Impact of Pulse Magnetic Field Treatment on Hot Tearing Tendency of Al-Zn-Mg Alloy

Hot tearing is a common defect in aluminum alloy casting and welding, significantly compromising component integrity. Grain refinement can effectively reduce such defects. In this study, we employed a novel low-energy electromagnetic pulse grain refinement device to systematically investigate the suppression effect of electromagnetic energy on solidification-induced hot tearing in aluminum alloys. The effects of current intensity and magnetic field frequency on the grain size, phase precipitation, and solidification shrinkage stress during the solidification process of aluminum alloy was systematically analyzed. The study found that the magnetic field concentrated precipitates at grain boundaries, with a small amount dispersed inside the grains, mainly consisting of θ(Al₂Cu), T(AlZnMgCu) and T(Al₂CuMg) phases. With increasing current intensity and magnetic field frequency, the content of precipitated phases gradually increased, and the layered precipitated phase at the grain boundaries changed to a block-like structure. The application of the magnetic field shortened the solidification shrinkage stress curve’s plateau, greatly improved the compensation ability of the residual liquid metal shrinkage, and reduced the tendency of hot tearing. Simultaneously, the pulsed magnetic field significantly refined casting grains. When the current was 30 A, the frequency was 30 Hz, and the duty cycle was 20%, the grain refinement rate reached 47.5%.