Al-Cu-Li合金多道次热变形过程中的力学行为与微观组织演化

Mechanical behavior and microstructure evolution of Al-Cu-Li alloy during multi-pass hot deformation

摘要:

对Al-2.5wt%Cu-1.58wt%Li-0.3wt%Mn-0.12wt%Zr-0.06wt%Mg-0.05wt%Ti合金进行连续、不连续、双道次和多道次热压缩，研究其力学行为和微观组织演化。采用Gleeble-1500试验机进行热变形，变形温度为420℃，应变速率分别为0.001，0.1和 10s-1，对合金不同热变形阶段进行EBSD和TEM分析。双道次热压缩表明，道次间隔时间的延长有利于促进静态软化。通过改变变形过程中的应变速率，可控制合金的晶粒尺寸。多道次热变形过程，道次间的静态软化促进动态软化，反之亦然。在多道次热变形过程中(T=420℃, =0.1s-1)出现T1和θ′相动态析出。变形初始阶段，应变诱导位错为T1和θ′相提供形核位置，促进它们的析出和粗化。随应变的增加，T1和θ′相尺寸减小并趋于稳定，δ′相密度降低。试验合金多道次热变形过程中的流变应力受动态软化、静态软化和动态析出综合影响。

Abstract:

Continuous, discontinuous, double-pass and multi-pass hot isothermal compression tests were conducted to understand the mechanical behavior and microstructure evolution of the Al-2.5wt%Cu-1.58wt%Li-0.3wt%Mn-0.12wt%Zr-0.06wt%Mg-0.05 wt%Ti alloy. The tests were conducted in the temperature of 420℃ and at strain rates of 0.001, 0.1 and 10s-1 on Gleeble-1500. EBSD and TEM were used to investigate microstructure evolution at different deformation stages of the alloy. Double-pass hot deformation results show that the extension of interval time between two passes is conductive to promoting static softening. It is possible to control the grain size in the test alloy by changing the strain rate at different deformation stage. During multi-pass hot deformation process, static softening between the deformation pass is beneficial to the dynamic softening, vice versa. Dynamic precipitation of T1 and θ′ phase is observed during the multi-pass deformation process(T=420℃, =0.1s-1). In the initial stage of multi-pass deformation, strain-induced dislocations provide the nucleation site for θ′ and T1 phase, promoting their precipitation and coarsening. With increasing of strain, the size of the precipitates T1 and θ′ phase decreased and then tend to be stable, the density of δ′ phase decreased. Flow stress of the test alloy during multi-pass hot deformation is influenced by dynamic softening, static softening and dynamic precipitation.