微量Zr对6082铝合金晶粒亚结构演变的影响

Effect of Trace Zr on Grain Substructure Evolution of 6082 Aluminum Alloy

通过研究不同应变速率(10−3~1 s−1)下6082、Zr-6082铝合金的热变形行为以及微观结构演变,采用准原位EBSD对热处理前后晶粒组织的演变过程进行了分析,进一步探讨了Zr的加入对晶粒亚结构的调控作用,两种合金的流变应力曲线表明在低应变速率(10−3~10−1 s−1)下,动态软化作用大于加工硬化,主导了变形过程;在高应变速率下,动态软化和加工硬化达到平衡。随着应变速率增大,峰值应力水平增大,且Zr-6082合金的流变应力和峰值应力水平相比6082合金更大,其中应变速率为0.01时峰值应力相比6082合金增大21.1%。微量Zr合金化后亚晶体积分数、位错密度增加,再结晶水平降低,且应变速率越高的试样再结晶水平越低,Zr的加入促进了6082合金在热变形过程中动态回复的延迟和动态再结晶的抑制。在后续的热处理过程中,Zr同样起到了抑制再结晶的作用,变形态产生较多亚结构的样品热处理后保留较多的亚结构。在较高的应变速率下变形的样品,力学性能较好,Zr的加入促进了亚结构的形成,含Zr的6082合金热变形态和时效态的硬度值均高于6082合金。

By studying the thermal deformation behavior and microstructure evolution of6082 and Zr-6082 aluminum alloys under different strain rates (10−3~1s−1), the evolution process of grain structure beforeand after heat treatment was analyzed by quasi in-situ EBSD, and the effect ofZr addition on grain substructure was further discussed. The flow stress curvesof the two alloys showed that the dynamic softening effect was greater thanwork hardening at low strain rates (10−3~10−1 s−1), dominated the deformation process;At high strainrate, dynamic softening and work hardening reach equilibrium. With the increaseof strain rate, the peak stress level increases, and the flow stress and peakstress level of Zr-6082 alloy are greater than that of 6082 alloy. When thestrain rate is 0.01, the peak stress increases by 21.1% compared with that of6082 alloy. After microalloying with Zr, the volume fraction of subgrain anddislocation density increased, the recrystallization level decreased, and thehigher the strain rate, the lower the recrystallization level. The addition ofZr promoted the delay of dynamic recovery and the inhibition of dynamicrecrystallization of 6082 alloy during hot deformation. In the subsequent heattreatment process, Zr also played a role in inhibiting recrystallization. Thesamples with more substructures produced by morphology change retained moresubstructures after heat treatment. The samples deformed at higher strain ratehave better mechanical properties. The addition of Zr promotes the formation ofsubstructure. The hardness values of 6082 alloy containing Zr are higher thanthose of 6082 alloy in both thermal deformation morphology and aging state.