Effect of Oscillating Field on Microstructure of Twin-roll Cast 7075 Aluminum Alloy

摘要:

研究了在670 ℃下，振荡磁场双棍铸轧对7075铝合金成型板材微观形貌和硬度影响。结果表明，同传统方式铸轧相比，采用振荡电磁场铸轧板材的枝晶被严重碎断、细化和等轴化。在此条件下7075板材的表面及中心的偏析程度大幅减轻，并且在交变振荡场的作用下偏析完全消失。普通铸轧条件下板坯横向和轧向的HV硬度值分别为1104和1356 MPa；采用电磁场后，在交变振荡场下获得最大硬度为1615 MPa；除此之外，当磁场强度增加，板材性能会进一步提高。另外发现，无论在何种磁场条件下，升高浇注温度后，外加电磁场的细化作用效果增强。

Abstract:

The morphology and the hardness of 7075 Al alloy during oscillating twin-roll casting (TRC) process at 670 °C were investigated. It was observed that compared with that by traditional process, the dendritic grains of the strips by oscillation field TRC process were severely broken, refined and equiaxed. Segregation bands at the surface and the center of 7075 strips were dramatically reduced in electromagnetic oscillatory field conditions, even completely disappeared in alternating oscillatory condition. The transverse and the rolling direction HV hardness of 7075 strips manufactured by traditional process were 1104 and 1356 MPa, respectively. Upon applying the electromagnetic field, the maximum hardness of 1615 MPa was obtained in alternating oscillating TRC process. Besides, the properties of strips will be further improved with increasing of magnetic field. No matter in what conditions, the refinement of electromagnetic field to strips will increase at elevated temperature.