Effects Of Trace Zr Elements And Homogenization Annealing On The Microstructure And Properties Of 5052 Aluminum Alloy

Al-Mg alloy is a sort of widely used antirust deformation aluminum alloy in areas of national defense and military industry,traffic construction,aerospace,electronic machinery,sealing packaging and other fields because of high strength,high plasticity,corrosion resistance,fatigue resistance,easy processing,easy welding,recyclability etc.It is one of the most widely used and the largest amount of lightweight alloy materials currently.With the rapid development of new industrialization in our country,the demand for Al-Mg alloy is increasing day by day,and more and higher performance requirements are put forward at the same time.Microalloying is a research hotpot in recent years owing to its effectiveness of promoting the microstructure and comprehensive properties of Al-Mg alloy.5052 is one of the most typical and widely used aluminum alloy grades in Al-Mg alloy.However,the weakness of cracking easily in the actual processing process-especially the rolling deformation of ingot with large width thickness ratio leads to the cutting amounts increasing and sheet yield decreasing,which severely limits the application scope of 5052 aluminum alloy.Researchers in the field are trying their best to explore the means to improve the edge strength and reduce cracking tendency of5052 aluminum alloy ingot with large width thickness ratio.In this paper,the self-designed 5052 aluminum alloy ingot with large width thickness ratio was used as the research object.With the help of universal mechanical testing machine,optical metallographic microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS)and other experimental equipment and characterization means,the effects of different Zr content modification and homogenization annealing temperature on 5052 aluminum alloy ingot with large width thickness ratio were studied in order to provide some reference for the industrial modification and application of 5052 aluminum alloy thick plate.The results are as follows:(1)The addition of Zr to 5052 alloy can improve the second phase,grain structure and mechanical properties.The microstructure of as cast 5052 alloy without Zr addition is mainly composed of?-Al and acicular and skeletal second phases(mainly Al₃Fe,Al₆Fe,Mg₂Si phase,Al₆(Fe Mn))with the size of about 50?m;the grains are nearly equiaxed with the size distribution of about 220?m;the tensile strength is 197MPa,the yield strength is 100MPa,and the elongation is 22.2%.With the increase of Zr content,the network second phase gradually decreases and refines.When the Zr content exceeds0.15%,some second phases coarsen;when the Zr content is 0.47%,rod like Al₃Zr is observed.XRD results show that except the second phase mentioned above,5052 with Zr addition has Al₃Zr phase.The grain size coarsens first with the increase of Zr content,and gradually refines when Zr content exceeds 0.15%.When the content Zr is 0.47%,the tensile strength,yield strength and elongation are 203MPa,107MPa and 23.2%,respectively,which are higher than those without Zr.The effect of Zr on the microstructure and mechanical properties of as cast 5052 alloy is related to its content and existing form.(2)Homogenization annealing can improve the microstructure of 5052+0.47%Zr alloy.After homogenization annealing at different temperatures,the grains and the second phase are significantly refined.With the increase of homogenization temperature,the second phase breaks down gradually,and dissolution and spheroidization finally occurs.Homogenization annealing at 500?has the best effect on refinement of grain and second phase,the average grain size is about 75?m,and the second phase size is less than 50?m.when the homogenization temperature is higher or lower than 500?,the grain and the second phase coarsen relatively,but the microstructure is still refined compared with that of as cast 5052+0.47%Zr alloy.With the increase of homogenization temperature,the strength decreases,the elongation first decreases and then increases.When homogenization temperature is 400?,tensile strength is 180 MPa,yield strength is 91MPa and elongation is 17.1%.