Effect Of Ag On Micro-structure And Properties Of Al-4Mg Alloy

5XXX series alloy is widely used in various fields due to its small density,high specific strength and good corrosion resistance,weld-ability and form-ability,etc.Although the solubility of Mg element in Al-Mg alloy decreased rapidly with decreasing temperature,resulting in the poor aging strengthening.of Al-4Mg alloy due to nucleation,core less precipitates,new phase and matrix were lattice.Therefore,the alloy is non-heat treatable,which greatly limits its strengthening.Recent researches show that micro-alloying can change the structure of precipitates in 5XXX series alloy,thus it can improve the strength of the alloy during aging.In this paper,a trace of Ag element was added into the Al-4Mg melt to form new phases during solidification and to change the morphology of the precipitates during aging.The aim is to make the alloy heat-treatable while retain its comprehensive performance.Several conclusions were obtained as follows:(1)With the increase of Ag content,the hardness of Al-4Mg alloy was increased after solution treatment at 500? for 2h followed by aged 2h at 210?;especially,when the content of Ag was increased from 0%to 0.6%,the hardness of the alloy was increased from 72.5HV to 101.2HV.But when the Ag content was increased from 0.6%to 0.8%,the increment of hardness was slowly,which increased from 101.2HV to 102.2HV.Therefore,it is reasonable to add 0.6%Ag in Al-4Mg-Ag alloy.(2)Ag element had no apparent effect on the size and shape of crystal in solidification structure of Al-4Mg alloys.With the increase of Ag content,new phases with rod and dot shapes were formed and these phases were T(Mg2(Al,Ag)3);After homogenization treatment at 500? for 24h;T phases were blended into the ?(Al)matrix.(3)The hardness and strength of rolled Al-4Mg alloy traced 0.6%Ag were increased somewhat after solution treatment at 500? for 2h followed by aged 2h at 210?.The hardness of the alloy was increased from 73.6HV to 101.2HV,about 37.5%.The strength of extension of the alloy.was rose from 240MPa to 280MPa,about 16.7%.The yield strength of the alloy was increased from 105MPa to 200MPa,about 90.5%.(4)Compared Al-4Mg alloy,there were new phases in the alloy traced 0.6%Ag after aging treatment.The new phases were ?" phase(Al3Mg,b.c.c,a=0.408nm)and T phase.The ?" phase was The main strengthening phase of Al-4Mg-0.6Ag alloy in the period of aging treatment.