**Yanjin Xu 1,\*, Lijun Wei 2, Baoshuai Han 1, Enyu Guo 3,\*, Mingyue Wang <sup>2</sup> and Yanqing Su <sup>4</sup>**


Received: 14 May 2018; Accepted: 5 June 2018; Published: 12 June 2018

**Abstract:** The effect of traveling magnetic fields (TMFs) on the grain and micro-pore formation in an Al alloy was studied by scanning electron microscope and X-ray microtomography in this work. The results show that with the increasing magnetic flux density, the three-dimensional morphology of the micro-pores transformed from dendrite to a relatively equiaxed structure. Quantified results show that both the micro-pore volume fraction and the average grain size of the primary phase decreased as the TMF density increased. The analyses show that the forced convection induced by TMF can break the dendrites, refine the grain size, and promote the liquid feeding, leading to the decrease in the volume fraction of the porosity and improved mechanical property. The TMF performed at different stages during solidification reveal that the maximum effect of TMF on reducing the micro-pore formation was found when TMF was applied in the stage of nucleation and the early stage of grain growth during solidification.

**Keywords:** aluminum alloy; solidification; X-ray tomography; porosity defects; magnetic field treatment
