A356铝合金铸件局部补压偏析及偏析组织的研究

摘要

A356铝合金挤压铸造的储气筒在其局部补压位置附近出现环形斑,对应一次补压和二次补压为单环斑和双环斑,环形斑直径分别为33和61 mm,斑痕宽度0．6~2 mm；环形斑处硅含量高于平均值29％,其中共晶体相对含量约是合金平均值8．5倍；局部补压使处于固液两相状态区域内的液相与固相分离,液体流动方向与补挤方向相反,因此造成成分偏析和偏析组织；偏析处微观组织与正常基体之间保持键合完整性、无裂纹等缺陷,储气筒零件仍然满足使用要求的气密性和耐压性.%Circular spots take place on the surface near local filling squeezing puncher pin of an A356 aluminum alloy squeeze casting air cylinder.Corresponds to one filling squeezing and the twice filling squeezing monocyclic and bicyclic spots,the circle spot diameter were 33 and 61 mm,its width 0.6-2 mm.The silicon content at circle spot exceeds 29% above the average of the alloy,about 8.5 times the average relative content of the eutectic in alloy.Local filling squeezing in the area of solid-liquid two-phase resulted in the liquid separating from solid, liquid flow direction opposite to the direction of extrusion,then resulting component segregation and segrega-tion microstructure.Segregation microstructure with normal matrix microstructure to maintain the integrity of the bonding,no defects such as cracks,the air cylinder part still meet use airtight and pressure resistance re-quirements.