sn are combined intoMg2Sn firstly. Then, the excess Sn enriched in intergranular. Al, Cu and Zn will formAl4.2Cu3.2Zn0.7if the content of them are almost same, or else, they will generate some morestable inter-metallic compounds such as CuAl2like. High-entropy effect gives the alloys goodmechanical properties. Among them, Al7MgSnCu4.6Zn6.4alloy exhibited a higher strengthwhich was2.245×105(N/m2)/(kg/m3) and a greater hardness which was shown as270.75HVin the rapid cooling samples.For Al-Mg-Zn-Sn-Cu-Ti based alloys, Mg and Ti will not coexist in the same phase.Al7Mg3.6Cu1.2Zn7Ti1.2alloy is composed of a kind of HCP phase and two kinds of FCC phase.The alloy exhibited a high specific strength which reached1.491×105(N/m2)/(kg/m3) with itsdensity was only3.84g/cm3. The alloy also showed a great hardness which was434.3HV inthe slowly cooling sample. As the main components ofAl-Mg-Ca-Li-M based alloys are light weight metal elements,the densities of the alloys are low. Densities of AlMgCa0.5LiCu alloy and AlMgCa0.5LiZnalloy are2.63g/cm3and2.65g/cm3respectively, which are close to the densities of Al alloys.AlMgCa0.5LiCu showed a very high specific strength which was1.15×105(N/m2)/(kg/m3).Through the above analysis, we found that when we design the composition of a newkind of high-entropy alloy, we should not only consider the mixing enthalpy of the alloys, butalso take the mixing enthalpy between the various components and the atomic radius intoaccount to avoid excessive generation of inter-metallic compounds or a large number ofcomponent segregation.