Papers by Author: Meng Ou Tang

Abstract: Annular electromagnetic stirring (A-EMS) process, developed by General Research Institute for Non-Ferrous Metals, is an advanced processing technology for conditioning liquid metal prior to solidification processing. A-EMS can avoid skin effect effectively, impose a higher shear rate and a higher intensity of turbulence to the liquid metal, and increase the area of the melt heat dissipation by means of innovatively combining noncontact electromagnetic stirring and an annular chamber with specially designed profiles. The solidification structure, composition macro-segregation and property of 7075 alloy were investigated under the conditions of the conventional casting, the conventional electromagnetic stirring casting and A-EMS casting. The results indicated that A-EMS melt processing technology had significant effects on grain refinement, reduction of composition macro-segregation and improvement of mechanical properties.

Abstract: 7075 aluminum alloy melt conditioned by annular electromagnetic stirring(A-EMS) was cast in the TP1 mould, and the effects of pouring temperature, stirring current, stirring frequency and annular gap width on microstructures were analyzed. The A-EMS process exhibits superior grain refinement and remarkable structure homogeneity compared with conventional casting(N-EMS) and conventional electromagnetic stirring casting(EMS). With the increasing of the pouring temperature, the microstructures of the sample conditioned by A-EMS are inclined to become coarse and non-uniform compared with which have the more serious inclination conditioned by N-EMS. With the stirring current or stirring frequency increasing, the rosette-like or dendritic primary α(Al) phase decreases significantly on the sample microstructures, and the non-dendritic primary α(Al) phase is finer and more spherical. Narrow annular gap is advantageous to obtain uniformly fine spherical solidification microstructures.

Abstract: Annular electromagnetic stirring (A-EMS) process is an advanced semi-solid metal processing technology. It could avoid the effect of skin effect, increase the shear rate, reduce the temperature gradient and refine microstructures. A three-dimensional computational model sequentially coupling electromagnetic stirring with a macroscopic heat and fluid flow in A357 alloy semisolid slurry preparation by A-EMS has been developed. Comparison between microstructures of A357 alloy produced by EMS and A-EMS has been made. The results show that the annulus gap avoids the part of low magnetic induction intensity and A-EMS avoids the effect of skin effect. The annulus gap prohibits the circular flow and increases the shear flow. The circular flow is more effective than the shear flow on heat dissipation. A lower temperature difference in the stirred melt and subsequent uniformly fine microstructures were obtained as compared with the normal electromagnetic stirring.