Effects Of Homogenization Heat Treatment And Microalloying On Microstructure And Hardness Of Secondary Aluminum Alloys Containing Iron

The presence of impurity iron will do great harm to the performance of t he secondary aluminum alloy,and it is difficult to remove the impurity iron p hase in the secondary aluminum alloy,which greatly reduces the quality of the aluminum alloy products and limits the recycling utilization of the secondary al uminum alloy.It is found that the modification of coarse acicular iron phase ca n reduce the harm of iron impurities.Based on secondary aluminum alloy as th eresearch object,an iron impurity for iron-rich phase practical problems of thes urface defects of the extruded aluminium profile,observed by optical microsco py(OM),scanning electron microscope(SEM),backscattered electron(BSE)mi croscope,energy spectrometer(EDS),X-ray diffraction(XRD),transmission ele ctron microscopy(TEM),microhardness meter characterization methods,such as the aluminum surface defect causes,follow-up and adding trace alloy modified by the homogenization process industrialsecondary aluminum alloy iron rich ph ase morphology and the impact on the material surface hardness,in order tosol ve the problem of extruded aluminum surface defects.Specific studies are as follows:1.The main components of the granular burr defect on the surface of extr uded aluminum profile were Al,Fe,Si and Mg elements,and the phase comp osition was iron phase(Al₈Fe Mg₃Si₆);There are two reasons for granular burr d efects on the surface of extruded aluminum profiles caused by acicular phase(Al₈Fe Mg₃Si₆):(1)the presence of acicular phase(Al₈Fe Mg₃Si₆)splits the matri x,reducing the alloy's shaping and machinability.(2)The intermiscibility of thea cciform iron phase(Al₈Fe Mg₃Si₆)is poor in compatibility with the?-Al matrix and is easily separated from the matrix.The iron phase crusher and adhere to the inlet end when passing through the working zone of the mold,andas the e xtruded aluminum profiles continue to be extruded,the crushed iron phase crus her and adhere to the surface of the profiles causing a"granular burr"defect.2.When the homogenization temperature is lower than 580?,part of the s econd phase is dissolved in the matrix,with smaller size and spheroidizing stat e;After homogenized treatment at 600?for 1h,obvious Ostwald ripening phen omenon occurred in the second phase,which presented large size blocks with high melting point and was difficult to dissolve in the matrix.After 1h of unifo rm insulation at 580?,the corresponding dendrite structure disappeared and pr esented the characteristics of equiaxed grain structure.After 1h of uniform insu lation at 600?,equiaxed grain became enlarged and overfired.The hardnessofs econdary aluminum alloy ingot increases with the increase of homogenizationte mperature.Under the condition that no alloying elements are added,the second ary aluminum alloy ingot can obtain better microstructure by taking 580?unif orm heat preservation for 1h.3.When 0.5%Al-5TI-B refiner was added,the grain refinement structure of the regenerated al-Al matrix was obvious;The microstructure of refined grain affected the distribution of iron phase,and the hardness of corresponding alloyi ncreased to 50HV.The addition of Mn element can change the morphology of acicular iron into meshed shape.After the addition of Sn element,Mg₂Sn phase was formed by combining with Mg element.Mg₂Sn phase and iron(Al₈Fe Mg₃Si₆)grew together,which hindered the growth of iron(Al₈Fe Mg₃Si₆)and signif icantly reduced the number of aciculate iron(Al₈Fe Mg₃Si₆).When 0.5%Sn elem ent was added,the heat preservation was homogenized at 580?for 1 hour,and the iron phase refinement effect was the most obvious.The hardness of therege nerated aluminum alloy was further increased to 63HV due to the partialsolutio n of the iron phase(Al₈Fe Mg₃Si₆)and the formation of a higher contentof Mg₂Sn strengthened phase.