Study On The Microstructure And Properties Of Novel High-strength Aluminum Alloys

High-strength aluminum alloys,due to their low density,high strength,high hardness,good processing and welding performance,are one of the main structural materials in industry.High-entropy alloys(HEAs)take up five or more than five principal elements.Simple crystal structures,FCC and/or BCC solid solution phases instead of complicated intermetallic compounds,tend to form in HEAs during solidification due to the significantly high entropy effect.This makes the microstructure and properties of High-entropy alloys different from the traditional alloys in many aspects,so HEAs have great potential for practical applications.Generally,high-entropy alloys are often composed of Co,Cr,Fe,Ni,Mn and other transition metal elements with high density.From the point of view to reduce the densit,we prepared a series of light-weight HEAs based on the Al-Zn-Mg-Cu high-strength aluminum alloy using Al,Mg,Zn,Cu,Si,Li and Sn in the present work.According to design principles of high entropy alloys,Al-Mg-Zn-Cu-Si-Li and Al-Mg-Zn-Cu-Sn-Li alloys were designed and the alloys ingots were prepared by medium frequency induction furnace.The crystalline structures were characterized by using X-ray diffraction(XRD).The microstructure and chemical compositions were studied by using SEM equipped with EDS.The hardness,wear-resistance,compression and electrochemical properties were tested.The XRD,SEM and EDS show that the eutectic microstructure of AI and CuAl2 occurred in the alloy mesh.In S5 alloy,except CuAl2 matrix,there were Mg2Si phase;With Li,the number of Mg2Si phase decreases greatly,Mg2Si phases and primary Si phases transformed into finer AlLiSi phases.When Si content increased to 15%,the polygon primary silicon is precipited in alloy.With the add it ion of Li,there are finer AlLiSi phase in the matix.The hardness of experimental alloy was much higher than the traditional 6061,7075 as-cast alloys.The Wear-resistance of alloys prepared in the study was better than the as-cast 7075 alloy.The compressive strength of these alloys wre more than 600 MPa.The yield strength of S5L5,S15L5 alloys were 668MPa,593MPa,respectly.The corrosion current of L5 alloy was higher than other alloys,this indicated that the corrosion rate of L5 was lowest when only adding Li elements.In Al-Mg-Zn-Cu-Sn-Li alloys,Sn and Mg combine to generated Mg2Sn phase.The hardness of L5,CS5,CZS5 alloys was higher than 7075,6061 aluminum alloys.The hardness and wear resistance existed proportional relationship.Because the self-lubricating properties of Sn appeared in the process of wear-resisting,the wear-resistance of alloys was greatly improved.The plastic deformation capacity of ZS5 alloy was the best,and its compression strain can reach 20%.CS5,ZS5 and CZS5 alloy had a passivation effect,which slowed down the corrosion rate.These two series new type high strength aluminum alloys all showed good properties and were expected to have a great application potential for materials.