超声对熔盐电解法制备Al--7Si--Sc合金组织的影响

Effects of ultrasound on the microstructure of Al-7Si-Sc alloy prepared via molten salt electrolysis

Al-Si系合金在现代工业、交通等领域广泛应用,合金元素钪可进一步改善其加工和使用性能.采用超声协同熔盐电解法制备Al-7S-Sc三元合金,研究探索超声作用对合金组织及强化相分布的影响.发现超声协同熔盐电解制得合金中Sc含量提高,团簇共晶硅组织和AlSi2Sc2相显著细化,共晶硅团簇尺寸由约500降低至200μm,减小约60%,细化后AlSi2Sc2相分布均匀.超声协同电解法可显著优化Al-7Si-Sc合金组织,有助于控制改善现行工艺中合金元素偏聚、组织不均匀现象.

Al-Si alloys are widely used in modern industries,transportation,and other engineering applications.Processability and mechanical properties of Al-based alloys can be improved via the addition of scandium.Sc added to Al metal for fabricating Sc-containing Al alloys using molten salt electrolysis has been recently considered as promising technology.However,alloying elements,such as Sc and Si are often unevenly distributed in such Al-based alloys.In this study,Al-7 Si-Sc ternary alloy was prepared via molten salt electrolysis aided with ultrasound to investigate the effects of ultrasound on the microstructure and distribution of the strengthening phase.Electrolysis was performed on molten salts of Na3AlF6-19%KF-29%AlF3-2%CaF2 at a temperature of 800℃and current density of 1 A·cm2,in which Sc2O3(99.99%purity)and Al-7 Si alloy served as the raw material and cathodic metal,respectively.Ultrasound(20 k Hz,200 W)was introduced into the cathode metal from the cell bottom.Sc contents in the as-prepared alloy samples were determined using inductively coupled plasma atomic emission spectrometry(ICP-AES).Microstructures of the alloy samples were characterized using optical microscope and scanning electron microscope coupled with an energy dispersive X-ray analyzer.Results reveal that ultrasound can increase Sc content in the ternary alloy prepared via molten salt electrolysis and refine the eutectic silicon clusters and the ternary AlSi2 Sc2 phase.Compared with the alloys made without ultrasound aid,the silicon cluster size decreases from approximately 500 to 200μm(~60%)and the refined ternary phase of AlSi2 Sc2 uniformly distributes in the metal matrix.Results also indicate that ultrasound can considerably optimize the microstructure of Al-7 Si-Sc alloy prepared via molten salt electrolysis.This process can prevent problems such as the segregation of alloying elements and uneven microstructures observed when using the traditional alloy-making process.