In this paper, AZ31 magnesium alloy is cast by applying the semi-continuous casting process with a low-frequency electromagnetic field. By studying the influence of electromagnetic field frequency, excitation current intensity and casting velocity on the microstructure and mechanical properties, the optimum process under oil-slip electromagnetic casting conditions was determined to improve the degree of grain refinement, yield strength, elongation and tensile strength of AZ31 alloy. An improved microstructure refining effect and higher hardness can be obtained with a current intensity af 60 A. The microstructures and mechanical properties obtained for different casting velocities of V = 200 mm/min and V = 230 mm/min at processing parameters of f = 30 Hz and I = 120 A were compared. Our results suggest that a higher casting speed does not lead to grain refinement or improved mechanical properties. Frequency

A new type of SiC_f/TiC-Ti₃SiC₂ composite was prepared by the Spark Plasma Sintering (SPS) method in this work. The phase transformation and interface cracking of this composite under ion irradiation (single Xe, Xe + He, and Xe + He + H ions) and subsequent annealing were analyzed using transmission electron microscopy (TEM), mainly focusing on the interface regions. Xe ion irradiation resulted in the formation of high-density stacking faults in the TiC coatings and the complete amorphization of SiC fibers. The implanted H ions exacerbated interface coarsening. After annealing at 900 °C for 2 h, the interface in the Xe + He + H ion-irradiated samples was seriously damaged, resulting in the formation of large bubbles and cracks. This damage occurred because the H atoms reduced the surface free energy, thereby promoting the nucleation and growth of bubbles. Due to the absorption effect of the SiC_f/TiC interface on defects, the SiC fiber areas near the interface recovered back to the initial nano-polycrystalline structure after annealing.

The thermal deformation behaviour of semi-continuously electromagnetic casting AZ31 magnesium alloy was investigated by compression tests with strain rate controlled for 0.001~0.1 s-1 at 473 K~623 K. A detailed analysis with respect to the influencing parameters was then conducted based on the true stress-strain curve, including calculating the deformation activation energy under various magnetic field conditions. Extrusion tests of AZ31 alloy under different casting conditions were performed. The testing parameters were optimized by the available hot compression data. The fracture morphology of pre- and post-deformation were compared to evaluate the effects of casting conditions on the microstructures and performances of the extrusion bars. The results show that dynamic recrystallization takes place under all the experimental conditions. The stress-strain curve exhibits a peak firstly, and then a drop followed to a stable value stage followed with the subsequent strain accumulation. The value of the stable stage, which decreases with the increase of temperature but decrease of theand strain rate. The dynamic recrystallization leads to a refinement of the grains size and hence enhanced the mechanical performance of the materials. In addition, a hereditary effect was found on the properties of the extrusion AZ31 alloys for electromagnetic field frequency.