Study On Solidification Structure And Properties Of Recycled Aluminum

ADC 12 aluminum alloy is a kind of cast aluminum alloy recovered from waste aluminum,which effectively recycles and utilizes recycled aluminum alloy,and has become the current development trend.However,there are too many recycled aluminum impurities currently produced,and performance is difficult to improve.Therefore,this paper takes aluminum alloy ADC 12 as the research object to prepare recycled aluminum alloy,and uses optical metallographic microscope(OM),scanning electron microscope(SEM),X-ray diffractometer(XRD),micro hardness tester and electronic universal testing machine.Analytical test equipment was used to study the effects of adding rare earth elements Y and Gd and the two-stage aging process on the solidification structure and properties of the alloy.The optimum rare earth addition amount and the best heat treatment process were summarized,and in order to improve the mechanical properties of the alloy.The main findings of the study are as follows.(1)After adding rare earth elements Y and Gd,the research shows that the defects of regenerated aluminum are significantly optimized,the number of pinholes is significantly reduced,and the a-Al phase in the solidified structure can be remarkably refined,and the eutectic silicon is deteriorated.When 0.5wt.%Y and 0.5wt.%Gd were added respectively,the refining effect of Yd was better than that of Gd and Y.The secondary dendrite arm spacing of a-Al phase was 12.73?m and 14.64?m,respectively.The alloys decreased by 55.1%and 48.4%;the effect of Y on eutectic silicon was stronger than that of Gd,and the morphology of eutectic silicon changed from a long long needle to a short rod.In addition,the addition of rare earth to the alloy reveals the formation of a rare earth compound which strengthens the structure of the alloy and improves the mechanical properties of the alloy.(2)After adding the same content of rare earth elements,the research shows that Y has more mechanical properties than Gd.Adding 0.5 wt.%Y,the hardness and compressive strength of the alloy are 60.3 HV and 585 MPa,respectively,which are increased by 27.8%and 21.9%respectively compared with the performance of the alloy without added rare earth;0.5 wt.%Gd is added,the hardness of the alloy,The compressive strength reached 58.6 HV and 580 MPa,which was 24.2%and 20.8%higher than that of the alloy without added rare earth.(3)The regenerated aluminum alloy having a rare earth addition amount(0.5 wt.%Y,0.5 wt.%Gd)was separately heat-treated.Studies have shown that under the same conditions,the eutectic silicon in the solidified structure is spheroidized into rounded particles compared to Gd,and a finer dispersed phase is precipitated.In addition,the precipitation of the dispersed phase in the rare earth aluminum alloy structure enhances the aging optimization effect of the alloy.(4)After two-stage aging treatment,the research shows that under the same conditions,Y improves the mechanical properties of the alloy more than Gd.The hardness and compressive strength of the 0.5wt.%Y at the secondary aging temperature of 170? were 86.5HV and 785Mpa,respectively,which were increased by 43.4%and 34.2%respectively before the heat treatment;and 0.5wt.%Gd was added at 170.The hardness and compressive strength after heat treatment at 2 aging temperature were 83.9 HV and 775 MPa,respectively,which were 43.2%and 33.6%higher than those before heat treatment.