A new approach to applying the electric current pulse （ECP） with parallel electrodes to the promotion of the transition from columnar crystal to equiaxed crystal and the improvement of macrosegregation was introduce...A new approach to applying the electric current pulse （ECP） with parallel electrodes to the promotion of the transition from columnar crystal to equiaxed crystal and the improvement of macrosegregation was introduced. The ECP was applied to different stages of the solidification. The results showed that the application of the ECP in both the initial stage （the thickness of solidified shell reached 2 mm approximately） and the late stage （the thickness of solidified shell reached 14 mm approximately） of solidification can promote the columnar to equiaxed transition （CET）. The analysis showed that during solidification, a large number of nuclei around the upper surface fell off due to ECP, which subsequently showered on the melt and impinged the growth front of the columnar crystal. Therefore, the CEToccurred. In addition, this method was also employed to influence the solidification process of bearing steel, and the results showed that the structure was changed from columnar crystal to equiaxed crystal, indicating that ECP can enhance the homogeneity of structure and composition of bearing steel.展开更多
The application of electric current pulse（ECP） to a solidification process refers to the immersion of electrodes into the liquid metal and the employment of thermal insulators on the upper surface of metal.In order ...The application of electric current pulse（ECP） to a solidification process refers to the immersion of electrodes into the liquid metal and the employment of thermal insulators on the upper surface of metal.In order to ascertain the effects of these two factors on the structure refinement by the ECP technique,three groups of experiments were performed with different types of electrodes or various thermal insulators.By the comparison between solidification structures under different conditions,it is followed that the electrode and the thermal insulator have an obvious influence on the grain refinement under an applied ECP,and further analysis demonstrates that the thermal conditions of the liquid surface play a vital role in the modification of solidification structure.Also,the results support the viewpoint that most of the equiaxed grains originate from the liquid surface subjected to an ECP.展开更多
The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied. The results indicated that the cementite was decomposed in a short time by high current density electropulsin...The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied. The results indicated that the cementite was decomposed in a short time by high current density electropulsing. With increasing electropulsing time, the in situ nucleation of graphite in cementite was accompanied with the quick decomposition of cementite. The dislocation accumulation adjacent to the cementite and the quick diffusion of carbon atom by electropulsing were main reasons for the quick decomposition of cementite. The in situ nucleation of graphite in the cementite resulted from the dislocation climbing crossing the cementite lamellae.展开更多
基金Item Sponsored by National Natural Science Foundation of China(50674064,50734008)
文摘A new approach to applying the electric current pulse （ECP） with parallel electrodes to the promotion of the transition from columnar crystal to equiaxed crystal and the improvement of macrosegregation was introduced. The ECP was applied to different stages of the solidification. The results showed that the application of the ECP in both the initial stage （the thickness of solidified shell reached 2 mm approximately） and the late stage （the thickness of solidified shell reached 14 mm approximately） of solidification can promote the columnar to equiaxed transition （CET）. The analysis showed that during solidification, a large number of nuclei around the upper surface fell off due to ECP, which subsequently showered on the melt and impinged the growth front of the columnar crystal. Therefore, the CEToccurred. In addition, this method was also employed to influence the solidification process of bearing steel, and the results showed that the structure was changed from columnar crystal to equiaxed crystal, indicating that ECP can enhance the homogeneity of structure and composition of bearing steel.
基金Project(2009AA03Z110) supported by the National High Technology Research and Development Program of ChinaProject (2011CB012902) supported by the National Basic Research Program of China
文摘The application of electric current pulse（ECP） to a solidification process refers to the immersion of electrodes into the liquid metal and the employment of thermal insulators on the upper surface of metal.In order to ascertain the effects of these two factors on the structure refinement by the ECP technique,three groups of experiments were performed with different types of electrodes or various thermal insulators.By the comparison between solidification structures under different conditions,it is followed that the electrode and the thermal insulator have an obvious influence on the grain refinement under an applied ECP,and further analysis demonstrates that the thermal conditions of the liquid surface play a vital role in the modification of solidification structure.Also,the results support the viewpoint that most of the equiaxed grains originate from the liquid surface subjected to an ECP.
基金supported by the Department of Edu-cation of Liaoning Province, China (No. 2008T089).
文摘The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied. The results indicated that the cementite was decomposed in a short time by high current density electropulsing. With increasing electropulsing time, the in situ nucleation of graphite in cementite was accompanied with the quick decomposition of cementite. The dislocation accumulation adjacent to the cementite and the quick diffusion of carbon atom by electropulsing were main reasons for the quick decomposition of cementite. The in situ nucleation of graphite in the cementite resulted from the dislocation climbing crossing the cementite lamellae.
