分级时效热处理对7A85铝合金结构壁板组织性能的影响

Effects of Hierarchical Aging Treatment on Microstructure and Properties of 7A85 Aluminum Alloy Panel

以7A85铝合金结构壁板为研究对象,结合力学性能测试与微观组织分析,研究了分级时效热处理温度与时间对7A85铝合金结构壁板组织性能的影响。结果表明,7A85铝合金单级时效热处理析出相主要为Al_(2)Cu相、Mg_(2)Zn_(11)相与G.P.Ⅱ区,与α-Al基体呈半共格关系,在保持较高强度的基础上兼具了良好的塑性。双级时效处理后合金析出相为Mg_(2)Zn_(11)相、Mg_(3.5)Zn_(1.5)相与MgZn_(2)相,强化机制为G.P.Ⅱ区和Mg_(2)Zn_(11)析出相与α-Al基体的半共格晶格畸变强化,屈服强度与硬度有所上升,塑性随之下降。随着时效保温过程的持续进行,析出相转变为Mg_(2)Zn_(11)相、MgZn_(2)相与Al_(2)CuMg相,且MgZn_(2)为主析出相,与α-Al基体的晶格关系转变为完全非共格,强度随之下降,塑性受α-Al基体影响连续上升。

The influence of hierarchical aging temperature and time on the microstructure and properties of 7A85 aluminum alloy panel was investigated by the mechanical property test and microstructure analysis. The results indicate that the precipitate phase in 7A85 aluminum alloy after single stage aging are mainly composed of Al_(2)Cu phase, Mg_(2)Zn_(11)phase, and G.P.Ⅱ region, which are semi-coherent with the α-Al matrix, showing excellent plasticity while maintaining high strength. The precipitates of two-stage aging are Mg_(2)Zn_(11), Mg_(3.5)Zn_(1.5),and MgZn_(2), and the strengthening mechanism is characterized by the semi-coherent lattice distortion strengthening between the G.P.Ⅱ region or Mg_(2)Zn_(11)phase and the α-Al matrix, showing a rise of yield strength and hardness as well as descent of the plasticity. The precipitate phase is transformed into Mg_(2)Zn_(11), MgZn_(2),and Al_(2)CuMg phases as the aging process continues, where MgZn_(2)is the major, and the lattice relationship between the MgZn_(2)phase and the α-Al matrix is converted to incoherent completely, leading to a decline of strength, and continuous increase of plasticity under the influence of α-Al matrix.