电磁铸造镁合金大规格板坯偏析与组织研究

Study on macrosegregation and Macrostructure of large scale Magnesium slab by LFEC process

摘要:

研究了不同铸造速度条件下截面尺寸为300 mm?800 mm的大规格AZ31镁合金板坯的宏观偏析及组织。结果表明，偏析区域出现在距离锭坯表面20 mm ~ 30mm范围内，板坯心部偏析小。宏观组织可分为表面激冷区，粗大的柱状晶区和内部等轴晶区。低速铸造可减轻宏观偏析，随铸造速度增加，整体晶粒尺寸先增大后减小，表面粗晶区宽度减小。高速铸造时晶粒尺寸最小，但不均匀。合理的铸造速度为32 mm/min。

Abstract:

The low frequency electromagnetic casting(LFEC) process was used in casting the large scale AZ31 magnesium slab with the cross section of 300mm×800mm, and its macrostructure and macrosegregation were investigated at different casting velocities. The result shows that the segregation was slight in the centre and become serious in region about 20mm~30mm near the slab surface, There exist three zone in AZ31 magnesium alloy slab, surface chill zone, columnar crystal zone, internal equiaxed crystal zone. With the casting velocity increasing, the size of grain increases first and then decreases, the width of columnar crystal zone decreases drastically as well as the macrosegregation. At high casting velocity, the grain size is finer, but more uneven. Thus, the appropriate casting velocity in this process is 32mm/min.