Mg、Ce和Cu对2D70铝合金显微组织的影响

Effects of Mg,Ce and Cu Content on Microstructure of 2D70 Aluminum Alloy

通过向2D70铝合金中添加不同含量的Cu、Mg和Ce,并借助OM、SEM和EDS等手段对铸态组织进行分析。结果表明,随着Cu含量增加,2D70铝合金中Al_9FeNi相逐渐减少,产生非平衡共晶反应,析出的共晶组织θ-Al_2Cu相呈花纹网状或者汉字形,当Cu含量过大时,析出降低合金性能的Al_7Cu_4Ni相和Al_7Cu_2Fe相。添加Mg后,多余Cu原子被捕获,形成片层状S-Al_2CuMg相,此时Al_9FeNi相受Cu的影响较小,几乎不再分解。加入Ce,导致Cu原子溶质再分配并充分溶解于基体中,提高了Cu在铝合金中的固溶度,晶界处不再出现大量难熔相,使合金显微组织均匀,并细化晶粒尺寸。

By adding different contents of Cu,Mg and rare earth element Ce to the 2D70aluminum alloys,microstructure of the alloy was analyzed by OM,SEM,EDS.The results reveal that with the increase of Cu content,the Al9FeNi phase in 2D70aluminum alloy is decreased gradually,resulting in the non-equilibrium eutectic reaction.The precipitated eutectic phasesθ-Al2Cu exhibits in the pattern of mesh or Chinese character.With the excessive content of Cu,Al7Cu4Ni phase and Al7Cu2Fe phase which are harmful to mechanical properties of the alloy are precipitated.After the addition of Mg element,excess Cu atoms are trapped to form a lamellar phase S-Al2CuMg,in which the Al9FeNi phase is affected slightly by Cu and hardly reduced.When rare earth element Ce is added,the solute redistribution of the Cu atom appears,so that it can be dissolved fully into the matrix.Thereby,the solid solubility of Cu in the aluminum alloy is increased,and a large amount of refractory phase are absent in the grain boundary,so that the microstructure of the alloy presents uniform with refinement of grain size.