喷射成形7055铝合金初生相在形变前预热处理中的演变行为

Evolution Behavior of Primary Phase During Pre-heat Treatment Before Deformation for Spray Formed 7055 Aluminum Alloy

采用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)以及X射线衍射(XRD)研究了喷射成形7055铝合金初生相在形变前预热处理过程中的演变规律。结果表明:初生相为AlZnMgCu相和Al7Cu2Fe相,其中晶内相呈小尺寸棒状,晶界相为AlZnMgCu相和Al7Cu2Fe相的共生组织,呈粗大不规则状。低温(≤400℃)调控时,由于合金元素扩散能力弱,初生相少量回溶,但相中Zn元素质量分数明显降低;中温(≤450℃)调控时,小尺寸晶内初生相基本回溶,但是粗大晶界相演变为椭球状的Al2CuMg相(S相);高温(470℃)调控使晶内晶界初生相完全回溶且避免了Al2CuMg相(S相)的大量出现。单、双级调控效果比较表明,双级调控下初生相的演变规律取决于第二级热处理温度。

Evolution of the primary phase of spray formed 7055 aluminum alloy during pre-heat treatment before deformation was studied by OM,SEM,TEM and XRD test.The results show that the primary phases of as-sprayed 7055 alloy are AlZnMgCu phase and Al7Cu2 Fe phase.The AlZnMgCu phase is fine in the grain while coarsened on the grain boundary.The grain boundary phase is formed as a symbiotic microstructure including AlZnMgCu and Al7Cu2 Fe phase.When the treatment temperature is≤400℃,the dissolution of primary phase is less due to the low diffusion coefficient.However,the Zn content has an apparent decline in both intragranular phase and grain boundary phase.When the temperature increases to 450℃,the fine primary phase is completely dissolved,while the coa rsened phases on grain boundary transform to an ellipsoid-like Al2CuMg phase.When treated at 470℃,inner phase has the same dissolv ing behavior but the transformation of grain boundary phase to Al2CuMg is avoided.The comparison between the single stage and two stage pre-heat treatments indicates that the evolution of primary phase depends on the second pre-heat treatment temperature.