Hot Tearing Susceptibility of AXJ530 Alloy Under Low-Frequency Alternating Magnetic Field

Abstract

Herein, a hot tearing measured system with external excitation coil and a differential thermal analysis system with applied magnetic field were used to study the effects of low-frequency alternating magnetic field on the solidification behavior and hot tearing susceptibility (HTS) of the AXJ530 alloy under different magnetic field parameters. The hot tearing volume of the castings was measured via paraffin infiltration method. The microstructure of the hot tearing zone of the casting was observed using optical microscopy and scanning electron microscopy, and the phase composition was analyzed using X-ray diffraction and energy depressive spectroscopy. The experimental results show that the solidification interval of AXJ530 alloy was shortened and the dendrite coherency temperature of the alloy decreased with the increase in frequency of alternating magnetic field. Under appropriate magnetic field parameters, the electromagnetic force could enhance the convection in the melt to promote the flow of the residual liquid phase, refine the microstructure, and optimize the feeding channel in the late solidification stage, which reduced the HTS of the alloy. However, when the magnetic field frequency was increased to 15 Hz, the induced current generated excessive Joule heat to the melt. At this time, the thermal action of the magnetic field coarsened the microstructure of the alloy, resulting in an increase in HTS of the alloy.

Influence of a low-frequency alternating magnetic field on hot tearing susceptibility of EV31 magnesium alloy

“…The hot tearing experiment was performed on a "T-shaped" hot tearing mold with a solidification shrinkage force acquisition system, as shown in Fig. 1 [12] . The device mainly consists of a hot tearing testing system, a load sensor, a magnetic field system, and a data-acquisition system.…”

“…As shown in Fig. 2 [12] , two thermocouples were placed at the center and edge of the crucible to measure the temperature at the center (T c ) and the temperature at the edge (T e ) of the alloy. To ensure the heat transfers in the crucible along the radial direction of the crucible, the top of the crucible was covered with a thicker asbestos net.…”

“…Refining the alloy structure can effectively reduce Fig. 1: Hot tearing measurement setup with an optional magnetic field (a) [12] and hot tearing sample (b)…”

“…Currently, research concerning the effect of the magnetic field on the HTS of magnesium alloy has become a hot spot. Du et al [12] found that, under a low-frequency alternating magnetic field, with increasing magnetic field frequency, the HTS of AXJ530 alloy decreased firstly and then increased. The HTS of AXJ530 alloy at different magnetic field frequency was ranked as follows: 10 A, 10 Hz<10 A, 15 Hz<10 A, 5 Hz<0 A, 0 Hz.…”

“…Vol.18 No.3 May 2021Research & Development Fig.2: Differential thermal analysis setup with a magnetic field[12] …”