The melt structure of Al-Fe alloys in magnetic fields

By Tom Sharp on April 6, 2017

Could alloy melt structure in an electromagnetic field be accurately characterized by electrical parameters? What`s the relationship between these electrical parameters and solidification microstructures? We find out in a recent Journal of Physics: Condensed Matter paper from Qing Lan. Read on to find out more form the authors themselves:

Metal solidification occurs due to nucleation and grain growth. When solidification occurs, microstructures are formed through nucleation. Therefore, the short-range melt structure before solidification is the key to the nucleation process. The short-range melt structure is related to physical fields like electromagnetic and ultrasonic fields, because thesy refine the solidification microstructures. However, how do we determine the influence of physical fields on melt structure?

Electrical parameters, such as thermoelectric power and electrical resistivity, are sensitive to melt structure, which can be measured by the four-probe method in electromagnetic fields. The research group of Professor Le has focused on measuring electrical parameters of low melting point alloys and light metal alloys in electromagnetic and ultrasonic fields.

In our paper, we measured thermoelectric power (TEP) of Al-Fe alloys at different temperatures in AC magnetic field. The liquid quenched ingots retain more structure features by rapidly “freezing”, therefore the relationship between the solidification microstructures of the liquid quenched alloy and the electrical parameters of the melt could also be determined.

The results show that a-Al phase refinement contributes to persistent variation in melt structure. The persistent variation of TEP can be characterized by the variation of a-Al phase size. Therefore, some characteristic parameters of TEP can be used to represent the variation in melt structure.

Schematic of the clusters and the atoms in the melt affected by the AC magnetic field (AC MF). Schematic of the clusters and the atoms in the melt affected by the AC magnetic field (AC MF). Taken from J. Phys. Cond. Mat. 155101 © IOP Publishing 2017.

Professor Le`s research team at the Northeastern University of China are now trying to predict the melt structure changes in physical fields using electrical parameters, and control solidification microstructures in the pre-treating melt using physical fields. These methods could be used to pre-treat other liquid materials (such as metal alloys, inorganic materials, and polymers) in high magnetic, pulsed magnetic, ultrasonic, or electrical fields.

This work is licensed under a Creative Commons Attribution 3.0 Unported License