电磁搅拌法制备铝合金半固态坯料的研究

Study on the Aluminum Alloy Semi-Solid Billets Prepared by Electromagnetic Stirring Process

摘要:

分别研究了搅拌电流及搅拌频率对2A50铝合金半固态坯料中心及边缘位置微观组织的影响规律。结果表明：无搅拌电流及搅拌频率时,坯料的微观组织主要由粗大的树枝晶组成,部分枝晶臂长度甚至超过200 μm,不能用于半固态成形。随着搅拌电流或搅拌频率的增加,中心与边缘位置的平均晶粒尺寸均不断减小并在搅拌电流超过30A或搅拌频率超过30Hz时略有增加；中心与边缘位置的形状因子都不断增加并逐渐趋于平缓,但当搅拌电流为40A或搅拌频率为40Hz时略有下降；同时,中心与边缘位置微观组织的均匀性越来越好。在搅拌电流30A、搅拌频率30Hz条件下,能够制备出平均晶粒尺寸和形状因子分别为75.6 μm及0.73的具有理想微观组织的半固态坯料。

Abstract:

The effects of the stirring current and frequency on the microstructure of the semi-solid 2A50 alloy at the central and peripheral parts of the billet were studied. Results showed that the coarse dendritic particles were the main constituent of the microstructure without electromagnetic stirring, where the length of the dendrite arm was larger than 200 μm. This type of semi-solid billet was unqualified for the semi-solid forming. With the increase in stirring current or stirring frequency, the average size of the grains located at the central and peripheral regions decreased first and then slightly increased when the stirring current and stirring frequency is over 30A and 30Hz, respecitvely; the shape factors at centeral and center parts gradually increased and then slightly decreased when the stirring current is 40A or the stirring frequency is 40 Hz; Furthermore, the uniformity of the grain size and shape at the central and peripheral parts was improved with the increase in the stirring current or the frequency. The optimal average grain size and the shape factor were able to be obtained as 75.6 μm and 0.73, respectively under the stirring current of 30A and stirring frequency of 30Hz.