Composition Homogenization Evolution of Twin-Roll Cast 7075 Aluminum Alloy Using Electromagnetic Field

摘要:

在利用双辊连铸机生产7075铝合金中，会发现许多微观缺陷，如粗大完整的枝晶和严重偏析等。利用金相和SEM测定了7075板坯组织形貌和相成分，并通过与传统生产方式的对比，研究在铸轧工艺中施加0.13 T大小的电磁场对溶质成分分布的差异。就板材显微组织大量细化和偏析带缩小而言，最有效的方式是386 A，50 Hz工频电流下交变振荡电磁场铸轧工艺。另外，晶界处存在大量t（AlZnMgCu）相，并按照直流磁场、半波振荡磁场和交变振荡磁场顺序逐渐均匀细化。并且在振荡电磁场下网状沉淀相完全消失。

Abstract:

Many microstructural defects such as well-developed dendritic crystal and severe segregation have been found in 7075 aluminum alloy strips by continuous twin-roll casters. Morphology and phase composition of 7075 alloy strips were tested in this paper. Electromagnetic field of 0.13 T was applied during a twin-roll casting (TRC) process to study the difference in solute element distribution compared to conventional process. The most soundest method by which the microstructure of slabs was greatly refined and equiaxed, and segregation bands narrowed down efficiently, was an alternating oscillating process with industrial frequency current and frequency of 386 A and 50 Hz, respectively. In addition, t (AlZnMgCu) phase with high density was formed at (sub) grain boundaries, which was refined and homogenized consecutively in accordance with direct chill (DC) electromagnetic field, half-wave oscillating field and alternating oscillating field; moreover, netlike precipitates completely disappeared at oscillating TRC processes.