Commercial pure Al can be refined by Pulsed Magneto-Oscillation(PMO) treatment applied via a plate induction coil above the top surface of the melt. The proportion of the equiaxed zone area increases with decreasing H...Commercial pure Al can be refined by Pulsed Magneto-Oscillation(PMO) treatment applied via a plate induction coil above the top surface of the melt. The proportion of the equiaxed zone area increases with decreasing Height to Diameter(H/D) ratios from 3.5 to1.8 and further to 1.0. Meanwhile, it increases and then decreases with increasing peak current for the three kinds of ingots with H/D ratios of 3.5, 1.8 and 1.0, respectively. However, when the H/D ratio decreases to 0.44, the area proportion of equiaxed zone can reach the maximum value with a lower peak current. FEA software simulation indicates that smaller H/D ratio results in larger current density, electromagnetic force and convection on the top surface of the melt, favoring nucleation and subsequent grain formation. Through evaluating Joule heating effect by PMO, it was found that the proper amount of Joule heating benefits grain refinement. Excessive Joule heating can reduce the size of the equiaxed zone and change the growth morphology of the grains.展开更多
Distributions of electromagnetic fields and induced forced flow inside a metal melt are crucial to understand the grain refinement of the metal driven by pulsed magneto-oscillation(PMO).In the present study,PMO-induce...Distributions of electromagnetic fields and induced forced flow inside a metal melt are crucial to understand the grain refinement of the metal driven by pulsed magneto-oscillation(PMO).In the present study,PMO-induced electromagnetic fields and forced flow in Ga-20 wt%In-12 wt%Sn liquid metal have been systematically investigated by performing numerical simulations and corresponding experimental measurements.The numerical simulations have been confirmed by magnetic and melt flow measurements.According to the simulated distribution of electromagnetic fields under the application of PMO,the strongest magnetic field,electric eddy current and Lorentz force with inward radial direction inside the melt are concentrated adjacent the sidewall of cylindrical melt at the cross section of middle height of coil.As a result,a global forced flow throughout the whole cylindrical column filled with Ga-20 wt%In-12 wt%Snmelt is initiated with a flow structure of two pair of symmetric vortexring.The PMO-induced electromagnetic fields and forced flow in Al-7 wt%Si melt have been numerically simulated.The contribution of electromagnetic fields and forced flow to the grain refinement of Al-7 wt%Sialloy under the application of PMO is discussed.It indicates that the forced flow may play a key role in the grain size reduction.展开更多
Heavy ingots,especially the ingot of more than 10 t,often contain detrimental heterogeneous defects,such as macrosegregation,shrinkage pipes,and cracks.Hot-top pulsed magneto-oscillation(HPMO)can refine the solidified...Heavy ingots,especially the ingot of more than 10 t,often contain detrimental heterogeneous defects,such as macrosegregation,shrinkage pipes,and cracks.Hot-top pulsed magneto-oscillation(HPMO)can refine the solidified structure of ingot and improve their homogeneity.However,it may exacerbate the positive segregation at the upper part of the ingot body.Thus,a round table HPMO riser with a feeding part was designed,and the microstructure and macrosegregation of Al–Si alloy ingots solidified with and without HPMO were investigated.The simulation and experimental results indicated that round table HPMO riser could enable fine and uniform solidified structures in the whole ingot body;in the meantime,feeding part allowed the melt with enriched solute to gather in the upper part of the riser until the last solidification stage of ingot.This provides an effective approach for obtaining highly homogenized ingots.展开更多
Pulse magneto-oscillation(PMO)added during solidification could affect the solidification structure and macrosegregation.A modified thermal simulation equipment was applied to prepare GCr15 bearing steel continuous ca...Pulse magneto-oscillation(PMO)added during solidification could affect the solidification structure and macrosegregation.A modified thermal simulation equipment was applied to prepare GCr15 bearing steel continuous casting billets with different PMO peak currents.Then,metallographic analysis,component analysis and numerical simulation were adopted to study the influence of PMO peak current and its mechanism.The sample with 150 K_(I)A PMO peak current treatment has little difference with the samples without PMO treatment on solidification structure and macrosegregation.As the peak currents are 250 and 350 K_(I)A,the columnar zone increases and macrosegregation aggravated.When 450 K_(I)A peak current is selected,the equiaxed grain ratio is enlarged,and the dendritic grains are refined,and the macrosegregation of C,Cr,Si and Mn is decreased significantly.By analyzing,different convections induced by PMO with various peak currents are the key factor to change the solidification structure and macrosegregation.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51320105003)the Australian Research Council Centre of Excellence for Design in Light Metals and,ARC Discovery Project DP140100702the Exo Met Project co-funded by the European Commission’s 7th Framework Programme(Contract FP7-NMP3-LA-2012-280421)
文摘Commercial pure Al can be refined by Pulsed Magneto-Oscillation(PMO) treatment applied via a plate induction coil above the top surface of the melt. The proportion of the equiaxed zone area increases with decreasing Height to Diameter(H/D) ratios from 3.5 to1.8 and further to 1.0. Meanwhile, it increases and then decreases with increasing peak current for the three kinds of ingots with H/D ratios of 3.5, 1.8 and 1.0, respectively. However, when the H/D ratio decreases to 0.44, the area proportion of equiaxed zone can reach the maximum value with a lower peak current. FEA software simulation indicates that smaller H/D ratio results in larger current density, electromagnetic force and convection on the top surface of the melt, favoring nucleation and subsequent grain formation. Through evaluating Joule heating effect by PMO, it was found that the proper amount of Joule heating benefits grain refinement. Excessive Joule heating can reduce the size of the equiaxed zone and change the growth morphology of the grains.
基金the National Key Research and Development Program of China(Grant No.2017YFB0304205)the National Natural Science Foundation of China(Grant Nos.U1760204,51704210)。
文摘Distributions of electromagnetic fields and induced forced flow inside a metal melt are crucial to understand the grain refinement of the metal driven by pulsed magneto-oscillation(PMO).In the present study,PMO-induced electromagnetic fields and forced flow in Ga-20 wt%In-12 wt%Sn liquid metal have been systematically investigated by performing numerical simulations and corresponding experimental measurements.The numerical simulations have been confirmed by magnetic and melt flow measurements.According to the simulated distribution of electromagnetic fields under the application of PMO,the strongest magnetic field,electric eddy current and Lorentz force with inward radial direction inside the melt are concentrated adjacent the sidewall of cylindrical melt at the cross section of middle height of coil.As a result,a global forced flow throughout the whole cylindrical column filled with Ga-20 wt%In-12 wt%Snmelt is initiated with a flow structure of two pair of symmetric vortexring.The PMO-induced electromagnetic fields and forced flow in Al-7 wt%Si melt have been numerically simulated.The contribution of electromagnetic fields and forced flow to the grain refinement of Al-7 wt%Sialloy under the application of PMO is discussed.It indicates that the forced flow may play a key role in the grain size reduction.
基金This work was financially supported by the National Key Research and Development Program of China(Nos.2020YFB2008400 and 2017YFB0701800)the National Natural Science Foundation of China(No.U1760204)In addition,the authors would liketo thankHui Shaoand Zi-hao Yin from Centerfor Advanced Solidification Technology,Shanghai University for their help in the experiment and data analysis.
文摘Heavy ingots,especially the ingot of more than 10 t,often contain detrimental heterogeneous defects,such as macrosegregation,shrinkage pipes,and cracks.Hot-top pulsed magneto-oscillation(HPMO)can refine the solidified structure of ingot and improve their homogeneity.However,it may exacerbate the positive segregation at the upper part of the ingot body.Thus,a round table HPMO riser with a feeding part was designed,and the microstructure and macrosegregation of Al–Si alloy ingots solidified with and without HPMO were investigated.The simulation and experimental results indicated that round table HPMO riser could enable fine and uniform solidified structures in the whole ingot body;in the meantime,feeding part allowed the melt with enriched solute to gather in the upper part of the riser until the last solidification stage of ingot.This provides an effective approach for obtaining highly homogenized ingots.
基金financially supported by the National Key Research and Development Program of China(2020YFB2008400)National Natural Science Foundation of China(U1760204)Key Research&Development Program of Hebei province(20311006D).
文摘Pulse magneto-oscillation(PMO)added during solidification could affect the solidification structure and macrosegregation.A modified thermal simulation equipment was applied to prepare GCr15 bearing steel continuous casting billets with different PMO peak currents.Then,metallographic analysis,component analysis and numerical simulation were adopted to study the influence of PMO peak current and its mechanism.The sample with 150 K_(I)A PMO peak current treatment has little difference with the samples without PMO treatment on solidification structure and macrosegregation.As the peak currents are 250 and 350 K_(I)A,the columnar zone increases and macrosegregation aggravated.When 450 K_(I)A peak current is selected,the equiaxed grain ratio is enlarged,and the dendritic grains are refined,and the macrosegregation of C,Cr,Si and Mn is decreased significantly.By analyzing,different convections induced by PMO with various peak currents are the key factor to change the solidification structure and macrosegregation.
