Cu含量和热处理工艺对Al-Si-Mg-Mn-xCu铸造铝合金显微组织和力学性能的影响

Effects of Cu content and heat treatment process on microstructures and mechanical properties of Al−Si−Mg−Mn−xCu cast aluminum alloys

采用三维X射线显微镜、光学显微镜、扫描电子显微镜、透射电子显微镜及硬度测试系统研究Cu含量及热处理工艺对真空压铸Al-Si-Mg-Mn-xCu合金显微组织和力学性能的影响。研究发现,虽然Cu含量增加会提高铸锭中气孔的密度和尺寸,但是Cu添加将促进凝固过程中含Cu初生相(Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu)的形成,从而提高合金性能。合金中形成5种不同结构的初生相,包括共晶Si、α-Al(Fe,Mn)Si、β-Mg_(2)Si、Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu相。随着Cu含量增加,θ相的面积分数迅速增加,α-Al(Fe,Mn)Si相面积分数首先降低,随后缓慢增加,而Q相的变化趋势与α-Al(Fe,Mn)Si相相反。这些初生相在热处理过程中会出现不同的演变规律。在随后的时效处理过程中,Q'和θ'相的协同析出能显著提高合金的时效硬化潜力。

The effects of Cu content and heat treatment process on the microstructures and mechanical properties of a series of Al-Si-Mg-Mn-xCu cast aluminum alloys prepared by the vacuum die casting process were investigated by three-dimensional X-ray microscopy,optical microscopy,scanning electron microscopy,transmission electron microscopy and microhardness testing.It was found that the number density and size of gas porosities increase with increasing Cu content.However,the Cu addition will promote the formation of Cu-containing primary phases(Q-Al_(5)Cu_(2)Mg_(8)Si_(6) andθ-Al_(2)Cu)during the solidification,which will improve the properties of the alloys.Five different primary phases were observed,namely eutectic Si,α-Al(Fe,Mn)Si,β-Mg_(2)Si,Q-Al_(5)Cu_(2)Mg_(8)Si_(6),andθ-Al_(2)Cu phases.With increasing the Cu content,theθphase area fraction increases significantly,while theα-Al(Fe,Mn)Si phase area fraction decreases initially,followed by a slight increase,with the Q phase area fraction displaying the opposite trend relative toα-Al(Fe,Mn)Si phase.These primary phases present different evolution rules during heat treatment process.During subsequent aging,the synergic effect of precipitating Qʹandθʹphases can significantly increase the alloy hardening response.