脉冲电流频率对Al-Cu合金定向凝固组织演变的影响

摘要

The directional solidification behavior of Al-Cu alloy was investigated with directional solidification device designed by ourselves and the evolution of the microstructure characteristics of Al-5 ％ Cu alloy was researched under the action of pulse current.The results showed that the solidifying organization form of A1-Cu alloy was obviously changed by the pulse current and the influence would be different if the frequency of pulse current was different:when the frequency was 100 Hz,the directional solidification characteristics of the alloy would be strengthened and the dendrite structure was not obvious,but the columnar crystal radius of directional solidifying organization increased.As the current frequency increased to 200 Hz,the secondary dendrite structure began to emerge,making the organization a dendritic structure.When the current frequency increased to 300 Hz,the organization structure would exhibit skeleton structure of neat rows.As the current frequency continued to increase to 400 Hz,the organization would change into minute dendritic structure and the organization was fine and uniformly distributed as a whole.However,the organization would be bulky,displaying the trend to isometric transformation due to the effect of 500 Hz high frequency current.%采用自行设计的定向凝固装置进行Al-Cu合金定向凝固行为研究,研究Al-5％Cu合金在脉冲电流作用下微观组织的演变特征.结果发现:脉冲电流的导入明显改变了定向凝固的A1-Cu合金凝固组织形态,不同频率的脉冲电流具有不同的影响效果,在100 Hz的小频率电流作用下,合金的定向凝固特征加强,枝晶结构不明显,但定向凝固形成的柱状晶半径加大,随着电流频率增大到200 Hz,二次枝晶结构开始显现,组织呈现树枝状结构特征,当300 Hz电流频率时,组织结构呈现排列整齐的的骨架结构,随着电流频率继续增加到400 Hz时,组织变为细小的树枝状结构特征,组织整体比较细小,而且分布较均匀,在500 Hz高频率电流作用下,组织又显得粗大,呈现向等轴晶转化趋势.