Study On The Formation Mechanism Of Inclusions In 2219 Aluminum Alloy Ingots By Electromagnetic Stirring

2219 aluminum alloy has been widely used in the field of aerospace due to its excellent mechanical properties and processing properties.The size of its ingots is increasing with the application of large integral components,which require 2219 aluminum alloy manufacturing technology,quality stability,reliability,etc.to be more advanced.However,problems such as non-metallic inclusions and agglomeration of coarse compounds often occur in ingots produced by electromagnetic stirring semi-continuous casting,which lead to unqualified ultrasonic flaw detection,greatly increased rejection rate,and severely reduced production efficiency.In this paper,the inclusions in 2219 aluminum alloy ingots prepared by electromagnetic stirring is studied,and the formation mechanism of non-metallic inclusions and coarse intermetallic particles in the ingots are explored,which provides a reference for improving the quality of 2219 aluminum alloy ingots.This paper characterizes the size,morphology and distribution of inclusions in the ingot by ultrasonic inspection and microstructure.The results show that the defects in the 2219 aluminum alloy ingot are mainly distributed in the center of the ingot,and as the size of the ingot increases,the inclusions inside the ingot increase.The inclusions by ultrasonic inspection in the 2219 aluminum alloy ingot inspection are mainly composed of non-metallic inclusions and coarse intermetallic particles rich in Zr and Ti.Through the quantitative analysis of the inclusions,it is found that the non-metallic inclusions on the round section of the ingot are mainly distributed in the grain boundary,and mainly distributed in the center of the ingot.The numerical simulation of electromagnetic field,flow field and distribution of inclusions under different stirring currents are studied.The results show that the electromagnetic field is distributed at the surface of the ingot and the electromagnetic stirring position.Electromagnetic stirring causes the melt to flow in a rotating manner,and an upward stream appears in the center of the melt.The maximum stirring speed in the melt increases with the increase of the stirring current,and the upward stream velocity in the center of the melt also increases.As the current intensity decreases and the particle size of inclusions increases,the percentage of inclusions captured by the solidification front increases,and the percentage of inclusions floating to the free surface decreases.The inclusions of larger size are easily distributed in the center of the ingot,when the electromagnetic stirring is applied low current intensity.We analyzed the different factors that affect the formation of coarse particles.It is found that the high content of Zr and Ti elements in the ingot and the segregation of Zr and Ti in the center of the ingot will provide the composition conditions for the nucleation and growth of the coarse particles.The upward stream of the melt center makes the melt in the sump move upward,forming a lower-temperature area in the center of the hot top.The low-temperature area will cause the primary phase to nucleate in advance.The electromagnetic stirring can hinder its sedimentation process,even make it float to the upper layer of the hot top,which increased the time for its growth.Electromagnetic stirring may cause the oxide film to break and gather in the center of the melt,making the oxide film and other non-metallic inclusions gather in the center of the melt.The rough surface of the oxide film can be used as the nucleation point of the primary phase or collide with it to form large-scale defects.By optimizing the electromagnetic stirring process parameters,controlling the composition of alloy elements,and increasing the casting temperature,the non-metallic inclusions and the agglomeration of coarse particles in the 2219 aluminum alloy ingot are effectively controlled,and the quality of the ingot is stable and controllable.