Effect Of Rare-Earth Er On The Microstructures And Tensile Properties Of 1420 Al-Li Alloy

Al-Li alloys containing different percent of Er were prepared with castMetallurgy processing in this paper. By means of many experimental techniques suchas TEM, SEM, XRD, EDS, and so on, effects of Er on microstructure and mechanicalproperties of 1420 Al-Li alloys under different states (as-cast, aged) were investigated.The existing forms and interactions with alloying elements of Er in Al-Li alloys, thestrengthening of Al-Li-0.2Er alloy were profoundly studied. Moreover, the effects ofEr on anisotropy of Al-Li alloys were preparatory discussed. The results are asfollows: There are seldom effects of Er on the size of grain when Er additions are lessthan 0.2wt%, but the grain will be refined significantly when Er additions are 0.2wt%or more. The addition of different content Er was found to improve the mechanicalproperties (strength and hardness) of experimental alloys to different extent. When Eradditions were 0.2wt%, the strength was considerably improved(5～40%) while theductility keeps stable or decreases slightly. With the increase of Er additions, thestrength keeps stable but the ductility decreases markedly. There are threestrengthening mechanisms in experimental alloys: precipitation strengthening, finegrain strengthening, substructure strengthening. Of all three strengtheningmechanisms, the former plays more important role than the latter two. In themeanwhile, The effects of Er on anisotropy of Al-Li alloys were also preparatorydiscussed in this paper. The experimental results indicated that adding a certainamount of Er addition into alloys 1420 could reduce the anisotropy of mechanicalproperties. The decrease is caused by the pinning effect of dispersed and fine Al3Erprecipitates on dislocation and subgrain boundary. This pinning effect could blockmovement of dislocation and decrease the tendency for conplane slip, thereby weakenanisotropy in this alloy. In a word, The effect is main caused by the existing of Al3Er particles and othercomplex phase. These phases would have effect on melt freezing, dislocationtransferring and coplanar slip of Al-Li alloy. The results above-mentioned show thatEr is an effective trace element for Al-Li alloy, the addition of 0.2wt% Er will makeexperimental alloys have more excellent complex properties.